Model Engine Maker

Supporting => Engine Ancillaries => Topic started by: Roger B on May 01, 2015, 06:56:18 PM

Title: Fuel injection systems
Post by: Roger B on May 01, 2015, 06:56:18 PM
Most of my future projects require fuel injection systems, both paraffin (kerosene) and diesel. These will be around 20 - 25 cc per cylinder and as the smallest commercial engines with mechanical injection are around 200 cc per cylinder I decided that I need to start experimenting and developing some manufacturing techniques.
The first step will be a fuel pump and injector hopefully suitable for a 25 cc engine. The fuel pump will have a plunger diameter of 2mm and a target stroke of 2mm. The injector will have 1.5mm diameter needle with a 0.35mm diameter nozzle.
I hope to trial this on my current horizontal engine injecting petrol into the inlet with a later step of injecting paraffin into a vaporiser.
This will require lower pressures than for direct injection in a diesel engine, but petrol is of low viscosity and has no lubricating properties.
I have made a start on the injector with a body from 10mm square black bar. To make the nozzle concentric I need to drill the hole from the needle side so I had a go at drilling a deep (12mm) hole in the end of some brass bar turned down to 1.5 mm diameter. This seemed to work (the centre drill has a 0.5mm diameter tip.
Next I need to look at making a needle and seat cutting tool from hardened silver steel (drill rod).
Title: Re: Fuel injection systems
Post by: Roger B on May 02, 2015, 06:12:15 PM
I had decided to try and grind the D bit and the needle as with these small sizes even at full speed (2000rpm) the cutting speed is minimal. For a previous project I had made a tool post support for my Proxxon hand tool, this is not so rigid but was sufficient for some trials.

The lathe bed was protected with a sheet of plastic covered with a damp paper towel. I arranged the setup so that the sparks would be downwards. This required running the lathe in reverse.

I was able to grind 30° and 45° points as well as parallel without the Proxxon colliding with anything.

The D bit was hand filled to half thickness and then hardened by heating to dull orange and quenching in water.

I am happy with the basic techniques but they will need some refinement.
Title: Re: Fuel injection systems
Post by: Roger B on May 02, 2015, 06:19:52 PM
Next I tried some of the steps for making a nozzle to see if I could drill the 0.35mm hole from inside.

Starting with some 6mm round brass I drilled a 1. mm hole 20mm deep and then reamed it out to 1.5mm. Using my D bit I then went down to 24mm which would leave around 1mm for the nozzle hole.

Finally I put my nozzle drill in, marked the expected starting depth with a marker pen, put a drop of oil on the brass shaft, started the lathe at 2000rpm and carefully pecked until the resistance went away.

The drill came out complete and removing the bar showed the hole had gone through  :whoohoo: 
Title: Re: Fuel injection systems
Post by: Admiral_dk on May 02, 2015, 07:31:49 PM
Hi Roger

Very interesting project - many has tried and few has succeeded in making a working injection system in miniature size.

I for one hope that you will be among them   :ThumbsUp:

That way the rest of us can learn  ;)   .....  :popcorn:
Title: Re: Fuel injection systems
Post by: Roger B on May 03, 2015, 08:04:50 PM
Thank you  :)

I am well aware of the level of the challenge I have set myself  ::) From these first trials I need to improve the finish and fit by an order of magnitude to have any chance of success  :headscratch:

Maybe my machines and I can reach this, but anyway it will be good experience. The 1.5mm silver steel I am using is actually 1.49 mm. This is within specification,  but if my 1.5mm reamer cuts on size the clearance is already too much before I start lapping/polishing.

I have source of reamers in 0.01mm steps, but they are not cheap  :( Acrolaps also supply needle laps in this size range so I have some ideas for the next steps.

Valves for the injection pump are another challenge. The current Bosch type jerk pump with the spiral spill edge is out of the question in this size. I need to look to earlier designs with inlet and exhaust valves with variable stroke or fixed stroke with a separate spill valve. The earliest Benz design I have a drawing of used cone valves and the Lanz Bulldog used cone valves backed up with ball valves. Good cone valves 3 or 4 mm in diameter will be interesting to make :thinking: .

I am always happy for people to learn from me, even if it is how not to do things  ;)

Suggestions of how to do things better are also welcome  :)
Title: Re: Fuel injection systems
Post by: jerry kieffer on May 03, 2015, 10:58:20 PM
Thank you  :)

I am well aware of the level of the challenge I have set myself  ::) From these first trials I need to improve the finish and fit by an order of magnitude to have any chance of success  :headscratch:

Maybe my machines and I can reach this, but anyway it will be good experience. The 1.5mm silver steel I am using is actually 1.49 mm. This is within specification,  but if my 1.5mm reamer cuts on size the clearance is already too much before I start lapping/polishing.

I have source of reamers in 0.01mm steps, but they are not cheap  :( Acrolaps also supply needle laps in this size range so I have some ideas for the next steps.

Valves for the injection pump are another challenge. The current Bosch type jerk pump with the spiral spill edge is out of the question in this size. I need to look to earlier designs with inlet and exhaust valves with variable stroke or fixed stroke with a separate spill valve. The earliest Benz design I have a drawing of used cone valves and the Lanz Bulldog used cone valves backed up with ball valves. Good cone valves 3 or 4 mm in diameter will be interesting to make :thinking: .

I am always happy for people to learn from me, even if it is how not to do things  ;)

Suggestions of how to do things better are also welcome  :)

Roger
  I suspect that your .35mm injector hole is far to large to get the spray needed for air saturation if that is the final hole size.

For example.
                   My 1/8th scale grease fittings have a .25mm passage with ball and spring and the 1/8th scale grease gun easily pumps regular grease through them.       I suspect with Diesel fuel you will need to be less than .1 mm but a good starting point for experimentation.         

Jerry Kieffer
Title: Re: Fuel injection systems
Post by: Roger B on May 04, 2015, 09:01:55 AM
Thank you for the interest Jerry.  My intention (hope) is that this will operate more like a pintle injector with the actual orifice being the annulus between the nozzle hole and the point of the needle (hence the 30° needle and the 45° needle seat). The 0.35 mm hole is much to big to act as a conventional jet. Full size engines tend to be around 0.2mm so in this size I think it would have to be less than 0.1mm (outside my current abilities  :(  ).
Title: Re: Fuel injection systems
Post by: Graham Meek on May 04, 2015, 09:58:10 AM
Hi Roger,

A tip given to me by a Designer at Woodward's Diesel engines was to have a Pintle nozzle for a small engine. That way the orifice can be more easily controlled as the pintle diameter can be made just a shade smaller than the hole. Some of the full size Pintles were tapered, such that as the pintle lifted off the seat the taper closed the orifice slightly thereby giving a finer spray. The biggest problem I have had is seeing the pintle to grind the shape and to get a very fine finish. My latest attempts have been with Diamond charged rotary lap after rough grinding which has given a big improvement, but it is still early days, I hope this helps.

My best regards
Gray,
Title: Re: Fuel injection systems
Post by: Roger B on May 04, 2015, 11:04:19 AM
Thank you Gray, If I remember correctly you are also working on a diesel engine (along with everything else  :) )
Title: Re: Fuel injection systems
Post by: lohring on May 04, 2015, 02:20:33 PM
I've been thinking about variable stroke pumps for flash steam engine control.  There is a lot of information if you search on variable stroke or variable valve mechanisms.  The Pattakon site (http://www.pattakon.com/) has a lot of ideas for variable valve lift.  My favorite variable stroke pump designs are pictured below.  The first two pictures are the same mechanism.  The last picture is the valve timing method used on large marine diesels.

Lohring Miller
Title: Re: Fuel injection systems
Post by: Roger B on May 04, 2015, 06:19:21 PM
Thank you Lohring, those are some interesting variable stroke linkages to think about  :headscratch:  I guess that flash steam uses a significant quantity of water. I am looking a maximum of 2 - 3 mm3 per stroke.

These are the pump mechanisms I have been looking at. The Lanz pump uses a wedge between the eccentric and the plunger to vary the working stroke. The Benz pump uses a linkage to vary the stroke and the timing. The Compur pump has a separate spill valve and also allows the timing to be varied.

The Lanz picture is taken from 'Lanz von 1859 bis 1929' by Kurt Häfner  (Franckh-Kosmos)

The Benz picture is taken from 'Schlepper' by Armin Bauer (Bechtermünz Verlag)

The Compur  pump is taken from 'The Modern Diesel' Fifth Edition (Iliffe & sons Ltd)
Title: Re: Fuel injection systems
Post by: Graham Meek on May 04, 2015, 08:23:51 PM
Hi Roger,

Yes my Diesel is coming along, but my progress is very slow, the injector pump has been a bit of a stumbling block up until recently. I had been going down the variable stroke route and tried all sorts of different designs. Then talking to Jim at Woodward's he suggested restricting the in-flow. Apparently this was how they used to vary the fuel supply in the very beginning. He said the type of engine that I am building is not going to have such a demanding injection regime as one fitted to a vehicle.

I have therefore been experimenting with some differential screw thread combinations to give me a range of fuel supply that I think the engine will need.

The real problem now is getting this design to fit my engine, I do not want end up with an injection pump as big as the 10 cc engine.

My best regards
Gray,
Title: Re: Fuel injection systems
Post by: Roger B on May 04, 2015, 08:43:44 PM
Hi Gray,

I choose to start at around 25 cc as the biggest I could comfortably make with my machines to give me more chance of getting the bits to fit.

I have looked at a couple of simple variable stroke mechanisms, but the problem is keeping the angle of injection commencement the same (or similar. I don't know how important this really is  :headscratch: ). I am probably going to try a cam like the one on the Benz pump where the working angle is quite small to start with. This should also give a quick pump stroke (less time to leak  ::)  )
Title: Re: Fuel injection systems
Post by: Graham Meek on May 06, 2015, 10:16:43 AM
Hi Roger,

Several years ago when I started out on my Diesel engine design I came across the engine below. The photograph was all the information I could find, not helped with my limited knowledge of German. I was wondering if you, or anyone else on the Forum has come across this engine before and knows more about the design?

My best regards
Gray,
Title: Re: Fuel injection systems
Post by: Roger B on May 06, 2015, 12:21:10 PM
Hi Gray,

A limited search suggests that the drawing you have is an Eisfeld. I have a short German description that I will translate later, but it suggests that it was 15cc, ran, but was too heavy to fly.

http://www.kleinstmotoren.eu/histori15.html

I have attached a picture of a petrol Eisfeld engine, there are similarities.
Title: Re: Fuel injection systems
Post by: Roger B on May 06, 2015, 12:48:10 PM
And a little bit more. I found the article your drawing came from along with a translation on the RC groups forum:

http://www.rcgroups.com/forums/showthread.php?t=1054975&page=148

Thank you to JMP_blackfoot  :ThumbsUp:  :ThumbsUp:
Title: Re: Fuel injection systems
Post by: Ian S C on May 06, 2015, 01:48:42 PM
Twenty or so years ago i made a new injector piston for a Lanz Bulldog, can't remember the actual size, but near an inch diameter, the stroke is only a few thou. Other than the Lanz, the only fuel injection system I'v had anything to do with is that used by Continental on their aircraft engines,ie., the IO 470 etc. this system is a constant flow directed directly behind the intake valve, probably not the most economical method, but it's simple, and it works, and at a low pressure.
Oops, forgot there is also the Ruston Hornsby HR 6 at the museum.
Ian S C
Title: Re: Fuel injection systems
Post by: Graham Meek on May 06, 2015, 04:16:18 PM
Hi Roger,

Thank you for finding out so much information on this engine, as well as the translation. I honestly did not expect to find any more information, given the date I am surprised the information has survived at all, especially as this developement was going on before and during WWII.

My best regards
Gray,
Title: Re: Fuel injection systems
Post by: Roger B on May 08, 2015, 02:24:36 PM
Hi Gray,

The search required some lateral thinking as well as using German  ::)

The stated injection pressure seems very high, especially as the article suggests that an open nozzle was used. The fuel metering looks to be using the inlet valve as a spill valve (like in Lohring's picture) but part of the mechanism is not illustrated. It's always encouraging to know that someone has made it work before.

I also have a copy of Maschinen in Modelbau in the attic in England that has some details of a 7cc true diesel based on a Deutz horizontal prototype. I must dig that out next time I go back.
Title: Re: Fuel injection systems
Post by: Roger B on May 09, 2015, 10:25:59 AM
A few more tries at making bits. I made a new bracket for the grinder. Its only two bits from the offcuts drawer with a few holes but I managed to get both wrong the first time  :facepalm:

I then tried to improve the finish from the grinding operation with the following variables: Lathe at 2000rpm or 250rpm, grinder at 5000rpm or 25000rpm, aluminium oxide or silicon carbide grinding wheel, grinding with or against the workpiece direction.

None of the results were very good, but the best so far was both at low speed, aluminium oxide wheel and grinding with the workpiece. I need to get some sort of microscope to really see what is going on  ::)

Next I wanted to make some filing/polishing guides for the D bit. They were to be 8mm silver steel with a 1.5mm hole down the middle, a flat milled on the end to just over half diameter and hardened. On the first attempts the drill wandered way off the centre line  :headscratch: I then tried a brand new, hopefully good quality, drill which seemed to improve things. Yet more to learn  :headscratch:
Title: Re: Fuel injection systems
Post by: cfellows on May 09, 2015, 04:13:37 PM
Don't know if you are familiar with Find Hansen's engines, but he has had a fair degree of success with model injected engines.  Here is a link to his youtube channel...

https://www.youtube.com/channel/UCxv370lnEXq7MLmLuXMqklA (https://www.youtube.com/channel/UCxv370lnEXq7MLmLuXMqklA)

and a link to his website...

http://www.findsminimodelhotbulbengines.dk/ (http://www.findsminimodelhotbulbengines.dk/)

Here's some further links to his website that show pictures of his injectors and injector pumps...

http://www.findsminimodelhotbulbengines.dk/Side9.html (http://www.findsminimodelhotbulbengines.dk/Side9.html)

http://www.findsminimodelhotbulbengines.dk/Side1.html

He doesn't offer any drawings or plans for his work but he did tell me that a possible method for making the injector pump was to fill the pump cylinder with melted solder then insert the plunger, coated with oil.  You can see pictures of his pumps on his website.  His website makes tantalizing reading and is worth exploring thoroughly.

Chuck
Title: Re: Fuel injection systems
Post by: Roger B on May 09, 2015, 05:07:17 PM
Thank you Chuck  :ThumbsUp: Yes I do know his website, and he doesn't give many details. That's a rather interesting way of making a very close fitting cylinder  ::)  :headscratch: it deserves some thought  :wine1:
Title: Re: Fuel injection systems
Post by: Roger B on May 11, 2015, 08:13:22 PM
Next steps on the D bit guides.
I mounted both in the milling vice and milled flats down to almost half thickness. The silver steel was 7.98mm diameter so the one for filling was taken down to 4.10mm and the one for polishing to 4.03 so that the flat on the D bit will not quite reach the centre.
Whilst still in the vice both were drilled and tapped for an M2 grubscrew. I don't like doing hot work at the end of a session so I will harden them tomorrow.

I don't know if I am taking this too far  ::) , but it seems to me that the quality of the finish from the D bit, especially on the cone, will depend on the finish of the cutting edges. The literature generally says 'file to exactly half diameter' but again it seems to me better to be slightly above half than below  :headscratch:
Title: Re: Fuel injection systems
Post by: Roger B on May 12, 2015, 07:15:35 PM
I hardened and tried my D bit guides. The results look much better than my free hand efforts, but I need to do some more work on grinding the tips   ::)

I also received some 0.01 mm step reamers and pin gauges ready for my experiments on making precision bores. I am also going to order the appropriate needle laps from Acrolaps.

Looking at the pin gauges and their cost (~12 CHF/EUR/USD or £7) they are much better finished than anything I could achieve with my current machines and may be a useful/sensible source of precision pump plungers  :headscratch:
Title: Re: Fuel injection systems
Post by: Frank Boyle on June 05, 2015, 10:00:28 PM
Hi.   Rodger
I am trying to make an injector in 3" scale ,if succesful will continue with the hot bulb hornsby engine.I have the full plans for the injector and the fuel pump and have scaled these down to construct the injector .I would be willing to send a copy of these to you they may help.
Regards Frank
Title: Re: Fuel injection systems
Post by: Roger B on June 06, 2015, 07:40:39 AM
Hello Frank,

That would be very kind of you  :) All information is helpful  :ThumbsUp:  :ThumbsUp:
Title: Re: Fuel injection systems
Post by: Ian S C on June 06, 2015, 02:46:51 PM
I can hardly imagine making a working nozzle, I'v got 4 nozzles from a Continental IO-470 engine (some where), these ones are not direct injection, but inject petrol into the intake manifold, just behind the inlet valve, so they work at low pressure.  They are about 1.5" long.  The only other one I'v had anything to do with would not be too hard to scale, it's on a Ruston Hornsby 6 HR, and is about 6" long, my nephew, a diesel mechanic, over hauled it for me, he'd never seen anything like.
Ian S C
Title: Re: Fuel injection systems
Post by: petertha on June 23, 2015, 04:31:57 AM
I'm fascinated by your micro-drilling Roger. Very interesting tooling arrangements.

Would these 35K dental type drills provide appropriate rpm for those teeny drills & reamers? The electrics like pic tend to go for $100-150-ish with dedicated speed control boxes (ebay). I'm told by my dentist friend the pro versions have pretty high quality ceramic bearings & low run-out, but he might be referring to pneumatic drive which I thought he said was higher rpm yet. No idea if that's what is contained in these units.
Title: Re: Fuel injection systems
Post by: Roger B on June 24, 2015, 08:34:44 PM
Peter (I guess),

I do have a Proxxon hand drill which will reach 25,000 rpm and a Proxxon bench drill that will do 8,000 rpm. The problem is drilling in the lathe which has a top speed of 2,000 rpm.

I decided to make some experiments on an injection pump. The first version will have an inlet port in the barrel like a full sized one. If this is not successful I will make one with an inlet valve. The piston will be 2mm Silver Steel (drill rod) hardened and polished/lapped. The body is from 10mm square hot rolled mild steel. The bore was drilled 1.8mm and reamed 1.95mm. My 1.98mm pin gauge would not enter so there is hope. The delivery valve will screw into the recess at the square end. the other end is turned down to 6mm for a return spring.
Title: Re: Fuel injection systems
Post by: fumopuc on June 25, 2015, 04:10:45 AM
Hi Roger, I am following along.
Title: Re: Fuel injection systems
Post by: Roger B on June 25, 2015, 05:57:03 PM
Thanks Achim.

Finishing the inlet port (except for the thread, I'm waiting for an M5x0.5 tap) and starting the plunger.
Title: Re: Fuel injection systems
Post by: Admiral_dk on June 25, 2015, 09:06:36 PM
Still on the "straight and narrow" are we ?  ;)

I think there are more than a few following this thread quietly  :)
Title: Re: Fuel injection systems
Post by: Roger B on June 29, 2015, 07:55:37 PM
Hopefully straight and definitely narrow  :)

I hardened the non threaded end of the plunger by heating to dull read and dropping it into water. It grew from 1.99mm to 1.995mm. I polished back to 1.98mm using fine abrasive cloth (I may need to make a proper lap, time will tell   :headscratch:  ).

I then tried out my needle eye lap. With some diamond paste and oil I slowly opened up the bore until my 1.98mm pin gauge just fitted. (I know it's bad practice to mix measuring instruments and abrasives  ::) ) The plunger was then a tight but smooth fit  :whoohoo: .

Next I need to wait for the M5 fine tap, thread the inlet and exhaust ports and then put it all in the ultrasonic bath.
Title: Re: Fuel injection systems
Post by: Roger B on July 01, 2015, 07:19:15 PM
I received my M5 x 0.5 tap and set about tapping the holes. Unfortunately I was a little clumsy and stripped the thread on the inlet port  :facepalm: I decided to silver solder a 6mm plug in the hole and re-tap although the heat for silver soldering will probably damage the bore.

After soldering and tapping the plunger no longer fitted so I lapped the bore a little more until it fitted again. I will keep going with this body for the moment, but I expect I will have to make a new one  ::) .

Finally I cleaned the body, plunger and pin gauge in the ultrasonic bath to remove any traces of diamond paste.

The next step is to machine the ends of the two unions so they seal on the end faces not on the hexagon.
Title: Re: Fuel injection systems
Post by: Roger B on July 02, 2015, 06:04:42 PM
I turned the ends of the unions to size and then soldered a temporary plug into the end of the delivery union. With a bit of fiddling I filled it with oil so that the plunger felt solid as soon as the inlet port was covered.

As a first test I rested 1kg piece of steel on the plunger and it moved down over a few seconds. This is a pressure of 30 bar (450psi) on a 2mm plunger so not too bad but I will need to remake the body and probably the plunger. Diesel is somewhat less viscous than the oil I used.

https://www.youtube.com/watch?v=2cG9q194h8w
Title: Re: Fuel injection systems
Post by: Graham Meek on July 04, 2015, 11:57:42 AM
Hello Roger,

I have been following your progress from the wings. I am progressing steadily with my design but keep getting bogged down with other things. As regards your leakage test, I intend to use penetrating oil to test my pump fits. If the pump will stand up to this then I am certain it will work with diesel. There has to be some clearance no matter how small to allow the two parts to slide. Labyrinth seals down the pump stem are a good idea as they also trap fuel to act as a lubricant.

When I worked for Dowty Fuel Systems, (aircraft fuel systems) the fits of the various spool valves were permitted a certain amount of leakage per unit time. These systems were never ever static as the effects of acceleration, rpm and altitude were all accommodated mechanically.

My best regards
Gray,
Title: Re: Fuel injection systems
Post by: Roger B on July 05, 2015, 09:18:29 AM
Hello Gray,

Thank you for the thoughts. As I am moving into a new area of precision for me I want to make a few experiments to see what is possible and what is not. I want to make a running trial with petrol injection on my horizontal engine I was going to use alcohol as a test fluid (it doesn't smell as bad as petrol or diesel for use in the cellar). I suspect that quite a lot of leakage is acceptable as the injection time is quite short.
Title: Re: Fuel injection systems
Post by: Roger B on August 15, 2015, 07:40:03 PM
Back on this one. First I would like to thank Frank Boyle for copying and sending me the information he has collected on hot bulb injection systems  :ThumbsUp:  :ThumbsUp:

I also located the details of the German model diesel. This is in Maschinen in Modellbau 3/06. Erich Beyer wanted to make a 6.5 cc model of a Güldner hopper cooled horizontal diesel (as fitted to the family tractor). He started when at technical college, but without success and then over many years made various trials including converting a moped engine to diesel operation. Finally, after 38 years, he produced a working model with the following details:

Bore 20 mm
Stroke 22mm
Capacity 7 cc
Compression ratio 21:1
Injection pressure 100 Bar
Injection volume 1 mm3 at full load
Pump plunger diameter 2 mm
Pump stroke 0.3 mm
Running speed 2,000-3,000 rpm
Two 90 mm diameter flywheels
This engine has a Lanova style combustion chamber and operates on pump diesel. He claims that it will cold start without any aids.

I have started making a new injection pump. To try and keep things concentric I set the body up 1mm eccentric in both planes and turned the boss for the return spring. I then centred and drilled 1.5 mm halfway through. The boss was then held in a 5mm collet and I drilled 1.5 mm from the other end. This was followed with a 1.8mm drill and a 1.95mm reamer. Finally I drilled 4.5mm 4mm deep for the M5 x 0.5 thread and flattened the bottom with a 4mm end mill. This should form the seat for the delivery valve.
Title: Re: Fuel injection systems
Post by: Admiral_dk on August 15, 2015, 08:11:00 PM
Hi Roger

Hot Bulb and "normal" Diesel injection are two very different things (as I'm sure you're aware off) .....

I'm guessing that you are pursuing the Diesel injector pump - though I'm sure many off us here would like the Hot Bulb info too - or rather, we would like to be able to do both  ;D

Still following and hoping that you succeed  :ThumbsUp:

Per
Title: Re: Fuel injection systems
Post by: Brendon M on August 23, 2015, 02:52:37 PM
Hello Roger, I am following along with great interest in how this turns out :)

For fuel metering, one design to consider could be based off the "Sleeve Metering" system:

http://constructionmanuals.tpub.com/14264/css/14264_173.htm

It does require drilling some very small holes since it's a 2mm plunger!
Title: Re: Fuel injection systems
Post by: Roger B on September 26, 2015, 06:46:25 PM
Thank you both for your interest. This is intended to be a normal diesel injection system (although its first trial will be as petrol injection). I have looked at various metering systems and will initially stick to variable stroke. I also looked a another sleeve metering system (the EH pump) but these seem to require the pump to be immersed in diesel oil with attendant sealing problems.

I've made a little more progress with the new pump body.
Title: Re: Fuel injection systems
Post by: Roger B on October 07, 2015, 07:50:13 PM
A couple more little bits. First the end piece and return spring for the plunger. Nothing special there just a DIY store spring cut to length.

I then decided to make a lap for the plunger rather than using fine abrasive cloth as I did on the first one. Its a piece of 16mm dia. brass 10mm long, the central hole was reamed 2mm. I added the possibility for a grub screw to open it up/limit the closure. I don't know if I will need it. When it came to slitting it the easiest solution was to clamp it in the lathe tool post.

Next step make and harden a new plunger from 2mm silver steel then some more lapping.
Title: Re: Fuel injection systems
Post by: Roger B on November 04, 2015, 08:06:46 PM
On with the lapping. My external lap seems to work quite well and the plunger is 1.98mm diameter and parallel  :) . I purchased an additional 1.97mm pin gauge for checking the bore so I can go first to 1.97 and then to 1.98 to try and keep things straight.
Title: Re: Fuel injection systems
Post by: cfellows on November 04, 2015, 08:37:39 PM
Interesting territory you're exploring here, Roger.  I applaud your efforts and hope against hope you come up with something that really works.  I think many of us would like to explore fuel injection considering the vagaries and uncertainties of carburetion in model engines.

Chuck
Title: Re: Fuel injection systems
Post by: Roger B on November 08, 2015, 08:01:58 PM
Thank you Chuck, I think this is going to be long slow process as I gradually learn new skills.

This pump body was not successful  :( I lapped it with 5 micron diamond paste until the 1.97 mm pin gauge would just pass and the 1.98 mm wouldn't. Unfortunately it appears that the original hole was slightly bent and the gauges go much deeper from the wrong (delivery valve end) than they do from the correct end.

On the first body I drilled all the way from the valve end but the other end was noticeably off centre. This time I drilled from both ends but seem to have got a bent hole  ::)

I think that next time I will open up the first part of the plunger end to 2.00mm to reduce the length I have to keep straight.
Title: Re: Fuel injection systems
Post by: Roger B on November 11, 2015, 07:36:25 PM
Next attempt. I still have enough raw material for around 30 pump bodies so maybe one day I will get it right  :headscratch:

This time I finished the delivery valve pocket before drilling through with a new good quality 1.8mm drill. The hole depth is just over 20mm so not too far away from the 5d rule of thumb. It looks fairly central at the other end so I have some hope. I have started lapping and this time the 1.97 pin gauge passes through quite easily and the 1.98 still doesn't enter.
Title: Re: Fuel injection systems
Post by: Roger B on November 15, 2015, 05:30:13 PM
I finished lapping this body and gave it a try. It was difficult to get the air out of the pump until I found that the back fixing screw hole had just broken through into the pump bore  :facepalm:  :facepalm:  :facepalm: Time to start body number 4  :(

I have a set of diamond lapping paste syringes from RDG. I used the coarsest (40) for lapping the cylinders on my engines and the first pump body. I then realised that this may be too coarse and used 5 until I got to 1.97mm and then 1 to reach 1.98.

Once I got the pump cavity full with the same grade oil as I used in the last test the plunger was essentially solid. With the same weight on top it just sat there, probably taking around 10 mins to fall, so no video.

I then cleaned the oil out with some cooking alcohol (as used in spirit lamps) and tried with this alcohol as a fluid in this case the plunger sank in 3-4 seconds so it should work well enough with petrol as the require injection pressure is much lower.

I think that this body, in spite of my mistake, will be good enough to test an injector. So an injector here we come  :)
Title: Re: Fuel injection systems
Post by: cfellows on November 15, 2015, 05:38:41 PM
Hate having to redo things because of mistakes.  However, it happens to me much too often.

What did you use as a lapping tool?

Chuck
Title: Re: Fuel injection systems
Post by: Roger B on November 15, 2015, 06:15:08 PM
I have plenty of 'trial' pieces   ::)  like many others on here I suspect   ;)

I'm using Acro needle eye laps for the fuel pump and injector. I also have some of their larger barrel laps that I have used for my cylinders.

http://acrolaps.com/index.htm



Title: Re: Fuel injection systems
Post by: Roger B on November 22, 2015, 08:20:56 PM
The next stage was to make a new D bit to cut the seat for the injector needle. This was a piece of 1.5mm silver steel (actually 1.49mm) lapped down to 1.45 mm. The 60° point was ground and polished with the Proxxon grinder held on the tool post. The flat was then filed and polished with the fixture I made and the end was hardened.

The needle was hardened before grinding, the point is 50° and the reduced section is 1 mm.
Title: Re: Fuel injection systems
Post by: Roger B on November 22, 2015, 08:32:42 PM
The shank of the needle was lapped to 1.48mm and it was cut to length.

The spring adjusting screw and nozzle were made from a piece of 8mm brass rod threaded M8x1 for 20mm.  If (when  ::) )I make another nozzle I will cut the thread at the end. The spring adjuster was no problem, but the 0.35mm drill pulled out of it's holder (I'd tried soft soldering it in place). Luckily by tapping the end of the nozzle with a small hammer I was able to get the drill out  :)

This time I used Loctite to hold the drill in place and was able to drill the jet hole.

When I tried to put the parts together I found another problem  :( The D bit had opened the bore out to 1.48+ mm and the needle was already a running fit  :facepalm:

New D bit and nozzle time  ::)
Title: Re: Fuel injection systems
Post by: Roger B on November 24, 2015, 07:33:44 PM
Found the problem  :) There was a little burr on the edge of the D bit (probably from the filing  :facepalm: ) that was enough to open out the hole the extra couple of hundredths. I carefully stoned the edges and made a quick trial hole. The 1.47 pin gauge wouldn't go in so just another nozzle to make  ::)
Title: Re: Fuel injection systems
Post by: Don1966 on November 25, 2015, 01:17:30 AM
Cool Roger, I am still following you. I am really interested in how this turns out. It would be interesting to make an electrically solenoid version. I have even considered looking into making and electronic governor for these engines. I am still making steam engines but will be venturing into IC's later.

Don
Title: Re: Fuel injection systems
Post by: Roger B on November 25, 2015, 06:12:21 PM
Thank you Don  :ThumbsUp: There are a few people following this little exercise, I hope I manage to make something that works but anyway I am learning a lot  :)

If you are looking at solenoid injectors this is some pretty amazing stuff:

http://www.f1-2000.co.uk/index.php?f=fuel_injectors

Title: Re: Fuel injection systems
Post by: Roger B on November 28, 2015, 05:54:43 PM
The new nozzle was machined more conventionally, cutting the thread (turning the lathe by hand) at the end. This time it all went smoothly including the 0.35mm hole and there is some material to lap out for the needle  :)
Title: Re: Fuel injection systems
Post by: Don1966 on November 28, 2015, 10:37:17 PM
Hi Roger, have you ever thought of using a clock bushing for the nozzle orfice? They do make them in multi sizes. I use one on my mini propane burner. Time savers has them http://timesavers.com/search.html?q=Bushings&go=Search.


Don
Title: Re: Fuel injection systems
Post by: Roger B on November 29, 2015, 08:25:14 AM
Thank you Don, I didn't know that such things existed   ::) I will have a look for European suppliers (I was surprised that the US ones were metric  :headscratch: are clocks generally metric?)
Title: Re: Fuel injection systems
Post by: 10KPete on November 29, 2015, 09:56:24 AM
Yep, generally metric.

Pete
Title: Re: Fuel injection systems
Post by: Roger B on November 30, 2015, 08:19:37 PM
Before I can lap the nozzle for the needle I need to drill the feed hole. I have been through many iterations of this design. The whole high pressure side of the system needs to the minimum number of sealing faces and the minimum number of places where air can be trapped. Rubber O rings are out as they will give too much under the pressure pulses.

In the end I went back to an earlier idea with a 60° cone directly in the side of the nozzle. As this is the same as a centre drill the cone and connecting hole could be drilled as one using the union nut as a guide. The union nut is turned from 8mm hex steel with an M5 x 0.5 thread and a 3.15 mm bore to suit the centre drill. The centre drill has a 0.8mm dia. tip.

I now need to make the brass nipple. I have some 1mm bore 2mm od copper tube for the connecting pipe.
Title: Re: Fuel injection systems
Post by: Myrickman on November 30, 2015, 10:28:13 PM
Roger, been quietly following along with great interest. Your perserverance in this challenge is admirable. All those teeny tiny bits and requiring such a high degree of precision....it will be so neat when you get it sorted out. I'm fascinated with your work. Paul
Title: Re: Fuel injection systems
Post by: Admiral_dk on December 01, 2015, 08:23:35 PM
Quote
Roger, been quietly following along with great interest.

Me too - the very few who has solved this puzzle before are not sharing their knowledge (not that I blame them), but you are doing it in public and if (I should say when, shouldn't I ;) ) you solve it = we all win  :whoohoo:
Title: Re: Fuel injection systems
Post by: Roger B on December 02, 2015, 07:53:24 PM
Thank you both for your interest and support as I slowly plod away at this  :ThumbsUp:   :wine1:

I turned the nipple with a 59° cone to try and ensure that it sealed at the end. A quick check with marking blue suggests that it's a reasonable fit. Unfortunately I did it up a bit too tight for the trial and crushed the end so the pipe no longer fits  :(  I will make a new one with a slightly shorter land to get an extra thread engaged.

When I make the next one (for the actual diesel I will need to silver solder a clamping flange on) I will offset the bore to get yet another thread and also probably use M6x0.5 instead of M5x0.5
Title: Re: Fuel injection systems
Post by: Roger B on December 06, 2015, 06:41:08 PM
A little bit more: This time I soldered the pipe into the nipple before screwing it up tight. The 1mm drill is in the end of the pipe to stop any solder getting in. The bore for the needle was lapped in the same way as the pump bore and the pieces were all cleaned in the ultrasonic bath.

Next I need to sort out the delivery valve for the pump as well as an operating mechanism.
Title: Re: Fuel injection systems
Post by: Admiral_dk on December 06, 2015, 11:26:11 PM
Great progress  :ThumbsUp:
Title: Re: Fuel injection systems
Post by: Don1966 on December 07, 2015, 12:56:24 AM
So does this mean we have a working injector? Looks great and you have my attention.

Don
Title: Re: Fuel injection systems
Post by: Roger B on December 08, 2015, 11:21:29 AM
Thank you both  :ThumbsUp: I don't know yet if it will work, but I have managed to make all the parts according to my plans  :) I need to order a selection of springs to allow me to set the injection pressures. The first planned trial with petrol injection into the intake will require a much lower pressure (10 Bar ??) than for the true diesel operation (50 Bar+). I did think about winding my own, but to get consistency I would rather pay a little and have correctly post heat treated ones.
Title: Re: Fuel injection systems
Post by: Stuart on December 08, 2015, 05:35:33 PM
Roger

When you come to silver solder very small stuff I use silver solder paste no extra flux required

I have used it for doing nipples on 1/16 odd copper pipe and never had a bung up you need just a smear

Cup alloys have it

http://www.cupalloys.co.uk/home/

Lee springs are good and provide the data that you will need


Stuart
Title: Re: Fuel injection systems
Post by: Roger B on December 09, 2015, 08:59:08 PM
Thank you Stuart  :ThumbsUp: This time I have soft soldered the nipple to the pipe so I can remove it later if needed but that paste looks interesting for the future. I have ordered the springs from HPC as they also had 2mm key steel which I have been looking for as well as no minimum order quantity  :)
Title: Re: Fuel injection systems
Post by: Roger B on January 04, 2016, 07:08:07 PM
Finally back on this. I have started making a simple stroke adjuster that will use a tapered wedge based on the system used on the Lanz Bulldog. I have also received my selection of springs so I can continue with the pump delivery valve and injector.

As I don't have a 2mm slitting saw I cut down the middle of the plunger with a 1mm saw and then made two additional cuts to bring it to 2mm. I was concerned about the saw deflecting but this did not seem to be a problem.

Unfortunately I broke the tip of a centre drill in the stroke adjuster body  :( This time I followed a suggestion from one of the posters on here and ground the middle of the broken drill away and used it to trepan around the broken tip so I could remove it  :)
Title: Re: Fuel injection systems
Post by: fumopuc on January 04, 2016, 09:12:45 PM
Hi Roger, I am quietly following along.
Title: Re: Fuel injection systems
Post by: Don1966 on January 04, 2016, 10:52:22 PM
Still with you Roger.............. :cheers:

Don
Title: Re: Fuel injection systems
Post by: Roger B on January 05, 2016, 07:04:51 PM
Thank you both  :wine1:

I milled out the slot for the control wedge and then milled the wedge (4mm key steel) to 10° and used this to set the plunger to mill a matching 10° on the end.
Title: Re: Fuel injection systems
Post by: Roger B on January 31, 2016, 03:32:08 PM
As I had received the required springs I decided to try the pumping system. The delivery valve holder was drilled 3.1 for a 3mm ball. The annulus left is of similar area to the 1mm bore connecting pipe.

Unfortunately, but not unexpectedly, the thread on the injector union failed so I opened out to M6 x 0.5. I was able to centre the nozzle using the original 0.8mm centre drill then cut the old thfread out with a 5 mm end mill, open out to 5.5 mm and retap. I also made a new nut with a small recess to allow an extra thread or so to engage.
Title: Re: Fuel injection systems
Post by: Roger B on January 31, 2016, 03:39:18 PM
Having fixed the damaged thread I could put the system together with a temporary tank (part of a float chamber for my first engine) and try it with some cooking alcohol. It took a lot of effort to get the air out of the system but was finally rewarded with some dribbles and drips along with one or two good sprays  :whoohoo:

There was quite a lot of leakage from the back of the injector. I'm not sure if it was past the needle or from the union.

I've tried to capture some of the spraying on video, but it's not very good  :(

https://www.youtube.com/watch?v=Au2usbHQmKg
Title: Re: Fuel injection systems
Post by: Don1966 on January 31, 2016, 04:00:40 PM
Cool Roger, it's a start anyway. It does look like some progress to me. Keep it coming......... :ThumbsUp:

Don
Title: Re: Fuel injection systems
Post by: Kim on January 31, 2016, 04:13:33 PM
That's great Roger!  You're getting there!  :ThumbsUp:
Quite the fiddly little gizmo isn't it?
Kim
Title: Re: Fuel injection systems
Post by: Roger B on May 20, 2016, 06:54:22 PM
The next step is to make an excentric so I can drive the pump. The excentric rod is a piece of 2mm brass. I could have had lots of fun with the RT but decided in this case a hacksaw and file would be quicker.
Title: Re: Fuel injection systems
Post by: Roger B on May 26, 2016, 07:10:30 PM
The excentric was turned from free cutting mild steel to 16mm and then offset 1.5mm in the four jaw chuck and turned down to 12mm.

I then needed to put a slot in the end of the stroke adjusting wedge. This is made from 4mm square key steel and the deflection was too much using a 2mm end mill. I couldn't hold it sensibly to use a slitting saw or slot cutter so finally hacksawed and filed the slot. Next time I will cut the slot before cutting the wedge face.
Title: Re: Fuel injection systems
Post by: Jo on May 26, 2016, 07:38:59 PM
Next time I will cut the slot before cutting the wedge face.

 ;)

Jo
Title: Re: Fuel injection systems
Post by: fumopuc on May 26, 2016, 07:45:05 PM
The next step is to make an excentric so I can drive the pump. The excentric rod is a piece of 2mm brass. I could have had lots of fun with the RT but decided in this case a hacksaw and file would be quicker.
Hi Roger, sometimes this old fashioned way is the best and easiest way to go.
Title: Re: Fuel injection systems
Post by: Roger B on May 28, 2016, 06:36:00 PM
Thank you for your interest and support  :ThumbsUp:  :ThumbsUp:

I finished off the excentric and then made a mounting plate to fit the pump and stroke adjuster onto the side of my horizontal engine. For the trial video I removed the spark plug and motored the generator with a 6V battery.

https://www.youtube.com/watch?v=Gh_DrUwlSgI
Title: Re: Fuel injection systems
Post by: Roger B on May 29, 2016, 06:10:35 PM
I then set the pump in place, using a 1mm drill in the inlet port to ensure it was fully open. The next pieces were a link to connect the wedge to the adjustment block and the adjustment block. As the adjustment block was brass rather than key steel I could cut the 2mm slot without problems using a 2mm end mill.
Title: Re: Fuel injection systems
Post by: Roger B on May 29, 2016, 06:16:15 PM
I had a commercial (RC Machines?)M2 bolt that was suitable for the top pivot pin of the link. I still need to make a couple of proper 2mm pivot pins as well as the adjusting screw and top bearing but enough bits moved to make another video clip (apologies for the quality, poor light and hand held).

https://www.youtube.com/watch?v=W5TFGkM3ujo
Title: Re: Fuel injection systems
Post by: fumopuc on May 30, 2016, 02:20:09 PM
Hi Roger, interesting mock up. Waiting for the next experiments.
Title: Re: Fuel injection systems
Post by: Roger B on May 31, 2016, 06:03:19 PM
Thanks Achim  :ThumbsUp: With luck I will be trying petrol injection in a couple of weeks  ::)

Before I went back to lathe mode for the pivot pins and adjusting screw I decided to make the inlet manifold/adaptor for the injector. I milled an 8mm diameter recess at 30° in some 6mm dia. brass tube and silver soldered it onto the side of some 8mm dia. brass tube. The passage was then opened out with a centre drill followed by a 5mm drill. I will reuse the flanges from an existing carb adaptor so I can use a carb simply as a throttle.
Title: Re: Fuel injection systems
Post by: Roger B on June 04, 2016, 07:58:52 PM
I fitted the flanges to the manifold. Unfortunately the engine end flange cracked when I removed it from the original pipe but I was able to soft solder it back together.
I finished off the pivot pins and adjusting screw and put it all together. As expected the pump had problems reaching a suitable pressure with cooking alcohol so I will need to make a new pump body and possibly a new plunger.
Title: Re: Fuel injection systems
Post by: Roger B on June 18, 2016, 06:36:29 PM
I took a video clip of the adjuster in operation but the aspect ratio seems to be confused  :headscratch: The engine was being driven with a 6V battery via the generator. I have started on a new pump body and plunger, I'm following the same way as before but hopefully without mistakes  ::)

https://www.youtube.com/watch?v=4kLwTbrFDtA
Title: Re: Fuel injection systems
Post by: Roger B on October 02, 2016, 04:24:27 PM
I started making a new body but was still puzzled as to why I got the pump to work by hand for the first test. Careful measurement showed that the last 2mm of the plunger tapered by around 5 microns, this being the section used when being driven by the engine. When I did the hand trials I was using more of the plunger length.

I decided to try and cut the tapered 2 mm off the plunger using a cutting disc in the Proxxon as the plunger was otherwise a 'trial piece'. The mounting screw holes were then slotted to compensate.

This actually produced a sort of spray that could be adjusted and seemed to have a range of 100-150mm  :)  :)  :)

https://www.youtube.com/watch?v=1LbJLUJa0-k
Title: Re: Fuel injection systems
Post by: Brendon M on October 09, 2016, 02:30:22 AM
5 microns is not much! If I understood your posts correctly, this was enough to prevent sufficient pumping?
Title: Re: Fuel injection systems
Post by: Roger B on October 09, 2016, 07:18:51 AM
5 microns clearance is definitely too much. With careful lapping I am trying to get to 1 micron or less clearance.
Title: Re: Fuel injection systems
Post by: fumopuc on October 09, 2016, 12:33:35 PM
5 microns clearance is definitely too much. With careful lapping I am trying to get to 1 micron or less clearance.


Hi Roger, very optimistic challenge, I wish you good luck.
Title: Re: Fuel injection systems
Post by: Brendon M on October 09, 2016, 03:16:49 PM
5 microns clearance is definitely too much. With careful lapping I am trying to get to 1 micron or less clearance.

Oh, my apologies, I have conveyed the wrong meaning.

I was expressing my surprise at how 5 microns (roughly 0.2 thou) was able to stop the pump from functioning properly.

Given the tolerences involved, I wonder how much life you will get out of a pump before wear on the punger causes a malfunction? Or do you not anticipate this to be a problem?

Title: Re: Fuel injection systems
Post by: Roger B on October 10, 2016, 05:58:32 PM
Thank you Achim  :wine1:

brendonm, no problem  :) When I started thinking about this project I thought that a piece of ground silver steel (drill rod) in a reamed hole would be sufficient. As I move on it became clear that this was nowhere near good enough so I am no trying to reduce the clearances as much as I can with the equipment that I have.

The plunger is hardened and the pump body is mild steel. I have no idea how long they will last, but if I can get it to run even for a few minutes I will be happy  ::)
Title: Re: Fuel injection systems
Post by: Laurentic on October 13, 2016, 05:10:48 PM
Roger, Have only just become aware of both this thread and your other one on making a horizontal 2 stroke diesel engine.  I have now read threads both from start to finish and am full of admiration for what you are doing and the skill you are doing it with.  I will be following both with upmost interest and wish you well - I sincerely hope you are successful in your quest and am sure you will be, seeing what has gone before.

Whenever I have wondered in idle moments about the making of a model diesel the big block has always been "but to be a diesel it needs a HP fuel pump and injector, not things that the vast majority of home workshops can produce".  Having worked with diesels of all sizes extensively in an earlier life I am only too well aware to which the very fine tolerances diesel pumps and injectors are made, which is why I thought it beyond the scope of most workshops.  You seem to be showing a way of achieving that standard of engineering required.

Also of interest is the use of the injectors for low pressure use in petrol or glow plug engines, in particular in 2 stroke engines where instead of the fuel/oil/air mixture being pumped into the cylinder via the crankcase and the action of the piston, the air, devoid of fuel or fuel/oil glow plug mixture, is pumped into the cylinder via a blower and the fuel injected after the exhaust port has closed.  This would have the benefit of ensuring complete scavenging without blowing excess unburnt fuel into the exhaust.  Whether the oil in the fuel/oil mix would cause a problem in blocking the injector nozzle holes I don't know; in theory not, as it readily vaporises going through a carby, but the injector nozzle holes present a much finer hole.  Just a thought.

Keep up the good work,

Regards, Chris
Title: Re: Fuel injection systems
Post by: Roger B on October 20, 2016, 06:33:44 PM
Thank you for your interest Chris  :) I know others have made small, true, diesels successfully and I hope that I can follow in their footsteps  ::) I think that I am moving in the right direction, but lapping to these tolerances is definitely something to practice  :headscratch:
Title: Re: Fuel injection systems
Post by: Roger B on October 20, 2016, 06:49:14 PM
A sort of success  :)  :wine1: It was a sunny evening here so I thought I would try the petrol (gasoline) injection on my horizontal engine.

I warmed it up with the carburettor and then fitted the injection manifold with a carb as a throttle. The tank was filled with petrol, there may have still been some alcohol in the pipes from the last trial. Then came the fun, I had a throttle lever, a stroke adjustment handwheel for the pump and a starter button to press (and a drip oiler for the cylinder to remember) all with two hands. After various adjustments it started  :whoohoo:  Control was somewhat difficult as due to the leakage from the system the fuel quantity increased significantly with speed so as I opened the throttle I had to reduce the pump stroke. If the revs dropped for any reason it would just stop and I had to increase the stroke to maximum again to get it to start. There was a significant quantity of fuel dripping out of the injector pressure adjustment screw.

So it worked, my calculations regarding the size of pump required were not too far out, I just have to tighten up the tolerances even more  ::) (actually it might be better with diesel as it is more viscous and may leak less).

Apologies for the video quality, it was starting to get dark and I was quite excited  :cartwheel:

https://www.youtube.com/watch?v=dKPaKwHfrPs

https://www.youtube.com/watch?v=dKPaKwHfrPs
Title: Re: Fuel injection systems
Post by: Jo on October 20, 2016, 06:58:26 PM
 8) Nice one

Jo
Title: Re: Fuel injection systems
Post by: Admiral_dk on October 20, 2016, 10:22:22 PM
Congratulations on reaching this point  :praise2: and look forward to see improvements  :)
Title: Re: Fuel injection systems
Post by: Brendon M on October 21, 2016, 08:53:34 AM
Yes indeed, congratulations. :)

I wonder if you can do away with the throttle altogether and control engine speed through the amount of fuel injected alone?

*edit: apparently not (http://www.eng-tips.com/viewthread.cfm?qid=75499). The reason why it works for Diesel is that it works with a wide range of air/fuel mixture ratios.

Essentially the throttle is there to help control the air/fuel ratio in injected engines.
Title: Re: Fuel injection systems
Post by: steamer on October 21, 2016, 11:31:12 AM
That's Awesome!!!!


Dave
Title: Re: Fuel injection systems
Post by: Roger B on October 25, 2016, 07:27:51 PM
Thank you all for your kind comments and support  :ThumbsUp:  :wine1:

This project is really on the limit of my abilities and equipment, but maybe I will get there  :headscratch:
Title: Re: Fuel injection systems
Post by: Roger B on December 10, 2016, 10:26:27 AM
I dismantled the injector to see what I could do to tighten up the tolerances and found that I had left the strong spring in  :facepalm: This gives a needle loading of around 10N which is a calculated opening pressure of 50bar, rather more than is needed for manifold injection. If we get some good weather I will try again with the correct spring.

I have also been looking at the pump again. I originally thought that using a metering helix like the full size pumps would be too difficult, but I came across a design that just used a simple helical groove. A quick sketch suggests that a groove around 0.6mm wide and a pitch of 4mm could work. My lathe only goes to a 3mm pitch but by playing with the gears I can reach 4mm, which should be ok as it will only be hand turned. If I can mount the Proxxon tool with a cutting disc at the required angle and on centre I will have a go at cutting a helix on a scrap plunger.
Title: Re: Fuel injection systems
Post by: BillTodd on December 10, 2016, 05:33:47 PM
Excellent :)  and really impressive !

Bill
Title: Re: Fuel injection systems
Post by: Roger B on December 10, 2016, 07:49:16 PM
Thank you Bill :ThumbsUp:

I put the correct spring in the injector and had another more successful trial  :cartwheel: There was more throttle response than I expected and it generally ran quite steadily. One puzzling point was the appearance of bubbles in the fuel pipe to the injection pump  ::) As far as I can see the only possible air leak could be down the plunger and if air leaked in there should have been a significant fuel leak out  :headscratch:

https://www.youtube.com/watch?v=7eHHEhll59U

https://www.youtube.com/watch?v=7eHHEhll59U
Title: Re: Fuel injection systems
Post by: Brendon M on December 11, 2016, 03:02:34 AM
Wow, that's working really well! Fantastic. :)

By the way, I had a look at your helix plunger diagram, and I look forward to seeing it be made. Mind you, I will have to wait until you build it to understand what I was looking at (d'oh)

Keep up the good work. I've been trying to build a simple part that requires a smidgen of accuracy (I'm on my fourth attempt :facepalm:), and I now have an appreciation for how much precision is required in a fuel injection pump!
Title: Re: Fuel injection systems
Post by: fumopuc on December 11, 2016, 07:29:21 AM
I am following with interest.
Title: Re: Fuel injection systems
Post by: BillTodd on December 11, 2016, 02:43:13 PM
Quote
bubbles in the fuel pipe to the injection pump  ::) As far as I can see the only possible air leak
May not be air , could be fuel vapour if the pressure is low.

Bill
Title: Re: Fuel injection systems
Post by: Roger B on December 11, 2016, 02:52:59 PM
Thank you  :ThumbsUp:

Brendom, the diagram was the helix unrolled and scaled up 10 times. It was unrolled along the long edge and as it was 2mm diameter it is 2 x pi x 10 = 62.83. The other direction was the pitch, 4mm so times 10  = 40 mm. This diagram then gave me the helix angle, 32° and allowed me to see how it would work with the 1mm port in the pump. The pump stroke will be 3mm so the first mm closes the port and the next two mm will do the pumping. As soon as the port reaches the helix the pressure will drop and the pumping will stop.

The next thing was to try and grind a trial helix  ::) I added a few holes to the Hobbymat milling support angle plate so I could mount the compound slide along the axis of the lathe and at the helix angle. The 4mm pitch required the change gears to step up 1-4. I found a suitable set up with the available gears, 70-35 and 60-30, but the arm hit the spindle before I could get a good mesh. As the foul point was just rough cast a quick bit of filing made enough clearance.
The actual feeding will be done with the leadscrew handle so I left the drive belt off and the lathe unplugged. I also made a quick 'sanity check' that four turns of the leadscrew handle gave one turn of the chuck.
Title: Re: Fuel injection systems
Post by: Roger B on December 11, 2016, 02:59:44 PM
I made an initial attempt on a piece of unhardened 2mm silver steel. I let the wheel cut in both directions but that may have been a mistake due to the general play and lack of rigidity of my set up. The second attempt on a hardened scrap plunger was made with a different grinding wheel held in a collet rather than the drill chuck. This time I only cut on the in stroke. The cut was taken to 0.5mm deep in 0.05mm steps. I think that it was harder to get a good picture of the helix than it was to make it  :headscratch:
Title: Re: Fuel injection systems
Post by: Roger B on December 11, 2016, 03:02:43 PM
Thank you Bill, I was coming to that conclusion as well. The only mechanical petrol injection systems I know of (Lucas and SPICA) fed the petrol into the metering pump under pressure rather than a very small head. At least vaporisation shouldn't be a problem with diesel fuel  ::)
Title: Re: Fuel injection systems
Post by: Graham Meek on December 11, 2016, 06:21:39 PM
Hi Roger,

You are to be congratulated on your progress.

I have been looking in from time to time but totally missed the engine running. You have been busy, and I like your helical groove. You are doing some real methodical trail blazing as regards the small "True Diesel" engine. I do hope that one day you will publish your design.

My best regards
Gray,
Title: Re: Fuel injection systems
Post by: Don1966 on December 11, 2016, 06:46:00 PM
That's awesome Roger and congrats I do hope you perfect it. Great following your progress...... :praise2:

Don
Title: Re: Fuel injection systems
Post by: philjoe5 on December 11, 2016, 10:40:27 PM
Fantastic Roger.  A real leading edge effort at fueling these small engines :ThumbsUp:

Cheers,
Phil
Title: Re: Fuel injection systems
Post by: BillTodd on December 12, 2016, 12:01:28 AM
Just came across this :

https://oldmachinepress.com/2013/01/02/inside-the-cylinder-of-a-diesel-engine-by-harry-ricardo/

worth a read :-)

Bill
Title: Re: Fuel injection systems
Post by: Roger B on December 12, 2016, 01:50:21 PM
Thank you all  :ThumbsUp:

I looked up the vapour pressure of petrol and it is around 0.5 Bar at normal temperatures. When the plunger on the 'jerk' type pump returns it will create a vacuum which will certainly vapourise the fuel. If the feed pressure is not higher than the vapour pressure the vapour will remain and this is probably what I have been seeing in the feed pipe. Petrol vapour is around three times the density of air. The initial air bubbles I get when I prime the system tend to flow back up into the tank. The bubbles when running tend to float just above the intake pipe.
The SPICA (Alfa Romeo) and Bosch (Mercedes Benz) mechanical petrol injection systems both fed the metering pump at around 1 Bar which should be enough to overcome the vapour pressure.

Based on this I think that my current metering is probably fairly random and I will need a pressure fed system to get consistent results. The vapour pressure of diesel fuel is much lower so vaporisation won't be a problem but I don't think that I am ready for that step yet.

Next challenge: Design and build a ~1 Bar constant pressure petrol feed pump that can be fitted on my horizontal engine (which already has two unplanned pumps  ::) ). Another option may be a separate electric feed pump, but the more pressurised petrol I have around the more nervous I become  :zap:
Title: Re: Fuel injection systems
Post by: Admiral_dk on December 12, 2016, 02:20:15 PM
Congratulations Roger - nice step forward  :praise2:

All diesel engines I know of has a feed pump before the metering pump - often together with the filtering system .....

Best wishes

Per
Title: Re: Fuel injection systems
Post by: Graham Meek on December 13, 2016, 11:00:44 AM
Hi Roger,

You could pressurise the delivery by raising the height of the fuel tank above the pump. You might find in doing this that by increasing the tank volume you can also influence the amount of pressure. I am not saying this will give you what you need, but you can do this with relatively little work and it might prove your theory.

My best regards
Gray,
Title: Re: Fuel injection systems
Post by: Roger B on December 13, 2016, 07:29:14 PM
Hi Gray,

I think I will need a few meters of head to overcome the vapour pressure. I am looking at a couple of electric pump options, one from Conrad:

http://www.conrad.ch/ce/de/product/224413/Kavan-Kraftstoff-Zahnradpumpe-Foerdermenge-18-lmin?ref=list

This is capable of 3.8 Bar however it is not continuously rated at full output. It may be ok on reduced voltage but would need a pressure regulating/release valve. It is suitable for petrol and diesel fuel.

The other slightly larger option is an automotive pump:

http://www.fuelpumpsonline.co.uk/facet-solid-state-fuel-pump-40107-70-10psi-9-p.asp

I used to use Facet (or Bendix as I think they were then) fuel pumps on my competition cars and they are certainly robust and reliable. There are other versions available up to 15psi/1 Bar.

I am tempted by the Facet pump as I am certain it will do what I want. I will just have to make some NPT adaptors.

Title: Re: Fuel injection systems
Post by: Roger B on January 20, 2017, 08:48:43 PM
I have purchased a Facet pump with a 10psi rating along with a couple of 1/8" NPT fittings that I will be able to adapt. As the R&D Dept is closed again due to snow the next tests may be a month or two away.
Title: Re: Fuel injection systems
Post by: Roger B on January 25, 2017, 07:48:30 PM
The 1/4 NPT fittings that came with the fuel pump had 5.5mm bores and the connections I wanted to use had M5 or M5 x 0.5 threads so I had to make a couple of adaptors from some 8mm brass hex. The fittings were tapped M6 x 0.5 to allow for future developments.
I have fitted the pump to the engine base and connected it up. The copper pipe was bent using my old Girling former (Autojumble? Don't remember  ::) ) and I had purchased some small bore automotive fuel hose that is supposed to be OK with Petrol, Diesel and Alcohol to connect to the tank. The pump will be switched together with the coil.
Title: Re: Fuel injection systems
Post by: fumopuc on January 26, 2017, 06:57:41 PM
Waiting for the next pops.
Title: Re: Fuel injection systems
Post by: Roger B on January 28, 2017, 06:33:48 PM
The weather was kind today so I was able to try the new fuel pump. It was quite difficult to get all the air out as it is designed to feed into an open float chamber rather than a closed system. In the end I used a temporary pipe to circulate the fuel back to the tank for a couple of minutes.
The response was quite different, I was able to reduced the pump working stroke from maximum (around 1.5mm) to ~0.5mm. It would also run quite steadily without needing frequent adjustments or restarts.
The throttle response is also quite interesting, off load it will run over quite a wide speed range without needing to adjust the pump stroke. I haven't tried this system under load and may wait until I have the helix spill system working as it will be quicker to adjust/respond.

https://www.youtube.com/watch?v=uXUiAfTQvHQ

https://www.youtube.com/watch?v=uXUiAfTQvHQ

https://www.youtube.com/watch?v=bI5pCyaTkbY

https://www.youtube.com/watch?v=bI5pCyaTkbY

Title: Re: Fuel injection systems
Post by: Admiral_dk on January 28, 2017, 07:47:11 PM
Wonderful Roger - it sounds very good with a very even running / firing  :ThumbsUp:
Title: Re: Fuel injection systems
Post by: Roger B on February 07, 2017, 09:07:13 PM
The next step was to work out a control rack system for the metering helix. I had some 0.5 Mod 20 tooth pinions for the diesel engine lubrication pump with a 5mm bore. The projection on the fuel pump body is also 5mm but unfortunately the one I have already was only rough turned to support a spring not finish turned as a bearing surface. It will work for the first trials.

I could purchase some 0.5 Mod rack, 4mm x 4mm from Conrad. I cut off 30mm and milled it down to 3mm thick. The boss of the pinion was turned down to 7mm for a return spring. I decided to leave the existing system intact and start again on a new 5mm thick aluminium back plate. This now has fixing holes to attach to my horizontal engine, fixings for the pump body and a couple of slots for the rack. This all fits together and has 13mm rack travel which is around 150° rotation.

I need to devise a coupling between the pinion and the pump plunger and make a fixed guide rod for the excentric in place of the existing variable stroke one.
Title: Re: Fuel injection systems
Post by: Roger B on February 16, 2017, 06:54:27 PM
Having recently purchased a 4 jaw self centring chuck I thought I would see how it helped with the new excentric guide, new injection pump body and new injector body.

The excentric guide and injection pump both have the bore offset 1mm in both directions. This was easily resolved with two 2mm thick aluminium shims. Set up time effectively zero. The stub on the injection pump was finish turned to a good running fit for the rack pinion. I also turned a 0.8 mm deep 7mm dia. recess on the end of the body to locate the return spring. The 5mm dia. stub will then be held in a collet to machine the bore and the delivery valve recess and seat.

The injector body was even easier as it is concentric. The bore for the nozzle was drilled 5.9mm and then reamed 6mm. The end was flattened to the correct depth with a 6mm end mill. The top of the body was then opened out to 7mm and tapped M8 x 1
Title: Re: Fuel injection systems
Post by: Roger B on March 26, 2017, 07:36:05 PM
I'm still struggling with this one. I tried reaming out the next pump body with the tailstock clamped as tight as possible this resulted in the bore being even more oversize. The 1.97 plug gauge would pass through a nominal 1.95 reamed hole. I think that I will have to get a floating reamer holder  ::) £ £ £
I decided to continue with the body anyway. I turned a bronze bush to fit the tappet guide and then set the tappet guide and the pump body in the Proxxon to drill and tap the fixing holes. The centre drill tip broke off in the pump body  :facepalm:  I couldn't get the broken bit out, so another trial piece  :( At least it's only 25mm of 10x10mm black bar.
I then turned up the start of another injector nozzle and spring plug. I will wait for the floating reamer holder before I finish the injector (and the pump)
Title: Re: Fuel injection systems
Post by: Tennessee Whiskey on March 26, 2017, 07:38:31 PM
Roger, make sure you aren't bottoming out the reamer, this will cause an oversized hole.

Eric
Title: Re: Fuel injection systems
Post by: Roger B on March 26, 2017, 07:52:37 PM
Thank you Eric  :ThumbsUp: It's a through hole, but I am trying to work to micron tolerances and it appears that the reamer has to be aligned to better than the desired tolerance to get the best results  ::) I'm still in the learning phase on this, but think I am going to have to spend some money  :headscratch:
Title: Re: Fuel injection systems
Post by: freefuel on May 06, 2017, 11:56:29 PM
Hi Roger,

for small holes have you taken a look at EDM wire cutters? the process might prove you with the ability to cut holes smaller then your tools permit.

https://en.wikipedia.org/wiki/Electrical_discharge_machining
Title: Re: Fuel injection systems
Post by: Roger B on May 15, 2017, 09:17:27 AM
Thank you for that. The link suggests that EDM drilling will work down to around 0.3mm which I can currently drill. I am not sure if there is a need to go any smaller. Full size nozzles tend to be around 0.2 mm but I think that attempting to scale them down would just result in frequent blockages.
I chose to use an open needle valve (Pintle type) as the annulus gives quite a fine opening. Graham Meek is also working in the same direction.
I am not completely sure of the Physics/Fluid Dynamic but for a small engine the fuel pressure and penetration must be less than for a full size one otherwise the fuel will just be sprayed onto the combustion chamber walls or the piston.
Title: Re: Fuel injection systems
Post by: freefuel on May 15, 2017, 03:05:45 PM
the trend in modern diesel fuel injector design is for even finer fuel droplet size to maximize combustion efficiency, this is a problem compounded by our desire to use much smaller displacements and thus combustion chambers. it's a physics problem we are working against, in that we are not scaling the molecules of fuel and air we are working with down with our machines.

from what I can recall about full size diesel engines is that the injection pressures have increased as the nozzle orifice sizes have decreased to produce smaller fuel droplets. another major innovation has been the introduction of the multi event injection procedure, where a series of small injections precede the main delivery of fuel. doing do permits better control of the combustion chamber temps and noise reduction.

some more fun reading material, http://www.mmsonline.com/articles/non-traditional-methods-for-making-small-holes and https://en.wikipedia.org/wiki/Electron_beam_machining
Title: Re: Fuel injection systems
Post by: Roger B on July 04, 2017, 06:48:43 PM
Having learnt how to ream holes accurately (see the floating reamer holders thread) and had the engine running as a petrol engine it was time to move back to the injection system.

I started yet another pump body, this time with the correct size drilled hole and controlling the reamer at the correct feed rate with a floating holder I got a good bore without bellmouthing.

I then used the same experiences on the injector nozzle. Drilling 1.4mm was too much, the 1.45mm reamer passed straight through. Using a 1.3mm drill produced an acceptable result. I don't have a 1.46mm pin gauge, but the 1.47 didn't enter.

I then cut the seating with my previously made D bit, taking more care over the hole depths than on the last attempt.
Title: Re: Fuel injection systems
Post by: Roger B on July 04, 2017, 06:53:28 PM
The nozzle was then drilled 0.35mm with the same drill as before. I then moved onto the flange for the injector body as this one will have to be clamped to the cylinder head rather than just resting in the inlet manifold. This was done the traditional way with hacksaw, files and filing buttons rather than setting up the mill.
Title: Re: Fuel injection systems
Post by: Brendon M on July 19, 2017, 11:42:41 AM
I am amazed that a 0.35mm drill bit actually drills and not simply disintegrate. How do you do it?
Title: Re: Fuel injection systems
Post by: Roger B on July 20, 2017, 05:45:15 PM
No real problems. I am drilling less than a millimetre through brass. These are some good quality drills, some of the cheaper ones I looked at did not have real points and would not cut. I would have liked to have used a higher speed but my lathe will only reach 2000rpm.
Title: Re: Fuel injection systems
Post by: Roger B on July 23, 2017, 11:20:32 AM
The next step was to make the pump plunger and injector needle from 2mm and 1.5mm silver steel respectively. They were cut to length end the end of the pump plunger was threaded M2 before hardening. The pump plunger was lapped to 1.98mm diameter and the bearing surface of the needle was lapped to 1.48mm. The 50° point was ground on the end of the needle as before.
When I tried to grind the shank of the needle down to 1mm diameter the finish was bad and the end snapped off  :( I tried again with the same result  :headscratch:
I looked back to see how I successfully made the first one and what was different.
The solution was as follows:
Harden ~20mm of the 1.5mm silver steel, don't cut to length yet.
Grind and polish the point.
Grind the shank to 1mm diameter with the lathe at 250rpm in reverse and the grinding wheel at ~5000rpm.
Reduce the depth of cut from 0.05mm to 0.025mm.
Feed in at the chuck end and cut towards the point.
Polish the shank.
Lap the bearing surface to 1.48mm and cut to length.
Title: Re: Fuel injection systems
Post by: Roger B on July 23, 2017, 12:33:00 PM
Next I needed to change to milling mode to cut a screwdriver slot in the end of the nozzle so I could insert and remove it.
Whilst in this setup I cut a slot in the end of the operating plunger for a small ball race to run on the cam and cut the slot in the control gear for the piece that will turn the plunger and set the helix position.
I then went back to lathe mode and lapped the bores of the nozzle and pump body.
Next step put it all in the ultrasonic bath to remove the diamond paste residue.
Title: Re: Fuel injection systems
Post by: Roger B on August 06, 2017, 04:37:59 PM
Having removed the contact breaker from the diesel engine I wanted to try the roller follower for the injection pump. The follower housing was held onto the crankcase with a small milling clamp and a steel ruler was used as a return spring. Unfortunately, but not unexpectedly (which is why I did the trial) it tended to run at an angle  ::)

I could either slot the plunger and add some sort of guide pin or key or change the design to a swinging link type follower  :headscratch:

https://www.youtube.com/watch?v=vjbnAhMha0Q

https://www.youtube.com/watch?v=vjbnAhMha0Q
Title: Re: Fuel injection systems
Post by: Brendon M on August 17, 2017, 09:00:57 AM
I am up to date again Roger, keep at it :)

I found the procedure for forming the injector needle quite interesting.
Title: Re: Fuel injection systems
Post by: Roger B on September 03, 2017, 04:46:02 PM
Thank you Brendon  :)

I made the union and nipple for the injector in the same way as before. This time I drilled the cone in the nozzle a little deeper and filed a flat on the nozzle to allow a couple more threads to engage.

I then ground the helix in the plunger and trimmed it to length, again as previously. The next bit was the tappet to go on the end of the plunger and transmit the rotation from the rack gear. This was sawn and filled from a piece of 4mm square silver steel so I can harden it. Having just purchased a set of edge finders I tried one out to centre the hole in the tappet.
Title: Re: Fuel injection systems
Post by: Roger B on September 03, 2017, 05:52:57 PM
Problem  :( When I assembled the system it would not turn freely and jammed completely in a couple of places  :headscratch: After a series of checks I found that the bore was not concentric with the running surface for the rack gear by ~0.2mm. This was a result of drilling from the other end to give the delivery valve seat a better chance  ::)

OK, start yet another injector pump body with a different machining sequence. This time I turned the spigot for the rack gear and then drilled and reamed the bore. As a further, hopeful, refinement I started with the drill as far into the chuck as it would go and then moved it out in stages as the hole got deeper. The process was the optimum one from my experiment with the floating reamer holder.
Run at 2000rpm
Center drill deep enough to leave a countersink.
Drill 1.85mm
Ream 1.95mm with a controlled feed of 0.08mm per rev.
This seemed to work, the 1.96mm pin gauge passed straight through, the 1.97 mm barely entered. It was also concentric to better than 0.02mm and when reversed and mounted in a collet the run out of the bore was not detectable   :)
Title: Re: Fuel injection systems
Post by: Admiral_dk on September 03, 2017, 09:13:20 PM
Quite an improvement in precision  :ThumbsUp:

Hope that you will have much more "luck" with the next test  :)
Title: Re: Fuel injection systems
Post by: Roger B on September 30, 2017, 05:23:28 PM
Thank you Per  :ThumbsUp:
I lapped the bore as previously and this time it all fitted together and turned without jamming  :) All the bits that had been in contact with diamond lapping paste went in the ultrasonic bath for cleaning and I machined the unions and delivery valve.
I tried to repeat the oil pressure tests that I had done with the previous pump. The much shorter leakage paths were obvious and as it leaked it reached the spill point and collapsed. Maybe it will work, maybe it's a step too far  :headscratch:
I had to slot some of the holes in the mounting plate to get the correct positions of the pump plunger but otherwise it all seemed to fit together  :)
Title: Re: Fuel injection systems
Post by: Roger B on September 30, 2017, 05:32:55 PM
I tried the horizontal engine with the original fuel pump and injector as a check before I experimented with the new system. It didn't run as well as before  :(  :headscratch: but I was able to test the new injector which worked much  the same as the original.
When I went to install the new pump I noticed that the soldered joint holding the fuel inlet nipple had cracked  ::) The solder hadn't penetrated at all  :( I cleaned the parts and resoldered them, maybe this caused small air leak that upset the first trial. I then installed the helix pump and tried to get it to run, without success  :(
Many problems: The delivery valve leaked so the fuel feed pump would blow past it. A quick clean solved that, but I was not getting any pressure feed from the pump at all. If I took the spring out of the injector it would dribble but no jet/cloud  ::)
I need to recheck that I have phased the rack to the plunger correctly but otherwise back to the drawing board  :headscratch:
Title: Re: Fuel injection systems
Post by: Roger B on October 11, 2017, 05:33:00 PM
A bit of a post mortem on the problems  ::)

I had drilled the delivery valve too deep so that there was not enough pressure on the ball  :facepalm: The bore was also too big due to a drawing error. It should have been 3.1mm for a 3 mm ball. I had put 3.2mm on the drawing and the drill I used resulted in a 3.3mm hole. Solution: make a new valve body  :ThumbsUp:

The tip of the plunger was again too small yet it was a tight fit  :headscratch: Problem: the length of Silver Steel I was using was not straight and round. Solution: Try using the pin gauge.

I annealed the end of the gauge, holding it in an old pair of pliers to act as a heat sink, and was then able to thread it. I tried it in the existing pump body using a light machine oil and with a 4.5kg weight it sunk in around 10 seconds. This is a pressure of around 140 Bar / 2000psi. As the gauges cost CHF 10 and will make two plungers I will continue down this route.
Title: Re: Fuel injection systems
Post by: Roger B on November 19, 2017, 09:25:23 AM
The original gear train used to cut the helix didn't quite mesh properly so I tried a different set up this time. This was tight against the drive motor but was free from backlash.

I then needed to reduce the length of the pump to make it an easier fit on the diesel engine. I was able to shorten the tappet guide by 2mm and annealed the gear connector block for the pump plunger and milled 1mm off.

Title: Re: Fuel injection systems
Post by: Roger B on November 19, 2017, 02:20:22 PM
I had looked at the possibilities of using a swinging link rather than a tappet when the pump was installed on the diesel engine but decided that a slot and guide pin would be better/easier. I annealed the tappet an then using a rather dodgy set up I cut a groove with a 1.2mm slitting saw. Due to the various runnouts (the arbour was barely in the ER collet) the final groove ended up at 1.4mm.  I drilled and tapped an M2 hole in the guide, taking the centre from a length of 5mm SS. The end of an M2 x 5 grubscrew was turned down to fit the groove and Loctited into place. Finally I trimmed 2mm from the tapped and then re-hardened it and the gear connector.
As my horizontal engine had not run so well during the last trial I removed the piston and conrod to check the rings (I had had previous trouble with them sticking in the grooves). The piston is fairly rough due to previous seizures, but both rings were free although they did not look fully bedded in. I think it just needs some more running time.
Title: Re: Fuel injection systems
Post by: Roger B on November 26, 2017, 01:27:24 PM
I had enough of a break in the weather to try the new helix system. It was 3 or 4°C out there which may not have helped the running. The trials were more successful than last time (even though the plug cap popped off  :facepalm: ). It would run fairly consistently for a time but would occasionally suddenly stop. The response to the rack position seemed variable, sometimes there was an obvious richening/leaning and at other times the position made very little difference  :headscratch:

I experimented with the pressure on the needle valve. Running seemed to improve as I increased the pressure (until I reached the point where the needle was jammed shut). Looking at the spring details and the compressed length I was getting a maximum opening pressure of around 14 Bar.

When I was doing some bench trials with the pump reaching the spill point on the helix resulted in a shot of oil being fired out of the inlet port. May be this is causing a disturbance in the inlet tract? There is a small space under the union which may also cause some of the priming problems. I don't think I can easily reduce it to zero volume so making it bigger may help ::) At least there is very little time in making a new union if it doesn't work.

Apologies for the dark and grainy videos. I have tried both embedding and just putting the URLs as the embedded version is not always visible.

https://www.youtube.com/watch?v=hnD6E87YyTw

https://www.youtube.com/watch?v=hnD6E87YyTw

https://www.youtube.com/watch?v=YtH6HoTQbeQ

https://www.youtube.com/watch?v=YtH6HoTQbeQ
Title: Re: Fuel injection systems
Post by: Roger B on December 10, 2017, 05:40:39 PM
Well I have found some of the reasons for the running problems  ::) The exhaust valve was leaking and the water pump shaft that is used to drive the injection pump has some wear. The details are here:

http://www.modelenginemaker.com/index.php?topic=7701.new#new
Title: Re: Fuel injection systems
Post by: Roger B on January 07, 2018, 08:10:35 AM
There was a short break in the weather so I tried the helix pump on the diesel engine with diesel fuel. No success  :( The delivery valve would not seat properly and the system would not prime. My fingers were rapidly too cold to fiddle with these small pieces so clean it all off and back to the workshop.

I set it up on the bench with the fuel tank fixed to the front of the mill. After experiments with cleaning alcohol I found that the problem with the delivery valve seemed to be that the body was not quite concentric with the seating. I opened the hole out to 3.2mm and it sealed. This is probably due to modifying a commercial union rather than turning it all from brass hexagon in one operation.

I also wonder if the helix pump might be a step too far and am looking at fitting the earlier (and successful) variable stroke pump. For this I needed to modify the first plunger to take the small ball race cam follower and fit a guide pin to stop it twisting. I annealed the plunger, opened the fork out to 2.5mm and milled a 1mm deep 1.4mm wide slot for the guide pin.
Title: Re: Fuel injection systems
Post by: Roger B on January 07, 2018, 11:04:56 AM
I put the system back together and got it primed. The atomisation looks reasonable, but operation was not consistent. I think that there is still a problem with turbulence in the inlet port when the spill helix opens. I removed the fuel inlet flexible pipe and small droplets were shooting out. I'm not sure if they are visible in the video  ::)
According to the calculated injector spring load, 14N, the injector needle was opening at around 60 Bar.

https://www.youtube.com/watch?v=OTfKmEFqr94

https://www.youtube.com/watch?v=A5-OEu7dfp0
Title: Re: Fuel injection systems
Post by: Admiral_dk on January 07, 2018, 09:27:56 PM
The spray Looks fine - so far so good  :ThumbsUp:

Best wishes with the rest  :)

Per
Title: Re: Fuel injection systems
Post by: fumopuc on January 08, 2018, 07:06:55 PM
"Spannend"
Great project with a lot of interesting challenges.
Title: Re: Fuel injection systems
Post by: Laurentic on January 25, 2018, 11:00:21 PM
Can't believe you are still trucking on Roger, gees but you have some stamina and application.  More than 1 1/2 years on and you are still at it like a dog with a bone, well done that man, you have my admiration and respect, many a lessor man would have given up, but I am so pleased you are staying the course as you seem, little by little, to be winning.  Like how many body's have you made, I've lost count.  Really willing you on here, wanting and hoping you will finally succeed.  Where do you buy all your small - tiny even - drills, reamers and laps from?  Haven't been able to source them in the UK myself so far.

Cheers, Chris
Title: Re: Fuel injection systems
Post by: Roger B on January 26, 2018, 08:43:08 AM
Thank you all for your continuing interest in this somewhat long term project. I knew at the start it wasn't going to be easy  ::)

Chris, there have only been 5 or 6 pump bodies so far, but I made around 10 simpler versions when I was learning how to ream.

The 0.35mm drills came from a workshop clear out at work but are also available from Brütsch-Rüegger where I get the other drills:

https://www.brw.ch/3/BRW-ToolShop/1/Category/417/Product/Details/P_20532/Twist-drill-TITEX?pSearchId=18968cfa-1ccc-42c5-8874-feaaffc72f38&pOnlyPromotion=False

The 0.01 step reamers are from the same source:

https://www.brw.ch/3/BRW-ToolShop/1/Category/523/Product/Details/P_189574/Machine-reamer-MAGAFOR?pSearchId=375fe529-1341-4eb3-a3b8-cdaec2ffe2f5&pOnlyPromotion=False

As are the pin gauges:

https://www.brw.ch/3/BRW-ToolShop/1/Category/194/Product/Details/P_18228/Pin-gauges-MT?pSearchId=a6f6ce3f-a392-4ebb-86b7-5dd855770f9b&pOnlyPromotion=False

The needle eye laps are from Acro in the USA (I also use their barrel laps for engine cylinders):

http://acrolaps.com/index_007.htm

Title: Re: Fuel injection systems
Post by: Laurentic on February 02, 2018, 02:33:02 PM
 Many thanks for the info Roger, been away for a few days and only just catching up - will take a look at the links you gave right away.

Cheers, Chris
Title: Re: Fuel injection systems
Post by: Roger B on February 28, 2018, 08:09:24 PM
Not much is happening on here at the moment as I need to do some more trials with the horizontal engine but with -10°C and snow they are going to have to wait. I am continuing to modify the variable stroke pump to fit on the diesel. The problem with this is that the start of injection varies with the stroke. Maybe ok maybe not  :headscratch: I have made a new plunger from the other half of the pin gauge with a larger flange to suit the same spring type as the helix pump.
While doing this I did find that the inlet union to the pump was a failed delivery valve body and had been drilled out to ~3.3mm giving a reservoir above the pump inlet. I will modify the helix pump to match.
Title: Re: Fuel injection systems
Post by: Roger B on April 14, 2018, 07:44:30 AM
I modified the backplate of the variable stroke pump so I could access the unions if it is fitted to the diesel. Hopefully the helix pump will work though ::)
The inlet union of the helix pump was opened out to 3.2mm to hopefully give a space for surge/turbulence during spill. I then refitted the injection system to my horizontal engine. Previously the injector was vaguely held in place by the fuel pipe so I decided to make a proper clamp to keep the O ring compressed and remove the variable air leak. Ready for another trial  :)
Title: Re: Fuel injection systems
Post by: Vixen on April 14, 2018, 10:08:49 AM
Hi Roger,

Top marks for your persistence. A direct fuel injected model engine will be a remarkable achievement.

When you have a spare moment, could you please post the latest schematic of your injection system.

I for one, and I am sure there are others, have lost track of where all these individual piece parts and modified parts fit into the system.

Mike.  :ThumbsUp: :ThumbsUp: :ThumbsUp:
Title: Re: Fuel injection systems
Post by: Roger B on April 14, 2018, 04:31:21 PM
Thank you Mike  :ThumbsUp:  :ThumbsUp: Here is a summary of where I am today:

First system:

2mm bore variable stroke pump with 1mm diameter inlet port and ball delivery valve. Stroke adjustment 0-3 mm. The bore is drilled reamed and lapped. The plunger is made from a commercial pin gauge. I started out using hardened and lapped silver steel but had problems with a non-circular piece and at 11 chf each which will give 2 plungers they seem the best option.

The pump is driven by an eccentric to give a long injection period while the inlet valve is open.

Plain bodied injector with 1.5mm diameter needle ground down to 1mm. 0.35mm diameter nozzle. The nozzle seating is 60° and the needle 50° to give a line seal at the entrance to the nozzle bore. Adjustable spring tension, opening pressure around 15 bar. The needle is made from hardened and lapped silver steel.

This operated successfully as manifold petrol injection but required a feed pump to avoid vaporisation of the petrol.

Second system:

This pump has a helix ground in the plunger following full size practice. The plunger is rotated by a rack and gear. The gear is wide enough to allow for the 3mm stroke of the pump.

This pump can be driven by the eccentric for manifold injection or by a fast-acting cam for diesel injection.

The injector is the same as above except for a mounting flange to fit to the diesel cylinder head. A stronger spring can be fitted to give a higher release pressure (estimate 60 bar)

This has also run successfully as manifold petrol injection.

Reaming:

Reaming the bores has required significant development of my technique to avoid bell mouthing. I am following the manufacturers recommended speed and feeds for the reamers which are higher and lower respectively than I had been using. The drill size is important as is a slight lead on the hole. I found that a floating reamer holder gave less bell mouthing but was expensive.
Title: Re: Fuel injection systems
Post by: Roger B on April 14, 2018, 04:41:24 PM
I made some trials with the helix pump today. As ever priming is a problem and I have a small leak from the inlet union to the fuel pump due to partially stripped threads  ::) I may need to make a new pump body  :(

It ran well and would run between 1500 and 6000rpm at the same setting of the pump  :)

https://www.youtube.com/watch?v=wp67oG5sBqg

I then connected the load bank and was getting nearly 8A into 1ohm so around 64W. Previously I achieved a maximum of 80W using the same carb as I am using for a throttle. This was at the same setting of the pump as before.

https://www.youtube.com/watch?v=o7CmoHiClQs

Finally it settled down to a 1500rpm idle still at the same setting.

https://www.youtube.com/watch?v=tPpmX1Di32A

There were some problems with the feed pump. It seemed to keep pumping/clicking even into a closed pipe which resulted in the fuel overheating and vaporising  ::)

Generally a good day  :wine1:
Title: Re: Fuel injection systems
Post by: Vixen on April 14, 2018, 07:12:10 PM
Roger

Thanks for the update on your design and experiments

MIke
Title: Re: Fuel injection systems
Post by: Roger B on April 15, 2018, 01:55:05 PM
I tried to determine the working stroke of the injection pump. During the trials moving the rack up and down by one tooth each way produced too rich and too lean. Looking down the inlet port the start of injection was fairly easy to see but when the helix was exposed was more of a problem. I took the following measurements which I expect are too large due to chamfers on the edges:
Best running 1.2mm
1 tooth rich 1.5mm
1 tooth lean 0.8mm
With the variable stroke pump I estimated 0.5mm

I then decided to see if I could rescue the damaged thread. I set the body up on the mill and removed the damaged thread with a 5mm end mill. The hole was then tapped M6x0.5 and I made a bush to take it back to M5x0.5. This has been Loctited in and is curing.
Title: Re: Fuel injection systems
Post by: Admiral_dk on April 15, 2018, 05:26:46 PM
Still following along and glad to see some progress for you  :ThumbsUp:

The measurement will be extremely difficult if you insist on doing it geometrically - as you say yourself - how about camfers etc. ....

In my book you will have to ensure a reasonable constant rpm over a certain amount of time and measure the amount of fuel drawn from the tank / how long it will run on a known amount of fuel at a constant rpm.
I would use a calibrated syringe or laboratory "beaker" with a fine graded scale as the fuel tank.

Best wishes

Per
Title: Re: Fuel injection systems
Post by: Roger B on April 16, 2018, 08:42:57 AM
Thank you Per  :ThumbsUp:

The stroke measurements were more to confirm the mechanical design was ok and I was not reaching a limit. Making a proper test rig so I could also see how much the output varied with speed due to leakage would be interesting but is almost a project in itself  ::)

I was surprised how flexible the engine was with a fixed stroke set on the pump. It was better than with the carb (although the carb is not properly calibrated to the engine). I suppose that a metering pump takes speed out of the fuel map equation, the same amount of fuel will be injected per stroke however fast the engine is running. Throttle position and load may then by partially compensated for by the speed related leakage  :headscratch:  :headscratch:
Title: Re: Fuel injection systems
Post by: Roger B on April 21, 2018, 04:03:09 PM
As spring has finally sprung here I thought I would give the diesel a try  ::)

I primed and tested the injection system in the workshop with alcohol and then took it outside and filled the tank with diesel. As I first trial I held  lighter in front of the injector and got some puffs of yellow flame whilst turning the engine by hand.

https://www.youtube.com/watch?v=sGGEwvTHxKs

I then fitted the injector and gave it a try. There were a few puffs of blue smoke and then nothing. I removed the spring adjusting screw from the injector so I could remove and check the needle. Unfortunately I didn't realise how quickly it would fly out under compression pressure. Result one lost needle  :( I  hunted around with a magnet without success so I tried again with the needle from the other injector.

This time I got fairly consistent blue smoke that was controllable with the rack but no real firing  :headscratch:

https://www.youtube.com/watch?v=J7gFEoqR1bg

Obviously the needle was not the best so I need to make a new one. I think that the compression is sufficient but I could make a compression tester although the non return valve would have to be right where the tip of the injector is to get good results. The atomisation also seems ok, but the penetration may be too much and most of the fuel is just hitting the piston crown. Lots to think about but overall not to bad. Blue smoke was more than I was expecting  :wine1:
Title: Re: Fuel injection systems
Post by: Admiral_dk on April 21, 2018, 07:54:37 PM
I really hope that this indicates that you are close to a runner on diesel  :cheers:
Title: Re: Fuel injection systems
Post by: Roger B on April 27, 2018, 11:09:31 AM
I hope so too  :ThumbsUp: I have a few more things to try with this injector like a weaker spring and altering the timing. As the blast of fuel from the injector tended to blow out my lighter I think that it may be too strong.
I will make a compression tester to fit in place of the injector. It's always best to have real numbers to work with.
Title: Re: Fuel injection systems
Post by: Roger B on May 03, 2018, 05:38:55 PM
I decided to try and make a 'mushroom' valve injector. This is easier for petrol injection as it doesn't require a leak off and has also been used successfully in small diesels by Find Hansen.

The valve is turned from 3mm silver steel. I did wonder about upsetting the end of some 2mm silver steel but decided the heat treatment stuff was too much bother. The shaft was turned down to 2mm and the section before the valve was reduced to 1.6mm. The valve cone was turned to 15° inclusive. The top of the shaft was threaded M2 and the valve end was hardened. This was then finish ground and polished.
Title: Re: Fuel injection systems
Post by: Roger B on May 03, 2018, 05:42:44 PM
The nozzle is turned from a piece of brass bar. This follows the dimensions of my existing injectors but could be made smaller. I have some 3mm AF nuts for the valve that will fit inside the 4.5mm clearance for an M5x0.5 thread.
Title: Re: Fuel injection systems
Post by: MJM460 on May 03, 2018, 11:46:11 PM
Incredible work Roger.  Your whole thread has been a masterclass in tiny precision work, along with great instruction on the ins and outs of injectors.  I never miss following along

MJM460
Title: Re: Fuel injection systems
Post by: Roger B on May 06, 2018, 04:55:15 PM
Thank you for your support  :ThumbsUp:  :ThumbsUp: I know that progress is usually slow due to work, life, etc. but I think I have made some progress. I am fairly happy with both the injection pumps and operation as manifold injection for petrol engines. Diesel injection still holds some challenges (discussed in the diesel thread).

The injector body was turned from a piece of 7mm hex brass and tapped M5 x 0.5 at both ends. the first tests were not a success  :( I did not leave enough grinding allowance on the needle so the final diameter was too small. When I tried it in spite of this there was a fuel leak between the body and the nozzle. When I tightened it some more I stripped the threads  :facepalm:

The cause of the leak was running the die right up to the end when cutting the thread in the nozzle which resulted in some score marks in the sealing face. Luckily I could salvage both parts by reducing the lengths a little and re-cutting the threads. I then made a new needle, leaving the cone larger, then grinding it down to length at the end.

When the diesel has had a couple of days quarantine in the garage (after the last trials) I can bring it back into the cellar for some more trials with alcohol.
Title: Re: Fuel injection systems
Post by: Roger B on May 11, 2018, 07:30:45 PM
The trials with the 15° mushroom injector were not satisfactory so I decided to make a 30° mushroom. This was much the same as before except that the clearance when grinding the tip was somewhat reduced.
I also decided to open out the normal nozzle to 0.5mm and had to make an extension holder for a 0.5mm drill. This was ok, I had a 0.5mm centre drill to start off with and running the lathe at the maximum 2000rpm all went ok.
Title: Re: Fuel injection systems
Post by: Roger B on May 11, 2018, 07:38:21 PM
The drill was Loctited into the extension and the nozzle was open out to 0.5mm without problems  :) I then used the Proxxon micro mill to put a couple of spanner flats on the mushroom nozzle and set it up for a try.
Turning the engine over with the drill, as in a starting trial gave quite a close spray pattern at 30 cm, maybe still to much penetration  :headscratch:  ::)  :help:

https://www.youtube.com/watch?v=jQOuDg9Jv6k

I will try the conventional injector with a 0.5mm nozzle later.
Title: Re: Fuel injection systems
Post by: Admiral_dk on May 11, 2018, 08:32:40 PM
Looking good Roger  :ThumbsUp:

Regarding the "perfect" spray pattern -- I do believe that it depends on the size and shape off the tube you spray into and the angle of doing so. It's "fairly easy" to get it to run, at lot more work to make it run good and a hell lot of work to get it perfect.
So there are a great amount of solutions for the easy, still quite a good number that will run good, but probably not that many that will run perfect.

The simplest I remember is the "carburettor" on the Velo Solex moped. There is a membrane pump on the side of the crankcase driven by the pumping pressure in the crankcase. It lifts the gasoline from the tank to the "carb" where there is a very fine nozzle that sprays the gasoline into the venture, a spring operated valve that allows the surplus to return to the tank and a throttle ... and that is it (if memory serves some 43 years after I opened one). This system isn't a bad as it sounds even though the throttle isn't very good as you get between 60 to 90 Km. on a litre gasoline.
Title: Re: Fuel injection systems
Post by: Roger B on May 13, 2018, 04:05:41 PM
Thank you Per  :ThumbsUp: I have plenty of variables to play with on this before I start thinking about turbulence in the combustion chamber  :headscratch:  :headscratch:

I tried the normal injector with the nozzle increased to 0.5 mm (double the area of the original 0.35mm) I think that the penetration is reduced, but the real test will be on the engine. Until I get actual firing it's hard to know in which direction to go. I will also try the mushroom injector on the petrol engine.

https://www.youtube.com/watch?v=DzEasFkJXGk

Title: Re: Fuel injection systems
Post by: Admiral_dk on May 13, 2018, 09:10:30 PM
I forgot - the finer the mist, the better the mixture => less fuel needed for the same rpm.
Title: Re: Fuel injection systems
Post by: Roger B on May 19, 2018, 04:27:44 PM
I fitted the mushroom injector and variable stroke pump to the horizontal engine for a petrol trial. It ran well, still showing a surprising throttle response for a fixed stroke setting on the pump. The fuel feed pump is not happy pumping into a closed system and tends to heat up and vaporise after a while. I need to add some sort of bypass or try a different style of pump.

https://www.youtube.com/watch?v=kxjEgvc7Qos
Title: Re: Fuel injection systems
Post by: Vixen on May 19, 2018, 04:35:16 PM
Good progress Roger. The engine sounds like it is running nicely

Mike
Title: Re: Fuel injection systems
Post by: Art K on May 19, 2018, 10:59:27 PM
Roger,
I have to admit not having followed this thread much, due to how far along it is. Curiosity got to me and I finally tuned in. Very interesting lots of very fine work. At some time in the near future I'll have to start from the beginning. Won't belong and you'll have that diesel running.
Art
Title: Re: Fuel injection systems
Post by: Roger B on May 20, 2018, 06:42:38 PM
Thank you both  :ThumbsUp:  :ThumbsUp:
I am still surprised how well the petrol injection system works, I think the horizontal engine runs better than with the carbs.  :headscratch: I am tempted to make a 360° crankshaft and camshaft for my twin cylinder engine so I can try it with fuel injection using a single pump driven from the crankshaft. This would also work for Dave (Steamer's) Wallaby. 
If anyone else wants to try and build a system I am more than happy to support/help them  :)
Title: Re: Fuel injection systems
Post by: Roger B on July 11, 2018, 07:56:27 PM
As I said previously the Facet fuel pump I am using is not happy pumping into a closed system as it is really designed to work with a float chamber. All the mechanical petrol injection systems I am aware of circulate the fuel via a pressure relief valve. I bought a smaller gear type fuel pump designed for transferring fuel into the tanks of models. It is not continuously rated at full output but I am expecting I can significantly reduce the supply voltage so overheating shouldn't be a problem.
I then needed to make a pressure relief valve to operate somewhere between 0.7 and 1 bar. After playing with a few designs I decided to base it on the delivery valve of the fuel injection pump using a weaker spring. This puts the tank return at the top which will also help with bleeding the air out of the system. The body if 8mm square brass tapped M5x0.5 on the side and at the top to take the fuel inlet union and the valve cage/return union. The connection to the injection pump is via a long nipple soldered into the body.
Title: Re: Fuel injection systems
Post by: Admiral_dk on July 11, 2018, 09:33:13 PM
Still hoping that you solve all the problems with this project, but it is a bumpy road you travel here  :cheers:
Title: Re: Fuel injection systems
Post by: Roger B on July 30, 2018, 07:10:07 PM
I shortened a 'trial' delivery valve to use as the inlet connector and then having received some 0.2mm wire springs I put it all together for a trial. Using the Facet pump it would hold 0.6 Bar but if I unscrewed the valve body 1 turn (0.5mm) it would let by so the spring looks about right. Now I need to mount the gear pump and try again.
Title: Re: Fuel injection systems
Post by: Roger B on August 08, 2018, 05:54:47 PM
I mounted the pump with a couple of angle brackets and used some of the existing pipework along with a couple of flexibles. I intended to use a bench power supply for the trials but the ones I had had a maximum output of 1A which was insufficient at the start (after some running time the current did drop). The back up plan was my sealed accumulators with the load bank to give some variation. I started with the 12V battery but as things eased off was able to use the 6V one.

5V 0.9A gave the expected 0.8 bar with some warming of the motor. Adding another 1mm washer under the relief valve gave 4.5V 0.75A and 0.5 Bar. The return flow was quite sufficient at these values. More voltage resulted in splashing out of the cap.
Title: Re: Fuel injection systems
Post by: AlexS on August 23, 2018, 09:51:44 PM
Hey Roger, I admire your ingenuity and tooling skills!

Reading this topic I might have an idea for fuel pump. Just an idea.
Applying a stage plunger pump. If I am right, this is 'approximately' applied to the VAG diesel systems in the future. You could possibly pump this pump to the motor mechanically. Or by means of a strong electric motor.

The idea is that the supplied diesel is sucked in by the first plunger. Where then compressed to medium pressure, where the second plunger can actually generate a higher pressure. Above the plunger, the supply and discharge can be equipped with, for example, a membrane. A spring or the like can be mounted against the diaphragms. An amount of pressure can be generated on the basis of the bias, spring constant and surface of the opening of membranes. This could easily be changed.
An electric pump can supply the diesel under-pressure to the first plunger. The nice thing is that the amount of diesel can be dependent on engine speed. Optionally, the output membrane of the second stage would be opened externally during partial load or heating of the engine. However, the pump did labor on the diesel, which resolved in warming diesel.
Title: Re: Fuel injection systems
Post by: Roger B on August 26, 2018, 08:16:02 AM
Thank you Alex  :) An interesting concept for a pump  :ThumbsUp:

After some running time the electric pump would operate on 5V drawing less than 1A so I made up a board with a 7805 regulator and appropriate decoupling capacitors (based on previous experience). As I have now fitted a 12V coil to the horizontal engine the regulator could go where the 6V regulator for the previous coil was installed. This all seems to work although I have not had the opportunity for long runs.

I had previously ordered some Titex 0.2 mm drills for the next injector trials and wanted to see if I could actually drill some holes. This was going to be difficult as if I wanted to carry on as before I would have to drill a 5 or 6 mm deep hole in the brass drill extension. This is 25-30d which is hard enough with 'normal' size drills. I did manage to make a few holes with several broken drills but this was fairly obviously not going to work with the equipment I have.
The next trial was to drill 0.35 mm hole as before and try Loctiting a 0.2mm drill in, hoping that the surface tension would keep it central. This appeared to work, in the last picture it is turning at 2000rpm with no obvious runout.
Title: Re: Fuel injection systems
Post by: Vixen on August 26, 2018, 10:50:36 AM
Hello Roger,

Drilling 0,2mm holes 5 to 6 mm deep, in brass, is always going to be a big "ask".

I cannot tell you how to do it successfully, but here are some pointers.

Chose the hardest possible brass ie. one that produces fine chips NOT long spirals.

To achieve the recommended surface cutting speed for brass, you need a spindle speed in the order of 20k to 25K RPM. Wow thats fast!!!!

Peck drill at a few thou (50 microns) per step. This will break the chips which helps prevents clogging the drill flutes

Withdraw the drill completely every 0.5mm to clear the chips and re-apply lubricant (WD40 or kerosene)

Provide a very, very precise centre mark. A slightly larger drill may help start the hole.

Consider drilling part way with a slightly larger drill and breaking through with the 0.2mm drill.

Consider EDM with a fine wire

Consider using a watchmakers pivot jewel as the nozzle. You are in the right country for watchmakers.

Not sure if any of that will actually help. Let us know how you get on

Goodluck

Mike




Title: Re: Fuel injection systems
Post by: Admiral_dk on August 26, 2018, 12:01:53 PM
Best of luck with the drilling Roger.

I'm with Mike on the minimum rpm on the drill bits !!!!

I can't think of a single kind of injector system where the depth of the hole is more 5-10 times the diameter of the hole - the rest of the depth is done in a bigger diameter ..... are you sure that the only way your system is going to work are done with a single diameter the whole way ?
Title: Re: Fuel injection systems
Post by: 90LX_Notch on August 26, 2018, 03:59:21 PM
I haven't dropped in on this thread in a while Roger; awesome stuff going on here.  I need to get caught up.

-Bob
Title: Re: Fuel injection systems
Post by: Roger B on August 26, 2018, 04:06:29 PM
Thank you for the suggestions  :ThumbsUp:  :ThumbsUp:

This is not for the nozzle itself but for the tool to drill the nozzle. To keep the nozzle concentric with the seating I need to drill from inside. I successfully made extended drill holders for 0.5mm and 0.35mm. I was aware that moving down to 0.2mm would be a challenge. The most successful attempts were made starting with a spot from a 0.5mm centre drill, pecking at the hole and wiping the swarf off with my fingers every few pecks. My WD40 equivalent made things worse by causing the chips to stick together  ::)

I do have a back up plan as 0.2mm drills are available with a 1mm shank so drilling the brass extender 1mm is no problem. The actual nozzle hole is only planned to be 0.5mm - 1mm long.
Title: Re: Fuel injection systems
Post by: zeeprogrammer on August 26, 2018, 04:21:41 PM
Very interesting!  :popcorn:

I'm still confused about the use of WD40, kerosene, or equivalent when drilling/cutting brass.
I thought lubricant was not needed. I may also be confused with 'not recommended'.

For brass..

When is lubricant not needed?
When is lubricant recommended (or needed)?
Is there a case where lubricant is not recommended?
Is it a matter of the type of brass?
Title: Re: Fuel injection systems
Post by: Vixen on August 26, 2018, 07:13:47 PM
Hi Zee

Under normal circumstances (read normal size drills) lubricant is not needed for brass.

However, with a small diameter 0.2mm drill  (that's less than 8 thou, or 8 mils, as you guys say) rotating at something like 25, 000 RPM, it sometimes helps to use a light lubricant to cool the drill and flush the chips. But as Roger points out, even that does not always work as intended.

Mike
Title: Re: Fuel injection systems
Post by: zeeprogrammer on August 26, 2018, 07:24:48 PM
Thanks Mike.

Apologies Roger. I should have asked in my thread.
Title: Re: Fuel injection systems
Post by: Roger B on August 27, 2018, 05:37:00 PM
Absolutely no problem Carl  :) Everything I post on here is about learning and understanding (generally on my behalf  ::) )

I also have the same question about lubricants and cast iron. If you read some UK books it appears that using lubricants when machining cast iron will result in destruction of the world as we know it but my German books suggest using kerosene (which I guess is the most widely used description of Paraffin, Petroleum, etc maybe it should just be called Jet A1?).
I guess in the end it is what works  for what you are doing. My lathe will reach 2000 rpm therefore holes have to be drilled at 2000rpm. My Proxxon drill will do 8000 rpm and the Proxxon mini mill will reach 20 000rpm but they won't drill concentric holes in a round item.
On with plan B  :wine1:
Title: Re: Fuel injection systems
Post by: Roger B on August 31, 2018, 07:58:45 PM
I received some (expensive) reinforced shank 0.2 mm drills. The first attempt at a holder was made in brass as before, but it broke at the end of the 1mm hole. The 0.2mm wall thickness was not enough  :(  I then tried again with silver steel. I wasn't sure about drilling a 1mm hole 15mm deep but it was ok. I had made a trial nozzle to check the diameter and for polishing I supported the bore with a reversed 1mm drill in the tailstock drill chuck. OK so far  :)
Title: Re: Fuel injection systems
Post by: Roger B on September 01, 2018, 06:49:32 PM
Having made the drill I then tried to make the nozzle. The blank was 27.3mm long so it was drilled 1.3mm dia 26mm deep, reamed 1.45mm 25 mm deep and then finished with the D bit to 26.8mm. I then pecked with the 0.2mm drill until the resistance went and luckily the point was still there  :)

I had bought some stronger springs for the injector but they had a smaller bore so I had to turn down the adjuster and the needle cap. I normally use ER collets but the thin needle cap was a good use for the Hobbymat spring collets.
Title: Re: Fuel injection systems
Post by: Admiral_dk on September 01, 2018, 09:19:20 PM
Looks very good Roger  :ThumbsUp:

I really hope this one works to your satisfaction  :cheers:
Title: Re: Fuel injection systems
Post by: Roger B on September 04, 2018, 10:31:13 AM
Thank you Per  :ThumbsUp: The stronger spring certainly made a difference (video is in the diesel thread) but I need to lap the bore on the 0.2mm nozzle before I can try it.
Title: Re: Fuel injection systems
Post by: Roger B on October 07, 2018, 08:10:07 AM
When I tried the 0.2mm nozzle in the engine I had problems with fuel leaking from the injector union which I couldn't solve at the time. This area was not really designed, just made up as I went along so I decided to revisit it.

The original injection piping was 1mm bore 2mm od copper pipe sleeved into a commercial 3mm union at the delivery valve end with a home made nipple and nut at the injector end. The connection into the injector nozzle was via a cone made with a 0.8mm tip 3.15mm od centre drill.

Since this time I found some 2mm unions from Regner with the same M5 x 0.5 threads. They appear compatible with the original ones from Holzapfel Dampfmaschinen but I need to check the cone angles.

Looking at the original pipework the nipple at the delivery valve end seems quite distorted and the nipple at the injector end has a noticeable ring. I think that the Regner type nipple will be better at the delivery valve end. The problem at the nozzle end is that the nipple is 4mm diameter and the centre drill used was 3.15mm diameter so if the cone is drilled too deep it won't seal. I check the dimensions around that part of the nozzle and I can use a 4mm diameter 1.6mm tip centre drill which should resolve the problem. I will need to make a 4mm bore guide nut for the drilling operation. Previously I used the actual union nut. Some means of depth control will also be required.
Title: Re: Fuel injection systems
Post by: Vixen on October 07, 2018, 12:03:26 PM
Hello Roger,

Is there anything to be gained by hard soldering (use silver solder) a short length of pipe to the injector body and having a standard (bought in) union joint a little way away from the injector. That way you may be able to divorce the injector design from the union problems.

Just a thought

Mike
Title: Re: Fuel injection systems
Post by: Roger B on October 07, 2018, 02:42:20 PM
Hi Mike, the problem joint is between the injector body and the nozzle. This is why I have tried to make a cone fitting at that point. If I move the fuel connection to the body I would probably have to lap the nozzle into the body to gain an adequate seal. O rings are too elastic for the high pressures and small volumes. A variation on your thought is to combine the nozzle and the lower half of the body and then screw the spring assembly on top. This would allow me to silver solder the fuel connection to the nozzle and move the union away. I may move to this when I have the design more fixed but currently a new nozzle is a short length of 8mm brass rod and an evenings work.

I have attached a PDF of the current state of the injector design.
Title: Re: Fuel injection systems
Post by: Roger B on October 20, 2018, 07:58:53 PM
I moved on with this making a new union nut and a guide bush for the larger centre drill. The Proxxon drill makes it quite easy to set the depth using a drill of the appropriate diameter. I also used a drill shank to check the depth of the union nut.
Title: Re: Fuel injection systems
Post by: Roger B on October 20, 2018, 08:03:38 PM
I shortened a Regner nut to match the delivery valve and then silver soldered both ends on the pipe using my small Portosol torch rather than the big blowlamp.
Title: Re: Fuel injection systems
Post by: Admiral_dk on October 21, 2018, 08:41:43 PM
Looks nice - have you pressure tested them after soldering ?
Title: Re: Fuel injection systems
Post by: Roger B on November 05, 2018, 08:29:11 PM
Thank you Per  :ThumbsUp:  I can only test them by assembling the system, maybe I need to build a test fixture using something other than diesel oil.
Title: Re: Fuel injection systems
Post by: Vixen on November 05, 2018, 08:52:22 PM
Keep a close eye on the pipework, every injection pulse creates a shockwave which can fatigue the pipe joints.

I even had it happen with one of our companies cars. I was miles from home when one of the injection pipes fractured and the engine went on to three cylinders. I did not wish to be stranded, so limped slowly back to base. The engine sounded really rough and stank of the diesel oil which was being squirted all over the engine. Arrived back at base leaving an oil slick under the car.

Mike
Title: Re: Fuel injection systems
Post by: Roger B on December 15, 2018, 12:38:48 PM
Thank you Mike  :ThumbsUp: The diesel certainly puts shock waves everywhere  ::)

As I said on the engine thread the 0.2 mm nozzle seemed to wear very quickly so the fuel just leaked back along the needle guide. I am guessing the surface finish was not good and the peaks wore away very quickly  :headscratch:

On with some more nozzles. The first one was made much as before and I found that the 1.47 mm pin gauge would enter quite easily but the 1.48 mm gauge wouldn't go. That would work but didn't leave much for lapping. A 1.45 mm H7 reamer should have a maximum size of 1.46 mm but maybe brass reacts differently  ::)
For the second attempt I used the floating reamer holder for the D  bit as well. In this case the 1.47 mm pin gauge was tight and would not go all the way in. A little better  :)
Title: Re: Fuel injection systems
Post by: Roger B on December 16, 2018, 03:57:41 PM
I cut the union seatings with a center drill as before and then lapped the bores to just over 1.48mm to fit the needle. After a quick ultrasonic bath I built up the injector with one of the nozzles and gave it a try. I got atomisation and a rather strange exclamation mark pattern  :headscratch:

https://www.youtube.com/watch?v=TYKJX24Et1U

As it's below zero with snow outside it may be some time before there is a real test with diesel oil.
Title: Re: Fuel injection systems
Post by: Admiral_dk on December 16, 2018, 04:44:14 PM
Looks very fine to me Roger and I expect that the pattern is a result of the shaking of the injector (though the camera seems to shake too, so not completely sure)  :ThumbsUp:

Shame about the waiting time due to climate conditions, but we will have to endure the wait  ;)
Title: Re: Fuel injection systems
Post by: Roger B on December 18, 2018, 10:10:59 AM
I think you are right about the injector shaking, I was concentrating onholding the camera in one hand and turning the engine with the other. If not that would have been an excellent spray pattern for the Junkers  ::)
Title: Re: Fuel injection systems
Post by: Roger B on July 29, 2019, 06:57:32 PM
Having reached a bit of a dead end on the diesel with the 'conventional' nozzle design I decided to try some further experiments with the mushroom needle design. The first attempt was based on a 2mm shaft and is working fine on my horizontal petrol engine. For this series of experiments I have reduced the base size to 1.4mm. I have made two nozzles, one with a 30° angle and one with a 40° angle. Both were turned on my Proxxon PD150. As I don't have a tailstock die holder for it I glued a washer on the back of my small die stock to help keep things square. The M2 2mm AF nuts were made a while ago in anticipation of this step.
Title: Re: Fuel injection systems
Post by: Roger B on July 29, 2019, 07:00:27 PM
The second needle was made in the same way and then I moved onto the nozzle and body. As they are both from hex bar I started with the 3 jaw sc chuck and will move to an ER chuck for the final steps.
Title: Re: Fuel injection systems
Post by: Admiral_dk on July 29, 2019, 08:32:12 PM
Glad to see that you found another "angle" to try and solve the problem from  :ThumbsUp:

I really hope that you will "nail it" this time - nice start to the first parts of the next gen. :cheers:
Title: Re: Fuel injection systems
Post by: Roger B on August 01, 2019, 01:47:14 PM
 :)  :)  :)  :)  :wine1:

As the nozzle is quite short I used my ER11 chuck to complete it. The nozzle was drilled 1.3mm and reamed 1.45mm based on experience with the other injectors. The bore that the cone seats in needs to be round. I did consider lapping but will try without. The seating for the fuel supply union was cut with a centre drill and seemed to fit well with a Regner 2mm union and nut. When I first tried to assemble it the spring jammed on the needle so I drilled a small recess to keep it central.

Next step is to harden and polish the needles followed by a trial with petrol on the horizontal engine.
Title: Re: Fuel injection systems
Post by: Ye-Ole Steam Dude on August 01, 2019, 03:46:19 PM
Hello Roger,

Like the others, I do admire your efforts and appreciate the various parts that you are making.

Have a great day,
Thomas
Title: Re: Fuel injection systems
Post by: Roger B on August 01, 2019, 03:55:54 PM
Thank you Thomas  :ThumbsUp:

I hardened the ends of the two needles and then had to set up the Proxxon drill for polishing. The 30° setup was fairly easy but to get enough space for the 40° one I had to turn the drill support upside down and had very little clearance against the milling column. I need to look at a more compact toolpost grinder system, maybe even one that will fit the PD150  :thinking:
Title: Re: Fuel injection systems
Post by: Roger B on August 10, 2019, 05:29:30 PM
I made a clamping plate to suit the new injector and connected it up to my horizontal engine. Priming the system took some time as there is quite an volume in this style of injector compared to the needle type. Once primed I fitted it to the manifold and the engine started up without any problems. The response seems similar to the other injectors. One problem I found was that overtime the stroke adjusting system has become looser and now vibrates round on its own  ::) not useful  :toilet_claw: I am not sure whether just to add a friction spring somewhere or to make a new system that I can couple to the throttle opening  :thinking:

I also need to think about spring pressures for the diesel trials. With the needle type the compression pressure will tend to open the valve. With the mushroom type compression will tend to keep it closed  :headscratch:

https://www.youtube.com/watch?v=KtTG6vRN3CY
Title: Re: Fuel injection systems
Post by: Roger B on August 11, 2019, 08:04:41 PM
While looking at  a solution to the adjustment screw problem I realised that when I changed the petrol feed pump the pipe ended up much too close to the exhaust system. This was quickly corrected. There was enough material in the stroke adjuster that I could drill through 2.5mm and tap M3 for about 4mm deep. I turned a little pressure plug from 2.4 mm brass rod and using a piece of the 1.4 mm injector spring made a spring loaded clamp. This seems to work and also stops the adjustor block tipping as plunger moves. Ready for some more trials  :)
Title: Re: Fuel injection systems
Post by: Roger B on August 18, 2019, 07:00:50 AM
I decided that I needed to make a simple test pump for the injectors, fixed stroke and without a helix. There was a 18mm stub of 1.98mm pin gauge left from the previous pumps so I scaled it around that. The end of the gauge was annealed and threaded M2.
The frame is from piece of 50mm angle iron roughed out in the band saw. The spring seat as turned and the body bored and reamed as before.
Title: Re: Fuel injection systems
Post by: Roger B on August 18, 2019, 07:47:53 AM
I reversed the body in the chuck and drilled 4.5mm dia 4mm deep for the delivery valve thread and milled the seat to 4.5mm deep. This is where the problems started, there were no threads at the start of the hole  :headscratch:  :( I made a new body and got much the same result  :thinking: this is something I had done at least 10 times before. Then I realised the difference, previously I had used a 'once through' M5 x 0.5 tap. This time I had used a pair of progressive taps I had bought as I thought that they should be better in blind holes. They are all Volkel taps so the quality shouldn't be a problem. So cut a new blank and try again  ::) My metre length of 10mm black bar is slowly disappearing with my injection experiments.
Title: Re: Fuel injection systems
Post by: Roger B on August 21, 2019, 07:39:17 PM
The third version was no better  :( After some thought I tried with a  piece of 3mm flat bar. This was drilled first 2mm and then 4.5mm using the same drill. I then tried the once through tap, the progressive taps fully through and the taper just three turns followed by the plug. All were good threads  :headscratch: I then tried from the other end of the three trial (scrap) pieces, drilling 4.5mm again with the same drill. Once through tap pushing was ok. Once through tap with very light pressure was ok. Tape followed by plug was ok  :headscratch:  :headscratch:  ::)
I turned yet another body and tried again using the once through tap but withdrawing every couple of turns to see if all was ok. No problems  :thinking: Finally I milled the valve seating but there was plenty of clearance between the endmill and the thread so no problem there.
All is underway again but I have no idea what was going wrong  :toilet_claw: and hence no idea how to avoid it when I drill and tap the inlet port.
Title: Re: Fuel injection systems
Post by: Roger B on September 02, 2019, 05:27:35 PM
The inlet port was drilled and tapped without problems as were the fixing holes. The bore was then lapped to size and the body was cleaned in the ultrasonic bath. A bit more work on the bracket and then the tappet for the plunger was turned from 10mm silver steel and hardened.
Title: Re: Fuel injection systems
Post by: Vixen on September 02, 2019, 05:44:33 PM
More fiddly small parts. Nice  :ThumbsUp: :ThumbsUp:

Not sure my eyes would let me make those without a magnifier headband.

What ultrasonic bath do you use? I bought a cheap one once, it lasted a month before it failed. I may try again.

Mike
Title: Re: Fuel injection systems
Post by: Roger B on September 03, 2019, 07:20:48 AM
Thank you Mike  :ThumbsUp:  :wine1:

There was a thread on ultrasonic baths a little while ago:

http://www.modelenginemaker.com/index.php/topic,8499.msg184738.html#msg184738

Mine is just a cheap (as far as cheap is possible in Switzerland) unit from Conrad.
Title: Re: Fuel injection systems
Post by: Roger B on September 06, 2019, 05:20:33 PM
A little bit more on this. The pivot pin was turned and threaded and then I started the operating lever from a piece of 6mm thick aluminium mostly with a hacksaw and files. The slot for the ball bearing follower was milled out using the little Proxxon mill and the end profile was finished with some filing buttons I had made for finishing some pipe flanges. A quick check showed that I needed to relieve the lever a little more so the follower roller was always in contact with the tappet.
Title: Re: Fuel injection systems
Post by: Roger B on September 06, 2019, 06:49:18 PM
The next step was to turn the bronze bush for the lever. This was made from a little offcut, bored and reamed 4mm in a collet and then pressed onto a tapered mandrel for finishing. The washer from the end of the pivot was turned from a piece of 8mm steel of some sort. Then came the problem my 6mm aluminium was actually 1/4" so when I put it together there was negative clearance  :( A bit of filling solved that and finally I turned the follower pin from 2mm silver steel.
Next up the inlet union and delivery valve.
Title: Re: Fuel injection systems
Post by: Roger B on October 06, 2019, 08:07:31 AM
Next up was a little excentric bush to set the back position of the plunger so that the inlet port was just fully open. The fuel inlet union and delivery valve were made as before and the system was checked under pressure with a 1.2 kg weight at the end of the arm. This showed very little leakage.

https://www.youtube.com/watch?v=W5kyblQyUMQ

When I made the arm I added a hole at equal distance to the tapped bearing to allow me to measure the force on the plunger using a spring balance. The connecting link was made from a piece of wire coathanger with one end turned down to 2mm and tapped M2. The complete set up seems to work so I need to make another connecting pipe for the mushroom injectors and then start some real trials.
Title: Re: Fuel injection systems
Post by: Admiral_dk on October 06, 2019, 08:43:49 PM
I really hope that you get a better spray pattern soon. I know that special chambers, etc. in the combustion chamber could more or less cure some of your problems, but as you are planning on using the system on an opposite piston diesel engine, these are not the solution here.

Best wishes

Per
Title: Re: Fuel injection systems
Post by: Roger B on October 20, 2019, 07:29:17 AM
Thank you Per  :ThumbsUp:

I made some very unsuccessful trials with the needle injector. All three nozzles, 0.2mm, 0.35mm and 0.5mm just squirted and dribbled. A close inspection revealed the cause, the tip of the needle was bent  :facepalm: No idea how or when but  will have to make a new one (or two or three). I then tried the two mushroom injectors with a slightly better but still not satisfactory results. Time for more thinking  :headscratch:

I needed to make a new lap for the 1.5mm needles so cut another 10mm of 16mm brass and continued as before.
Title: Re: Fuel injection systems
Post by: Roger B on October 20, 2019, 07:39:31 AM
As the machine was in milling mode after completing the lap I decided to make a start on an experimental slide throttle to go on the horizontal engine. The fuel injection will be downstream of the throttle so small air leaks will not be a significant problem especially on a single cylinder. They may make getting an even idle on a multi cylinder engine more difficult. The body is a piece of 20mm x 5mm brass and the slide will be 10mm x 2mm. The bore will be 7mm.
Title: Re: Fuel injection systems
Post by: steamer on October 20, 2019, 01:54:45 PM
Cool!   Watching along....

Dave
Title: Re: Fuel injection systems
Post by: Kim on October 20, 2019, 02:31:35 PM
This is fascinating Roger!  Everything I know about fuel injection I've learned from reading your thread here (Just so you know where I'm coming from :)).

Can you explain your test setup?  It looks interesting, but I don't understand how it works or what exactly it's doing.  I assume it is providing some fuel under pressure so you can see the spray pattern out of the injector?  But how does that setup get you there?

Thanks,
Kim
Title: Re: Fuel injection systems
Post by: Admiral_dk on October 20, 2019, 07:46:16 PM
Roger - I have thoughts in the back of my head, regarding spray patterns from an oil burning heater, every time I have read your post on the subject the last many times. So I did a bit of Googling today, and found this http://www.airheaters.info/oil-burner/oil-burner-nozzles.html (http://www.airheaters.info/oil-burner/oil-burner-nozzles.html)

I'm not sure if it will work in your application, as it might end up clogged after a while in the combustion chamber  :thinking:  But besides the small sizes, it looks like a rather reasonable simple solution, so maybe - if nothing else - an inspiration if you need it ....
Title: Re: Fuel injection systems
Post by: Roger B on October 23, 2019, 03:48:23 PM
Thank you all  :)

Kim, the test setup is a fuel pump of the same design as on the engines mounted on a bracket with a bell crank to allow me to operate it rather than being driven by a cam or excentric. This will allow me to test various injector designs on the bench. There is also a hole to allow me to use a spring balance to estimate the force on the pump plunger and hence the pressure in the system.

Per, a design like that was used on the Lanz Bulldog tractor (hot bulb engine). The small passages/grooves will be a problem  :thinking:  I hope that if I can refine the current designs I will get somewhere. The needle injector was obviously not working as expected in the later trials with a higher compression so I need to repeat them.
Title: Re: Fuel injection systems
Post by: Roger B on October 23, 2019, 08:12:11 PM
On with the slide throttle. I milled an 8mm recess in the back of the body for the pipe stub to connect to the manifold. This joint is not really needed but adds some flexibility in the experimental phase. The pipe stub and end plate were then soft soldered in place. The cover is held in place with M2 screws and the idle and full throttle stops are M1.4.
Title: Re: Fuel injection systems
Post by: Vixen on October 23, 2019, 08:23:49 PM
Hello Roger

The slide throttle looks neat and functional.  :ThumbsUp: :ThumbsUp:

What clearance did you give between the slide and the body? I guess it needs to be as small as possible, to prevent air leaks, while still allowing the slide to move.

Will you lap the slide to the body?

Mike
Title: Re: Fuel injection systems
Post by: Roger B on October 24, 2019, 07:46:43 AM
Thank you Mike  :)

As the fuel injection will be downstream of the throttle small air leaks should not be a problem so the faces are as milled with a light clean up with a fine file. Making a system for a multi cylinder engine like this Porche 917 would be more of a problem in getting balanced slow running between all the cylinders on a slide. That's a problem for the future  :headscratch: I need to trial this system first.
Title: Re: Fuel injection systems
Post by: Vixen on October 24, 2019, 09:18:02 AM
Making a system for a multi cylinder engine like this Porche 917 would be more of a problem in getting balanced slow running between all the cylinders on a slide. That's a problem for the future  :headscratch: I need to trial this system first.

Slow running balance would always be a problem with a multi cylinder engine like the 917. That's probably one of the main reasons for all the throttle 'blipping' as the cars line up on the grid before a race. The other reason is it sounds great.

Mike
Title: Re: Fuel injection systems
Post by: Admiral_dk on October 24, 2019, 12:57:00 PM
The main reason for blipping the throttle before electronic control off the fueling, is simply because that the engine would be lousy at picking up revs, after a not very long period off idling .... Oh and you're right about the "mine is bigger / badder, than yours" too - just listen here  :Director:

EDIT - I just remembered that for instance in Road Racing in the old days, the bikes were not allowed to be able to idle, as a safety precausion - or put in another way - it should not be able to continue at full throttle down the road without a rider onboard ...!!!!
Title: Re: Fuel injection systems
Post by: Roger B on October 24, 2019, 07:51:15 PM
I fitted the throttle and sorted out a control linkage.

https://www.youtube.com/watch?v=3I2Xo3_UcPY

And then as there was fuel in the tank even though it was in the cellar I connected up the battery and gave it a quick try  :whoohoo:

https://www.youtube.com/watch?v=LoSw0Lc6kpI

It's currently running on cooking alcohol so it doesn't smell too bad  ::)

Next step make some more needles for the diesel injectors.
Title: Re: Fuel injection systems
Post by: Roger B on November 03, 2019, 07:05:42 AM
On with the needles. I followed the procedure I used before to grind the first needle without problems but the next two snapped during grinding of the shank  :(  After some thought I realised that I had hardened too much of the needle so I was holding a hardened piece in the chuck. The increased stiffness caused more vibration (as shown by the chatter marks on the grinding wheel) and the brittleness resulted in the needle breaking.
I tried again just hardening 20mm (as far as I could judge) and this looks to be successful  :)
Title: Re: Fuel injection systems
Post by: steamer on November 03, 2019, 11:25:49 AM
I like it Roger!....Still watching!

Try drawing the temper just a touch before grinding....back to straw perhaps...you'll need a tray with some brass chips or sand to do this....finicky little part!

Dave
Title: Re: Fuel injection systems
Post by: Florian Eberhard on November 03, 2019, 12:13:59 PM
Hey Roger

Those are some very delicate needles to grind. I have been playing around with a small grinding attachment quite a few years ago.
A few things I learned was:
- You need to dress the grinding wheel in the lathe, using a fixed dressing tool. (not hand guided!) I couldn't see that step - but you may have done this? (If not, RDG tools sells very affordable diamond dressers)
- If you reduce the contact area to approx.  1/3 of the wheel width, you will have less deflection.  This can be done by bevelling the rear side of the wheel.
- If you need to remove "lots of material", you should angle the dremel so only the edge of the wheel is cutting. This also reduces the cutting forces in general but concentrates them to one point which is more effective.
- Always dress before the finishing pass
- I suspect this pink wheel is from proxxon? You should use them only for rough grinding. The green silicon carbide wheels work better for finsihing.
- For a very good surface finish, you can use wd40 on the workpiece (applied with a brush or so)

Just as a hint: The elastic modulus and therefore rigidity of steel doesn't change if you harden steel. All that happens is that the "resistance against plastic deformation" is increased.
Practically it means, that hardened steel will not  have any (or barely any) plastic deformation, all there is left is the elastic deformation which is reversible.
Title: Re: Fuel injection systems
Post by: steamer on November 03, 2019, 12:23:57 PM
Florian is quite correct about the stiffness of steel and dressing the wheel.     You will be able to get better finish with a hardened part vs a soft part.    That said....if it's full hard it will be very brittle, and if your wheel isn't dressed, it will have 1 section of the wheel hitting it every revolution.....and that impact could break a full hard needle......definitely dress the wheel every time it's mounted

Dave
Title: Re: Fuel injection systems
Post by: Roger B on November 03, 2019, 01:05:36 PM
Thank you both for your thoughts and interest  :)

When I start the setup I grind the point first with a short overhang which dresses the wheel quite well.

I am increasing the depth of cut by 0.025mm and running backwards and forwards until there are no more sparks then going in another 0.025mm. I increase the depth when the wheel is at the chuck end and things are more rigid and then work out towards the point which I hope reduces the cutting load.

In my initial trials I found that the pink Proxxon wheels gave a better finish than the grey (green?) ones. Maybe I need to revisit this  :thinking: As a final step I polish the ground surfaces with a Proxxon rubber polishing drum.

As ever lots to learn and think about  ::)
Title: Re: Fuel injection systems
Post by: Roger B on November 05, 2019, 05:40:00 PM
The other end suffered from severe vibration but didn't break as the part in the chuck was not hardened. As a trial I held a small offcut of hardwood against the point and the vibration stopped and the surface finish improved significantly. As both Dave and Florian explained the stiffness does not change with hardening, just the likelihood of it breaking  :headscratch:

I was able to finish grinding both ends and moved onto lapping the shanks.

During the rather repetitive lapping process I realised that I had a traveling steady that Jo made to which I could fit some form of spring loaded support for the point of the needle and then use the top slide for moving the grinder. The reduced shank does not have to be that precise, It's the point that has to be concentric with the lapped shank.
Title: Re: Fuel injection systems
Post by: Roger B on November 09, 2019, 03:10:25 PM
I finally ended up with three nozzles with matched needles, 0.2mm, 0.35mm and 0.5mm so I can do some bench testing.

As the weather wasn't too bad I opened up the R&D department to try the slide throttle properly.

https://www.youtube.com/watch?v=kbVACrm-duk

I ended up with a similar result to that from the large slide carburettor of around 120W~(~11A at 11V) however as before the cooling system is struggling. Once again I didn't seem to need to adjust the pump stroke from full load to idle  :headscratch:
Title: Re: Fuel injection systems
Post by: Admiral_dk on November 09, 2019, 08:53:11 PM
Sounds like it is running very evenly and well Roger  :ThumbsUp:
What kind of fuel was this test run on ?
Title: Re: Fuel injection systems
Post by: Roger B on November 11, 2019, 01:54:07 PM
Thank you Per.
This trial and the two cylinder engine trial both used Alkylate fuel. I have no idea if it produces more or less power than cooking alcohol  :headscratch: I tend to use alcohol for testing the injection systems in the cellar as a hangover from when I ran the engines on normal pump petrol and wanted to minimise the smell.
Title: Re: Fuel injection systems
Post by: Ye-Ole Steam Dude on November 11, 2019, 03:19:35 PM
Hello Roger,

That is just too cool....electric start and all the electronics  :cartwheel: and to top it all off, a really smooth running engine. Great job on a very nice looking engine.  :ThumbsUp:

Have a great day,
Thomas
Title: Re: Fuel injection systems
Post by: Roger B on November 16, 2019, 07:31:47 AM
Thank you Thomas  :)

I started to re assemble the injector test rig but had problems getting a seal to the injector. On close inspection the thread on the union screw seemed worn/tapered. The union cone itself seemed ok as did the thread in the body. I'm not sure if this was a bad thread from the start or if it had worn with frequent dismantling and re assembly  :headscratch: The guide bush I use for cutting the cone in the nozzles was also a loose fit in the body so I decided to remake both parts and case harden them.

When I removed the pipe from the pump I saw that the thread on the delivery valve was also damaged  ::) This is a problem I have found with some of the Holzapfel unions. The top of the thread is not relieved and when tightened the thread spreads damaging the thread in the nut which then damages the union. The Regner unions are relieved. I made a replacement from a Regner union which meant I had to lengthen the thread a couple of mm.
Title: Re: Fuel injection systems
Post by: Vixen on November 16, 2019, 12:37:47 PM
Hi Roger,

I've been quietly following your fuel injection journey through all it's twists and turns. I and am sure everyone else were pleased when you got the engine to run so well. I must congratulate you on your persistence and dedication to the task. So many remakes.

I must admit that along the way I have lost track of the overall system design. Is it possible to post a diagram of your fuel injection system.

Cheers    :wine1: :wine1:

Mike
Title: Re: Fuel injection systems
Post by: Roger B on November 17, 2019, 11:04:20 AM
I was unable to remove the old nipple from the pipe to replace the screw and had to make a replacement for that as well. The new nipple needs to be silver soldered on and then back to testing  ::)
Title: Re: Fuel injection systems
Post by: Roger B on November 17, 2019, 11:10:16 AM
Thank you Mike  :)

I will try and summarise my progress to date (this is also useful for me as I don’t have to keep digging back through what is becoming rather a long thread).
When I looked at the list of engines I would like to make most of them had some form of fuel injection so I decided I needed to do some experimentation. At the start I rather naively thought that a piece of ground silver steel in a reamed hole would be sufficient. This is obviously not the case and I moved on with learning how to lap internally and externally and then how to ream properly which required much higher speeds and lower feeds than I imagined along with the benefits of a rather expensive small floating reamer holder. After some problems with a piece of trilobed silver steel I moved onto using commercial pin gauges for the pump plunger.

First system

This was always intended to be for petrol and is fitted to my 25cc horizontal engine. The pump is 2mm bore and variable stroke, 0-2mm, driven by an excentric running at camshaft speed. The stroke is adjusted by a wedge and injection is timed to take place when the inlet valve is open. This initially ran with a needle valve injector but there was too much leakage along the needle so I tried a mushroom valve design which seems to work well.

At the start the pump was gravity fed but operation was rather inconsistent and bubbles appeared in the inlet pipe. This was due to the petrol vaporising as the plunged moved back and was solved, as in full sized mechanical petrol injection systems, by pressurising the fuel feed. I tried an automotive fuel pump but this wasn’t happy with the low flow rates so I am now using a model fuel transfer pump running at 5V instead of 12V and a relief valve that opens at about 0.8 Bar.

The first trials used a barrel type carb as the throttle and then I made a slide throttle which is now in use.

I had always planned to link the pump stroke adjustment to the throttle but that has so far not been necessary.

Second system

This is intended to be a full diesel so a different type of control is required to ensure a constant timing point for the start of injection. I decided to follow full size practice and ground a 4mm pitch helix in the plunger. I tried this successfully on the horizontal engine driven by the excentric. The helix is rotated by a rack and a wide pinion which drives a rectangular foot on the plunger.

For the diesel the pump is driven by a cam giving a short injection period, around 10°, which results in some high loads on the cam follower.

I have tried needle valve type injectors with 0.2mm, 0.35mm and 0.5mm nozzles as well as two sizes of mushroom valve injector with limited success. For the first trials the compression ratio was too low as I had not made enough allowance for the clearance between the piston and the head. With a compression of around 30 Bar I was getting combustion but I think the fuel was being ‘carburated’ as it passed by the piston.

Test system

To allow me to better understand the injectors I made a hand test pump to the same design as the first system. This immediately showed that my injectors were not performing as they should and will require various reworkings.

I have attached some pictures as well as my current drawings (makes a good backup) and will be happy to try and clarify any points.
Title: Re: Fuel injection systems
Post by: Vixen on November 17, 2019, 12:28:42 PM
Hello Roger,

Thanks for the brief history and the drawings. It is now clear just how many goes you have had at making and improving each design of pump and injector. The Swiss have a fine reputation for precision watchmaking and that's clearly what's required for a working fuel injection system

I assume the .dwg is the same as the .pdf one. That would be fortunate, as I have an incompatible version of AutoCAD (very early) which cannot open the .dwg file. It's interesting to see all the information on very large sheet. That's the way i do it as well.

It's going to take time to study and try to assimilate your design, as most of the important detail is still in your head.

Thanks

Mike
Title: Re: Fuel injection systems
Post by: Roger B on November 17, 2019, 01:46:08 PM
Mike,

The PDF is slightly trimmed. I have attached an ACAD 2002 version. I can go back to R12.
Title: Re: Fuel injection systems
Post by: Vixen on November 17, 2019, 01:51:07 PM
Hi Roger

R12 would be good for me

MIke
Title: Re: Fuel injection systems
Post by: Roger B on November 17, 2019, 02:01:08 PM
R12 Version
Title: Re: Fuel injection systems
Post by: Vixen on November 17, 2019, 02:36:25 PM
Roger, Roger.   :ThumbsUp: :ThumbsUp:

Thats an even bigger sheet than the .pdf

Mike
Title: Re: Fuel injection systems
Post by: Roger B on November 17, 2019, 03:57:50 PM
Having reassembled the test setup I tried once again. The initial trials were not very good with sideways squirts rather than atomisation.

https://www.youtube.com/watch?v=ZmZQnIggiqA

As an experiment I tried lapping the seating to the needle using 1 micron diamond paste as before. This has it's risks as I can't keep the abrasive away from where the shank runs in the nozzle and properly cleaning the orifice will be difficult especially in the smaller sizes. The initial trial looked better with more atomisation and less side squirt  :)

https://www.youtube.com/watch?v=kTGw2eSNbr8
Title: Re: Fuel injection systems
Post by: Roger B on May 19, 2020, 05:39:02 PM
I have come back to this topic as I know I need to do some more work on the injector nozzle seatings to get good atomisation. Unfortunately as mention in the carb thread my stocks of the key 1.5mm diameter silver steel are no good and I will have to wait for some more. I think I had reached a reasonable compression ratio and will modify the cast iron head to the latest dimensions.
Title: Re: Fuel injection systems
Post by: Roger B on May 19, 2020, 07:15:44 PM
I tried a couple of the old nozzles and the pattern was not good  :( One was not too bad so I tried igniting the jet (with alcohol). I had a wet towel to hand and a fire extinguisher by the door (run away!!!)

https://www.youtube.com/watch?v=jpkbryz4h78


Title: Re: Fuel injection systems
Post by: Vixen on May 19, 2020, 07:48:02 PM
Hello Roger,

That short jet of flame in the video looks very impressive.  :ThumbsUp: :ThumbsUp: :ThumbsUp:

Would you expect the jet to bounce off the piston and cylinder walls to fill the whole combustion chamber with burning fuel, or do you need to develop a broader fan shaped jet.

Still following with the injection and carburetter developments with great interest.

Mike
Title: Re: Fuel injection systems
Post by: Admiral_dk on May 19, 2020, 09:44:27 PM
Looks like your spray pattern would work nicely in a bigger engine  :thinking:
Title: Re: Fuel injection systems
Post by: nj111 on May 20, 2020, 09:38:58 AM
That's great I really like your experimentation here!
Title: Re: Fuel injection systems
Post by: Roger B on May 20, 2020, 05:18:50 PM
Thank you all  :ThumbsUp:

The injection will take place into air compressed to hopefully 30 Bar or more so the density will be much higher and the range of the jets much less. This is one of the great unknowns  :headscratch: The injection pressure must be more than the compression pressure but how much more  :thinking:
Title: Re: Fuel injection systems
Post by: Roger B on May 22, 2020, 07:44:14 PM
Starting off on some new mushroom injectors. I have tried to reduce the internal volume as much as possible as the current versions are difficult to prime. If the air space within is much more that the pump volume it is difficult to get the air out.
Title: Re: Fuel injection systems
Post by: Roger B on May 23, 2020, 04:37:47 PM
The rest of the operations went without problems. The bore was reamed to hopefully give a good seating for the needle.

The injectors are gradually getting smaller, I think I will concentrate on the mushroom design. There are too many compromises in the needle version.
Title: Re: Fuel injection systems
Post by: Roger B on May 26, 2020, 05:13:23 PM
Next up was the valves for the injectors. These were made much as before, the longitudinal slide was set true with a couple of trial cuts, the 1.4 mm section was parallel within a couple of hundredths (mm). I have reduced the cone angle from the first experiments to 10° and 15° included to see if I get better results.
Title: Re: Fuel injection systems
Post by: Roger B on May 26, 2020, 06:37:08 PM
The needles were polished as before and then I made some M1.4 nuts from 2mm hex stock. Amazingly none escaped  :wine1:
Title: Re: Fuel injection systems
Post by: Admiral_dk on May 26, 2020, 08:57:06 PM
This are very small parts and you need a very good finish too .... but it looks like you have achived it - does the small lathe make it any easier to do those sizes ?
Title: Re: Fuel injection systems
Post by: Roger B on May 27, 2020, 08:17:11 AM
Thank you Per  :ThumbsUp:

The small lathe certainly makes it easier to see what is going on. If I was using an ER32 chuck and 10mm tooling the parts would be almost completely hidden and it would be difficult to get a micrometer in to measure. It is certainly a different process to using the big lathe (well big to me). I will be running at 2000rpm plus with depth of cut less than 0.2 mm often down to 0.05mm or less but the feed is as fast as I can turn the handle.
Title: Re: Fuel injection systems
Post by: Roger B on May 29, 2020, 05:34:59 PM
The other benefit of the small lathe (and mill) is that to clean them down you hold them over the waste bin and shake them  :)

I put the 10° nozzle together and gave it a try with the test pump. As expected it was just scattered droplets.

https://www.youtube.com/watch?v=9mkeQkbctW0

I then lapped the seating with 2.5 micron diamond paste for a few minutes. I allowed the valve to swing in the hope of making a slightly less sensitive bell shaped seating. With the spring screwed down quite tightly, it would just open with a 1.2kg weight on the end, I got a good pattern and the characteristic 'squeak'

https://www.youtube.com/watch?v=GNTDtZHmCzY

Finally I reduced the spring pressure a bit (not calibrated) and still got a fairly good result:

https://www.youtube.com/watch?v=qj2zM52aiLc








Title: Re: Fuel injection systems
Post by: Vixen on May 29, 2020, 05:40:20 PM
Roger, More incredible watchmaking skills on display with the newer, small injectors.  :ThumbsUp: :ThumbsUp:

The spray pattern looks neat and compact. but I still prefer the flame thrower test.

Stay safe

Mike
Title: Re: Fuel injection systems
Post by: Roger B on May 30, 2020, 06:02:03 PM
Thank you Mike  :)

The 'flame thrower' test takes a little preparation but I tried it on the new 10° and 15° needles. There is a significant difference but I am not sure if it is the design or due to  construction tolerances. The spray patterns are also different so I think I will have to make another 10° injector and see if I get similar results  :headscratch:

https://www.youtube.com/watch?v=46-s4e_2zbk

https://www.youtube.com/watch?v=MMYXSOJmW0Q

https://www.youtube.com/watch?v=yAhQjSBYtsM

Title: Re: Fuel injection systems
Post by: Vixen on May 30, 2020, 07:06:23 PM
Hello Roger,

I am not sure of the scientific value of the flame thrower test but they do look a lot more spectacular. :ThumbsUp: :ThumbsUp:

To me, as a layman, the 15 degree cone appears to reach complete combustion in a shorter distance and time compared to the 10 degree injector. I guess it's because the wider jet entrains more air and so burns quicker.  Any thoughts?

Stay in and stay safe

Mike
Title: Re: Fuel injection systems
Post by: Roger B on June 01, 2020, 06:52:42 PM
Thank you Mike,

I am also very much a layman in this field, my qualifications are in electrical engineering   :zap:  The bit I am struggling with at the moment is the difference between what I see in free air and what is happening at 30 Bar  :thinking: :headscratch:

The needle type injector is trying to keep closed against compression pressure but the mushroom type is trying to open against compression pressure  :thinking:
Title: Re: Fuel injection systems
Post by: Roger B on June 06, 2020, 04:28:24 PM
As mentioned in the diesel thread the helix pump had worn to a level that it would not prime. Wear problems in the mild steel body had always been at the back of my mind and I had started a new pump design using a round element made from silver steel in an aluminium body. This would also allow multi element pumps for future developments. I have some concerns about distortion when hardening as I just have a 'Camping Gaz' blowtorch for heating but we will see what happens.
The pump element is generally made as before but has a couple of O rings to seal the inlet side to the pump body and a locating flat to ensure that the inlet port will line up with the one in the body. I was in two minds as to cut the locating step and then the flat or cut the flat and then the step which left more to hold the element with until the final operation.
After reaming the 1.96mm pin gauge would pass through but the 1.97 would barely enter, much as before.
Title: Re: Fuel injection systems
Post by: Roger B on June 06, 2020, 06:37:12 PM
The element was then moved to the vice for drilling the inlet port and milling the locating flat before moving back to the lathe to turn the locating step. It may have been better to turn the step first  :headscratch: but the finished surface was below the interrupted cut. The element was then heated to middle red and dunked into cold water. The file test suggests that the surface is hardened, I have no idea about the bore  ::) Interestingly I can't even get the 1.95mm pin gauge to enter  :thinking: maybe it's scale or maybe it's some form of growth/distortion???
Title: Re: Fuel injection systems
Post by: Roger B on June 08, 2020, 07:08:45 PM
Next up is the body. This is from the same DIY store 15.5mm aluminium I used for the carburettor project. A the inlet side must be flat to make the seal I had to slightly asymmetrically mill this down to 15mm. The bores are not central to give a space for the control rack so this was set up in the 4 jaw independent chuck. The steps were drilled undersize, reamed and then finished to depth with appropriately sized end mills. The slot for the rack was milled on the Proxxon mill so I didn't have to change the Hobbymat back to milling mode.
Title: Re: Fuel injection systems
Post by: Roger B on June 14, 2020, 08:16:02 AM
After the rack slot was finished I drilled and tapped the inlet port and the retaining grub screw holes. The element was lapped to fit the helix plunger. If it is too worn I can make a new plunger and lap out the bore to suit. The parts were all cleaned in the ultrasonic bath and assembled.
Problem  :( I didn't allow for the effective PCD of the rack so it barely engages with the gear  :toilet_claw:

Having received a 1.99 and a 2.00mm pin gauge I cut the old body in half and carefully deburred the bore. The 1.99mm pin gauge would not go in so the wear was less than 0.01mm. I also noted that that body was one were I had silver soldered a replacement thread in the inlet port so the bore may have been damaged even though it was lapped to 1.98mm.

I could have milled the rack slot deeper and used a shim behind the rack but having received some 15mm square aluminium (rather than the DIY Store 15.5mm with grooves) I decided to make a new body.
Title: Re: Fuel injection systems
Post by: Roger B on July 21, 2020, 07:33:28 PM
Things are going somewhat slowly at the moment. The Board of Directors has just signed off a multi million factory consolidation project. I now have to supply a new electron beam crosslinking facility from an American supplier who I cannot visit. We are trying to use Microsoft Teams etc. but it is very inefficient. In the past everyone involved would have gathered in a conference room with drawings all over the table and on the walls and in a couple of days would have produced an fairly optimised design. Now we are trying to work with multiple A0 drawings on a couple of computer screens  ::)

Back to model engines  :) I cut the slot for the rack on the little Proxxon mill and it all seemed to fit together OK. I received the O rings for the element and that also seemed to fit without ripping chunks off them. The next step was the tappet mounting block. This is fixed to the end of the body with a couple of M2 bolts or studs (tbd). It was bored to 6mm in the lathe and will have a 5mm bore bronze bush to accept the existing tapped (possibly with a new bearing for those who are following the diesel thread).
Title: Re: Fuel injection systems
Post by: Roger B on July 21, 2020, 07:34:25 PM
-
Title: Re: Fuel injection systems
Post by: Roger B on August 02, 2020, 07:32:33 AM
The tappet bush was turned from a length of bronze bar and pressed into place. The locating peg hole was drilled and tapped M2. As the body is larger than the original I can lock it with an M2 x 3 grubscrew. The fixing holes were counterbored 4mm and then taken to a depth of 3mm with an endmill. Next up is the mounting plate.
Title: Re: Fuel injection systems
Post by: Roger B on August 02, 2020, 07:51:18 AM
Before I changed to milling mode I turned a pair of 10mm dia 15mm long aluminium spacers to fit the pump to the diesel crankcase. When I made the body I had not cut the recess for the element deep enough so the inlet port did not quite line up. I decided to take out the 0.5mm in the mill (it was originally done in the lathe). The body was centred and I bought the 8mm end mill into contact using the quill. The quill was then locked and the 0.5mm cut was taken using the Z feedscrew.
As I was in milling mode I cut the 3mm slot in the mounting plate for the rack adjuster. With an ER25 chuck and a 3mm short cutter you can't really see what is going on  ::)
Title: Re: Fuel injection systems
Post by: Roger B on August 05, 2020, 06:25:54 PM
I put it all together for a trial fitting. Unfortunately due to a build up of tolerances there was a 1mm gap between the tappet roller and the cam  ::) As the Hobbymat was still in milling mode I was able to elongate the slots so everything lines up. The top spacer also fouls the locking grub screw for the tappet guide pin so I need to turn down the middle a bit.

Whilst looking for something else I discovered that the GM 5.7L diesel engines used a mushroom type injector. This was called a poppet injector and so far I have only found limited details. In one scanned copy of a GM service manual there is a poor quality drawing. Like the Lanz Bulldog injector it has a helical section to induce swirl in the fuel spray and seems to have a very shallow angle seating. I will have to ask some American colleagues if they can find me a discarded one I can dismantle and investigate.
Title: Re: Fuel injection systems
Post by: Roger B on September 01, 2020, 06:42:38 PM
I fitted the new injection pump and after some effort primed it. Unfortunately I couldn't get any good results from the injectors  ::) I tried again with the test pump and got the same results  :headscratch: When I started up the horizontal engine with petrol injection it also did not run so well  :thinking:
I think that the brass body for the nozzle is not good enough. They work fine when initially lapped but are rapidly hammered or eroded. The first needle injectors had brass nozzles to deal with thermal expansion but I think that I need to try some stainless steel nozzle for better resistance. The needles/pintles are hardened and should not be a  problem.
Title: Re: Fuel injection systems
Post by: Don1966 on September 01, 2020, 07:09:21 PM
I can say one thing about you Roger you are persistent. I been follow quietly and very interested in your thread. Have you tried a vain type fuel pump? Since Centrifugal force comes into play they make a good seal. The ones I am familiar with also have a relief valve since they are positive displacement pumps. Just me rambling.......


Regards Don
Title: Re: Fuel injection systems
Post by: Roger B on September 02, 2020, 05:22:35 PM
Thank you for your interest Don  :ThumbsUp: I know there are a few people following in the background hoping I can make this work. I will keep trying, even if it doesn't work I have learnt a lot  ::)

I am aware of sliding vane pumps as vacuum pumps on our accelerator but don't know them as pressure pumps. I will have to do some research. As I have said before all comments and ideas are welcome, I am just making this up as I go along  :headscratch:
Title: Re: Fuel injection systems
Post by: Roger B on September 02, 2020, 08:02:14 PM
I drilled the clearance holes and then drilled the seating bore 1.35mm and reamed it 1.40mm. The different needle depths between the new SS nozzle and the original brass one were interesting. The brass nozzle seating has sunk somewhat  :thinking:  Next I milled some spanner flats on the Proxxon. If the first trial is good I will try to find some 8mm SS hex bar. Now I need to lap the seating and put it all in the ultrasonic bath.
Title: Re: Fuel injection systems
Post by: Vixen on September 02, 2020, 08:25:47 PM
Hello Roger,

You deserve a big prize for persistence.  :praise2:

That last photo showing the newly completed injector against the background drawing, suddenly brings meaning to all the machining operation photos. I guess that if you live in Switzerland, you are bound to pick up on then their watchmaking traditions.

Keep up the good work,  especially on the SU.

Mike
Title: Re: Fuel injection systems
Post by: steamer on September 02, 2020, 09:34:07 PM
Looking good Roger!    Yes  you get a prize for persistence, that's for sure!

Dave
Title: Re: Fuel injection systems
Post by: Roger B on September 23, 2020, 08:10:18 PM
Thank you all for your support  :) This is very much a long term project  ::)

I lapped the valve into the nozzle with 1 micron diamond paste and gave the system a go on the test pump with alcohol. The pattern looks good without any individual jets. I hope to get a chance to try this injector on the diesel this weekend (supposed to be bad weather).
Title: Re: Fuel injection systems
Post by: Vixen on September 23, 2020, 08:14:36 PM
Ha ha. It's  the old psychological inkblot tests again.

Nice pattern :ThumbsUp:

Mike
Title: Re: Fuel injection systems
Post by: Roger B on September 26, 2020, 03:13:57 PM
The 10° needle tended to jam, I guess it's more a locking taper than a self releasing one. I lapped the 15° needle into the ss nozzle which seemed to work better. I had a chance for a quick trial outside which was rather smoky but I think I was getting proper combustion rather than running on piston blow by.

https://www.youtube.com/watch?v=U2iddDkIWOY

There is still plenty of clag dripping from the exhaust drain  ::) I need to find a better test area for this engine as it is rather antisocial. Hopefully it will clean up as I get better combustion.
Title: Re: Fuel injection systems
Post by: Brendon M on October 06, 2020, 06:19:38 AM
Hello Roger, it's been a while since I've been on the forum.

I feel somewhat bad as I've been aware of the GM poppet style injectors for quite some time, I could have told you sooner.

Are you familiar with the engines in this thread on the smoke stak forum?

https://www.smokstak.com/forum/threads/scratch-built-diesel.50410/

Keep up the good work!

Cheers,
Brendon
Title: Re: Fuel injection systems
Post by: Roger B on October 06, 2020, 08:14:14 PM
Welcome back Brendon  :ThumbsUp: I hope Jo has been able to sort out your access issues.

I am aware of the engines you have mentioned and also of Lucas poppet (mushroom) injectors. I started with needle type injectors as they were used on my prototype engines and I hoped I could scale them down. Sometimes nature is hard to scale  ::)
Title: Re: Fuel injection systems
Post by: Roger B on October 25, 2020, 07:59:34 PM
Making some new needles for the mushroom injectors. I will make a 15° one to compare with the one I have made already and a 20° one to see the difference. They are turned from 2mm silver steel so the cones can be hardened. Turning speed is around 2500 rpm with an aluminium tip.
Title: Re: Fuel injection systems
Post by: Admiral_dk on October 25, 2020, 09:31:18 PM
Not exactly easy to get them that long, slim, precise and with good finish ....

I know I can't do it with what I got - but 'cheating' is also acceptable - like using a hone to get the required finish and exact diameter .... so that's what I do  ;D
Title: Re: Fuel injection systems
Post by: Brendon M on October 26, 2020, 11:16:36 AM
Not exactly easy to get them that long, slim, precise and with good finish ....

I know I can't do it with what I got - but 'cheating' is also acceptable - like using a hone to get the required finish and exact diameter .... so that's what I do  ;D

I agree Admiral_dk, that looks like it would be a difficult operation... wow
Title: Re: Fuel injection systems
Post by: Roger B on October 29, 2020, 08:06:33 PM
Thank you both  :ThumbsUp:

If this design works it is not so complicated. The surface finish on the needle is not so important and the cone will be lapped in after hardening. I thought about keeping everything precise and concentric (hard) but wondered if I gave the needle a bit of freedom I could lap a sort of bell shaped curve as the seating which would be much simpler. After turning I hardened the cones and then have hopefully lapped them into the bodies with 1 micron diamond paste. There seems to be an even lapped area but the real test will be with fuel after a dip in the ultrasonic bath.
Both bodies and needle are marked so they can be kept as pairs.
Lapping is interesting as in theory the harder component receives more abrasion as the abrasive particles are imbedded in the softer material. Hopefully the stainless steel nozzle is not much softer than the needle. The earlier versions with brass and hardened silver steel may have had more problems  :headscratch:  ::)  :toilet_claw:
Title: Re: Fuel injection systems
Post by: Brendon M on October 30, 2020, 11:42:03 PM
Hello Roger, I look forward to seeing the test results :)
Title: Re: Fuel injection systems
Post by: Roger B on November 02, 2020, 07:57:32 PM
Thank you Brendon  :ThumbsUp:

The trial were quite interesting  ::) I checked the load on the injector springs which was more than my 1.2kg test weight, so with a 1.4mm bore more than 90 bar. The new nozzles tended to give a single jet but the previous version where I had ground and polished the cone gave a good spray with the characteristic noise. With a 2.5kg load on the test pump the nozzle wouldn't open. This equates to around 90 bar which matches the opening pressure being nearer 100 bar. the original nozzle used in the last engine trial:

https://www.youtube.com/watch?v=aA9N_aqstOY

One of the new nozzles:

https://www.youtube.com/watch?v=yNZc0OVarIQ

Title: Re: Fuel injection systems
Post by: Don1966 on November 03, 2020, 02:36:19 AM
Still with you Roger...... :ThumbsUp:    :Love:


 :cheers:
Don
Title: Re: Fuel injection systems
Post by: Roger B on November 03, 2020, 08:12:37 PM
Thank you Don  :ThumbsUp:  :wine1:  I am learning a lot and will hopefully be able one day to offer a solution for small fuel injection systems  :headscratch:  :old:

As grinding the needles before lapping seems to be important I ground and polished the 15° and 20° needles as I did before and will lap them into the respective nozzles and make some more trials. I think that the compression pressure and the injection pressure that I am reaching is sensible, I now have to ensure good atomisation and find a new test area until I can reduce the smoke and clag (is clag just an English word or is it generally understandable?)
Title: Re: Fuel injection systems
Post by: Roger B on November 10, 2020, 05:17:30 PM
I lapped the two new nozzles with 1 micron diamond paste and gave them another swim in the ultrasonic bath. They and the previous stainless steel nozzle were set to open at more than 1.2kg load and then then checked with the hand test pump. All tests were using cooking alcohol.

Original 15°:

https://www.youtube.com/watch?v=A2oiODI8HA0

New 15°:

https://www.youtube.com/watch?v=883pMDXYUvM

New 20°:

https://www.youtube.com/watch?v=fNCy_J4aUVg

Only the original had the characteristic 'creak', the 20° seemed still to give a side squirt. More to think about and learn  :thinking:

After this I set them up on the engine for an output check and to see how they sprayed at higher speed (battery drill 550 rpm).
Title: Re: Fuel injection systems
Post by: Brendon M on November 11, 2020, 11:44:34 AM
 :help:Hello Roger, for me at least, clag has always been a type/brand of glue :)

Just to clarify, the original 15 degree injector was needle based, and the new is the cone (poppet) injector?

I have forgotten, were your engines direct injection? *edit* just went and skimmed the 20cc 2 stroke diesel thread, it would appear to be direction injection. Reason I bring it up is I think the current spray pattern would suit indirect injection with swirl chamber - assuming I understood your post, of course.
Title: Re: Fuel injection systems
Post by: Roger B on November 11, 2020, 05:05:06 PM
Hi Brendon,

All the injectors in this series are poppet type. I was wanting to see if the results are reproducible. The engine is direct injection but as I understand the idea behind the prototype design it is fairly high swirl. The angled ports and coned piston should produce rotation in one plane  and as the piston reaches TDC the air in the anulus is forced into the central cylindrical combustion chamber producing swirl in the other plane.
Title: Re: Fuel injection systems
Post by: Roger B on November 14, 2020, 05:31:48 PM
I took the engine into the welding bay at work and had another play. The injection timing seems quite critical so I need to work on a better adjustment system  :headscratch: The three stainless steel nozzles all reacted much the same. I got a short burst of firing which kicked the drill out and then it stopped. As things warmed up I got the impression it was running longer, may be 5 seconds. This is one test, drill in the right hand camera in the left. I like the smoke ring at the end  :)

https://www.youtube.com/watch?v=Iqg5QoRzw9Q

Title: Re: Fuel injection systems
Post by: Roger B on February 21, 2021, 11:24:31 AM
I wanted to check/improve the nozzles before I tried the diesel again. The initial results were much as before. The first 15° stainless steel nozzle gave reasonable results with a 'creak' the other two were not so good.

https://www.youtube.com/watch?v=EEaA5kEaFOY

I decided to try some additional lapping of the seatings as before. All three had around 1/2 hour of lapping with 1 micron diamond paste followed by a clean up in the ultrasonic bath. The results were somewhat disappointing. The first 15° nozzle was about the same the second 15° and the 20° nozzles were worse  :headscratch:

https://www.youtube.com/watch?v=gTaJL29Ywac

I carefully checked all three nozzles to try and determine why one worked better than the others  :thinking: Eventually I found the difference  :) The spring seating recess in the body of the first  nozzle was 2.4mm diameter, in the other two it was 2.5mm. As the spring is ~1.4mm ID and ~2.4mm OD it was acting as a guide for the first unit. My thoughts about allowing the needle to float a bit and having a bell shaped seating were obviously not good  :toilet_claw:

I now need to work out how to form a guide section on the 1mm diameter section of the nozzle which will allow the fuel to pass. It may be easiest to leave the needle at 1.4mm for longer and mill/grind some slots for the fuel to flow through. Off to the drawing board.
Title: Re: Fuel injection systems
Post by: Admiral_dk on February 21, 2021, 07:42:52 PM
At least you found out why  there is a difference  :ThumbsUp:

One must admire your patience / perseverance regarding this project  :praise2:

They say that the more tribulations - the bigger the satisfaction when you succeed -> I really hope that you get reason for a big happy dance  :cheers:
Title: Re: Fuel injection systems
Post by: Don1966 on February 21, 2021, 09:08:36 PM
At least you found out why  there is a difference  :ThumbsUp:

One must admire your patience / perseverance regarding this project  :praise2:

They say that the more tribulations - the bigger the satisfaction when you succeed -> I really hope that you get reason for a big happy dance  :cheers:
Yep agree awesome work keep it up!

Don
Title: Re: Fuel injection systems
Post by: Roger B on March 06, 2021, 05:43:31 PM
Thank you both for following with this long term project  :ThumbsUp:

I have started making a needle for the mushroom injectors with a guidance section. Most of it is as before but the 1.4mm section is extended by 4mm and there are 4 0.2 x 0.5mm slots milled in this section to allow the fuel to flow through. Photography with standard equipment starts to get difficult at these sizes  ::)
Title: Re: Fuel injection systems
Post by: Chipmaster on March 06, 2021, 05:55:21 PM
Very skilful Roger, wish I could machine small diameters like that.

Andy
Title: Re: Fuel injection systems
Post by: Roger B on March 12, 2021, 08:23:00 PM
Thank you Andy  :ThumbsUp:  :)

A lot of it is to do with thinking about the scale you are working in. Most 'industrial' lathes have a better intrinsic accuracy than the cheap (GBP 700???) little Proxxon FD150  I am using. Could I make these parts on a Hardinge or Schaublin , probably not  ::) In the first case you can't get close to see what is going on and in the second case the slides are so heavy you have no feel for the cut.  If I wanted to turn a piece of 20mm silver steel 300m long down to 14mm without a travelling steady I would probably use a speed between 250 and 500 rpm and a depth of cut between 0.5mm and 1mm. If I reduce this to 1/10th (what I am doing here, 2.0mm down to 1.4 mm) I will use a speed of 2000rpm or more and a depth of cut 0.05 to 0.1mm. The cutting tool also has to be sharp so I use aluminium finishing inserts.

The tip of the needle was hardened, ground and polished ready to be lapped into the body.
Title: Re: Fuel injection systems
Post by: Chipmaster on March 12, 2021, 08:47:28 PM
Thanks for that Roger.

Andy
Title: Re: Fuel injection systems
Post by: Roger B on March 14, 2021, 03:17:08 PM
The needle was lapped with some 1 micron diamond paste and then cleaned in the ultrasonic bath along with the parts of the injection pump for my two cylinder engine. Next it was assembled and tested with cooking alcohol. It has the characteristic creak and a spot about 30mm diameter at 100m, so a spray angle of around 16°  :)  :)  :wine1:

https://www.youtube.com/watch?v=HGLnoBil0tQ

I will make a 20° version next to see if I can repeat the results.
Title: Re: Fuel injection systems
Post by: Roger B on March 25, 2021, 08:46:46 PM
The 20° needle was started in the same way. I tried to take a video clip of turning the needle down to size:

https://www.youtube.com/watch?v=OTLVDq7Za4Y

Unfortunately this nozzle wouldn't seal even after significant lapping  :( This may be due to the effect on the body of the previous floating needle  :thinking: It may be better to start again from scratch, it doesn't take long now.

If Andy is still following, another critical point is getting the tool on centre. If you are turning a 50mm bar and the tool is 1mm low it will still cut reasonably well. If you are turning a 2mm piece and the tool is 1mm low it will miss completely  ::)

Title: Re: Fuel injection systems
Post by: Chipmaster on March 26, 2021, 05:07:38 PM
I'm still following Roger,  :ThumbsUp:

Andy
Title: Re: Fuel injection systems
Post by: Zephyrin on March 26, 2021, 05:21:39 PM
always interesting to follow, to turn and to mill at such a small size...
I wonder how far "conventional" machining with machine tools can go down...what is the smaller limit?
Title: Re: Fuel injection systems
Post by: Admiral_dk on March 26, 2021, 10:13:17 PM
I'm in the middle of taking my MC apart. It just turned 17 and 100000Km. so in need of a bit of TLC ....
This evening I got the throttle bodies of the engine and could see the four tiny holes in each injector and this made me remember that they are LASER drilled at the factory .... and already oldschool - the new ones are up to twelve much smaller holes in them  :o

I'm pretty sure I will continue to follow this thread until completion .... and I really wish that you succeed Roger - simply because it would be nice and the rest of us will be enlightened along the way  :cheers:
Title: Re: Fuel injection systems
Post by: Roger B on June 08, 2021, 05:27:11 PM
Thank you for your interest and support  :)

Zyphyrin, I think that Dave (Steamer) did some very fine milling with a conventional machine at work using a barely visible cutter but I can't find the thread at the moment.

The trials with the diesel and the two cylinder engine have highlighted several problems that I will try and work through on here.

- The first one is the inlet port on the separate element pump. If the cone on the tapping drill goes to deep it will destroy the O ring seal. I have ordered some 4.5mm endmills to try rather than a drill which should reduce that risk.

- The delivery valve seating builds up some scale when hardening the pump element. I lap out the bore and will have to try the same with the seat. A piece of 4mm brass rod should work.

- The dynamic forces on the injection pump plunger are quite high. The ball race cam followers on the diesel broke, the bronze follower has spread, I think solid hardened steel is the next phase. The stroke adjuster on the two cylinder engine is also affected.

Lots to do and think about  ::)
Title: Re: Fuel injection systems
Post by: Roger B on June 16, 2021, 06:39:40 PM
The lap was crosscut with two offset small slots to hold the 5 micron lapping compound and faced off. Several boring evenings were spent lapping the delivery valve faces for the diesel and the two cylinder petrol engine. Both look ok but I need something different to get good photographs  ::) I was surprised  how much the lap had worn  :headscratch: maybe I should have refaced it more often  :thinking:

Next I will make a new body for the two cylinder engine pump and clean them all in the ultrasonic bath.
Title: Re: Fuel injection systems
Post by: Admiral_dk on June 16, 2021, 10:46:03 PM
Re: Lap wear - as far as I remember it's the harder of the two materials that will be worn when you use a lap ... Why - the grinding particles imbed themselves into the softer of the two materials (if it can), and therefor cuts the hard material ....
So I guess that if both materials are hard it becomes unpredictable where the cutting happens ....
Title: Re: Fuel injection systems
Post by: steamer on June 17, 2021, 01:01:46 AM
Thank you for your interest and support  :)

Zyphyrin, I think that Dave (Steamer) did some very fine milling with a conventional machine at work using a barely visible cutter but I can't find the thread at the moment.

The trials with the diesel and the two cylinder engine have highlighted several problems that I will try and work through on here.

- The first one is the inlet port on the separate element pump. If the cone on the tapping drill goes to deep it will destroy the O ring seal. I have ordered some 4.5mm endmills to try rather than a drill which should reduce that risk.

- The delivery valve seating builds up some scale when hardening the pump element. I lap out the bore and will have to try the same with the seat. A piece of 4mm brass rod should work.

- The dynamic forces on the injection pump plunger are quite high. The ball race cam followers on the diesel broke, the bronze follower has spread, I think solid hardened steel is the next phase. The stroke adjuster on the two cylinder engine is also affected.

Lots to do and think about  ::)

It's around somewhere....I'll dig it up if anyone's interested.....Lapping and grinding can be non-deterministic..meaning that both the part and the tool change size as they interact.....the good news is it's pretty repeatable...

Been watching this thread....glad to see you sticking with it Roger....that's no easy feat!.....Detroit Injectors have a total tolerance of 33 millionths on diameter...for the plunger anyway....

Dave
Title: Re: Fuel injection systems
Post by: steamer on June 17, 2021, 01:15:26 AM
.001 end mill.....

https://www.modelenginemaker.com/index.php/topic,8860.0.html
Title: Re: Fuel injection systems
Post by: Roger B on June 20, 2021, 03:19:40 PM
Thank you both  :ThumbsUp:

In theory the hardened steel body should have worn faster that the brass lap but it there was only motion in one plane it wasn't really true lapping. The real test is if they seat better when put back together.

As the weather here is currently hot and sticky (supposed to be a big storm tonight) I cut the blank for the body with the bandsaw rather than by hand. It is made in much the same way as before with a few more dimension checks. The fixing screws were moved 0.5mm so that they didn't break into the bore. The inlet valve port was finished with a 4.5mm end mill rather than a drill to avoid the cone breaking into the bore for the element as happened last time stopping it sealing properly.
Title: Re: Fuel injection systems
Post by: Roger B on June 25, 2021, 05:41:41 PM
So the slot for the stroke adjusting wedge was cut with a 4mm (throwaway) endmill. The improvement in the positions of the various holes is quite obvious and after a good swim in the ultrasonic bath the petrol injection pump went together with very good alignment. Hopefully that means it will all seal under the 0.8-1.0 Bar from the feed pump (If the petrol feed pressure is too low it vaporises on the suction stroke).
Title: Re: Fuel injection systems
Post by: Roger B on August 09, 2021, 07:20:00 PM
The next step is to try a 10° nozzle for the diesel. This was made much as before with a quick reflection over various trial needles and the evolution of injectors from my first experiments.

There is also a drawing of my current design and a picture of the Oldsmobile injector this design is based around.
Title: Re: Fuel injection systems
Post by: Minh Thanh on August 13, 2021, 03:24:45 PM
Hi Roger !
Thanks !
 I will try with this injector
Here is my injector design, if you are interested !
Title: Re: Fuel injection systems
Post by: Roger B on August 15, 2021, 04:48:01 PM
Thank you Thanh  :)

What CAD package do you use? All my drawings are .DWG (AutoCad, DraftSight) which I am happy to share if you can read them.

With all my injection components I have tried to minimise the number of joints and possible places where air could be trapped. The needle type injectors will always leak a little past the needle shaft which is not good with petrol (gasoline) injection. I moved to the mushroom (poppet, pintle) type to avoid this problem. Don Comstock who has made some working diesels (W7CJ on YouTube and Flickr seems to be his son) appears to have used cut down Oldsmobile poppet injectors.
Title: Re: Fuel injection systems
Post by: Minh Thanh on August 16, 2021, 10:25:17 AM
Hello Roger !
I have autocad, but usually use inventor
About adding 1 or 2 joints: I think - the way I think, of course - it doesn't matter, and it doesn't hold any extra air.

"The needle type injectors will always leak a little past the needle shaft which is not good with petrol (gasoline) injection."

You are correct, even though I try to do it as best I can, always leak a little past the needle shaft
I will design the injector like yours, I will try both ways

Thanks !
Title: Re: Fuel injection systems
Post by: Roger B on August 19, 2021, 07:09:40 PM
Full size diesels with needle injectors always have piping to feed the fuel that leaks past back to the tank.

I made a new body for the 10° injector and cleaned it up in the ultrasonic bath. when assembled on the test rig it made a very satisfactory 'creak' and gave a tighter patten that the 15° nozzle from the last trial. To open the nozzle required more than 4kg on the 2mm plunger so well over 100 Bar.

10°

https://www.youtube.com/watch?v=VlOvH4qkcD0

15° from the last trial

https://www.youtube.com/watch?v=bXWBzXdXy08
Title: Re: Fuel injection systems
Post by: Admiral_dk on August 19, 2021, 11:05:45 PM
Sound good - but it's very hard to tell how fine the 'atomizing' is .... and as that has a very direct influence on the end result .... I don't think that you (and the rest of us) will know before you have it running in one of your engines  :cheers:

I will admit that there are more factors in the engine as you already has discovered.
Title: Re: Fuel injection systems
Post by: steamer on August 20, 2021, 12:42:08 AM
Full size diesels with needle injectors always have piping to feed the fuel that leaks past back to the tank.

I made a new body for the 10° injector and cleaned it up in the ultrasonic bath. when assembled on the test rig it made a very satisfactory 'creak' and gave a tighter patten that the 15° nozzle from the last trial. To open the nozzle required more than 4kg on the 2mm plunger so well over 100 Bar.

10°

https://www.youtube.com/watch?v=VlOvH4qkcD0

15° from the last trial

https://www.youtube.com/watch?v=bXWBzXdXy08

That's amazing Roger!    I do hope you could do a show and tell on how you  make those!....Tolerances must be tight!....

Dave


PS>...I'll need 13 and the pump......1/4 scale.....
Title: Re: Fuel injection systems
Post by: bent on August 20, 2021, 06:16:21 PM
I am always in a little bit of awe as I read your reports, Roger.  You are one persistent and methodical guy!
Title: Re: Fuel injection systems
Post by: Minh Thanh on August 21, 2021, 03:11:27 AM
Hi Roger !
I'm making an injector similar to yours
I have a question : With the spring so small , can it hold the needle to maintain high pressure in the oil pipe ?
    How to adjust the injector to only inject at a certain pressure range, for example at least 50 bar?
Title: Re: Fuel injection systems
Post by: Roger B on August 21, 2021, 12:44:35 PM
Thank you all  :) I'm still learning but will certainly present a summary when I think I have a realistic solution.

Directly measuring pressures with these small volumes is very difficult so I try to calculate some values. When I assemble a nozzle I adjust the spring load so it just opens with a 1.2kg weight rested on it (nothing very special about 1.2kg, I just happened to have a bar end that weighed that to hand). As the bore of the nozzle is 1.4mm this calculates to around 80 bar opening.

My test pump has a linkage so I can apply force to the plunger with a spring balance. 2.5kg and a 2mm plunger also calculates to around 80 bar. In my last trial with the 10° nozzle I required 4 kg to get the spray in the video which is around 130 bar.
Title: Re: Fuel injection systems
Post by: Minh Thanh on August 21, 2021, 01:04:39 PM
 Roger !
Thanks for the explanation and pictures !  :ThumbsUp:
Title: Re: Fuel injection systems
Post by: Roger B on August 21, 2021, 07:16:36 PM
No Problem, I am happy that you are trying to do this as well  :)  :)  :)

Title: Re: Fuel injection systems
Post by: Minh Thanh on August 26, 2021, 10:12:42 AM
Hi Roger !
A copy of your injector   ;D
Title: Re: Fuel injection systems
Post by: cnr6400 on August 27, 2021, 12:00:41 AM
 :ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:
Title: Re: Fuel injection systems
Post by: Roger B on August 27, 2021, 07:16:41 PM
Looks good  :ThumbsUp:  :ThumbsUp: Have you tried it yet?
Title: Re: Fuel injection systems
Post by: Minh Thanh on August 28, 2021, 05:03:30 AM
Cnr6400 , Roger B !
Thanks !

I tested it with compressed air, it's completely sealed,
Due to the epidemic situation and travel restrictions ... I am not able to buy small tubes and pressure gauges to adjust.
I really hate it but I can't do anything else
Title: Re: Fuel injection systems
Post by: Roger B on September 18, 2021, 07:50:54 AM
I have been reviewing my work on fuel injection and have come up with a few problem areas to investigate:

Testing fuel:- I have been using cooking alcohol as a test fuel as it does not smell. Unfortunately it is not so compatible with the Viton seals and tends to absorb moisture causing some corrosion.

Delivery valves:- Although I have tried to improve the finish of the seatings I still don't think they are good enough.

Dead space:- There is too much deadspace between the top of the plunger at full stroke and the delivery valve making it difficult to get the air out of the system.

To resolve the first problem I purchased some lamp oil which is more like Diesel in consistency but doesn't smell. It also doesn't evaporate like the alcohol does and makes the 'ink blot' tests longer lasting. I tried a quick test with 100 strokes from the test pump which gave 1cc. The pump plunger is 2mm diameter and the stroke is around 4mm which gives a theoretical volume of 1.2cc so close enough.

https://www.youtube.com/watch?v=Ix2ve6jfvDk

I then did another quick trial with the helix pump on the diesel. 100 strokes (500rpm for 12 seconds) gave 0.5cc so as the theoretical stroke is 2mm again not too far away from reality. I will do a more controlled range of tests on the helix pump to look at linearity and speed dependence.
Title: Re: Fuel injection systems
Post by: Vixen on September 18, 2021, 01:08:09 PM

To resolve the first problem I purchased some lamp oil which is more like Diesel in consistency but doesn't smell. It also doesn't evaporate like the alcohol does and makes the 'ink blot' tests longer lasting. I tried a quick test with 100 strokes from the test pump which gave 1cc. The pump plunger is 2mm diameter and the stroke is around 4mm which gives a theoretical volume of 1.2cc so close enough.

Hello Roger,

Good to have a calibration test. Is the lamp oil you used the same a Colemens lamp fluid? I believe Colemans is naptha based and you can run engines on it. It's quite expensive, but as you live in Switzerland so you will be used to expensive.

Mike
Title: Re: Fuel injection systems
Post by: Roger B on September 18, 2021, 05:10:38 PM
Hi Mike,

As I understand Colemans is equivalent to the Alkylate Benzin (Petrol) that I use for my spark ignition engines (~CHF20 for 5 Litres at the local agricultural merchants). This lamp oil is a much heavier fraction somewhere between kerosene and diesel but virtually smell less  (~CHF3.60 for a Litre again at the local agricultural merchants).
Title: Re: Fuel injection systems
Post by: dieselpilot on September 18, 2021, 08:26:20 PM
I'm fairly certain diesel calibration fluid is essentially lamp oil or slightly wider, heavier fractions. Also makes for excellent cutting fluid for aluminum.
Title: Re: Fuel injection systems
Post by: Roger B on September 20, 2021, 05:03:56 PM
I have played a bit more with various pump strokes and speeds:

At 1200 and 2800 rpm the pump response is fairly consistent and linear. At 500 rpm the output has dropped off considerably.

There is another problem  ::) The metering helix is too narrow so at the nominal zero output and when turned beyond zero there is a significant delayed injection. I have tried to display this, the helix is 'unrolled' horizontally and the plunger moves vertically past the port. To the right of the diagram is the normal injection, to the left is this 'parasitic' injection. I will re-phase the rack to avoid going past 'stop' and try again.
Title: Re: Fuel injection systems
Post by: Roger B on September 21, 2021, 07:24:50 PM
After setting the rack to my theoretical zero I ran a full trial at 2800rpm and a couple of points at 500rpm. The 2800 rpm curve shows the mechanical stroke limit. The calculated fuel requirement is around 0.002cc for full output.
Title: Re: Fuel injection systems
Post by: steamer on September 22, 2021, 12:57:27 AM
Now I assume the volume should be linear with rpm....considering the volume pumped, that's AMAZING!

That's coming along nicely!   :cheers: When do I place my order for the 917?   8)
Title: Re: Fuel injection systems
Post by: Admiral_dk on September 22, 2021, 11:24:41 AM
I agree that it looks great  :ThumbsUp:

But to be a spoil sport - try to do a measurement with the "throttle lever" at the same position and do the plot for a big number of different RPM's - like 500, 1000, 1500, 2000, 2500, etc.  Or maybe better 500, 750, 1000, 1250, 1500, 1750, 2000, etc.

I expect that the liniarity increase with RPM until you get close to max pumping capacity for that position of the lever. Lower RPM will provide longer time for the fuel to leak past pumping parts ....

Why ...?... well if this is for a gasoline engine, you should have an injection that matches the throttle position, to get the right metering - if it's for your Diesel project it matters less.

Nice progress none the less  :cheers:
Title: Re: Fuel injection systems
Post by: Roger B on September 23, 2021, 05:13:32 PM
Thank you both  :)

I made some initial trials with various speeds but my easy choice is limited. my battery drill/screwdriver gives 500 rpm, my big SDS gives 1200 rpm and the mains drill I use for starting gives 2800 rpm. The difference in output between 1200 and 2800 rpm is a few percent. With 500 rpm the output drops to around half (note the different scale on the 500 rpm graph).

I intend to make a new, more compact version, of the helix pump and am currently awaiting some MOD 0.4 rack and 20T gears. The current helix plunger was the first successful one I made and has seen some abuse. I will make a new one with a wider grove for the new pump.
Title: Re: Fuel injection systems
Post by: Admiral_dk on September 23, 2021, 10:38:54 PM
OK - this last graph look better than I feared - you are doing very well, from what I would expect to be Idle for most engines up to a rather big size off cc's  :praise2:
Title: Re: Fuel injection systems
Post by: Roger B on September 26, 2021, 12:01:35 PM
The next step was too look at leaking delivery valves and injectors which I think is causing the loss of prime in the petrol systems. When I stop the engine heat soaks into the injector and pipework causing expansion of the fuel. If it can leak out air will be sucked back in as things cool.

I set up the test pump with the 20° injector I have been using on the twin. It gave a bad spray pattern and after just standing some 10s of seconds a drop started to appear from the nozzle. This is with a head of less than 0.5m  ::) The older style 30° injector I have been using on the horizontal engine did much the same. The 15° injector used in the last diesel trial did not leak at all  :)

Next I tried to test the delivery valve. I made an adaptor so I could pressurise the pump inlet with my foot pump to around 5bar and fitted a lower pressure gauge to the delivery valve union. With 5bar on the inlet there was around 0.5bar at the delivery valve as soon as I removed the pressure from the inlet the delivery valve pressure dropped to zero.

https://www.youtube.com/watch?v=weNjKGBM1DQ
 
The second test was just to pressurise the inlet. The pressure would slowly leak away, but if I moved the plunger forward to block the inlet port the leakage stopped.

Finally I removed the delivery valve to check that the spring compression was about as planned, which it was.

Lots of things to think about  :thinking:  :wine1:
Title: Re: Fuel injection systems
Post by: Roger B on October 07, 2021, 05:01:26 PM
While thinking about a solution to the delivery valves I decided to make a new injector and a new needle for the 20° injector.

The injector nozzle and body were made as before but I made a small change to the way I turned the needle. Even with a 0.5mm centre drill there is very little in a 1.4mm thread to take the centre so I made a small brass bush with a 1.4mm hole to support the needle when turning down the shank. As I wanted two identical 15° needles I used both ends of the piece of 2mm silver steel.
Title: Re: Fuel injection systems
Post by: Roger B on October 07, 2021, 05:03:02 PM
Next steps mill the feed slots, harden the cones, grind and lap.
Title: Re: Fuel injection systems
Post by: RReid on October 07, 2021, 05:26:25 PM
Hi Roger. That is some mighty fine work on those eensy-weensy parts! :ThumbsUp: :popcorn:
Title: Re: Fuel injection systems
Post by: Dave Otto on October 07, 2021, 09:48:21 PM
Yes, nice work on those fiddly parts.  :ThumbsUp:

Dave
Title: Re: Fuel injection systems
Post by: Admiral_dk on October 07, 2021, 10:56:41 PM
I really like your idea about using the bush - as down in those very small dimensions every detail counts  :ThumbsUp:

No way in Hell I could achieve your results (I might be able to learn to do it, but ...).

Crossing fingers that you will be satisfied with the result when you test them  :cheers:
Title: Re: Fuel injection systems
Post by: Minh Thanh on October 08, 2021, 05:17:55 AM
Hi Roger !
Your injector parts are great
Title: Re: Fuel injection systems
Post by: Roger B on October 09, 2021, 08:57:31 PM
Maybe not so great  :(  I milled the flats on the nozzle and then checked the pieces together. I had mixed up two different drawings of the needles and the thinned down part was 5mm too long  :facepalm:

Start again with another piece of 2mm silver steel  ::) This time all looks ok and both needles have been lapped with 5 micron diamond paste  :) Looking at the finish after turning I decided that the grinding and polishing step may not be needed. I will see what happens with the test rig  :thinking:
Title: Re: Fuel injection systems
Post by: Roger B on October 10, 2021, 10:40:09 AM
It looks like the grinding and polishing steps may be necessary  ::) Both the new injectors gave a similar almost sideways spray pattern  :( It was difficult to capture but there is a sort of spray at 45°downwards.

https://www.youtube.com/watch?v=zw6j7jsFvek

It may be that the needle extends further on the new builds as the diameter has not been reduced by grinding or it may be a surface finish effect  :thinking:  :headscratch:

After my mistake reading the drawing for the needles I have produced a new drawing with only the current parts on it to reduce my confusion  :old: It is attached as ACad R12 and PDF
Title: Re: Fuel injection systems
Post by: Roger B on October 12, 2021, 06:51:54 PM
As usual I made the mistake of changing two things at the same time  ::) I didn't grind and polish the cones and I went from 1 micron to 5 micron diamond paste. I could feel a distinct ridge on the new needles, whether this was due to removing the machining marks or the 5 micron paste I don't know, but it would cause the sideways spray. I ground and polished both the needles in the same way as before and lapped them with 1 micron paste so I can see if I can repeat the previous result  :thinking:

I also received what I hope is the solution to the delivery valve problem. I ordered two 3mm diamond charged lapping balls from a firm in the US. As these were custom they were not cheap but I will see how they can improve the valve seatings  ::)
Title: Re: Fuel injection systems
Post by: RReid on October 12, 2021, 08:25:13 PM
Roger, your perseverance and attention to detail just boggles my mind! :ThumbsUp:
Title: Re: Fuel injection systems
Post by: bent on October 13, 2021, 06:44:45 PM
Still following.  :popcorn:

Also agree with RReid, admiring your persistence.  Ah well, back to work.  We have finally found a supplier for hydraulic controls who isn't using Covid as an excuse for  :censored: all of our purchase orders.
Title: Re: Fuel injection systems
Post by: Zephyrin on October 14, 2021, 10:53:12 AM

the delicate point to obtain a regular spray could be related to the volume of the filling chamber behind the nozzle, I wonder if this chamber is not filled, the fuel does not form a ring around the rod and will give a tilted jet and not in cone?
Title: Re: Fuel injection systems
Post by: Admiral_dk on October 14, 2021, 12:02:46 PM
Interesting point Zephyrin - but as air is compresable and the liquid isn't - would that mean that when the pressure finally is high enough to open the Injector, that the air will be escaping too ...?

That said - there might be a very valid point about the internal shape behind the valve.

Still crossing my fingers for your succes Roger and may it happen sooner than later.
Title: Re: Fuel injection systems
Post by: Roger B on October 14, 2021, 02:14:04 PM
Thank you all for your interest  :) The problem was due to me changing the way I made the needles. Having ground and polished the cones as usual I got good results.

The old nozzle with a new needle:

https://www.youtube.com/watch?v=WH4rgoxanaE

And the new assembly fitted with a weaker (about half the force) spring. The pattern is still good but it doesn't give the characteristic buzz.

https://www.youtube.com/watch?v=8FJ3QuVLeQk
Title: Re: Fuel injection systems
Post by: Admiral_dk on October 14, 2021, 04:45:23 PM
I like the look of the latter, but honnestly (and please do not use me as a reason for buying this) I could use a fast recording camera and slow-mo playback, to really detailed see the pattern / mist :-[
Title: Re: Fuel injection systems
Post by: Roger B on October 14, 2021, 05:05:56 PM
Thank you Per  :ThumbsUp:

The second one is intended for petrol/Benzine/gas manifold injection. The first one is just a copy of the previous diesel ones to see if they are reproducible.

Nest step sort out the delivery valves  :thinking:
Title: Re: Fuel injection systems
Post by: 90LX_Notch on October 15, 2021, 12:49:49 AM
Great work Roger, stay at it.

-Bob
Title: Re: Fuel injection systems
Post by: Minh Thanh on October 15, 2021, 07:12:12 AM
Roger !
How much diameter pump are you using ?
Title: Re: Fuel injection systems
Post by: Roger B on October 15, 2021, 09:42:31 AM
Hi Minh,

I am using a 2mm diameter plunger. I calculated the theoretical stroke for full power from a 20cc engine as follows:

The density of air is around 1.2kg/m3 so 20 cc of air is around 0.024g. Taking a fuel air ration of 14-1 this would require 0.0017g of diesel fuel. The density of diesel fuel  is around 0.8kg /dm3 so at full output around 2mm3 of fuel would be required. This could be achieved with a plunger of 2mm diameter and a stroke of 1.5mm (plus a bit to allow for leakage).

I have seen the thread on HMEM and am happy for you to quote this.

I have designed the pumps to give 2mm of stroke after the inlet port closes, a total of 3mm. The working stroke is adjusted by the helix which makes it hard to determine what it is in reality. Test measurements have shown the output ranging from less than 1mm3 to 5mm3.
Title: Re: Fuel injection systems
Post by: Minh Thanh on October 15, 2021, 10:01:59 AM
 Roger .
Thank you very much !
And one question : the pump has 2mm , does it create enough oil pressure to pump into the cylinder ?
Title: Re: Fuel injection systems
Post by: Roger B on October 15, 2021, 11:09:08 AM
I need a load of 4kg on the end of the 2mm plunger to open the injector, this calculates to around 100 bar. The compression pressure is around 30 bar so it does inject as the running trials show.
Title: Re: Fuel injection systems
Post by: Minh Thanh on October 15, 2021, 11:21:15 AM
Thanks !
 i'm testing with a 2mm diameter pump, it doesn't seem to generate enough pressure, i'm looking for the cause
Title: Re: Fuel injection systems
Post by: Roger B on October 15, 2021, 12:13:30 PM
With the small plunger any trapped air will stop the pressure building up. It can take me several minutes to get all the air out.
Title: Re: Fuel injection systems
Post by: Minh Thanh on October 15, 2021, 12:43:15 PM
 Thanks !
I plan to reduce the bottom diameter of the piston  4mm, making it about 3  or 2mm, I think this will reduce the amount of fuel, for test the amount of fuel ...
 what do you think ?
Title: Re: Fuel injection systems
Post by: Roger B on October 15, 2021, 12:59:08 PM
The 4mm part is still moving so it will displace the same amount of fuel. Does your 2mm pump work without any pressure? Does it deliver the amount of fuel you would expect? Are you using ball valves? The movement of the ball must be very small with small volumes otherwise it takes too long to reseat.
Title: Re: Fuel injection systems
Post by: Minh Thanh on October 15, 2021, 01:14:37 PM
Roger !
 I drew it wrong,
this is correct, I'm sorry
 I use ball valve
 amount of fuel :  i think it's fine, but the pressure is weak,     
with a 4mm cylinder, I can be sure it's fine, but with a 2mm cylinder I'm not sure
Title: Re: Fuel injection systems
Post by: Minh Thanh on October 15, 2021, 01:33:01 PM
   And one more thought:
I use a 4mm cylinder, but I increase the spring force of the needle
  the needle will open when the pressure is at a higher pressure range, This results in less fuel being injected
  This video is I tried with the above method, the stroke is about 0.8 mm
  (that injector is not very good)
  what do you think ?
  https://www.youtube.com/watch?v=EkhVRjVBeHA
Title: Re: Fuel injection systems
Post by: Minh Thanh on October 27, 2021, 10:44:31 AM
Hi All !
It lives,
although still need to improve, but that's what i need right now

 https://www.youtube.com/watch?v=AZVPeWOeT5Y
Title: Re: Fuel injection systems
Post by: cnr6400 on October 27, 2021, 12:24:11 PM
 :ThumbsUp: :ThumbsUp: :ThumbsUp: well done!  :cheers:
Title: Re: Fuel injection systems
Post by: Admiral_dk on October 27, 2021, 12:35:21 PM
It runs very nicely - stable RPM and sound  :ThumbsUp: :ThumbsUp:

Shame that we can't see the injector and pump in the video ....
So I will have to ask - do you have direct injection or is it into a hot Bulb / PreChamber ?
Title: Re: Fuel injection systems
Post by: Minh Thanh on October 27, 2021, 01:00:00 PM
   cnr6400 !
Thanks !
   Admiral_dk !
At 20 seconds of the video, you can see the pump
I spray directly
 I put a lot of oil in the engine to prevent damage to the pistons and cylinders when the engine warms up ( I'm not sure  ;D ) because I didn't install the water pipes
so when the engine runs it bleeds oil
Title: Re: Fuel injection systems
Post by: Minh Thanh on October 27, 2021, 01:19:21 PM
 Hi Roger !
 I forgot this
Your injectors are pretty good, maybe even better than mine
so just focus on the valve, pump cylinder
  If the pump is ok (creates enough pressure) and the valve is closed I'm sure your engine will be fine!
Title: Re: Fuel injection systems
Post by: Roger B on October 28, 2021, 10:10:55 AM
Congratulations  :praise2: you must be happy with the first runs  :)

I need to find some more time to spend on my engines  ::)
Title: Re: Fuel injection systems
Post by: Roger B on October 31, 2021, 09:50:23 AM
A little more progress  :) I received some MOD 0.4 rack and pinions for a reduced size helix pump. 0.5 is easy to find 0.4 was rather more difficult  :headscratch: I can now confirm the dimensions and finish the design.

I then tried one of my diamond ball laps on the delivery valve of the test pump (I have a fine Email thread titled Diamond Charged Balls). The instruction said use a little light mineral oil and if possible don't apply any side pressure. I used the floating reamer holder and lapped for a couple of minutes at 500 rpm. After cleaning and reassembly there was no leakage and the system held it's prime for several days  :)  :)

Next I will repeat with the pump from the two cylinder petrol engine before moving onto the diesel.
Title: Re: Fuel injection systems
Post by: Roger B on October 31, 2021, 05:43:14 PM
The two cylinder engine ran better with the improved delivery valve so I had a look at the horizontal engine. There was a fuel leak past the delivery valve with only 0.8 bar from the fuel feed pump.

https://www.youtube.com/watch?v=QUn85ryqzMI

I removed and dismantled the pump. There was a significant amount of rusty clag in the inlet port and delivery valve, probably due to the high moisture content of the cooking alcohol I used to use for trials. After lapping the delivery valve seat I cleaned it all in the ultrasonic bath and reassembled, replacing the delivery valve spring as there were signs of corrosion  ::)
Title: Re: Fuel injection systems
Post by: Roger B on October 31, 2021, 08:06:26 PM
Seems to run well  :) 1000-4000 rpm

https://www.youtube.com/watch?v=2cAJzv1CCb0
Title: Re: Fuel injection systems
Post by: Kim on October 31, 2021, 08:44:45 PM
Wow!  I'll say!  That runs GREAT, Roger!   :ThumbsUp: :popcorn:

You have a daunting number of experiments, time, and effort into this!  What's your next step?  Are you satisfied?  Or is this still just one more step in your road toward perfection? :)

Kim
Title: Re: Fuel injection systems
Post by: 90LX_Notch on October 31, 2021, 09:57:47 PM
Outstanding.  Congratulations Roger, this has been such an impressive project.  It runs beautifully.

-Bob
Title: Re: Fuel injection systems
Post by: Admiral_dk on October 31, 2021, 10:10:17 PM
So now you have two engines running great with your system   :praise2:   :praise2:

I was almost thinking that you really had it all nailed until I realized that this is also running on petrol right now ....

Are all the rack bits for the diesel injector ?
Title: Re: Fuel injection systems
Post by: Roger B on November 02, 2021, 05:29:31 PM
Thank you all for your support  :)  :)

I don't think I can do much more with this version of this engine. The throttle response is excellent, I will also make some load trials to compare with the best carburettor version which may require a better radiator.

I am not yet happy with the twin. I think that the wedge stroke adjuster has too much mass/inertia for the speed range. The rack pieces are to make a smaller version of the helix control pump I am using on the diesel so I ca see if that will work better  :thinking: The biggest problem may be that the injected volume is 1/4 the volume of the horizontal so the pump working stroke is around 0.15-0.2mm. I am looking at a 1.5mm bore pump but that changes every component on the way  :headscratch:  ::)
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