Author Topic: Fuel injection systems  (Read 41098 times)

Offline Roger B

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Re: Fuel injection systems
« Reply #180 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  :)
Best regards

Roger

Offline Roger B

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Re: Fuel injection systems
« Reply #181 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.
Best regards

Roger

Offline Admiral_dk

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Re: Fuel injection systems
« Reply #182 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:

Offline Roger B

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Re: Fuel injection systems
« Reply #183 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.
Best regards

Roger

Offline Roger B

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Re: Fuel injection systems
« Reply #184 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.
Best regards

Roger

Offline AlexS

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Re: Fuel injection systems
« Reply #185 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.
« Last Edit: August 23, 2018, 09:56:25 PM by AlexS »

Offline Roger B

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Re: Fuel injection systems
« Reply #186 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.
Best regards

Roger

Online Vixen

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Re: Fuel injection systems
« Reply #187 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




It is the journey that matters, not the destination

Offline Admiral_dk

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Re: Fuel injection systems
« Reply #188 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 ?

Offline 90LX_Notch

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Re: Fuel injection systems
« Reply #189 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
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My Engine Videos on YouTube-
http://www.youtube.com/user/Notch90usa/videos

Offline Roger B

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Re: Fuel injection systems
« Reply #190 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.
Best regards

Roger

Offline zeeprogrammer

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Re: Fuel injection systems
« Reply #191 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?
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
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Online Vixen

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Re: Fuel injection systems
« Reply #192 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
It is the journey that matters, not the destination

Offline zeeprogrammer

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Re: Fuel injection systems
« Reply #193 on: August 26, 2018, 07:24:48 PM »
Thanks Mike.

Apologies Roger. I should have asked in my thread.
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
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Offline Roger B

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Re: Fuel injection systems
« Reply #194 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:
Best regards

Roger