Author Topic: Fuel injection systems  (Read 54900 times)

Offline Roger B

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Re: Fuel injection systems
« Reply #225 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.
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Roger

Offline Roger B

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Re: Fuel injection systems
« Reply #226 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.
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Roger

Offline Roger B

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Re: Fuel injection systems
« Reply #227 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.


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.
Best regards

Roger

Offline Admiral_dk

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Re: Fuel injection systems
« Reply #228 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

Offline Roger B

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Re: Fuel injection systems
« Reply #229 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.
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Roger

Offline Roger B

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Re: Fuel injection systems
« Reply #230 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.
Best regards

Roger

Offline steamer

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Re: Fuel injection systems
« Reply #231 on: October 20, 2019, 01:54:45 PM »
Cool!   Watching along....

Dave
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Damned ijjit!

Online Kim

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Re: Fuel injection systems
« Reply #232 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

Offline Admiral_dk

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Re: Fuel injection systems
« Reply #233 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

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 ....

Offline Roger B

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Re: Fuel injection systems
« Reply #234 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.
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Roger

Offline Roger B

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Re: Fuel injection systems
« Reply #235 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.
Best regards

Roger

Online Vixen

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Re: Fuel injection systems
« Reply #236 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
It is the journey that matters, not the destination

Offline Roger B

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Re: Fuel injection systems
« Reply #237 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.
Best regards

Roger

Online Vixen

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Re: Fuel injection systems
« Reply #238 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
It is the journey that matters, not the destination

Offline Admiral_dk

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Re: Fuel injection systems
« Reply #239 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 ...!!!!
« Last Edit: October 24, 2019, 01:00:28 PM by Admiral_dk »