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Vintage Diesel and Oil Engines Fairbanks Morse, Lister, Petter, Witte and other pump injected Diesel oil engines.

Vintage Diesel and Oil Engines

Looking for a Small Mechanical Injector


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  #91  
Old 08-01-2018, 08:59:34 AM
kwfiggatt kwfiggatt is offline
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Default Re: Looking for a Small Mechanical Injector

If my line of reasoning is correct, the clag is caused by incomplete combustion. Your injector is an outwardly opening poppet valve, correct? If I'm thinking correctly, as soon as the valve lifts off of the seat, you get a huge reduction in injector pressure, which reduces atomization, resulting in big fuel drops, which equals clag. You might want to modify the valve stem so that it has a shoulder behind the valve head and keeps the port mostly plugged as the valve lifts. That way you would still have high velocity through the valve and therefore should have better atomization.

If you've seen an old pintle style injector, the pin stays in the nozzle hole as it rises off of its' seat. IIRC, the pins have various tapers on them to change the injection rate as the needle lifts.

Instead of making new parts, you could try setting the injector pop pressure higher to see if it reduces clagging. Even if it only reduces it slightly, you know you're on the right path, and then could modify the injector...

One final idea - is your injector spray impinging on anything inside the combustion chamber? This would cause big drops and clag...

Hope these brain wheezes help, to borrow your term... 8-)

Kevin
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  #92  
Old 08-01-2018, 07:35:06 PM
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Elden DuRand Elden DuRand is offline
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Default Re: Looking for a Small Mechanical Injector

Kevin:

Thanks for your suggestions. I, too, have a few ideas I'm working on. First, I'm going to increase the cam durations to try to get the engine to breathe easier.

What I'm going to do is to swap the 200 degree exhaust cam to the intake. Then I am going to make a 240 degree exhaust cam. That will allow longer openings plus more overlap.

Right now, in open air, the injector makes a fog so I'm not "sure" that is the problem.

One thing that occured to me is that, since the pump element is from a much larger displacement engine, it might be dumping fuel too fast. Even though I've got a mechanical limit stop to keep the pump from totally drowning the engine; the pump cam may need to be modified to slow the rise of the plunger and allow a longer injection period.

Of course, there is the problem with the plunger rise being too slow making leakage cause delivery problems. To partially compensate, I can always move the limit stop to increase the maximum stroke and overcome the leakage.

This whole problem is made worse by the fact that this engine runs at 600 to 700 RPM as opposed to the 3,600 RPM of the Lombardini engine the pump came off of.
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  #93  
Old 08-01-2018, 07:50:17 PM
Thaumaturge Thaumaturge is offline
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Default Re: Looking for a Small Mechanical Injector

I take full blame.... did I mention that Lombardini blew chunks?
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  #94  
Old 08-02-2018, 05:53:34 AM
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Elden DuRand Elden DuRand is offline
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Default Re: Looking for a Small Mechanical Injector

Hey, Doc:

No blame to be had.

I don't look a gift horse in the mouth. The pump does work and, so far, hasn't caused this engine to blow chunks.
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  #95  
Old 08-02-2018, 09:57:08 AM
kwfiggatt kwfiggatt is offline
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Default Re: Looking for a Small Mechanical Injector

Quote:
Originally Posted by Elden DuRand View Post
Kevin:

Thanks for your suggestions. I, too, have a few ideas I'm working on. First, I'm going to increase the cam durations to try to get the engine to breathe easier.

What I'm going to do is to swap the 200 degree exhaust cam to the intake. Then I am going to make a 240 degree exhaust cam. That will allow longer openings plus more overlap.

Right now, in open air, the injector makes a fog so I'm not "sure" that is the problem.

One thing that occured to me is that, since the pump element is from a much larger displacement engine, it might be dumping fuel too fast. Even though I've got a mechanical limit stop to keep the pump from totally drowning the engine; the pump cam may need to be modified to slow the rise of the plunger and allow a longer injection period.

Of course, there is the problem with the plunger rise being too slow making leakage cause delivery problems. To partially compensate, I can always move the limit stop to increase the maximum stroke and overcome the leakage.

This whole problem is made worse by the fact that this engine runs at 600 to 700 RPM as opposed to the 3,600 RPM of the Lombardini engine the pump came off of.
I like the cam and breathing ideas. More air is always a good thing. Wonder if one of those keychain turbos would work?

I wouldn't think that too quick of an injection event would cause an issue - I would think that it would allow more time for mixing and would help improve things. But then again, it may be drowning everything out if there's not enough air.

Interesting stuff - thanks for sharing!

Kevin
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  #96  
Old 08-02-2018, 06:42:49 PM
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Elden DuRand Elden DuRand is offline
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Default Re: Looking for a Small Mechanical Injector

I got the cam made, installed and everything set in time. It still took a lot of heat to get it to run but I think that is because I left two shims out and the ratio is somewhere around 15:1. It ran all right albeit a bit smoky and suddenly quit after about 45 minutes.

When I first timed it, I set the injection timing a little before TDC and it slobbered out the exhaust. It ran better at a few degrees ATDC.

That was it for the day.

Tomorrow, I will increase the compression ratio to see if it will run without having to pull the head and clean the exhaust valve. I also intend to improve the valve rotator.
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  #97  
Old 08-02-2018, 08:52:40 PM
I like oldstuff I like oldstuff is offline
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Default Re: Looking for a Small Mechanical Injector

Elden I thank you for the thread and your efforts making this engine. I'm wondering if it's just being over fueled after seeing the drool passing past the rings and out the bottom.

If it has enough power I also wonder if loading it will help to clean it out and eliminate the wet stacking.
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  #98  
Old 08-03-2018, 06:29:21 AM
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Elden DuRand Elden DuRand is offline
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Default Re: Looking for a Small Mechanical Injector

When it is running well, the drool is minimized. As with any total loss lube engine, it does like to fling the glop around.

Like The Homebrew Hvid engine, this one requires a lot of learning to get right. It's gettin' there.
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  #99  
Old 08-03-2018, 10:18:00 AM
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Default Re: Looking for a Small Mechanical Injector

Quote:
Originally Posted by I like oldstuff View Post
Elden I thank you for the thread and your efforts making this engine. I'm wondering if it's just being over fueled after seeing the drool passing past the rings and out the bottom.

If it has enough power I also wonder if loading it will help to clean it out and eliminate the wet stacking.
If it was overfueled it would be running away. More fuel in a Diesel makes it run faster, in a no-load situation. The speed is regulated by the amount of fuel injected.

FWIW, I know it's a whole nother rabbit hole to go down, but a direct injection engine really never uses a pintle injector, always multi-hole type. The pintle is normally used in a precombustion chamber engine. Something about the spray pattern is impinging right on the valve, before it gets a chance to ignite. Multi-hole & high pressure is pretty much standard in direct injection engines.
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  #100  
Old 08-03-2018, 01:44:28 PM
The Diesel Doctor The Diesel Doctor is offline
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Default Re: Looking for a Small Mechanical Injector

Think of what Rudoff Diesel went through to get his first diesel engine running. If he had been a SMOKSTAK member in 1893 there would have been posts and threads like. I am going to use powdered coal for fuel. What is diesel fuel? Hope you recover fast after the explosion. Don`t cross the English Channel. We are all rooting for you Elden.Click image for larger version

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