The answer to more fuel, or recipe for disaster...

[laserjock]

Okay, we all know that one of the greatest limitations of the IDI is the lack of fuel from the DB2 pump. Great advances have been made recently on a couple fronts with hybrid pumps and really pushing the limits of the factory design. It seems to me that there is a another (possible) solution that I haven't seen talked about anywhere. What about adding fuel via the intake?

Okay, now that you've had a good laugh, let's discuss this a moment. This is typically how propane systems work but the obvious caveat is that it's also usually added as a gas. There are liquid propane injection systems too and there are advantages to that including cooling the intake with the latent heat of vaporization.

Okay, so let's discuss the obvious problems.

This isn't a gas engine and as such fuel addition is timed to the stroke and the ignition is via heat, not spark plug. Injecting fuel into the intake like a tbi is bound to screw up the timing. Alright. I think this is a surmountable problem. There actually were carbureted diesel tractors. So there's no reason it won't run. Second, I'm not thinking about ditching the injection pump. I'd just like the ability to add a little on top to help even out the fueling curve where it drops off. I think if you keep the extra fuel below the lean burn point, you could minimize timing problems and preignition.

Second problem I see is that, diesel being diesel, it's not going to stay suspended real well. With the amount of fuel we are talking about here, I don't think it's a huge problem.

So the way I see it, the possibilities are this.

1. You sneak up on it and it works great.

2. All that happens is you get a lot of smoke and no extra go.

3. It all goes to crap and blows the intake off.


The only other really viable way I see to go is to fit injectors in the glow plug holes. That won't make for easy starts though. Could possibly do a high (medium) pressure system on top of the standard pump through the injectors.


I like this idea because it's auxiliary. All the mechanical stuff stays completely in tact.


Well, how crazy am I? I may have to try this if I ever get the truck together. Enough mental ************ for one night.

Talk amongst yourselves.

 

[TahoeTom]

Well, these things burn oil introduced to the intake via the CDR, and that is heavier than diesel. I think the oil goes to the rear cylinders though. Factory clearance on the rear pistons was slightly larger than the others for this reason.

 

[dunk]

OK I kind of get propane in theory... But second injectors through glow plug ports? The threads and seat won't fit a standard injector, right? If there is a cost effective injector to run off the shelf in glow plug holes how are you gonna run a second pump and ensure timing is exactly the same as the regular pump? I'm not sure how that would work. Where would the second pump mount? How would it be timed?

Just a quick search there are 130cc and 180cc pumps available off the shelf from Conestoga Injection and IDI Performance. IDI Performance claims 400 HP and 800 ft/lbs before their pump runs out of steam. Are you currently around that power level and out of off the shelf options for more power? What sort of turbo setup are you running that you need beyond these options? What studs and head gaskets and how are they holding up at what level of boost?

Another issue that I don't entirely understand is the limitations of IDI vs DI. I've read here about how precups and throat size limit power and there are supposedly issues with opening up the throat or making the precup chamber larger. Too much pressure in the precup and too small a throat to let it act on the piston past a certain power level. Is the limitation on these engines related to being IDI or is it just a matter of cramming more fuel and air in and ensuring it doesn't lift the heads? Does bottom end strength become an issue at some point? What are the limiting factors? What ever happened to all the P pump talk?

I'm very curious because I would be thrilled for my IDI to get to what I consider to be normal power levels around 400 HP and 500 ft/lbs. If it can do that reliably I'll be thrilled as it'll be as good as a budget 460 build.

 

[laserjock]

Just to clear it up, the second set would be efi of some sort. Electronic and timed off the tac sensor probably. I've given that a little thought too. I know there are big pumps out there. There are really 2 reasons for auxillary fuel as I see it. Tuning and reliability. Cost aside, it's hard to beat the reliability of the stock or lightly modded stock pumps. It's also nice to be able to turn it on when you want it. There's a whole product line built around chips multiple settings.

Could even drill and tap the intake runners like a gasser multiport injector I suppose.

I don't know. Thought it might be an interesting conversation to have.

I'm not really thinking that's the way to go but I'm wondering about the whole tbi concept.

 

[riotwarrior]

OK I kind of get propane in theory... But second injectors through glow plug ports? The threads and seat won't fit a standard injector, right? If there is a cost effective injector to run off the shelf in glow plug holes how are you gonna run a second pump and ensure timing is exactly the same as the regular pump? I'm not sure how that would work. Where would the second pump mount? How would it be timed?

Just a quick search there are 130cc and 180cc pumps available off the shelf from Conestoga Injection and IDI Performance. IDI Performance claims 400 HP and 800 ft/lbs before their pump runs out of steam. Are you currently around that power level and out of off the shelf options for more power? What sort of turbo setup are you running that you need beyond these options? What studs and head gaskets and how are they holding up at what level of boost?

Another issue that I don't entirely understand is the limitations of IDI vs DI. I've read here about how precups and throat size limit power and there are supposedly issues with opening up the throat or making the precup chamber larger. Too much pressure in the precup and too small a throat to let it act on the piston past a certain power level. Is the limitation on these engines related to being IDI or is it just a matter of cramming more fuel and air in and ensuring it doesn't lift the heads? Does bottom end strength become an issue at some point? What are the limiting factors? What ever happened to all the P pump talk?

I'm very curious because I would be thrilled for my IDI to get to what I consider to be normal power levels around 400 HP and 500 ft/lbs. If it can do that reliably I'll be thrilled as it'll be as good as a budget 460 build.

Great discussion feeder questions...about precups and so forth...

without me knowing and getting into it, my basis of thought is that only so much is capable of flowing through precup throat at any given rate in a given amount of time. This comes down to a door and how much can flow through that doorway at any give momment in time.

But the other issue that comes to mind is hydrolics...based on a given fuel amount being SHOT into a small room in a mist and subsequently re-pooling as a liquid not a mist and creating a NON burning liquid vs a combustable air/fuel mixutre...

I've had some discussion with Justin on this and him and I agree to dissagree on precup throat opening...

Most like seriously all, but most of the combustion takes place in the precup, and is SHOT out of the precup not unlike a cutting torch blast, thus comes the issue of how much is to much in a tiny place and small port vs a tiny place and big port.

In my head...which I admit is not all that good.....a larger opening slows the process down some, thus this creates a longer burn cycle and thus more TORQUE, which is what we all want...cause that's what counts....

So I'll leave this here.....for my theory requires me to drhink more beer at this time.but it's my theory

Oh fuel via intake is not feasable...due to indiscrimant distribution..you would need some type of diesel carb to do so

Just my drinking fool head speaking out here

 

[79jasper]

If the precup was gone, would the injector be squirting at the piston?
I mean if one removed the precup and leveled off the precup wall into the cylinder opening, then maybe had some custom injector nozzles made, couldn't a person have a DI engine?

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[IDIoit]

i have no viable information for you guys. just subscribing.

what about alternitave forms of fuel being introduced right above the intake valve with solenoids, kind of like a N2O set up on gassers.

 

[FordGuy100]

Diesel needs to be atomized at a high pressure to work well. Has anyone seen a diesel engine with injectors that **** fuel rather than mist it? It runs like crap. That because diesel does not vaporize like gasoline does. Low pressure means large fuel droplets.

So your first step would be to figure out how to get it to be over 1000psi (which is still way low). Thats going to require an injection pump of some sort, either mechanical, or some sort of common rail setup. And now we are back to square one.

 

[laserjock]

Diesel needs to be atomized at a high pressure to work well. Has anyone seen a diesel engine with injectors that **** fuel rather than mist it? It runs like crap. That because diesel does not vaporize like gasoline does. Low pressure means large fuel droplets.

So your first step would be to figure out how to get it to be over 1000psi (which is still way low). Thats going to require an injection pump of some sort, either mechanical, or some sort of common rail setup. And now we are back to square one.

That's a good point. The assumption is that I'd use an injector. There are other ways of atomizing liquids...especially considering the amount of liquid I think would actually be required or possible.

Anyway, good discussion guys. So it looks like the main concern I'm hearing is atomization. With some discussions going on around here and in FB land, I have been searching for some modeling literature on the IDI. I found a couple articles that might shed some light on the real role the different parameters relating to the precup etc might actually have. Somebody has to have modeled this to prove the DI systems are better. Have to have made the an engineering case at some point in time. I figure the literature is out there if you can find it.

 

[fx4wannabe]

Been awhile since I've played with the newer diesels, but if I remember right my cummins was at about 32,000 psi with my programmer. More air required more fuel and higher pressure to atomize said fuel. There is also a timing element but I am way out of my realm here.

 

[79jasper]

^ that sounds like common rail pressures?

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