how to make real HP with your IDI

[jwalterus]

There's adapters now to put the NV on a powerstroke, so I'd say it wouldn't take too much to get one on a idi.

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as far as that goes, we already know how to bolt up a zf-6

on the compression and starting issue, dropping a 6.9/7.3 IDI to 17:1 is the equivalent (just running the percentage drop here) of dropping a psd or 6bt to roughly 13.5:1, see how well one of those lights off at that compression

 

[Ford F834]

...Read about the temp diesel needs to ignite and you will find it to be 942 degrees...

What?! I looked up numerous sources and found the auto ignition point of No.2 Diesel fuel to be around 210*C (410*F). On a cold start that is the temperature that must be achieved in the precombusion chamber for the engine to start. In my experience, the enthalpy of compression is not enough unless the ambient temperature is around 100*F or higher. Below that, heat from the glow plugs is needed.

One thing I would like to know is how much decompression affects the temperature in the precombusion chamber. The compression ratio to cylinder pressure is linear (Boyle's law), multiplied by the atmospheric constant of 14.7 psi. But the relationship between cylinder pressure and specific heat capacity is not linear. (Hess' gas law). Therefore a fairly small change in pressure can make a big difference in specific heat capacity... one of the reasons lowered compression helps EGT's no doubt. I know this is simplistic, since static compression is only a specification and dynamic compression and boosted compression are more relevant to engine performance.

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Does anyone have any first hand experience with decompression and cold starting on an IDI? What I have so far is the wav file posted here of a 17:1 truck that supposedly would not start with GP's AND ether at 60* temps. Wheeler's truck had the pistons shaved .080" giving him 16.5:1 and he said he had no problems starting it. And then there was Anderson's 6.9 that had .060" shaved pistons minus .010" decked block, putting him in the 18:1 range. He said it started fine also, but not in a particularly cold climate. Something's not adding up. Has anyone on this forum decompressed an engine? I don't mean with rebuild pistons intended to offset block decking, I mean /lowered/ to really shift the CR? Looking for cold start ability as well as running characteristics.

 

[laserjock]

It's still early in the morning here but I think the answer to your question of the relationship of heat to compression ratio comes from the WORK being done to compress the air. The higher the compression ratio, the more energy it takes to compress it and that energy has to go somewhere. Most of it will go into the air with losses into the cylinder walls, valves, etc.

What you really need to know is the dynamic compression as you noted. That has more to do with cam timing and valve overlap than anything as far as I understand. I suspect but can't confirm at this instant that the lowered egt's are a side effect of a few things. Probably better cleaner combustion resulting from more air crammed in by external forces (turbo) that usually comes with a decompressed engine.

 

[icanfixall]

Please read Rudolf Diesels book on what he found about ignition type diesel engines. There you will find the temps I posted about. He is the father of the engines that have his name describing them. I too felt the 900 plus degrees was kind of high but reading it changed by mind.

 

[no mufflers]

has anyone herd of a stroker kit for the IDI?

 

[79jasper]

Used to be one, iirc.

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[Ford F834]

has anyone herd of a stroker kit for the IDI?

This is the place that offered it:

http://barnetthighperformance.com

I don't see any such thing on their website now, you would have to give them a call. My thought is that it would be a very expensive way to add some power. I wish that IH/Ford had gone this direction when increasing the displacement from 6.9 to 7.3 instead of thinning out the cylinder walls.

 

[79jasper]

If money was no object. P-pump 7.3 psd.

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[jwalterus]

If money was no object. P-pump 7.3 psd.

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if'n you're sayin that, might as well get a custom flat crank to go with it, maybe get your revs up around 4500
god, now you have me thinking...

might be a feasible 400hp N/A diesel right there!!!!

 

[F350camper]

If I were to try to do a high hp IDI build, I think I would try to tackle the RPM first. My approach would be, how do I get this thing to hold together and stay boosted and fueled at 4k rpm. If I achieved that, then I'd dyno and go from there.

 

[icanfixall]

This is the place that offered it:

http://barnetthighperformance.com

I don't see any such thing on their website now, you would have to give them a call. My thought is that it would be a very expensive way to add some power. I wish that IH/Ford had gone this direction when increasing the displacement from 6.9 to 7.3 instead of thinning out the cylinder walls.

Yes... This was the shop that actually offered 2 different stroker engines in the idi family. They were are expensive. I learned they were doing the same exhaust port work I was doing long before they put it on their web site. We have an inside curve that is a huge bump in the floor of our exhaust port. Decreasing that bump allows an increditable exhaust flow increase. To do this you need a special burr that is shaped like an egg. And then you use the back side to remove the bump. Then using a sanding roll is the hard park....

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