Powerstroke Pistons?

[idi_or_die]

Alright guys, here is the story. I recently purchased an old idi engine from a local scrap yard for my build. I bought what i thought, and was told, was a 6.9 out of a 1986, however when i got her home and tore it down i knew instantly it was indeed a 7.3. Upon further inspection i discovered it is a 1993 turbo engine! Now the plan on this build was to use a pump from a cat 3208 along with twin turbos to reach into the 450-500 rwhp range. Knowing that the compression ratio would be insane for my goals, i had planned to use extra thick copper headgaskets to lower compression to around 17.5 to 1 compression while at the same time maintaining piston integrity. Now until today i had planned to simply use the same setup on this 7.3, but then i got an idea. If the wrist pins on the 7.3 idi turbo and psd are the same, wouldnt powerstroke pistons fit? And if they do fit, would they not lower the comp ratio to the same as the psd? Just trying to think of ways of keeping all that boost in the engine without shaving pistons. Thank you all for any info you can share.

 

[79jasper]

Don't think anyone has tried it, but the bores and wrist pins are the same. (Supposed to be anyways)

Sent from my USCC-C6721 using Tapatalk

 

[icanfixall]

i cant say the cr will be the same but any mathematician will be able to work that out.pin and bore sizes are the same.

 

[OLDBULL8]

You can't use PSD DI pistons in a IDI. The piston tops are a different configuration, if that's what your looking to do. The IDI pistons have indents for the valves and a "sluiceway" for injection, the PSD DI pistons are like a Mexican Hat design. Is this what your thinking to do?

 

[riotwarrior]

You would need to determine the volume of the combustion hole in the PS piston, also determine if it comes up above the deck and if so how much, and with all the info in hand including the volume of precup, you can do the math to determine the compression ratio.

I am guessing here it will be about 14.5-16:1 at most because the precup adds volume to which a PS does not have.

PS has no precup so that alone will lower the stock compression of the PS piston in an IDI bore, compared to a PS head and piston in PS block.

With that I have a strong suspicion it would lower the CR to the point it would not be a good running if it ran at all engine.

JM2CW

 

[laserjock]

I think Al hit on a biggie here. Just because the wrist pin and bore are the same, the location of the wrist pin relative to the top of the piston may not be and that may cause a serious clearance issue. I am however subscribed.

 

[Smokininmo]

Would like to see how that 3208 pump goes on.......

 

[freebird01]

i got my hands slapped for this...

the relief in the top of the pistons are not for the valves on an IDI piston. Its a swirl chamber for combustion. the divit in the middle is for the injection cycle out of the pre-cup.

the powerstroke piston has a big dimple/indent directly in the center of the piston

 

[riotwarrior]

Swept volume versus unswept volume of the PS piston in an IDI is not going to produce the compression needed to fire a diesel IMNSHO this time, just saying...you will loose a lot of comp buy using those pistons even if they could physically work.

Good luck with the math. If I knew the deck height of the PS piston in the IDI and the combustion depression volume of the piston, and the volume of the precup I could probably do that math...I know none of those dimensions...thus no math for you today.

Al

 

[icanfixall]

al makes a good point of piston pin height. but we can mill piston tops too. might want to buy or find a used psd piston and try it in one cylinder. see what clears or not. any 70 thousands fill for a head gasket will work fine for a test crank rotation on one cylinder ...

 

[FordGuy100]

The pistons were designed for different injection styles (IDI vs DI) and I would wager that you would get a much worse burn with a powerstroke piston just due to its design., if in fact it actually worked.

 

[riotwarrior]

Look it's stupid simple to do pin height comparison...put the pin in one piston leaving 1/2 pin out, then slide the damn thing into the other piston so they are side by side...you now have your height comparrison...but that's it...still no swept vs unswept volume for a static compression ratio.

JM3CW and yes I meant 3 this time!

 

[Jake_IN]

Assuming that they fit just fine and you could put them in. Then we get to look at how well will they work/last.

Basically you are taking a piston designed to have fuel squirted on top of a bowl where it will then ignite and move out and fill the bowl. In an idi engine instead flame will now be entering the piston right at the edge of the bowl. This is putting loads of heat on the edge of the bowl which I believe will either melt it or cause it to crack in a very short amount of time. You could probably get it to run....albiet very poorly and would then be tearing it down again in short order.

Here are some screenshots from the SAE papers i have for both the 6.9 and T444E engines.

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

I'd love to be proven wrong though so if you got the time and money to try it...i'd say go for it

 

[cpdenton]

i had planned to use extra thick copper headgaskets to lower compression to around 17.5 to 1 compression while at the same time maintaining piston integrity.

Aren't 93 and 94 factory turbo engines already lowered to 17.5 to 1 compression. Everything I have read says they are. If so, all you need is a new set of turbo engine pistons to achieve your desired compression.

 

[idi_or_die]

Thank you all for the info, i was never really worried about compression being to low, as this is not a street going engine, i was however worried about the fuel bowl and the possible effects of not hitting it directly. Now for another question, would shaving piston tops truly weaken them, or am i just paranoid? If not how much should be shaved off to achieve the correct comp ratio? Also has anybody ever tried o-rings in the block? I know this would be difficult in the heads due to the pre-cup but the block doesnt seem like it would be to much of an issue.