Need Help Deciding On Internals

[Jawnzard]

So I know the title would make you think this doesn't belong in this forum, but hear me out. I have an engine (factory NA) that I'm building and I'd like to run forced induction. I've done my homework on swapping internals around between engines but I can't decide which pistons to use. One of the options is the pistons of an EJ22E and the resulting compression ratio will be around 8.5:1. So my question is this: with a low compression ratio like that, could the stock EJ22E cast pistons withstand 15psi of intercooled boost? Assume I'm going to be getting a tune as well.

The other option is EJ22T pistons but those will drop the compression ratio down to 7.3:1 and I'm worried that might be too sluggish off-boost.

Any thoughts?

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[ballitch]

You "could" use the stock 22E pistons for 15 psi. intercooled, since many others have done it before you. But I just don't trust it, but that's me, other people would run that without a second thought. On the other hand, the EJ22E is so plentiful and cheap, you could almost go through 2-3 engines before you approach the cost of forged pistons.

The easiest way for you to lower your CR for boost is EJ25 heads. If your impreza has throttle body IAC, then use sohc EJ25 heads. If not, use EJ25D heads. That won't get you around the cast piston issue, but it should be fine for good DD power levels.

If you swap in EJ22T pistons, you get the same CR as the 22T, 8.0:1


~Josh~

[Jawnzard]

Originally Posted by ballitch

You "could" use the stock 22E pistons for 15 psi. intercooled, since many others have done it before you. But I just don't trust it, but that's me, other people would run that without a second thought. On the other hand, the EJ22E is so plentiful and cheap, you could almost go through 2-3 engines before you approach the cost of forged pistons.

The easiest way for you to lower your CR for boost is EJ25 heads. If your impreza has throttle body IAC, then use sohc EJ25 heads. If not, use EJ25D heads. That won't get you around the cast piston issue, but it should be fine for good DD power levels.

If you swap in EJ22T pistons, you get the same CR as the 22T, 8.0:1


~Josh~

I should have prefaced my questions by saying this is actually for an H6, so the compression ratios are a bit different than the 4-bangers. Thank you for the input Josh, I apologize for forgetting to give you one of the most important pieces of information.

[ballitch]

I don't know the piston dish of the EG33 pistons, or the chamber volume.........or the stroke.....

I guess i'll have to enlighten myself. I guess you could use any EJ22 piston as long as it has more dish. Since you stated that the EJ22E piston will drop you to 8.5:1, I say go with that. Other than that, forged aftermarket is going to be your best bet, but also more expensive.


~Josh~

[Jawnzard]

Originally Posted by ballitch

I don't know the piston dish of the EG33 pistons, or the chamber volume.........or the stroke.....

I guess i'll have to enlighten myself. I guess you could use any EJ22 piston as long as it has more dish. Since you stated that the EJ22E piston will drop you to 8.5:1, I say go with that. Other than that, forged aftermarket is going to be your best bet, but also more expensive.


~Josh~

I have a complete EG33 dismantled in my garage. I used brake fluid and a graduated pipet to measure combustion chamber volume, I had a machine shop measure piston protrusion, and I know bore/stroke, and gasket thickness. Using all that, I got a rough estimate of piston dish.

Anyway, long story short, my compression ratio numbers are more or less correct, assuming the piston dish info I got online for the EJ22E/T engines were correct.

Also, if anyone wants some cheap high-compression EJ22 pistons, the EG33 pistons should raise your compression ratio up between 11.5 and 12

[ballitch]

EJ22T piston dish is 28cc's, EJ22E is 12cc's. Unless the EG33's dish is 0, I don't know how much they would raise the EJ22's CR.

Spill the beans, I want to know what the stroke is , I know the bore is pretty much the same as the EJ22E.


~Josh~

[Jawnzard]

Originally Posted by ballitch

EJ22T piston dish is 28cc's, EJ22E is 12cc's. Unless the EG33's dish is 0, I don't know how much they would raise the EJ22's CR.

Spill the beans, I want to know what the stroke is , I know the bore is pretty much the same as the EJ22E.


~Josh~

According to my research, the EJ22E (2.2L 1996 and earlier) has 14cc of piston dish and EJ22EZ (2.2L 1997 and later) has 12cc of piston dish. I can't personally confirm this, but I spent months collecting data from every source I could find and a couple sites confirmed the slight differences in the 2.2L engines. I compiled it all on my local club's site here.

I calculated the EG33 piston dish to be about 8cc. I just ran it through a compression calculator and it would raise your EJ22E compression ratio up to 11.8 unless I was wrong about the piston protrusion on the 2.2's.

[thorne]

I built a 205+22e setup that lasted for a descent amount of time at 365+awhp(18g) being beat on.

I ran 26psi on a stock bo (spiked it and let it fall) 315tq 265awhp I was not nice i'd wager she would have held together had i kept her at 300.

[Jawnzard]

Originally Posted by thorne

I built a 205+22e setup that lasted for a descent amount of time at 365+awhp(18g) being beat on.

I ran 26psi on a stock bo (spiked it and let it fall) 315tq 265awhp I was not nice i'd wager she would have held together had i kept her at 300.

What other supporting/protective mods did you have? ECU tune, alcohol injection, intercooler, anything else? If I could get by with the 22E pistons with just an intercooler and a tune, that'd be perfect.

[geronimo81]

I think 15psi on 22e pistons at that comp ratio will be fine. An EG33 at 15psi would be an absolute blast!

[Jawnzard]

Originally Posted by geronimo81

An EG33 at 15psi would be an absolute blast!

That's what I'm hoping Eventually, I'd like to pull the engine again, have it bored out to 99.5mm, sleeved, then run stock STi pistons in it. It'd be a 3.5L beast. So right now it's kind of "stage 1" of the build. If it goes pop, it won't matter too much as all of my parts have not amounted to more than $350 so far. I will eventually post a build thread for others interested in following this route.