Raising Compression... - Honda Prelude Forum

Padge · 05-07-2004, 08:33 PM

Quote:

In an H22a, USDM pistons are 10:1, and JDM are 10.6:1.
However the h23 has a smaller combustion chamber and larger displacement so in an H23 motor

UDSM H22a pistons: 11.1:1 CR
JDM H22a pistons: 11.8:1 CR
Type-S: 12.3:1 CR (highly not recommended!)

I am ordering a set of stage 1 crower cams for my h23 (since I have to rebuild the head). Currently my h23 is at stock compression which is about 9.5:1 (or close to it, i think). If I get a set of usdm h22 pistons for my engine, can they just replace the pistons I have now or is there a lot of tuning involved? Does the EVU have to be messed with (obd2)?

I really just dont know what extra work would need to be done to raise the compression. Thanks.

MugenPoweredLude · 05-07-2004, 09:57 PM

yes, youre going to need a standalone if you bump up your compression
Hondata or AEM EMS

as for the highest compression you would want to run on the bottle would be ~11.5:1

Padge · 05-07-2004, 10:40 PM

why thank you Anthony... I guess that takes that out of the question... for now

laughin2.2 · 05-08-2004, 05:04 PM

You can always toss in a thinner headgasket and see how that works for you. I'm assuming that you'll be getting cam gears anyways, so you can compensate for the loss of distance between the crank and head.

axion68 · 05-08-2004, 06:37 PM

Quote:

Originally posted by laughin2.2
You can always toss in a thinner headgasket and see how that works for you. I'm assuming that you'll be getting cam gears anyways, so you can compensate for the loss of distance between the crank and head.

From the aftermarket head gaskets I've seen you aren't going to gain much compression from running a thinner head gasket, as the OEM is already fairly thing.

NXLude · 05-08-2004, 10:12 PM

yeah...OEM is .30 or so and the thinnest cometic gasket is .25 if I recall. So youll have to mill the head if you want more numbers

Padge · 05-09-2004, 10:17 AM

wouldnt milling the head and just changing the pistons be the same thing basically? wouldnt i still need to get a hondata or something.

prelude2sin · 05-09-2004, 11:27 AM

^^^ i have ask this question in h-t.com and the response is that you can swap out the h23 pistons for h22 pistons w/ no mods to the pistons. i would use the usdm pistons. hondata would be a great compliment for the mods you are planning to do.

Padge · 05-09-2004, 06:09 PM

so you are saying that I CAN swap pistons with no other change?

any idea where i can pick up a set of h22 usdm pistons.