i'm in strict california, and i want my car to be completely legit. i'm not going for big numbers, just want a decently quick DD that still passes smog in cali.

i have a 92 civic with an OBD-I gsr swap which has been certified through the ref. i'm looking to go turbo via the carb legal edelbrock kit. before i go turbo i'm going to rebuild my bottom end.

i initially was thinking of just thinking of going w/jdm itr pistons to bump up compression since i'm not looking to boost high. or should i go w/lower compression pistons since it would be turbo'd.

what compression would be better to keep my emissions low enough to pass?

 

Generally speaking, increasing compression does not change emissions much. It might reduce hydrocarbons and carbon monoxide a little due to a more complete burn, but raise nitrogen oxides because of the higher combustion temperature. Of course, it all depends on how high you go. But keep in mind that there ARE cars that have 11:1 compression from the factory that are sold in California.

A bigger concern, though, is running JDM ITR pistons with boost in a GSR. With a GSR head, JDM ITR pistons are probably going to give compression in excess of 12:1 (compression on the JDM ITR is 11:1 with the B16A head casting). 12:1 is risking detonation with 91 octane gas even if you are running allmotor. But 12:1 while boosting is just asking for trouble. Even the stock 10:1 compression of the GSR is definitely on the high side for boost. Most people run around 9:1 or less.