Originally Posted by Patman015
if you were to drop compression, would you be able to run MORE boost? How would you go about lowering compression (Pistons? head gasket?) What compression ratio would you go with, and what bore0 would you recommend goin with. Im asking because you guys are masterminds in my eyes! Are you considering this?
EDIT: Somebody in my auto class at school told me that if I were to get new pistons and rings to replace the ones in my GS-R then I would have to bore my motor. I thought I would just have to hone the cylinder walls...any input you may have?
Yes, you could run more boost, but the main reason to lower compression is to allow a larger margin of error when tuning because of the turbo's propensity to lead to pre-ignition. Higher compression motors will always make more power but to compensate for a higher boost level being run, the octane of the fuel must also be increased.
I would probably drop the compression down to 9.5:1 with some forged, dished pistons and some stronger rods. Using a thicker headgasket is the worst way to lower compression, so I don't recommend it. A 2.0L bored out and sleeved GSR motor would be a very nice and safe setup, so a bore of 84mm is about as much as you want to go.
I would consider doing this, but the Greddy turbo kit has limitations. For all that work, I would also want to swap a larger turbo in that can flow a much greater volume of air to take full advantage of all the bottom end upgrades. You also have to keep in mind that this is my daily driver. I can't afford to have long down-times when the engine is torn apart and being worked on.
About having to bore the motor when replacing pistons, you only need to have it done if the pistons are oversized. Then the appropriate bore would have to be made. You will want to rehone any time the rings are replaced, though.