What affect does compression ratios have on h.p.? I know it affects what type of fuel you need to run. I have a 2.8 VR6 motor that I am in the process of boring out to a 3.0. I believe the stock 2.8 is a 10:1 and the pistons I have for the 3.0 are 9:1. I know I will have a hp increase due to the displacement but would I have seen better gains on the 3.0 with 10:1 compression?

 

It's hard to say w/o a lot more info. If you're really curious, buy a computer program like Mr. Gasket Desktop Dyno. It'll let you 'build' an engine on paper & give you surprisingly accurate estimates of its power output.

 

compression=hp, but simply increasing compression ALONE is usually only good for 6% hp gain per 1kg increase in compression.
I highly doubt your car came stock with 10:1 comp. anything over 9.5 will not run well on pump gas. But with German engineering anything is possible.