compression

i have a question about compression ratios. Im asking with turbo in mind. If i get the bigger 11.5:1 compression pistons will it give a better performance than a 9.0:1 compression?

you cant run a turbo with a high compression ratio....you really dont even want the stock 9.0:1 if you can help it...


gunnmen01

so basically im better off with the biggest compression i can get?

no, the lower the compression the more boost you can run. you can run with higher compression but it isnt as safe or good for the engine. the lower the compression you can get is better for turbo.

it depends on how much boost you wanna run, say like you only wanna run like 8psi, then you wanna get your comp ratio as high as you can safely, maybe like 10.5 or soemthing. but yeah you wanna get your comp ratio is high as you can but safely, like no detenation

lowering compression is strictly for a safety reasons. the only way to get more power out of a motor is to compress more air into it so more fuel can be burnt. lowering the compression creates a drop in power, while raising boost compensates for this loss, rather than creating more power. a general paradigm on this board seems to be that more boost automatically means more power, even if it comes at the cost of lowered compression. this is untrue, however, because of the linear relationship between air and fuel. whether the air is comressed before it enters the cylinder or not doesnt matter, its solely based on the pressure during ignition. the goal when building a turbo or super setup is to have as high of a compression ratio without achieving detonation, as civickiller was saying. what that compression ratio is depends on the setup and how well its tuned.