Originally Posted by RandomTask

I'm going to re-iterate what on what Fabrik8 is saying. Its not necessarily about your compression ratio, rather its about the dynamic cylinder pressures. Its ALSO about reaching that limit in the most efficient way possible. For example, you might have a motor with an 8.0:1 that you can run say 20 lbs of boost. OR you can have the same motor with a 10:1 ratio and only run 12 lbs of boost. Now you need to consider ambiatic efficienies. On setup a (20psi) the turbo may be running at 62% efficiency, where as setup b (10psi) will be running at 76% efficieny. Superchargers (centrifugal style) usually max out around 80% efficiency peak. You're dealing with curves, NOT straight lines in forced induction. The goal is to match your needs/purpose, to that peak.