Originally Posted by zetecfocus
But doesn't the turbine push a certain psi based on wastegate springs? In return only pushes a certain CFM correct?
The term "PSI" is a measurement of restriction. One turbo may have to spin much faster than another to obtain a the same psi. If you're running a certain turbo passed it's efficiency range, you're only heating up the exhaust gasses/intake charge and losing hp. This is why you compare compressor maps to see what is the best size turbo for you.
Remember 10psi is 10psi. The increase in power is achieved by a cooler/denser intake charge. More air molecules can occupy the same space with a lower temp. Not only this but a larger turbo will help to reduce back pressure which will increase your overall VE of the engine.
The CFM rating is not dictated by the turbo, but instead by the displacement of the engine and the rpms you're at. That is a constant unless you change something in the system.