Originally Posted by sohc_mshue

You have your definition of adiabatic efficiency all turned around here. It has nothing to do with a restriction on the ve of the motor or the exhaust flow. Adiabatic efficiency is a measure of how efficiently the compressor compresses the air without raising air temperatures too high. A compressor working in the point of a compressor map where efficiency is very low will be putting out very high air temps.

Typically a roots style supercharger will have a lower adiabatic efficiency than a properly sized turbo for the application. Centrifugal style superchargers are basically like a turbo where the compressor is fed a work input off of a belt driven shaft by the motor rather than the exhaust producing a shaft input from the turbine. The big problem with these is that they produce less than desired powerbands because they dont reach full boost until high rpms.

Most of the time on a given engine a proper turbo setup with a large enough turbine that isn't going to restrict ve will make more power, but not all setups are equal so its hard to say 9psi on the turbo motor will make more power than 9psi on the supercharged motor. Too many variables.