Centrifugal blowers are the compressor side of a turbo w/ a pully attached to the "exhaust" side of the "turbo". its JUST Like a turbo; itll go past its efficiency just like a turbo will if yofu try to run more boost than the wheel is sized for. The problem is that the Centrifugal blower is linear.. meaning you make more airflow with crankshaft RPM.... its directly proportional to the pully rpm... you cant get more boost at a lower RPM even if you wanted to

now w/ a turbo, that of course has problems if you try to overboost the compressor beyond its limits. but, when a turbo hits boost, it SPOOLS up... its NON-linear and does not depend on crankshaft speed...necessarily. You can get FULL boost by 3500 or whatever.. whereas the crank drivin supercharger will make more airflow as the rpm's increase... it doesnt really SPOOL per se. a turbo can go from a few psi to full boost in a few seconds depending on what RPM the engine is at. it only boosts when you need it too.... but a pully driven compressor is trying to push air any time the pully is being turned... even if you are at 10% throttle and cruising.

a Roots type, doesnt really Compress the air like a turbo or centrifugal unit does... it simply MOVES the air. if you ever look at a roots blower, it just grabs air and spins it agains the case, and down into the lower half of the blower manifold and into the engine. the "Boost" comes from the air's resistance to flow as its being MOVED into the cylinders... i mean, it sort of compresses i guess, depending on how you look at it. but not in the same sense as a centrifugal or turbo.

idunno, my traine of thought just derailed... i hope i answered your ?