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Its more centrifugal versus positive displacement — totally different goes of superchargers. A centrifugal by design will make roughly the square root of peak boost at half peak rpm. In other words, a centrifugal that makes 9 psi at 8400 rpm will make only 3 psi at 4200 rpm. This law holds true whether you put a tiny centrifugal on the car or a giant one. The popular V3 Si trim is actually a pretty good match since for the S65 given that about the best anyone can do on pump gas is 600 rwhp SAE Dynojet and the blower would be maxed out probably before 700 rwhp.
The positive displacement, in contrast, will reach peak boost before the centrifugal is at 2 psi and maintain it all the way to redline unless it is undersized. I don’t think it is undersized. It is limited more by the fact that any more boost in the low to midrange would cause knock on pump gas. In that sense, the centrifugal that builds boost over rpm and does not make high boost (relatively speaking, from the S65 perspective) is better suited to the 12.0:1 compression S65 if more than a 50% power increase is desired.
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