I haven't seen any posts about the possibility of improving the Comptech style supercharger through a CVT or multiple clutch system. The big issue about centrifugal S/C, to me, is how boost only comes up at relatively high RPM. One advantage of turbos is the wastegate regulates the impeller drive. That allows a small turbo to spool up early but not be overdriven later.

A similar concept could be applied to a centrifugal supercharger by using a continuously variable transmission or a several clutches driving different belt/gear ratios. The S/C could be made to spin up sooner and then gear-switched to stay below an "overdriven" speed. In a similar technology, Mercedes uses a magnetic clutch to disengage the supercharger for cruising gas mileage.

I assume the complexity is in the packaging of such a variable drive system for a tight engine compartment (and ultimately cost). Have any of you tried or seen something like this?

 

Indeed Pen, multispeed superchargers (and clutched units) have existed for a long time. I believe early usage was on piston driven aircraft which saw high altitude duty.

As for why they aren't used now, I don't know. Expense would probably be the number one concern. Also, improvements in turbos have made multispeed SC's less attractive for high performance apps. For low performance, a single speed positive displacement type is sufficient.

With the ongoing tightening of cold start emissions, perhaps someone will look to a CVT driven centrifugal charger to replace the difficult to certify turbo engines of today. It would be really interesting to drive the charger off the output shaft of the tranny somehow. Doing so would eliminate the need for separate gearing/clutching, etc. The faster you went, the more boost the charger would produce - of course, at that point, you might need a blow off valve in the high gears :-)

UL