The Studebaker Packard ( and modern Paxton?) system used throttle position to engage the planetary ball friction drive and rev up the 'charger with no change in engine rpm.
Snow mobile drives balance rpm and torque sensing in curious ways. They keep the engine at a fairly even, fairly high rpm, when the engine's main job is to drive the rear wheels. I'm not sure how a fairly standard one would drive a supercharger.
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On the snow -
The front (drive) pulley "size" is always trying to be "larger", limited only by what the rear pulley allows it to be.
At part throttle, low load, they shift "up" by means of the front pulley being allowed to get larger, and the rear one relenting and getting smaller. But, If the engine revs rise, the front pulley tries extra hard to be narrow, and a large diameter, and the rear pulley gives up, and becomes smaller (high gear), and the engine revs drop back a bit.
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Driving a 'charger on the highway -
Apply throttle, and the denser manifold pressure would mean more charger load/torque, and the drive would "down shift," because the rear driven pulley's torque sensing ramps would force it to assume a bigger diameter, and hard enough to overcome the front pulley and force it to be smaller and slow down the charger for less boost. Then when the engine did speed up a little, the drive pulley would get narrow, and bigger diameter, and drive the 'charger faster.
I'm thinking that with standard kinds of pulley logic the 'charger response >might< be even more logarithmic than the natural behaviour of a centrifugal 'charger. boooooOOOOST.
