Abstract: A supercharger clutch system has a clutch housing (52) in which a clutch pack (84) is disposed to transmit torque from an input, such as a pulley (66), to one of the timing gears (58). The clutch pack (84) is disposed within a cage (92), having a spring seat member (98) adjacent thereto. A set of springs (104) biases the seat member and the clutch cage (92) to engage the clutch pack (84). On the opposite side, axially, of the clutch pack there is a piston (76) including a portion (80) surrounding the clutch cage (92) and engaging the seat member (98). The piston (76) and the clutch housing (52) define a pressure chamber (106) which, when pressurized, causes movement of the piston in a direction compressing the springs (104) and disengaging the clutch pack. With the invention, the clutch system can be operated by engine lubrication oil, while still achieving rapid engagements (short response time), wherein the rate of engagement can be modulated to suit vehicle operating conditions.