Secondary Valve
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2007 MINI Cooper, 2006 MINI Cooper, 2005 MINI Cooper, 2004 MINI Cooper, and 2003 MINI Cooper. However, it is still accessible from the selected car via links, so may be relevant.
The secondary valve determines the clamping force on the secondary pulley by regulating the pump pressure. The higher the clamping force, the higher the torque that can be transmitted.