Primary 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 function of the primary valve is to regulate primary pressure, controlling the primary pulley, and changing the transmission ratio. The pressure in the primary cylinder defines the position of the primary pulley mobile half. The greater the distance between the pulley halves the smaller the primary radius of the belt and the higher the transmission ratio.