One of the best ways to increase the power on a Cooper S is to turn up the boost. The Cravenspeed Supercharger pulley will create more boost by spinning the supercharger quicker. There are 2 types of pulleys available, 15% and 17% reduction from standard.

15% is most suited to competition, or for the driver that pushes their car most of the time as the strain on the engine is less. The 17% pulley is better suited to drivers that want more power for occasionally short bursts, although can be used more competitively if you uprate your standard intercooler to accommodate for the increased temperatures.

Cravenspeed's supercharger pulleys are formed perfectly and should never throw or chew through your belt as long as the correct size is being used.