Courtesy of IL Motorsport in Germany this steel pulley is used to slow down the belt, alternator and water pump speeds. Excessive alternator speeds waste power and can potentially damage your alternator. Water pumps can cavitate when they are run outside normal engine speed resulting in a negative cooling effect.
Running any auxiliary items faster than required is simply a waste of power. Changing your underdrive pulley to our race part can give good gains and the pulley also features an integrated trigger wheel that is more lightweight and reliabile.
Fits all Mk3, 3.5 & 3.75 models, 2005>2015