Changing the pulley ratio results in the supercharger working at a higher speed and producing more boost. Because this just directly increases airflow through the car’s existing sensors, the ECU is kept aware of the increased flow and no further alterations or remapping are needed to benefit from this modification (though for some models further gain can be achieved through remapping). These upgrades have been fitted now to many cars and discussion on forums and bar stools usually refer to about a 35-40bhp/ftlb gain from this size of pulley modification. That is true for the midrange gain, though the Eaton M112 supercharger becomes less efficient at high rpm so peak power gain at high rpm may realistically be about 10-15bhp. Irrespective of the increase tailing off a little towards redline.
