What does a bigger supercharger pulley do?
A smaller supercharger pulley will spin faster and increase boost, while a larger pulley will spin slower and decrease boost. This means that by changing the size of the pulley, you can fine-tune your supercharger’s performance to match your driving needs. When sizing pulleys, remember, pulley diameter and RPM are inversely proportional: if the pulley gets bigger, the RPM gets slower, and as a result, torque increases, and the reverse is true, the smaller the pulley, the higher the RPM, and the lower the torque.Bigger the pulley the more distance a fixed point on the rim has to travel in order to complete a revolution therefore the slower the pulley turns.The bigger your driven pulley (vs the driver), the slower it will turn but the more torque it will produce. The smaller your driven pulley (vs the driver), the faster it will turn but the less torque it will produce.
Will a bigger pulley increase speed?
Put simply: To speed up a driven pulley (and achieve less torque) it should be smaller than the drive pulley. To slow down a driven pulley (and achieve more torque) it should be larger than the drive pulley. In a pulley system, the smallest pulley usually turns fastest because it requires more revolutions to navigate the same length of the belt.