This Lightweight Underdrive Crank Pulley is made of 6061 Aluminum, and has a 20% accessory reduction.
While the stock crank pulley is made surprisingly light, the smaller diameter of this pulley allows the rotational mass required to turn it to be only two-thirds of what is required to turn the stock pulley. While this gives a slight increase of power, the majority of the increase will be from the underdriving of the accessories.
The pulley is 20% under-driven, as this is the best compromise of power and drivability. There are not any problems of battery charging, coolant temperatures, or steering assist in a normally functioning vehicle.
Testing has been done under full electrical loads for extended periods without any drops in charging capability.
The added benefit of this pulley is that it remedies the problem of the stock Power Steering Pump overheating during spirited driving, such as time at the track. The Power Steering Pump being driven at these lower rates keep it running cooler, without any difference in steering feel.
With the smaller diameter of the pulley, a shorter belt is also needed. This belt is a 6PK2087 belt, which is a 6-rib, 82.2 inch long belt, commonly found at most automotive stores for around $20. The bolt that holds the pulley in place is a one-use-only bolt. It should be replaced whenever it is removed. This bolt is Porsche part number 900.082.085.09 and is normally found for around $3.
Horsepower increases should be up to 15hp at the crank, and this estimate has been verified from dyno results with other similar pulleys. This pulley is intended to work with any Porsche that has a stock pulley number of 9188.8.131.52.
The Light-Weight Underdrive Crank Pulley offers the largest pulley possible, with a high polished finish, at a low price, and with the largest increase in power through the highest under-driven percentage without sacrificing drivability.
Standard shipping charges will apply to the rest of the world.