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An Unorthodox Racing's CNC-machined, billet aluminum underdrive pulley set was also added. This pulley set has been dyno-proven to add 6-wheel hp to the SR20. Additionally, the UD pulleys also help reduce a classic SR20 weak spot. The SR20's water pump cavitates at about 6500 rpm. This makes trackdriven SR20s prone to overheating. The UD pulley reduces the water pump drive speed and makes the engine a lot less likely to overheat when the car is road raced.