Modified D21 Superchargers will keep you at the head of the class. Superchargers add great performance. Make heads turn with upgraded D21 Superchargers. For more horsepower and torque, get a Supercharger. Do more with D21 Superchargers. Superchargers are great add-ons for cars and trucks that need extra towing or passing power. Superchargers are a fantastic addition to your ride.