The original Lotus Supercharger pulley has a 3.2" diameter.
By changing (decreasing) the diameter of the supercharger pulley, you make the supercharger rotors spin faster; therefore increasing airflow through the intake at a higher boost pressure, and yielding higher horsepower and torque.

Typical gains from the 77mm pulley upgrade are 8bhp and 10Nm of torque across the entire power range.

We've also reduced the weight of the pulley from the standard 497g to an exceedingly light 173g; reducing the rotational mass and reducing stress on the drivetrain.

We offer a range of pulley sizes for different levels of performance.
For the stock Lotus Exige S, we recommend a 77mm pulley. After many hours of testing, we decided that it was the best size for the perfect balance of performance, inlet temperatures and reliability.