Lightweight Crank Pulley!
The rule of thumb is that each pound of weight taken off the engines rotating assembly is worth approximately 2.7HP. The concept is that the crank is a parasite; it does not put power to the drive train but still requires the traditional harmonic damper to protect against crank failure from torsional movement. This is not necessary in the MINI or most modern engines because of the many advances in engine design and materials. Factors such as stroke, displacement, inline, V configurations, power output, produced by the engine to rotate. When you reduce this parasitic weight, you release power that was previously used only for spinning the supercharger and alternator.
Is this crank pulley safe? The pulleys on the R53's 1.6 and most new smaller engines have an elastomer (rubber ring) incorporated into the pulley that looks similar to a harmonic damper. The elastomer in the OEM pulley serves as an isolator, which is there to suppress natural vibration and noise from the engine itself, the A/C compressor, P/S pump, and alternator. The purpose of a traditional harmonic damper is to protect against crank failure from torsional movement.
Available in either stock diameter or 2% over-sized. The 2% pulley is a great match with a 15% supercharger pulley.