florsh

Farmer Jim here, looking for some input on installing a 180mm aftermarket supercharger pulley on my 04 E55. I purchased the car used with 70k miles, it has the chirp/squeak at low rpm throttle engagement. My local shop is saying that its the supercharger pulley/clutch. Makes sense to me, sounds about right. Anyways I'm thinking of installing a 180mm aftermarket SC pulley which will bypass the clutch and maybe resolve my squeak, plus add a bit more HP and from what I understand a quicker throttle response. My main concern is bypassing the SC clutch, which will mean that the SC will always be engaged. Will/could this this lead to excessive wear on the SC? Are there any benefits or downsides to doing this minor upgrade. Also, at this time I'm not planning on installing any tunes. Bad idea? Any input greatly appreciated.

HGMotorsports

You do not want to run a different diameter pulley without a tune, the pulley adds power by increasing the supercharger's boost pressure (by spinning it at a higher RPM) but without proper tuning, you would lean out your air to fuel ratio which is less safe for the engine. Besides increasing your risk of detonation if you lean AFR out too far, a slightly leaner Air to Fuel Ratio will still increase combustion temperature.

Besides, you definitely need a tune with a fixed pulley. For one thing, the stock ECU can use the supercharger clutch to quickly disengage it in situations when it needs to protect the motor (excessive intake air temperatures, for example) and you lose this ability when you get rid of the clutch so keeping IATs in check becomes critically important.