Thank you for your patience as I checked with our Technical Services Department regarding your question about installing a lightweight crank pulley. They advised that the crank pulley is an overweight pulley and Subaru designed it this way to maintain the 300 horsepower/300 torque goal that the company was aiming for. In future years, Subaru planned to lighten the pulley to give newer USDM STIs more power in conjunction with other parts, to make future models more attractive with more power. This is especially relevant since, at the time of designing the pulley, Subaru expected Mitsubishi to release a new lighter, quicker EVO in the 2004-2005 model year. In that event, Subaru positioned itself in such a way that it could quickly respond by lightening the pulley along with the flywheel coupled with some other modifications to give the STI the added oomph to once again top the EVO in overall performance tests.

Some more information I learned with this inquiry that I thought might interest you is that the the 2005 model year will include a new performance STI, called the STI-C. This will come with a twin scroll turbo, stainless steel brakes designed for the Brembo race rotors, and pillow ball rear suspension (full group-n race suspension). Estimated horsepower is expected at 345 while torque specifications are unknown until a prototype has been built, but look for 330 or so.

Thanks for the opportunity to be of assistance. I learned a lot and I hope you did too. If you need any future assistance, please feel free to contact us again, and specifically direct your questions to me because the more I learn the better I am in a position to direct SOA regarding warranty claims and the mods they should look for in an effort to void the manufacturer's warranty.

Best wishes,

Steven O. Allen
Subaru of America, Inc.