OK, so the car's been out of the body shop for almost 3 weeks now. And all of a sudden I have an itch. So, should I drop a 17% pulley into my factory JCW with RMW tune? Will I need to have Jan re-tune it?
Those running the 17: any long term negative effects?
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17 will give you help down low, but up high it'll spin faster than supercharger can handle, just generating a bunch of heat, but no improvement in power at higher RPMs. You're a track rat right? I'd stay with 15, it still helps down low, and is pretty much is the upper limit of what the supercharger can usefully handle at high RPM's. And it's not like there's going to be a huge difference in performance even down low going from 15 to 17, I don't think that small of a change is really going to be worth it, just my 2 cents.
I have the JCW, and eventually (when I'm having some other stuff done) probably swap out to a fifteen. Don't know why they didn't go with a fifteen in the first place....