Quote:
Originally Posted by pokeybritches
The only way you will get the gains you desire is by swapping out the final drive. I don't even think you can get 30 hp by running the car catless, so there's no way on this earth you will get 30 hp with a tune, intake, and exhaust that leave the cats in place. The Euro headers are already catless (and I believe hydroformed), so the OEM quality is good. It is just not possible to get 30 hp. The ones who say it is are probably trying to sell you something.
Spend $3k (US) and get a Performance Gearing limited slip differential with a 3.64 final drive. That way you improve your handling and ability to power out of turns at the same time. Someone correct me if I'm wrong, but:
3.64 (new ratio) / 3.23 (stock ratio) ~ 1.12693
265 hp (stock hp) * 1.12693 ~ 298.63 hp (new equivalent hp)
Your RPM will increase by about 12.7% in each gear so you will have to shift slightly more often, and thus you won't be able to hold each gear as long. Regardless, it will give you the equivalent of the 30 hp gain you desire. If you want more, you can even go with a 3.91 final drive.
This isn't guesswork or claimed gains. It's a mathematical fact that if you swap out the final drive, you WILL put more torque to the ground, and the precise number CAN be calculated. And, the handling benefits of having a limited slip in the back are even more useful than the extra grunt.
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Agreed on taller gearing... might as well throw in a limited slip while you're at it. For the 3.0si coupe, 3.64 is stock for auto, but manual is 3.46 - not sure what OP has, or if it's totally different for roadster. I ended up doing the opposite by going with the limited slip but kept stock gearing. I'm content with the shift points, but it was really a money thing... $500 on top of what I was already paying for the lsd was out of my budget. But 3.73 for auto-x was awfully tempting...