BoostedSi

I still have my hks hiper exhaust...55mm piping. Am i losing that much hp with that little piping. I've been wanting to get 3" piping from the muffler shop w/ resonator connected onto a apexi n1 universal. That should be my next mod eh?

btw...i have a '00 si w/ 12psi, 9:1 pistons....i only dynoed at 257whp, 185ftlbs..@12.3psi. I was very disappointed with the numbers...

could the exhaust be one of the things bringing my dyno down? ThankS

AutoboTxEK

Yes..you probably need a 3" system...and the turbo N1 would be an excelent choice...what size are your injectors?..you might want to go larger....and a 3" DP would hep too...if you dont have it already...

Damon B.

Yeah, get a larger exhaust, and remember, when you lower compression, it takes hp, but you make it up and some with more boost. If you have stock compression, the numbers would have more likely been higher.

maxim

Yes, you should go ahead and get a 3" exhaust and whle you're at it check with Arturbo, he has been known for his great 3" downpipes. That will make the whole system complete.

BTW..larger diameter exhaust will definetly help out with your your hp, but also help out with faster spool up time.