I'm trying to make my car as competitive locally as possible in SCCA Solo STS class. The class rulles allow a header and cat back exhaust, but not a hi-flow cat.

So what's worse, having the same or increasing pipe diameter the entire way out, or having larger piping in the beginning and end, but having a bottleneck along the way?

Would it be better to have a larger collector (say, 60mm) to a OEM cat, then to a 60mm cat-back exhaust or to have the stock size collector (2" I'm assuming) into the cat and then to my 60mm exhaust?

 

bottleneck is worse than stock piping. my RMF header with 2.5 collector was bolted up to my stock exhaust for a while and i lost gobs of power. it was running slower then it did when i was stock.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 91preyludesi &raquo;</TD></TR><TR><TD CLASS="quote">bottleneck is worse than stock piping. my RMF header with 2.5 collector was bolted up to my stock exhaust for a while and i lost gobs of power. it was running slower then it did when i was stock.</TD></TR></TABLE>

That's kinda what I expected. Any other experiences/thoughts?

 

as far as sts class goes suspension and the 615s large rear sway bar for the most part be all you need oh ya neg camber all the way around will help alot. unsprong wieght will help forge rims. if you dont DD the car toe out on the front will help and striping the car to make it as light as possible without going under the mimium wieght which is like 2k.

 

it seems like the bottleneck would be the OEM cat and not the header collector.. just my .02