im going to build a 1st gen for road racing and want to get as much power as possible. The class has srict rules and only alows smog equipment removal, straight pipe exhaust, and high flow intake filter. i was wondering what the best diameter pipe would be for the exhaust. A company that builds these cars use a 2.5 inch straight exhaust, but that seems a little big to me for such a small displacement engine. what do you guys suggest? also what are some suttle things i can change to get a few extra horsepower.

 

what road racng class are you setting this up to run?

 

well what year is it and is it a gsl or -se or what?

 

for a stock port 2.25 seams too big, 2 is usually the max for a even a bridge.

for a stock port you will get the most power from runnign uncollected dual 2in system with no mufflers.

(loudest thing you will ever hear)

 

im preping it for the pro-7 class. im not really fimiliar with all the classes but i think its even more restrictive than spec rx-7. i figured 2.5 was way to big. the engine will be a stock internal 12a with only a few mods. i guess i can try a few different sizes, but i just want to pick your rotorary brains. right now i have a honda prelude, and know practally nothing about rotorarys. anyways thanks for the suggestions

 

wow...my spelling sucks...sorry guys its rotary....i thought that looked wrong. hahahah

 

I'm just getting into Spec 7 racing myself and the SCCA Rules sheets I've seen say 3'' is the max and I've heard thats what some of the guys run. It seems a bit crazy to me but I guess you wouldn't need to worry about any restriction.

 

http://www.sevensonly.com
guys check this link out (:
has the rules and specs
Spec 7 is more restrictive than Pro 7

 

Run 2 inch primary pipes (preferably long), collecting into a 2.5 inch pipe somewhere before the diff, a straight through muffler, maybe a pre-silencer or two and you can't go wrong.

 

Peripheral Port!!! And it's not THAT loud...it's just louder than everything else

 

check out the race car forum

 

I know a few scca spec-7 racers. They use a Racing Beat header. The collector is welded to a long tube which expands to 3" and then flows through a 3rd gen muffler. These are 12A cars!

 

thanks for the link, buti have personal talked to sevens only racing. In fact they are the ones who got me interested in the pro-7 class. the exhaust from sevens only racing is 2.5 inch and supposedly makes 2 more horespower than any other exhaust. that 2.5 just seemed a little big. in a way i wish the class was less restrictive, but oh well thats makes it cheap and thats the reason i want to get into it. it is the only serious racing i could possibly afford.

 

i was talking to a guy that was in the spec-7 series, dont remembe his name, but his car was pretty damn sweet. they were racing on road america about 2 miles away from where i live THANK GOD , if any of you guys ever get a chance to go on it, trust me, do it, its one of teh funnest things i have EVER done!! its unreal.