thafox

it happened on accident ...yes accident, now i hear alot of ppl sayin that it's good an some ppl sayin it's bad cuz your not gettin enough exhaust backpressure so im lookin for answer's here an it's the stock header on a gsl-se

Rusty Shackleford

mine does little back fires anytime i let of gas and my friend told me it was from backpressure build up but i dont know i fell that it is ok i mean alot of people do it when i put my stright pipes on i started up in open headers to hear it

coldy13

Rotaries have no valves, there is no need for ANY exhaust backpressure. You'll gain some power from exhaust scavenging and tuning the length before the 2 pipes collect, but that's completely different from backpressure.

peejay

No engine needs backpressure.

Except for GSL-SEs and S4 N/As, since they use backpressure to open the aux ports.

Open header is loud, mkay? Also it makes you run real lean if you have a carb and don't retune it. (AFM-style EFI should have no issues)

thafox

yea since it happened it did smell really rich, i messed with the idle screw though an now it smell's like burnt exhaust instead of a rich exhaust smell, again is this good or bad?

alien_rx7

With just the stock exhaust manifold on either the 12a or 13b, running it open I believe you actually lose a little of the top end power, no scavenging effect to help pull out the exhaust. Even with a regular collected header or uncollected header, you wouldn't see much benefit on a stock or street ported engine and would lose a little power. Best to run the exhaust back to the back. Something like 89" long primaries is best IIRC.

On the other hand, bridge and peripheral ported engines run best with super short primaries to a collected megaphone with 2" inlet and 3" or 4" outlet. Sorry don't have the book in front of me.

Backfires are unburnt gas in the exhaust getting a fresh supply of oxygen that causes it to combust from the extreme heat existing in there. Usually they're created because of running a bit on the rich side and a leak in the exhaust somewhere. Not because of back presssure.

alien_rx7

BTW if you're not doing anything this weekend on Sunday, come over to East Lansing in MI for the mirotary club gathering.

http://mirotaryclub.com/forum/showth...=&threadid=571