What causes backfire?

[supra90turbo]

my car used to backfire, open dp...
felt like someone was firing off shotgun rounds below your ass...

but one day a cop pulled out in front of me, and i leisurely shifted from 2nd into 3rd, even without boost, and it backfired so fucking loud... he didnt even flinch... probably didn't suspect the little "celica" behind him... (that's what everyone around here thinks my car is, who isn't really into cars, which i don't quite get...)
that was when my TPS was misadjusted... decel was cool though. *pop*pop*blub*blub*blub*POP*POP*BANG!!!*

 

[IJ.]

Mine with the LPG Carb doesn't have decell cut so crackles a bit on overrun and agreed sounds way cool !

 

[Joel W.]

as a test, i stuck in the silencer that came with my megan gt muffler. this stopped the muffler explosions but greatly restricts the flow.. so i drilled it out in several steps testing each time as i went. i ended up putting about 8 half inch offset holes around the outer and inner cones and a few through the center tube..

Now its not as loud, it doesnt explode on decell and it still flows like it did without it.. my theory is that the 4 and 1/2 in diameter of the muffler tip may have been letting air back into the exhaust, but im not sure what really is happening.. but i like it this way... Also it does not resinate as bad at 2250rpm's...

 

[NDBoost]

Ive been running open downpipe for just over 1 week now and im used to the sound and backfire, i feel sorry for other drivers around me though :biglaugh: just havent had the time to remount my exhaust after it fell off.

 

[supra90turbo]

LMAO Sabotage, after my exhaust shop special started to de-weld it's own brackets, I took it off, and grew rather attached to the sound. I should've just cut the muffler off and run 3" pipe out the back.

 

[Ckanderson]

holy old post resurection batman!