what causes backfiring?
Thread Starter
Race Director
Joined: Nov 2000
Posts: 17,103
Likes: 39
From: stop the fun suckers
what causes backfiring?
at open loop, engine cold at startup i get one or two quite (muffled) pops.. more like poofs.. and under heavy deceleration at speed i might get one or two pops..
is this because i eliminated the cat. converters when they plugged? is this normal for a stroker motor? thanks!
is this because i eliminated the cat. converters when they plugged? is this normal for a stroker motor? thanks!
Racer
Joined: Oct 2003
Posts: 286
Likes: 1
From: Fairfax VA
Re: what causes backfiring? (BluByU)
It's just the fuel from the cylinder exploding in the header or manifold. That is probably caused by the lack of backpressure in your car due to the removed cat, there's nothing to keep the air/fuel in the cylinder, then it hits the flaming hot headers and explodes out there.
I'm not sure what to do to fix this aside from restore backpressure, but there has to be a way to mess with the valve timing to fix it.
Mike
I'm not sure what to do to fix this aside from restore backpressure, but there has to be a way to mess with the valve timing to fix it.
Mike
Melting Slicks
Joined: May 2001
Posts: 2,700
Likes: 3
From: Lebanon KY
Re: what causes backfiring? (ediconu)
:iagree: after removing my cats, it does that. not really a real loud backfire, just quite ones. if i'm driving down the road at 50 or so, and downshift, it'll really start doing it. but i like it :reddevil
Drifting
Joined: Nov 1999
Posts: 1,801
Likes: 2
From: St. Paul MN
Re: what causes backfiring? (corvettemaster)
Also make sure your exhaust manifold is bolted tightly to the heads and there are no leaks in the exhaust system. Leaks in these two areas can cause backfiring on deceleration.
Racer
Joined: Nov 2002
Posts: 478
Likes: 0
From: langhorne
Re: what causes backfiring? (BluByU)
Definatly a lack of back pressure if timing and A/F are correct. Race cars do this all the time. Some of the unburned charge is reaching the headers. Put speed chanel on and listen, especialy when they are showing road racing. :jester I ran an alcohol fueled circle track car for about 12 yrs. and sometimes when we would lift going into a corner flames would shoot out the pipe (open headers) but mostly if you were a little on the rich side. :steering:
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Re: what causes backfiring? (BluByU)
Backfiring occurs when fuel/air is still burning in the cylinder during valve overlap on the exhaust stroke. When you are decelerating there is no load on the engine and the fuel/air burns very slowly at low cylinder pressures (burning rate is directly proportional to the engine load) so near TDC on the exhaust stroke, the intake valve starts to open and the burning fuel ignites the intake manifold causing a backfire.
