LT1 backfire

My 95 RMW has an interesting exhaust system. Previous owner pretty much has straight pipes from the cats back, running into a pair of what looks to be Flowmasters. It's all welded from what I see, so it's probably a Meineke or similar hackjob. The car sounds like a Camaro which I'm not particularly happy about, but it seems to make folks laugh.

Anyway, I notice that when I rev the motor, upon deceleration I get a few backfires. One probable cause of this is an exhaust leak, probably upstream of the oxygen sensor- is there anything else I should look for? I'm aware that this super high performance exhaust (ahem) has different backpressure than the stock one, and that might screw up EGR, though I'm unclear if that would explain the backfire.

Lets examine definitions first. From Wikipedia:

"A back-fire or backfire is an explosion produced either by a running internal combustion engine that occurs in the induction system rather than inside the combustion chamber. Unburned fuel or hydrocarbons ignited from a slower burning, lean fuel air mixture that is still burning inside the cylinder when the intake valve opens.
Not to be confused with afterfire which is caused by an excessively rich fuel air mixture that is not completely burned during combustion. It is then ignited in the exhaust. A visible flame may momentarily shoot out of the exhaust pipe. Either condition causes an objectionable popping noise, together with possible loss of power and forward motion."

So if you have flames spewing out of the intake, you have backfire.

If your exhaust is popping or flaming it is not.

If popping, It's more likely a scavenging effect caused by the new exhaust system. generalyl thought of as backpressure issues. The engine revs up, the exhaust gases rush down the pipe, and then you let off the gas, but the previous gases still rush down the pipe. It creates someone what of a vacuum in the pipe and makes it pop

Lakeffect- thanks, yes indeed, I'm describing afterfire. Probably should have checked up on that particular terminology- but, it sounds like there's nothing that can be done about it except to replace the exhaust with something closer to the original when this one rusts out. Or, when I finally get annoyed enough, I suppose. I'm assuming then the condition is relatively benign.

I've got a lot of other things that probably need fixing much more badly than this, then, if it's not likely to cause any problems.

Thanks!

if i eat too many baked beans i also have problems with after fire,..

you need to make freinds with a good tuner who can modify your dfco tables,.

or put quieter mufflers on it,. it will still pop but you won't hear it,.

phantom 309 wrote:

you need to make freinds with a good tuner who can modify your dfco tables,.

Yep. Since NASCAR has switched from carbs to fuel injection, the stock cars do not belch fire anymore and they get better mileage too.

Thanks guys, that was helpful (and also very funny)

In case you were wondering.

DFCO is "deceleration fuel cut off."

There is no fuel supplied by that command. Why burn it in the pipe. As Nick said, it would require retuning of the chip.