Heavy backfire when under a load

**Lunatikgixxer** · 10-04-2011, 07:04 PM

Lately ive been getting a single heavy backfire every time i shift when im around 5k-6k rpms. The other night i had my cut out open and my friend was behind me and when i shifted from 1st to 2nd he said my car popped fire. Is this bad or what?

**cammed goat** · 10-04-2011, 08:57 PM

Not if you have an aftermarket cold air intake and exhaust. If I am correct, the factory airbox acts as a flame arrestor. Higher RPMs mixed with unburned fuel upon throttle release will cause a flame emittance from the exhaust. I might be wrong.

**Lunatikgixxer** · 10-05-2011, 08:09 AM

I have an SLP lid, not a CAI. So it wont hurt anything?

***SMWS6TA*** · 10-05-2011, 09:34 AM

It's normal - called header pop (I kid you not). When you had cats this is what they prevented. Cats help burn off the excess gases coming out of the engine.

You'll get it sometimes when you down shift while at a high rpm and let off the the gas to slow down.

Now if you have a constant backfire through out the rpm range then you have other issues.

**Lunatikgixxer** · 10-05-2011, 09:39 AM

ok that makes sense then! and no i dont have any constant backfires just one heavy pop when i shift at like 5-6k rpms... I was also thinking maybe its doing it because the cut out is open and its straight piped basically..

**cammed goat** · 10-06-2011, 10:40 AM

You're most likely backfiring out the cutout. Normal.

**0rion** · 10-06-2011, 12:19 PM

is it doing it when under load or when you hit the clutch to shift?

**Lunatikgixxer** · 10-06-2011, 03:42 PM

right when i shift it does it so yeah pretty much when i let off the gas to hit the clutch. It also did it through my catback today..

**0rion** · 10-06-2011, 03:55 PM

that's just unburned gases in the exhaust.....normal with free flowing exhaust.

**Cutlass** · 10-06-2011, 03:57 PM

If its running a little too rich, raw fuel builds up in the exhaust and can cause backfires.

**0rion** · 10-06-2011, 04:09 PM

yeah....being a little rich wouldn't help but I think it has more too do with free flowing exhaust scavenging gases out of the cylinder combined with a slight fueling delay when you jump out of the pedal. That's always been my thinking on it. You can have a factory exhaust car that never does it until you put on free flowing exhaust.....the fueling really hasn't changed much but your scavenging effect has. I'm sure it's a combination of everything really.

**Lunatikgixxer** · 10-06-2011, 07:10 PM

My car does smell like gas pretty bad sometimes.. Although i do have a cam and no cats it can be pretty heavy sometimes.. I dont know how it would be running rich though since i got my car dynoed about 7-8 months ago. Could possibly be the O2s being bad?

**derekbuckner1** · 10-06-2011, 07:51 PM

O2s or MAF could cause the car to run rich. If you've got a cam and tune, a wideband wouldn't be a bad idea to be able to keep an eye on your afr

**Lunatikgixxer** · 10-06-2011, 07:54 PM

yeah i was thinking about getting one but theyre so damn expensive!

**35th-ANV-SS** · 10-06-2011, 10:18 PM

Ruining an engine caused by a lean condition is more expensive

**0rion** · 10-07-2011, 01:57 AM

Originally Posted by Lunatikgixxer

yeah i was thinking about getting one but theyre so damn expensive!

you can get an innovate LC-1 with gauge on ebay for like $170 shipped......that's not bad at all in the car parts world. I wouldn't worry about your exhaust popping....sounds normal to me. It would however be a good investment to get a wideband to keep an eye on your AFR.

**mpfranks** · 10-07-2011, 05:32 AM

I recently have the same problem. Kept bottoming out and had to remove my cats. Now when letting the engine rev down from 4-6k rpms, I get a loud embarrassing backfire. Just wondering if there's anything I can do to prevent this?

I have stock internals, ls6 intake, lid, lts, ory, catback, rear o2 delete and mail tune by frost.

Would a real tune help out at all?

**Lunatikgixxer** · 10-07-2011, 06:52 AM

Originally Posted by 0rion

you can get an innovate LC-1 with gauge on ebay for like $170 shipped......that's not bad at all in the car parts world. I wouldn't worry about your exhaust popping....sounds normal to me. It would however be a good investment to get a wideband to keep an eye on your AFR.

Yeah youre right, i will check it out.

**0rion** · 10-07-2011, 08:26 AM

why are you guys embarassed by it? I like all the sound I can get out of mine. That popping on decel just means it's making so much power it's having to puke some through the exhaust.

**derekbuckner1** · 10-07-2011, 09:47 AM

Originally Posted by 0rion

why are you guys embarassed by it? I like all the sound I can get out of mine. That popping on decel just means it's making so much power it's having to puke some through the exhaust.

Oh I'm not, that's why I have my cutout. Magnaflow got rid if my growl on decal.