Little backfires

[PJR202]

I'm noticing I get a little crack of backfire when I go from first to second (manual). Any idea why? Engine is completely stock with no tune. Exhaust is an MBRP Street.

It's loose where the H pipe meets the cat on the passenger side right at the clamp. I only just now thought of that, but I always thought backfiring had to do with an engine running rich. I don't know when the backfiring started though. I've just noticed it a few times lately when I have the radio down and am accelerating more gently but still going up to 3500 rpm or so.

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[jasonstang]

Pretty normal.

 

[VinnAY]

lol...a backfire is back thru the intake, hence the name. I have the street on mine and it has a lot of burble and gurgle and pops I'm sure that's what all it is and nothing to worry about.

 

[AlmostFamous]

burble and gurgle and pops

I personally love that sound when driving in the lower gears.

 

[Hashbrownn]

mine does it.
If it wasn't normal, it would have gotten fixed.

 

[wireeater]

"afterfire"

 

[AlyourPal]

Mine does it occasionally, though seems to be a bit more frequent with the new tune and catback. I personally think those little pops (not actually a full backfire) are the best sound in the world and I get the fizz every time it happens.

 

[mm2015]

I have headers on stock catback. I also have a loose connection that I'm too lazy to fix (right where the midpipe meets the resonator), it does burble / gurgle when shifting slowly as you described. Totally normal.

 

[Joe 5.0]

I wish I had more backfire and popping!

SW Catted Headers > Borla Sport Catback

 

[None2Slow]

Quoted from a motorcycle site, still applies.


"When decelerating as that is what 99.9999% of the people mean. When at high rpm and you shut the throttle, you place the intake in a very high vacuum condition. No fuel can get sucked in, only some air. Way more air than the amount of fuel. So it is super lean and the engine cannot ignite it. However, after multiple engine revolutions and no ignition, the fuel accumulates somewhat in the exhaust. Eventually, enough is there and it ignites due to the hot exhaust. You have a backfire".

 

[melwff]

concerning that quote from a motorcycle site, were they referring to a carbureted engine? The ECM in a fuei injection system will not allow a superlean condition since it would cause an emissions issue with high NOX levels.

To the OP, you make no mention of how many miles are on the car?

 

[wireeater]

[ame]
[ame]

 

[TexasRebel]

you haven't seen a backfire until you've blown (at minimum) the air cleaner about 10 ft. high.

Backfire something with forced induction and you might just launch the whole darned fuel intake system...



after-fire (those pops in the exhaust when the butterfly is closed) is from unburned fuel passing the exhaust valve... could be from running rich, could be in the EGR, could be fresh from the valve overlap.
You can get extreme after-fire in a carbureted engine with a mechanical fuel pump by cutting ignition while at speed. The transmission continues to drive the engine, fuel pump and all, and fills the exhaust system with near-stochiometric A/F mixture. Spark the ignition again, and it all burns up in a fantastic blue flame that rids your drive of tailgaters.

 

[JaxS550]

I get pops and gurgles with my corsa extreme CB. I am about to get a tune put on this weekend and I am curious if I will hear more or less...

 

[TexasRebel]

I get pops and gurgles with my corsa extreme CB. I am about to get a tune put on this weekend and I am curious if I will hear more or less...

If the tune is correct the burbles should stay about the same, but the pops will be reduced. Fueling strategies depend on exhaust back pressure amongst other things. Reduced back pressure means more fuel can pass the exhaust valve during the overlap.
That's exactly what happened on my Harley. Swapped exhaust to something much more open and the after-fire on decel got BAD. Tuned it to the new air flow and the offensive high-frequency pops are gone while the low-tone burbling remains.

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