C7 Backfiring Question
Thread Starter
Instructor
Joined: Jul 2013
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2025 Corvette of the Year Finalist - Modified
C7 Backfiring Question
My friend and I both took delivery of our C7s last week, and have different break-in philosophies. I take it a bit easy for the first 500 miles, but he breaks his cars in hard from the get-go. He says his car is backfiring on full throttle bursts. Is this anything to be concerned about, or should he take it back to the dealer for evaluation? Any feedback will be appreciated.
Le Mans Master
Joined: Sep 2003
Posts: 8,847
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From: Longview Texas
No matter how you break it in, I would not be making any full throttle starts or stops. Remember, you are not just breaking in the engine, but also the transmission, differential, and brakes.
I would think that any back firing, no matter how many miles are on the car, would not be normal...
I would think that any back firing, no matter how many miles are on the car, would not be normal...
Tech Contributor
Joined: Jan 2006
Posts: 4,761
Likes: 240
From: Saint Louis MO
St. Jude Donor '14-'15
That's completely normal... It's big in the FI world, and it's a fueling/timing effect.
For example, in the MINI world it's called "pop-and-burble". I have a full race MINI and a full rally-spec MINI, and they both do it because of the timing.
The demo C7 videos all showed "backfiring" / popping on a full throttle shift. It's unspent fuel detonating in the cats (or in the case of catless, in the pipes).
Oh, and my C7 "backfires" quite often on those shifts (especially high-RPM downshifts). Completely normal. Not as fun as turbocharger fire coming out the pipes, but still nice to hear.
For example, in the MINI world it's called "pop-and-burble". I have a full race MINI and a full rally-spec MINI, and they both do it because of the timing.
The demo C7 videos all showed "backfiring" / popping on a full throttle shift. It's unspent fuel detonating in the cats (or in the case of catless, in the pipes).
Oh, and my C7 "backfires" quite often on those shifts (especially high-RPM downshifts). Completely normal. Not as fun as turbocharger fire coming out the pipes, but still nice to hear.
Last edited by Theta; Oct 16, 2013 at 01:56 PM.
Team Owner
Joined: Jul 2002
Posts: 36,951
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From: This city NEVER sleeps! Frank's back yard!
That's completely normal... It's big in the FI world, and it's a fueling/timing effect.
For example, in the MINI world it's called "pop-and-burble". I have a full race MINI and a full rally-spec MINI, and they both do it because of the timing.
The demo C7 videos all showed backfiring / popping on a full throttle shift. It's unspent fuel detonating in the cats (or in the case of catless, in the pipes).
Oh, and my C7 backfires quite often on those shifts (especially high-RPM downshifts). Completely normal. Not as fun as turbocharger fire coming out the pipes, but still nice to hear.
For example, in the MINI world it's called "pop-and-burble". I have a full race MINI and a full rally-spec MINI, and they both do it because of the timing.
The demo C7 videos all showed backfiring / popping on a full throttle shift. It's unspent fuel detonating in the cats (or in the case of catless, in the pipes).
Oh, and my C7 backfires quite often on those shifts (especially high-RPM downshifts). Completely normal. Not as fun as turbocharger fire coming out the pipes, but still nice to hear.
Melting Slicks
Joined: Jun 2004
Posts: 2,130
Likes: 54
From: Granbury, Pecan Plantation TX
Now that there have been a few out there on the street, this is relative to the A6 Z51, under full acceleration during the shifts there appears to be a bit of backfire another post above related this actually to fuel lighting up in the cats and that's what it sounds like. I am curious as to how many A6 owners have experienced this. Basically did this in the tour mode, will try it later in Sport & Track to see if results the same.
Instructor
Joined: Jun 2009
Posts: 245
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From: Moab UT
Now that there have been a few out there on the street, this is relative to the A6 Z51, under full acceleration during the shifts there appears to be a bit of backfire another post above related this actually to fuel lighting up in the cats and that's what it sounds like. I am curious as to how many A6 owners have experienced this. Basically did this in the tour mode, will try it later in Sport & Track to see if results the same.
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Instructor
Joined: Nov 2005
Posts: 108
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From: West Union SC
Pop!
I thought it was the rev limiter causing the pop! I wanted my A6 to shift before it pops, but I am still learning about this C7... I do not like it as it is not a smooth acceleration if it pops between gears- duh! There is a pause in momentum when this occurs and that is not desirable IMHO.
Tech Contributor
Joined: Jan 2006
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From: Saint Louis MO
St. Jude Donor '14-'15
I thought it was the rev limiter causing the pop! I wanted my A6 to shift before it pops, but I am still learning about this C7... I do not like it as it is not a smooth acceleration if it pops between gears- duh! There is a pause in momentum when this occurs and that is not desirable IMHO.
That momentary gap may only be 500ms, but break that down at 5000rpm and you have 333 cylinder fires in that time. Of course you're going to have a burble there, as that fuel is being expended and thrown through the exhaust system un-burned.
Hell, you should hear my rally car with anti-lag.
Tech Contributor
Joined: Oct 1999
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From: Charlotte, NC (formerly Endicott, NY)
Well, with a traditional automatic Torque Converter, you're going to have a momentary gap in acceleration., unlike DCT which already has the gear engaged.
That momentary gap may only be 500ms, but break that down at 5000rpm and you have 333 cylinder fires in that time. Of course you're going to have a burble there, as that fuel is being expended and thrown through the exhaust system un-burned.
Hell, you should hear my rally car with anti-lag.
That momentary gap may only be 500ms, but break that down at 5000rpm and you have 333 cylinder fires in that time. Of course you're going to have a burble there, as that fuel is being expended and thrown through the exhaust system un-burned.
Hell, you should hear my rally car with anti-lag.
Bill
Instructor
Joined: Nov 2005
Posts: 108
Likes: 1
From: West Union SC
So it appears I am stuck with this popping... Even with the cats removed, long tube headers, head work, AFM/DOD/VVT deletes, new CAI and medium size cam? I was hoping this would make it go away... I guess we'll see...
Tech Contributor
Joined: Jan 2006
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From: Saint Louis MO
St. Jude Donor '14-'15
Tech Contributor
Joined: Jan 2006
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From: Saint Louis MO
St. Jude Donor '14-'15
Drifting
Joined: Oct 2006
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From: Bristol, VT
Mines manual, and a C5, so take it with a grain of salt, but it does it only in deceleration in gear/engine braking situations. Or holding part throttle to avoid hitting the rev limiter while keeping the revs up, staying in the gas as much as possible while upshifting, etc.
So in sport mode if the C7 is holding gears to keep you in the power band, and has the most aggressive engine programming active, staying in the throttle as much as possible to minimize the lost acceleration from cutting the power, it makes sense that the C7 could do it.
Last edited by CPhelps; Dec 31, 2013 at 10:30 AM.