Back Pop on Rev Down? Tuner Men Advice Needed.

[Zee-Ell-One]

Have always been irritated by back pop on rev down. I've seen some people on this forum actually like it! Can anyone explain what causes back pop/firing (ZL1 seems prone to it) and what can be done to minimize or eliminate it. Thanx.

[jimmy5]

Pressure difference in the exhaust.

[kbar4782]

Did you pull the fuse for the exhaust? Mine didn't do it until I pulled the fuse and I have 1450 miles on mine now and it seems to have lessened. Or I'm just getting used to it.

[SlingShot]

All the V8's do it when slowing down, due to fuel cutoff programed into the ECM. It can be tuned out at the cost of losing your warranty.

[CAM....ZL1]

So if I have my car tuned and my EPS or my alternator,or my ac comp.
goes out and it has nothing to do with the tune it won't get repaired
under warranty. possibly it would only be repairs that could be
linked to the tune, if they could prove it. their is a law that prohibits
manufactures from voiding warranty's unless it says specifically in the
warranty that said changes will void the warranty. And it has
to specify exactly what changes will void the warranty.
I just read this a couple days ago I'll see if I can find it again.

www.wikipedia.org Magnuson Moss Act.
www.dummies.com Keeping your Mod's warranty in tact for dummies. Must read, explains act in the auto industry clearly.

[2012ZL1]

Its there to protect the cats. It would void the warranty on the cats because they could be damaged by overheating without the fuel cooling.

I am going to get rid of it when I take off the cats soon.

Also..YOU NEVER LOSE ALL YOUR WARRANTY. Some people on here assume all your warranty is out the window with mods. This could not be further from the truth. There are laws designed to protect individual consumers from such practices. In order to be denied warranty legally it must be proven that the changes you made had a direct cause on the fault in question.
So if you tune out the cat protection..cats and anything beyond cats in exhaust would no longer be covered under warranty at the discretion of the dealership of course, because that can be proven to have a direct cause to an effect.

[Russell James]

It's for fuel economy. There is a table in the calibration for decel fuel cutoff. Since no power/fuel is really needed for decel, they cut it almost completely off on decel. There is then not enough fuel for combustion in the chamber, and the last little bit goes out into the exhaust and pops when it hits oxygen.

You can turn that decel fuel cutoff off in the tuning, and have no pops and no problem with the cats. Just normal combustion on decel like cars did for 100 years. Harley's do the exact same thing. If someone on a newer injected Harley puts on free flowing pipes and leaves the tuning stock, they pop like crazy. Same thing on those, you just go into the decel table and richen the fuel up until no more pops on decel.

Cat protection is part of the tuning that if the throttle is held wide open for a long time, like a 5 mile highway blast at 180... if the computer senses certain conditions it will super richen up the WOT fueling. So if you're ever blasting down the highway rediculously fast, or maybe on a dyno, and the exhaust starts pumping out dark smoke... it just went into cat protection mode.

[9secs]

Originally Posted by 2012ZL1

Its there to protect the cats. It would void the warranty on the cats because they could be damaged by overheating without the fuel cooling.

I am going to get rid of it when I take off the cats soon.

Also..YOU NEVER LOSE ALL YOUR WARRANTY. Some people on here assume all your warranty is out the window with mods. This could not be further from the truth. There are laws designed to protect individual consumers from such practices. In order to be denied warranty legally it must be proven that the changes you made had a direct cause on the fault in question.
So if you tune out the cat protection..cats and anything beyond cats in exhaust would no longer be covered under warranty at the discretion of the dealership of course, because that can be proven to have a direct cause to an effect.

Heres the other view. They can void almost anything they want after you put a mod on. Install a tuner and the motor blows? guess what they blame it on. transmissions messing up? yep its the tuner. They can choose or not choose to honor your waranty over just about any mod but most dealerships are not that bad. I tend to take my cars to the more performance oriented dealers with higher end cars and they will overlook almost anything. And if you think those "laws" can protect you, goodluck hireing a lawyer and trying to fight GM in court over a warranty claim when the court costs will be 20x the repair.

[Higgs Boson]

it's not the dfco itself, it's the low timing that ramps in and out the dfco mode. the zr1 has way more, like 35 degrees to ramp it rather than like 3 in the camaro. you can just mimic the zr1 dfco spark tables and the decel burble goes away. magic, eh?

[Roger Ramjet]

I'm with Higgs. I have truned the DFCO off and still had decel poping on LS3 motors. Increasing entry and exit timing lessens the pop. The automatics don't seen to have any noticeable pop.

[sammyv]

If your exhaust has a leak it can cause popping on decel!

[SlingShot]

Originally Posted by 2012ZL1

Its there to protect the cats. It would void the warranty on the cats because they could be damaged by overheating without the fuel cooling.

I am going to get rid of it when I take off the cats soon.

Also..YOU NEVER LOSE ALL YOUR WARRANTY. Some people on here assume all your warranty is out the window with mods. This could not be further from the truth. There are laws designed to protect individual consumers from such practices. In order to be denied warranty legally it must be proven that the changes you made had a direct cause on the fault in question.
So if you tune out the cat protection..cats and anything beyond cats in exhaust would no longer be covered under warranty at the discretion of the dealership of course, because that can be proven to have a direct cause to an effect.

Not all your statements are true. The ECM tune can and will void your drive train warranty. They don't have to prove anything other than the ECM has been reprogrammed. You warranty is a service contract between you and the manufacture, and if YOU break any terms of that contract the warranty can and will be void. The act everyone talks about, is there to protect consumers from manufacturers changing the terms of the contract after purchase. Also the use of aftermarket parts only applies to OEM spec parts use for repair replacements.

[2012ZL1]

Originally Posted by SlingShot

Not all your statements are true. The ECM tune can and will void your drive train warranty. They don't have to prove anything other than the ECM has been reprogrammed. You warranty is a service contract between you and the manufacture, and if YOU break any terms of that contract the warranty can and will be void. The act everyone talks about, is there to protect consumers from manufacturers changing the terms of the contract after purchase. Also the use of aftermarket parts only applies to OEM spec parts use for repair replacements.

I respectfully disagree. It has to be proven that what you did caused the problem.

[Zee-Ell-One]

Originally Posted by Higgs Boson

it's not the dfco itself, it's the low timing that ramps in and out the dfco mode. the zr1 has way more, like 35 degrees to ramp it rather than like 3 in the camaro. you can just mimic the zr1 dfco spark tables and the decel burble goes away. magic, eh?

So how do you access the fuel tables to make the adjustment? Laptop program and experience or pay a tuner man? Thanx, I really want to have it sound perfect.