Popping noises coming from the exhaust are NOT backfires. In fact, with direct injection, it would be very difficult to induce a true backfire unless the there was a damaged valve or really screwed up cam phaser. Generally, what you're hearing is ignition occurring in the exhaust system. The most common cause is the transition from DFCO state back to normal injector operation temporarily passes through a condition where the proper mix of air, fuel, and heat allows combustion to take place in the exhaust manifold.

 

With the cold weather, I'm getting a consistent rasping/popping sound when accelerating and lifting off to the gas to make a shift. It makes the sound whether or not I actually make a shift, so it's definitely just from lifting off the gas. The noise seems to gradually go away as the engine warms. It's a little upsetting, but I'm not sure if it's normal or worth taking it in (I just got my SS last month).

 

What's the definitional difference between a pop and a backfire?

 

A backfire is ignition occurring in the intake manifold. This is virtually impossible to induce in a car with ported or direct injection. Popping is what happens when Orville does his thing.

 

If it's impossible then tell me why my car does it all the time?

 

Because it's likely not occurring in the intake side. Notice also, that I said virtually impossible. Nothing's completely impossible because anything can break. However, I can't envision any scenario that would cause an intake backfire in an EFI motor that would not also result in a motor that was highly crippled. On a "normal" engine, I would say it's DFCO related, as I stated above. However, the fact that you have a third party tune on an engine with a relatively small knowledge base leaves a lot of possibilities. I would have your tuner look into it.

 

Just to chime in on the subject, I have the Hahn DP w/ cat + exhaust + LNF upgrade. Whenever I drive in Comp. mode with the tranny in "I", it constantly pops and burbles when I let off the gas so yes it's a normal thing per se. Now if you're throwing fireballs out of your muffler tip, then that's a different story I'd assume.

Later
Allex

 

Please differentiate pop and burble.

 

Your tune is not handling the rich condition that occurs when you step off the gas. This area of the calibratiion (tune) takes a loft of work and is one of the areas our calibrators spends a lot of time in to make sure it doesn't happen.

 

It's the normal sounds the exhaust makes on on decel. If you've even driven or been behind or in an SRT4, THAT kind of popping + burbling is what I'm talking about, but in a much more muted (i.e. not hella loud) way. Hope that kind of explains what I'm talking about.

Later
Allex