Snap, Crackle, Pop Exhaust-- Stock or Not

[K Love]

Originally Posted by SSDan

Now with the cam and the cutouts open - I get it all -snap,crackle, pop, gunshots, bark, burble, rumble, chop, lope,roar, growl, snarl, drool, snot, quivering, shaking ( opps getting carried away ) - its a real orchestra and I love every note!

music to my ears!

[zztopo]

Originally Posted by TSSUNAMI

Best way to describe it:

Stock, the popping sounds kind of like popcorn in the microwave.

Aftermarket exhaust/muffler delete. the volume of the popping ranges from just louder than stock, to a small firecracker.

Long Tube headers, high flow cats, with a muffler delete: Drive by Shooting.

"Drive by shooting."

Yup, that's what mine sounds like. No wonder I see people dive in bushes when I lift.

[E.T.]

This is due to fuel cutoff on deceleration, right? Do the L99s have this, too? I get a few crackles and pops once in a while, but nothing like a drive-by shooting.

[Higgs Boson]

it's not due to the fuel cutoff itself, it's due to the timing settings during the fuel cutoff event.

[E.T.]

Originally Posted by Higgs Boson

it's not due to the fuel cutoff itself, it's due to the timing settings during the fuel cutoff event.

Interesting. Does the L99 have the fuel cutoff, or is that only an LS3 thing? Just wondering if the tune could be tweaked to make the L99 snap, crackle & pop more on decel...

[litle88]

My L99 with flowmaster C/b,vararam, kooks 1 7/8 catless and tune does it!

And I LOVE IT!

[Stingr69]

My 2010 did the "afterfiring" thing when factory new but I later had my ECM re-flashed at the dealer and the updated GM tune made the crackling on decell go away.

You are hearing the results of a lean misfire. Snap the throttle closed say while going down hill and you get very high vacuum. That high vaccum causes extra airflow to get past the throttle blades but no extra fuel. Not enough fuel is being added by the injectors for the amount of airflow so the mixture is too lean to burn properly. The partly burnt mixture gets into the exhaust and then ignites or explodes, causing the crackle and pop sounds you hear. A little is OK but a lot will damage stuff.

-Mark.

[DCC1464]

Originally Posted by Stingr69

My 2010 did the "afterfiring" thing when factory new but I later had my ECM re-flashed at the dealer and the updated GM tune made the crackling on decell go away.

You are hearing the results of a lean misfire. Snap the throttle closed say while going down hill and you get very high vacuum. That high vaccum causes extra airflow to get past the throttle blades but no extra fuel. Not enough fuel is being added by the injectors for the amount of airflow so the mixture is too lean to burn properly. The partly burnt mixture gets into the exhaust and then ignites or explodes, causing the crackle and pop sounds you hear. A little is OK but a lot will damage stuff.

-Mark.

if you dont mind me asking, why was your ECM re-flashed?
was it due to the pop/crackle or another problem and just had an additional side effect?

[Stingr69]

Originally Posted by DCC1464

if you dont mind me asking, why was your ECM re-flashed?
was it due to the pop/crackle or another problem and just had an additional side effect?

I have an early build and was about to install a supercharger. Some people with early build cars in the process of installing blowers had an issue where the car would not run after the supercharger was installed and the canned tune was loaded. There was supposed to be a "table" to reference in the factory code that was missing on the early builds that would allow the ECM to work after the new supercharger tune was loaded. The car would not run again without this missing table. No tuner would be able to install the missing table. If this happened to you, the car needed to be towed to the dealer and then have the ECM re-flashed, then re-install the supercharger tune yourself. NOT FUN! To prevent the potential problem, it was just a precaution to do the ECM update at the dealer before I did the supercharger install. It was not a wide spread issue but it did happen to some forum members here. BTW - Not all dealer's service departments would agree to do this re-flash without a "reason" they could understand :(. They certainly would not do it under warranty. I had to pay for it. Cheap insurance.

I drove the car a few weeks after the re-flash before installing the supercharger. I did notice the reduction in afterfiring at that time. It was just a side effect.

-Mark.

[Higgs Boson]

Originally Posted by E.T.

Interesting. Does the L99 have the fuel cutoff, or is that only an LS3 thing? Just wondering if the tune could be tweaked to make the L99 snap, crackle & pop more on decel...

L99's have it as well. It's an emissions thing, every car on the road that I know of since the late 90s has it.

If you measure a carb car with a wideband (or turn off DFCO in a fuel injected car) you will see that the fuel still flows but the throttle is shut and the readings are rich, very very rich, like 9.5:1, etc. Obviously you don't need fuel if you are not accelerating so why not stop the flow if you have the means? It cleans up emissions and saves a little gas.

[Higgs Boson]

Originally Posted by Stingr69

I have an early build and was about to install a supercharger. Some people with early build cars in the process of installing blowers had an issue where the car would not run after the supercharger was installed and the canned tune was loaded. There was supposed to be a "table" to reference in the factory code that was missing on the early builds that would allow the ECM to work after the new supercharger tune was loaded. The car would not run again without this missing table. No tuner would be able to install the missing table. If this happened to you, the car needed to be towed to the dealer and then have the ECM re-flashed, then re-install the supercharger tune yourself. NOT FUN! To prevent the potential problem, it was just a precaution to do the ECM update at the dealer before I did the supercharger install. It was not a wide spread issue but it did happen to some forum members here. BTW - Not all dealer's service departments would agree to do this re-flash without a "reason" they could understand :(. They certainly would not do it under warranty. I had to pay for it. Cheap insurance.

I drove the car a few weeks after the re-flash before installing the supercharger. I did notice the reduction in afterfiring at that time. It was just a side effect.

-Mark.

Do you have any more info on this? Seeing as how the ECM is used in other vehicles I wonder what GM did with the early operating systems in the camaro....or if it was an issue with a handheld tuner?

[edgehead2000]

I just purchased a used 2010 SS this past May and I ALWAYS get a loud rattle/pop out of the exhaust at startup, never during drive (unless you include the stock drone @ 1800 rpm). With 36k on the odo, is this normal or should I ask GM for an ECM reflash? To my knowledge, the car is all stock.

[edgehead2000]

Originally Posted by Superstreet14

Does it sound like mine?

Love the sound of your exhaust man. What's your setup?

[Stingr69]

Originally Posted by Higgs Boson

Do you have any more info on this? Seeing as how the ECM is used in other vehicles I wonder what GM did with the early operating systems in the camaro....or if it was an issue with a handheld tuner?

It was an issue with the early build factory tune. If you do a search for early supercharger installs you will find some threads on the subject. I did the ECM update as a precaution. Once the blower is all installed, you would load your custom tune and the car would not run. If you went back to the factory tune it would run but clearly you would not want to drive to the dealer for the ECM update with a blower running a stock tune. Those affected would have to flat bed to the dealer and then try to get them to cooperate with you on the ECM update. My dealer would not even do it for money. I had to go to another dealer that was more "performance oriented" for the ECM update and pay for it. It was MUCH easier to do the update first and then try the blower install. Only a few guys were affected on this board.

-Mark.