jtcamaro

I have had my Camaro SS2 RS now for about 6 months. I had the GM Exhaust upgrade installed prior to receiving the car by the dealer. The one annoying thing about the car is while driving at lower speeds it sounds like the transmission shifts into a higher gear causing the car to feel like it is struggling until you press the gas (no pickup at all for a second until it kicks into a lower gear). The muffler tone changes as well similar to the sound of driving in 3rd gear while doing 20mph on a manual transmission. Any ideas? Is there something not right or does everyone see the same issue? I thought at first it was the active fuel management.

JasonD

Are you sure it is not the AFM? When putting on an aftermarket exhaust, it really accentuates it when it is activated.

jtcamaro

The Exhaust is a genuine GM (Chevy) Exhaust system. Is there any way to know if it is actually the AFM?

Thanks for the response.

JasonD

Yes, but it is still an aftermarket (not stock/factory) exhaust. In fact, it is made by Borla.

Chances are, it is the AFM you are hearing and feeling. When cruising around, it kicks in and you are in 4 cylinder mode until you require more power, and then it switches back to 8. Just to be safe, take it to the dealership and have them check to make sure everything is working properly.

Are you losing any performance when you want to turn things up a bit? Does the car run rough or erratic?

jtcamaro

The car runs fine. No issues at all except the 1 sec delay until all the cylinders kick in (if that is what it is doing). Anyone who drives in the car always asks why the muffler tone changes as often as it does at low speeds. Anyway, highway driving is fine and when you really want the power there are no issues. I will take your advice and take it to the dealer just to have peace of mind. Thanks again. This is a great forum!

JasonD

I would almost say you don't need to take it in. Based on your last post, I am pretty confident it is your AFM. You described it exactly how it is. Remember, you are going from 8 cylinders to 4. That changes everything, including exhaust sound and such.

jtcamaro

This may be a stupid question but is there any way to disable the AFM?

JasonD

Not a stupid question at all. There is a way...sort of...but it is not easy.

You have to remove the mechanics of it...basically swap in the LS3 valvetrain and then have a tuner program the AFM out of the ECM. I don't think there is a way to do it with just programming alone, but you may want to look into it.

jtcamaro

I will look into it. I didn't buy this car to save on gas Thanks again for all your help!

JasonD

LOL, I didn't either but it helps the sales numbers.

However, I did want to play with the tap shift...so I got the L99 myself but I sorta took care of that AFM and VVT problem.

jtcamaro

Hmmm...can you share your procedure for taking care of those problems?

jtcamaro

I am reading online that if I purchase the DiabloSport Predator Tuner - U7194 - this will easily let you disable the AFM and also gain about 20HP? Do you have any experience using this and will it do any damage to the engine?

JasonD

I swapped in LS3/LS9 cam and valvetrain. The Magnacharger likes it more.

I haven't myself as I had a custom tune. As far as it doing damage, that is a sort of loaded question. Any time you make the engine work harder, the wear is increased (in theory). Diablo makes a good product so if it does what you need, I'd give it a shot.

jtcamaro

Thanks for your feedback and advice. Much appreciated. I will let you know what I decide to do and how it works out.

mudbone

As for a way to "tell" if AFM is the culprit -- Jason, does the DIC readout allow a display of V4/V8 mode like my Avalanche does? If so, he could set the DIC to that display mode and confirm the mode shift is accompanying the sound he is hearing. Just a thought.

BTW, this is one reason I have held off on an aftermarket exhaust for my Avalanche. I'm afraid it will sound weird most of the time.