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GTOholic
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Discussion Starter #1
Wasn't sure which forum to post this thread, but it sounds like a tuning issue.

When I rev the engine, the exhaust "burbles" and "pops" as the RPM comes down. It also happens when I downshift while approaching a stop. And one time I actually heard a BACKFIRE when accelerating up a hill.

Is this normal? If so, how is that explained? If not, I will have the dealer take a look at it on Monday when they install the "thunk in the trunk" fix.
 

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267 Posts
Mine does it too, and I would think its normal for a high flow exhaust.
The SLP exhaust on my GrandPrix GTX does too, and its an auto.

Have you ever seen a road race in person? (SCCA) all the cars do it when decelarating.
 

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:bubbrub Florit, Mine has done the same. I have an A4. Specially going down a mountain grade shifting from "D" into#3 gear to hold the car back.

COSMO
 

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Mine often makes a huge gurgling backfire as I decellerate around 1,500 rpm. I love that! :)
 

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May I quote you on that?
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Mine gurgles about 1/2 hour after hitting the drive-thru at Taco Bell. No backfires, at least not with the windows up. :eek:
 

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Growing up is an option
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mistermike said:
Mine gurgles about 1/2 hour after hitting the drive-thru at Taco Bell. No backfires, at least not with the windows up. :eek:
:D :D :D
 

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Disaster
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Just about all V8's will do that with a high-flowing exhaust. My truck does it, mothers WS6 does it.....
 

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GTOholic
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Discussion Starter #10
OK, I like the sound of it, too, but I wasn't sure it was "normal". Now that I know why it happens (high flow exhaust) I am more comfortable. Thanks for the input, folks.
 

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\m/ (>.<) \m/
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762 Posts
The "crossover pipe" in our exhaust isn't actually functional. It's really just a cross brace to hold the pipes together at that point. There is no connection between either side of the duals. The disconnected duals don't "balance out" like when you have an H, X or Y pipe connecting the two. Without any balance between the pipes, it burbles like that. The old GTO never had a cross pipe and it did that kind of burbling too. They made it that way on purpose.
 

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It's normal. Lack of crossover and highflow mufflers are the cause.

X pipe will help
 

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TREAD HERE. LIMP HOME.
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Its normal. I read an article where either Wangers or Lutz or somebody very much "in-the-know" was bragging about how the GTO really "racks the pipes" when you decelerate in gear or downshift. Enjoy.
 

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13 year owner
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16,379 Posts
It has nothing to do with the exhaust other than it being audible because of the better factory exhaust system.

It has to do with the camshaft. Every LS1 I've ever seen does this. It's the nature of the ramp speeds and lobe separation. In older pre-PCM days, it could also be caused by timing issues. But since our PCM controls all timing, it's a function of the cam.

Cammed LS1's do it more and are even more satisfying. :D
 
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