Exhaust popping on decel?

[phoneguy]

Just installed used cat bypass and B&B 1 in - 1 out and it sound great on acceleration! Only problem is it pops bad on the deceleration. Any ideas? Thanks in advance!

[bigchillcar]

i've heard of this happening with this change in exhaust configuration. i don't have an answer, but i suspect you'll be hearing feedback on the causes and solutions soon. if not try a thread search on the topic.
ryan

[ben parrish]

Most likely an exhaust leak. Go back and check all the connections and gaskets.
Ben

[A Quiet Boom]

This is most commonly an exhaust leak as stated previously. On decel the drop in pressure sucks fresh air into the exhaust causing the pop, it's worse if the mixture is on the rich side to begin with. An old trick I used on V8's with headers was to run two gaskets instead of one and a little Permatex Ultra Copper sealant, I did the same when I built my custom exhaust for the 911 and haven't had a problem. You can also check that your vacuum advance is working correctly since this can also cause the problem.

[Az911]

My 3.0 with headers/bursch muffler makes the poping sound also. I think that is one of the coolest parts to haveing an open exhaust. Also I do not have an exhaust leak.

[David]

If you used new gaskets and the parts were in good shape, I doubt it's a leak. My 930 does it as did my Honda Intercepter MC before I sold it. I've always thought it sounded pretty cool.

[Crude Rudy]

My 84 3.2 w/ GHL 1 in 1 out and a straight cat bypass did the same thing. Replaced the bypass with a Fabspeed Euro pre-muffler and the pop went away and the sound is much better, richer and less resonance.

[AirCooledExcellence]

My SC with SSI's & Dansk does it as well, no leaks, sounds cool!

Cheers,

Tim.

[Noel]

If this car is an SC and you have the vacuum line from the Deceleration valve disconnected and plugged (To help the revs drop faster between shifts) this is normal.

In fact the popping may have been there all along but merely muffled by the cat.

Noel

[JackT]

I am with Steve and Tim, I like that sound. I switch to SSI exchangers and a Dansk 2 in 1 out muffler and the one thing I miss is the popping on deceleration.