Downpipe vibration at cold start

[sl1kn1ck]

I've had an ATP clone downpipe for a few thousand miles and the past week or so it started to make weird vibrations at cold start and very low rpm at load. I just jacked the car up and confirmed everything was tight, and even loosened the v-band clamps and slip fitting at the resonator and repositioned it a little better. Then I retightened everything.

I started the car while it was up in the air, no exhaust leaks, it's not hitting anything, but still I have this strange vibration at cold start. It is a high frequency sound, almost like there's stuff inside the exhaust, but this is not possible.

It goes away after a couple minutes, but it just sounds like my new car is a jalopy when I start it lol.

The one thing this downpipe does not have, is a mount to the transmission like the stock piece does. Going through the threads, I've noticed that the aftermarket downpipes that do have this bracket, it tends to break off. Maybe this bracket does actually support the downpipe? I figured this bracket was more to support the weight of the heavy catalytic converter, so didn't really worry about it. If I fabbed a bracket, does anyone think this would help? Any other ideas?

Also it did just start to get cold here a couple weeks ago, so I have a feeling this is contributing to it as well.

Thanks!
Nick

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[TheLion]

I've had an ATP clone downpipe for a few thousand miles and the past week or so it started to make weird vibrations at cold start and very low rpm at load. I just jacked the car up and confirmed everything was tight, and even loosened the v-band clamps and slip fitting at the resonator and repositioned it a little better. Then I retightened everything.

I started the car while it was up in the air, no exhaust leaks, it's not hitting anything, but still I have this strange vibration at cold start. It is a high frequency sound, almost like there's stuff inside the exhaust, but this is not possible.

It goes away after a couple minutes, but it just sounds like my new car is a jalopy when I start it lol.

The one thing this downpipe does not have, is a mount to the transmission like the stock piece does. Going through the threads, I've noticed that the aftermarket downpipes that do have this bracket, it tends to break off. Maybe this bracket does actually support the downpipe? I figured this bracket was more to support the weight of the heavy catalytic converter, so didn't really worry about it. If I fabbed a bracket, does anyone think this would help? Any other ideas?

Also it did just start to get cold here a couple weeks ago, so I have a feeling this is contributing to it as well.

Thanks!
Nick

Might be vibrating at a resonant frequency. I would think an additional mount might keep it from resonating. Either that or your engine isn't running right and it's shaking the whole exhaust.

Also, did you check other parts of the exhaust? Might be another area and your just hearing the sound through the down pipe due to the lack of acoustic dampening through the fire wall. I've always been able to hear a lot more engine noise of all types in the mustang than any other car I've owned.

 

[sl1kn1ck]

Well I just figured out my problem..

The secondary o2 sensor wasn't tight all the way.. it was moving around.. Figured this out when I was removing the dp.

I have been running COBB Stage 1 tune for the past few weeks, and when the cold weather really kicked in, I started to get scared running this tune with a dp - which is why I decided to take it off.

Will put it back on in spring, and get pro-tuned.

Nick

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