Anyone have any idea what this exhaust vibration is?

[btoast]

Hey,

I'm trying to figure out what this exhaust vibration is that appears to be primarily present during cold starts.

Here is a cold-start audio clip

The clip includes the cold start then a cut to about a min later a few revs.

You can hear this paper like flapping vibration that seems to, for the most part, go away after the cold start.

You can see a visual representation of it when looking at the wav audio form as it shows up as high peaks:



Once the cold start has completed the sound is almost nonexistent.

I thought it might be the tips rattling but they seem solid and the sound does not change if I grip or cup them. As well, they don't make any abnormal sounds when tapping on them.

If I stick my fingers in the tips during a cold start (not touching any part of the tip) the vibration sound gets louder, which makes me think it might be something inside the muffler that is vibrating. Maybe fiberglass packing?

Any ideas? The exhaust is a Zeta CBE with about 500 miles on it. It is paired with a RevWorks UEL. Stock OP/FP.

Here is a drive-away clip after the car is warmed up, sounds pretty normal

[steve99]

If it only present during cold start its probablty resonance due to the -15 degree retarded timing at cold start. why it took 500milkes to show up dont know maybe packing in muffler settling in.

if you have nt already done the cold start tune mods.

could also be gasket leak

see OFT tune tweaks link for tune mods

[skye67]

I would check for exhaust leaks.

[tomaszjanczak]

I have a similar sound at startup with my Openflash header and invidia q300 catback. my sound comes from the header area and I don't have any leaks. Although, it sure does sound almost identical to an exhaust leak. I don't think it's an issue but you could data log it and smoke test it to make sure but it's most likely a normal sound coming from your revworks header thin walls plus the resonance during start up like steve99 said.

[btoast]

Originally Posted by steve99

If it only present during cold start its probablty resonance due to the -15 degree retarded timing at cold start. why it took 500milkes to show up dont know maybe packing in muffler settling in.

if you have nt already done the cold start tune mods.

could also be gasket leak

see OFT tune tweaks link for tune mods

Thanks for the response. That is probably it. I spent an hour looking over the entire exhaust for leaks, tapping on places to see if anything was loose, wiggling the system and anything else that could vibrate or be in contact with they exhaust (surprisingly my licence plate frame clicks and my rear bumper when pressed by the reverse light creaks) and I could find nothing that would make anything close to that sound.

It's not that much of an annoyance; it was just surprising. I'll look over the OFT tweaks.

[btoast]

Originally Posted by tomaszjanczak

I have a similar sound at startup with my Openflash header and invidia q300 catback. my sound comes from the header area and I don't have any leaks. Although, it sure does sound almost identical to an exhaust leak. I don't think it's an issue but you could data log it and smoke test it to make sure but it's most likely a normal sound coming from your revworks header thin walls plus the resonance during start up like steve99 said.

Thanks for the response. I checked for leaks earlier today and as far as I could tell there are none. If your setup makes a similar sound then it probably is as steve99 said. It just caught me off guard.

I'm going to do an oil change tomorrow, so I'll check again just in case.

[aznatama]

Probably just resonance. Move does that too, but if you force it out of cold start mode by driving a few feet, it goes away.