rk-d

I have a new muffler coming in (Fister III) and I was listening to my current motorsound Gillet exhaust. There is a irregular noise at idle that's louder if I rev. It's more prominent with cold start. I can't hear it while driving. It doesn't localize to the engine when I open the trunk - it's mostly from the exhaust.

Baffles? I don't see or feel anything obviously loose.

Car has 43k miles. Very little oil consumption in the past 1100 miles.

Churchill

That is a strange one. Never heard a sound like that before. It does sound like something's loose inside one of the muffler cans but I would double check the noise isn't coming from the engine -- sounds almost like it could be a collapsed chain tensioner. I'd use an automotive stethoscope on the chain boxes and valve covers to rule out the timing chains and valvetrain. Can also use it on the muffler can.

Railmaster.

Maybe not, but a muffler heat shield rattling?

pp000830

If this sound is not new but has always been present it could be post-ignition of fuel in the exhaust system, perfectly normal.
The pitch of such sounds can vary quite a bit based on the acoustic properties of the exhaust system.
Blipping the throttle injects a bit more fuel that passes into the exhaust and ignites there.
It is more prominent at cold-start because the fuel system sets up a slightly rich condition at the initial start that passes a bit more unspent fuel into the exhaust system that ignites there.
Some folks like this sound and go to great lengths to make their exhaust system pop and gurgle like this.
Andy

TheOtherEric

Yikes WTH is that noise?? I'd be terrified to drive it hearing that. Remove the mufflers and see if it's still there. Definitely figure it out.

rk-d

Just picked one up. Pretty clueless what I'm doing with it, but I can probe around

I had that thought - replacing the muffler soon, so that should rule out exhaust

The sound has been there since I've had it. Post ignition is what I'm hoping it is - my M5 does the fake exhaust farting thing and the gurgle here does sound a little similar.

Churchill

Just be careful with it, it transmits noise quite well. Don't bang it on the parts your probing.

rk-d

I'm actually a doctor, so comfortable with the stethoscope, haha.

I listened around - didn't really hear much in the engine bay. Could hear ticking of the valves when I probed the covers, but I would expect to hear that. Sound seems most localized to the exhaust.

I'm wondering if it's the cats. I found this video and it's similar (though this one sounds a lot worse than mine)

Skip to 1:10...


EDIT: Nevermind - don't think this is it. Drove my car today instead of sitting around listening to it. Doesn't have that rattling sound like this video, so I don't think that's it. Heatshield is not rattling either. Car drove beautifully this morning without weird noises or rattling. I had spent all afternoon doing DIY yesterday, so I might just be overthinking this. Going to have my Porsche guy look at it, but I'm thinking this is post-ignition noise and just a 20 year old exhaust.

pp000830

Accept the things one should not fix
Courage to fix the things one must,
And wisdom to know the difference!
Or something like that.
Andy

Churchill

Somehow reminded me of...

rk-d