OEM Exhaust Mod - Rattle at startup

[noremaC]

So I have a modified OEM muffler (ACM mod) paired with test pipes. Alpine Stage 2 tune, cold start still active. As of recent, I've had an obnoxious rattle coming from the rear of the car that my shop and I have identified as likely coming from within the muffler/rear section itself. It lasts about 10 seconds when the car is initially started, and goes away after that. Sometimes comes back at low RPM in 1st gear. It literally sounds like 2 pieces of metal violently banging together (I'll get a video when the car is back from the shop).

This is my second e9x with the same exhaust setup. 7 years total between the two cars and I have never experienced or heard of others having this issue.

Has anyone else experienced this?

I am looking at my options and right now it seems like I'll have to find a new muffler/box. I would think opening up the muffler, attempting to find & fix the issue (which is still unknown) may be going down a rabbit hole.

[amrazM]

Cracked weld, harmonics on cold start causing the rattle.

[Helmsman]

Yes, very irritating. Ran 2 pipe OEM mode for years. Started to develop a rattle that goes on till its warmed up (i.e. far longer than yours, you're lucky...). Took it to the shop TWICE, paid good money just to still have the rattle. These days I've kinda got used to it, swapped back to my original for a while which was nice, tried Borla ATAK as well as S system, back to my rattle can dreaming about a Corsa next time around but 3k+ Euro landed have hold me back...

[M43S7RO]

I have a Corsa with which the two prongs (point at one another) that slide into the hangers at the very rear of the muffler would rattle against one another on cold start.

More likely that they rattle against one another on the Corsa because the cans are independent and so can move towards each other but throwing it out there just in case.

[noremaC]

Originally Posted by Helmsman

Yes, very irritating. Ran 2 pipe OEM mode for years. Started to develop a rattle that goes on till its warmed up (i.e. far longer than yours, you're lucky...). Took it to the shop TWICE, paid good money just to still have the rattle. These days I've kinda got used to it, swapped back to my original for a while which was nice, tried Borla ATAK as well as S system, back to my rattle can dreaming about a Corsa next time around but 3k+ Euro landed have hold me back...

That's what I'm afraid of. Spending $$$ to open up, re-weld the crack/break, close back up and end up in the same place a few months down the road.

I'm also toying with the idea of just going back to the OEM muffler (still with test pipes intact) to quiet this puppy down + I've never tried this combo. Test pipes + ACM mod is LOUD, obnoxious and drones like a SOB. It just also happens to sound fantastic, which makes this a difficult decision LOL!

I really don't want to spend $$$$ on an aftermarket unit as I am likely moving to a new platform after being on this one since 2014, early next year 😳