OEM Muffler Modification

[pippin]

Back when I owned my e46 m3 I had trouble trying to find an exhaust that did not drone and/or sounded good. There were quite a few exhaust options that either were hard to source or expensive for me at the time. Although, looking back they were cheap in comparison to the existing options for the f10 m5.

Here is a picture of the OEM muffler modification I had done for my e46 m3 which got me thinking about the m5. It basically removed all the perforated / open chambers of the stock muffler and left only 1 chamber to do the work.



I was searching for photos of the exhaust system hoping that someone had done something similar and found a post by IND on this forum. This is the internal view of the m5 muffler.



The thing that wasn't shown under the packing was a perforated section with a j-pipe that leads to the second champer that is shown. The j-pipe allows for the exhaust to resonate when the OEM valve is closed. The idea is to weld up the perforations so that when the valve is closed it would operate/sound similar to stock but when the valves are open it would act more like a muffler delete.

Picture showing the j-pipe and areas that used to be perforated:










Part that I used to open/close the exhaust valve:
Exhaust Controller: https://valvetronic.com/products/bmw...21112798707771


How does it sound?

Muffler Delete
While this work was being done I had the mufflers off of the car so it was effectively a muffler delete.
Cold Start: Terribly loud. Sounds great but I live in a condo and within the underground parking garage it was deafening for 30 seconds.

Drone: I did not like the pressure/drone associated with the muffler delete under certain driving conditions. It can be avoided by shifting a certain way and keeping the car in S3 etc but an annoyance.

Overall exhaust tone: It was a nice improvement compared to stock but still a bit loud for me. I was searching for something that was an improvement over stock yet still refined.


Modified OEM Muffler
Cold Start: Pretty similar to OEM because I still have the valved system. Maybe slightly louder but nowhere near as loud as a muffler delete.

Drone:
Valve Closed: No drone and sounds slightly louder than stock during regular driving. Highway cruising is hard to tell that the exhaust is any different

Valve Open: You get more bass tones similar to the muffler delete but because the j-pipe allows some exhaust gases to reverberate within the OEM chamber it is a little quieter and deadens any drone. There is a deeper note but none of the ear pressure associated with drone. WOT sounds much better and makes driving the car more engaging. Sounds when shifting are better and more intoxicating.

Overall: Being able to have the option of refined sedan mode and being able to open up the exhaust when you want more sound is extremely beneficial to me. The wife doesn't complain about the sound like she did with the muffler delete and I can do long road trips without annoying drone even with the valves open.

[m5rosco]

So you did away with the perforations in the "Y" pipe in "chamber 1", also did away with the "J" pipe? Are the pipes in "chamber 2" solid? or is there perforations on the underside that cannot be seen from above? I wonder how the Competition muffler actually differs. Thanks for taking time to show us this.

[pippin]

Originally Posted by m5rosco

So you did away with the perforations in the "Y" pipe in "chamber 1", also did away with the "J" pipe? Are the pipes in "chamber 2" solid? or is there perforations on the underside that cannot be seen from above? I wonder how the Competition muffler actually differs. Thanks for taking time to show us this.

I have a competition package car. That is a picture of my actual muffler. For the purpose of this there are two chambers. The first chamber has that perforated "Y" section with the J-Pipe. There is a wall separating the two chambers but the J-Pipe allows for gas to exchange between the two chambers (hole in the wall). The second chamber is simply straight pipe (this is my assumption based on the IND documentation. I did not actually cut into the second chamber to confirm) but the J-Pipe that exists in the first chamber allows exhaust gas to mingle between chamber one/two. The perforation on the Y section is on both sides of the muffler (top/bottom).

I was surprised at how tame this modification actually was in comparison to the full on muffler delete. I would say it made the car roughly 15% louder if I had to guess. The muffler delete was annoying but somehow with the exchange of gases between chamber 1/2 even with the exhaust flap open it removes the drone from the cabin.

[Doctor_X]

Clean fab work man! Looks great