Quote:
Originally Posted by Ron1n
The muffler has inner and outer chambers. The inner chambers have 4 pipes (2 pipes that are pretty much fully perforated, and 2 others that only have a small amount of perforation. This is where the OEM mod comes into play. The 2 pipes that are mostly perforated are cut out and replaced with solid pipes (straight pipes, if you will), welded back in, and you get the sound that I have in my video.
The ACM (AUTOcouture Motoring) mod makes adjustments to the outer chambers. By default, the exhaust comes into the outer chamber, goes through the inner chamber, and comes out the other outer chamber, and then out to the end of the exhaust (this happens on both sides). What you do with the ACM mod is bypass the internal chambers completely, effectively making a straight-pipe. A y-pipe is used from the entry point to the outer chamber to the exit of the chamber (a y-pipe is needed because 2 exhaust pipes).
The sound that comes out as a result of each mod is very, very different.
This video might help you in comparing the actual audio. Far right E92 = stock exhaust, far left E92 = OEM Perf Mod, E93 in the middle - ACM mod
Hopefully this all gives you a better idea, and what direction you might want to head with this. If you're unsure, I'd suggest doing the OEM Perf Mod first, and decided whether you like it or not. If you don't, you can do the ACM mod (which will bypass your OEM Perf mod) and go that route without having to create too much more work.
The visual below may help in understanding how the exhaust is laid out. |
Wow thanks so much for all that info! I really appreciate it--no, really, I appreciated your post
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They did the perforated mod for only $375? Might be a silly question but, you didn't have to provide the extra piping or anything did you?