[elim11]

Originally Posted by x-ception

here is a video of this done on a 335, ACM in NJ does this mod for $500 I believe.

It sounds less "burbly" than a PE. Might be just the video. But does sound smooth. How can we figure out what they did? maybe call them?

[elim11]

Doing some quick research on the ACM mod, here is what they said

"The OEM cans have some funky stuff going on inside. One has a mini muffler and the other has perforated piping. We remove both and install non-perf ss piping."

http://www.e90post.com/forums/showthread.php?p=11964496

See post #1615

[e92oholic]

Originally Posted by elim11

Thanks for stepping up to the plate. Hopefully the videoprobe can be of some use!

It has already, i gave it a try in my stock mufflers and its very easy to see the holes in the pipes, making the turn to the connecting pipe is going to be tricky, if only he will let me separate them and go that way too.

Ive been thinking and what im going to do if I cant see the connecting pipe is just wrap it in sheet metal and clamp it and see what happens before i cut them out and make it permanent. Going to try different amounts off that insulation inside too. Hopefully I can clamp the top on and use some metal tape to hang them on the car and test sound.

Going to use a decibel meter and see how it gets compared to the PE.

[M BROK3]

Originally Posted by elim11

Doing some quick research on the ACM mod, here is what they said

"The OEM cans have some funky stuff going on inside. One has a mini muffler and the other has perforated piping. We remove both and install non-perf ss piping."

http://www.e90post.com/forums/showthread.php?p=11964496

See post #1615

here are some pics of what they do to m3 exhaust to get an idea

http://www.m3post.com/forums/showthread.php?t=609950

[Zebra99]

Keep this going guys....once this mystery is cracked everyone is going to be doing this.

I have a feeling from the M3 pics and just what I've seen in the stock cans that if you replace the perforated pipe with ss straight pipe and remove maybe 50% of the packing it'll be a PE. Everything else seemed to be the same.

Maybe there is a BMW engineer/employee who wants to step up to the plate and confirm the differentiating factors of stock and PE?

Keep up the great work guys!

P.S. to add volume if you're not happy with the end result just get DP's

[Gugs]

Lets be frank here-
This is a simple mod that has been done to mufflers for countless years. Even the local dump muffler shop can perform this task blindfolded.
500 seems about 350 too much.

[chrisk03]

I will cut open my BMW Performance Exhaust...


If you all come together and replace it with a new Akrapovic...

[TommyLights]

Let's do it!

[elim11]

Originally Posted by e60oholic

It has already, i gave it a try in my stock mufflers and its very easy to see the holes in the pipes, making the turn to the connecting pipe is going to be tricky, if only he will let me separate them and go that way too.

Ive been thinking and what im going to do if I cant see the connecting pipe is just wrap it in sheet metal and clamp it and see what happens before i cut them out and make it permanent. Going to try different amounts off that insulation inside too. Hopefully I can clamp the top on and use some metal tape to hang them on the car and test sound.

Going to use a decibel meter and see how it gets compared to the PE.

Any updates?

[e92oholic]

Originally Posted by elim11

Any updates?

Sorry ive been slacking here. I have to use my friends welder and hes been busy at work and ive been driving all over the place. Im hoping to do it next week.

But i did scope the BMW PE and it was solid pipe everywhere I could see.

[TommyLights]

Bump for updates...

[Beemw335]

Originally Posted by e60oholic

Sorry ive been slacking here. I have to use my friends welder and hes been busy at work and ive been driving all over the place. Im hoping to do it next week.

But i did scope the BMW PE and it was solid pipe everywhere I could see.

Hmm solid pipe everywhere would basically be a muffler delete?
Anyways, in for updates!!!

[e92oholic]

Originally Posted by Beemw335

Hmm solid pipe everywhere would basically be a muffler delete?
Anyways, in for updates!!!

Have you heard the BMW in person? Its loud, almost like a muffler delete but a bit more refined, i think it has something to do with the cross pipe between them making a helmholtz exhaust chamber to eliminate the drone. I could be way off but i have been doing research. I just need to make it to the dealer and pick up another exhaust clamp.

[shaginwagon13]

Originally Posted by elim11

It sounds less "burbly" than a PE. Might be just the video. But does sound smooth. How can we figure out what they did? maybe call them?

+1

I got a muffler delete a couple weeks ago welded on and it sounded just like that from the outside. Inside the cabin everything rattled, and around 3500 RPM on the highway it was so ridiculously loud in the cabin it was more annoying than anything. The guys who did this mod I am willing to bet just opened the muffler up, took all the 'wool' out and welded a pipe.... essentially making it a muffler delete. Personally I didn't like the sound, I got my OEM muffler welded back on the next day.

If someone can figure out how to get the PE sound with the OEM mufflers, I am for sure doing this mod.

Not sure if this is relevant but I seem to have found design specs for the DINAN Performance exhaust for an M3..... maybe we can make something of this? The second pic is the standard M3 exhaust.

[Beemw335]

Originally Posted by e60oholic

Have you heard the BMW in person? Its loud, almost like a muffler delete but a bit more refined, i think it has something to do with the cross pipe between them making a helmholtz exhaust chamber to eliminate the drone. I could be way off but i have been doing research. I just need to make it to the dealer and pick up another exhaust clamp.

Yes Ive heard the perf exhaust and alrhough it is loud, it doesnt drone so I doubt its fully straight pipes?
Anyways thanks for taking the time to do this, looking foward to updates!

[Alexm007]

I'm very interested in what you guys are working on.... Looking forward to some conclusions!!!

[TommyLights]

Any updates?

[StevenY.]

This sounds very interesting, I hope you guys can crack it so that we can all have a PE!

[335xi Kevo]

PE is so expensive for what it is, we must solve the mystery.

[e92oholic]

Originally Posted by tomz_335i

Any updates?

Waiting for my friend to help me, its his hell week at work so whenever he recovers were gonna pull the exhaust off and have at it

[TommyLights]

I just decided to pull mine off and replace the internal cat, h pipe and all perforated pipes with straight pipes. Will post a video once I get it back from the shop in a few days (I have straight pipes on for the time being, they are loud as hell).

[335imax]

Simply removing the inside baffles is not going to make it sound good. Just louder. There is a tuning issue as well. MMW CS has been making clone Performance mufflers for years.