Non-perf oem exhaust mod to ACM mod

[CorrectoMan]

Last month I had my stock oem exhaust modified using the non-perforated method. Although I think it's a vast improvement from stock, it's just not enough for me.

My question is, can I now go from the non-perf method to the ACM method?
As far as I understand, the ACM method is a muffler bypass?

I'm not only looking for a bit more volume, but I'm looking for a more deeper sound as well, without shelling out the $thousands.

I'm just concerned if it would be an issue now to re-modify the OEM muffler? In terms of reliability, quality, etc.

Would like to hear from anyone who went from non-perf method to the ACM method.

Thanks

[s85e90]

Yes as they're 2 diff things. The ACM mod bypasses the center section altogether. So yes you can.. IMO I would just use the OEM connecting pipes and do a muffler delete as it's the same thing as ACM but you lose the weight and ugly muffler.

[CorrectoMan]

Originally Posted by s85e90

Yes as they're 2 diff things. The ACM mod bypasses the center section altogether. So yes you can.. IMO I would just use the OEM connecting pipes and do a muffler delete as it's the same thing as ACM but you lose the weight and ugly muffler.

Any disadvantages to muffler delete? When I had the perf pipes replaced with non-perf, I had the muffler painted black, so It's kinda comouflaged right now.

[///M Power-Belgium]

Originally Posted by CorrectoMan

Any disadvantages to muffler delete? When I had the perf pipes replaced with non-perf, I had the muffler painted black, so It's kinda comouflaged right now.

Muffler delete = A lot louder !
Any disadvantages ? Yes !.....Drone !
If you want to keep the muffler and want to chance from perforated to straight through method (ACM) ?
Yes it's possible because perforated/method is the muffler opened in mid. section,and straight through (ACM) muffler needs to be opened left+right ouside sections on top of the muffler !
Only downside is you have allready welds in mid section from perforated method,and than with straight through you will have also welds left + right in outside positions on top of your muffler !
With other words...you will have welds all over the place on top of your muffler !
Positive advantage is...it's not visible, because all the welds are on top of your muffler !
Hope this will help with your dicision
And just saw this.....>http://www.m3post.com/forums/showthread.php?t=943379

[s85e90]

Originally Posted by ///M Power-Belgium

Muffler delete = A lot louder !
Any disadvantages ? Yes !.....Drone !
If you want to keep the muffler and want to chance from perforated to straight through method (ACM) ?
Yes it's possible because perforated/method is the muffler opened in mid. section,and straight through (ACM) muffler needs to be opened left+right ouside sections on top of the muffler !
Only downside is you have allready welds in mid section from perforated method,and than with straight through you will have also welds left + right in outside positions on top of your muffler !
With other words...you will have welds all over the place on top of your muffler !
Positive advantage is...it's not visible, because all the welds are on top of your muffler !
Hope this will help with your dicision
And just saw this.....>http://www.m3post.com/forums/showthread.php?t=943379

Muffler delete = acm mod. It's not louder and also doesn't drone. I have had both and can tell you first hand. OP look at what the acm mod is. It bypasses the muffler totally

[CorrectoMan]

Originally Posted by ///M Power-Belgium

Muffler delete = A lot louder !
Any disadvantages ? Yes !.....Drone !
If you want to keep the muffler and want to chance from perforated to straight through method (ACM) ?
Yes it's possible because perforated/method is the muffler opened in mid. section,and straight through (ACM) muffler needs to be opened left+right ouside sections on top of the muffler !
Only downside is you have allready welds in mid section from perforated method,and than with straight through you will have also welds left + right in outside positions on top of your muffler !
With other words...you will have welds all over the place on top of your muffler !
Positive advantage is...it's not visible, because all the welds are on top of your muffler !
Hope this will help with your dicision
And just saw this.....>http://www.m3post.com/forums/showthread.php?t=943379

Thanks for your reply.
Reading that thread may have been enough to scare me out of it. I don't want to be constantly waking my neighbours up...

[CorrectoMan]

Originally Posted by s85e90

Muffler delete = acm mod. It's not louder and also doesn't drone. I have had both and can tell you first hand. OP look at what the acm mod is. It bypasses the muffler totally

I'm going to have to hear this in person to make a decision. The way you describe it sounds acceptable to me.

///M Power-Belgium, are you talking about the same mod?

[s85e90]

It's gonna be Loud. You're bypassing the muffler. If that's not what you want look to pickup a used exhaust.

[///M Power-Belgium]

Originally Posted by s85e90

Muffler delete = acm mod. It's not louder and also doesn't drone. I have had both and can tell you first hand. OP look at what the acm mod is. It bypasses the muffler totally

Originally Posted by CorrectoMan

I'm going to have to hear this in person to make a decision. The way you describe it sounds acceptable to me.

///M Power-Belgium, are you talking about the same mod?

Yes i'm talking about the same mod ....
Look to make things "very" clear ,i have done "both" exhaust mod and "by myself" !
It's some work to post...but here we go...... !
Pic # 1 + 2 = ACM method or straight trough method ,but still inside the outside sections of the mufler ,delete wants to say here...delete the cris cross mid section part of the muffler...so straight through ,but still uses the muffler !
Pic # 3+4+5+6 =Replacing the 2 big perforated pipes by 2 full stainless steel pipes,"the perforated pipe method" and posted a personal thread with pics and video about it,and is now the method that i have on my car>http://www.m3post.com/forums/showthread.php?t=733817
Hope that the pics and the link to my thread make things clear.......
Feel free for further questions or PM....i'm here !

.

[s85e90]

Originally Posted by ///M Power-Belgium

Yes i'm talking about the same mod ....
Look to make things "very" clear ,i have done "both" exhaust mod and "by myself" !
It's some work to post...but here we go...... !
Pic # 1 + 2 = ACM method or straight trough method ,but still inside the outside sections of the mufler ,delete wants to say here...delete the cris cross mid section part of the muffler...so straight through ,but still uses the muffler !
Pic # 3+4+5+6 =Replacing the 2 big perforated pipes by 2 full stainless steel pipes,"the perforated pipe method" and posted a personal thread with pics and video about it,and is now the method that i have on my car>http://www.m3post.com/forums/showthread.php?t=733817
Hope that the pics and the link to my thread make things clear.......
Feel free for further questions or PM....i'm here !

.

Nice. I was looking for those pics to help the op.

[dparm]

ACM is indeed a muffler bypass, for all intents and purposes. You might get some slight sound-dampening from the mass of the muffler absorbing some vibrations generated, but it is quite loud. It's not unbearable since the factory resonators are retained, but you will absolutely hear it at most throttle angles.

[AMG_LAWL]

Hey guys!

I have the oem exhaust mod done to my car, its the perforated pipes which were replaced in the center piece. I don't notice anything special from oem sound. Can I still get the other ACM mod done??

[CorrectoMan]

Thanks for the pics.

My concern now is how loud this is under slow/low-rpm driving and cold-start as I don't want complaints from the neighbours as I start up and roll away. My work schedule has me returning and leaving at all hours of the day/night, and it is my daily driver.

The safer option for me is to remain with the non-perf mod, maybe remove the secondary cat... But I'm looking for a more desirable sound.

Is the secondary cat left untouched using the ACM/bypass method?

Again, I'll have to wait until I hear this in person to determine if this would be acceptable.

AMG_LAWL, that was one of my original questions, and yes, it can be done.

[///M Power-Belgium]

Originally Posted by AMG_LAWL

Hey guys!

I have the oem exhaust mod done to my car, its the perforated pipes which were replaced in the center piece. I don't notice anything special from oem sound. Can I still get the other ACM mod done??

Mannnnnnnnnn !
Is this serious ? Are you actualy reading this thread ?
Ok and again the anser to your question you can find "yes" on "this page" look at # 4 + 9 !

[///M Power-Belgium]

Originally Posted by CorrectoMan

Thanks for the pics.

My concern now is how loud this is under slow/low-rpm driving and cold-start as I don't want complaints from the neighbours as I start up and roll away. My work schedule has me returning and leaving at all hours of the day/night, and it is my daily driver.

The safer option for me is to remain with the non-perf mod, maybe remove the secondary cat... But I'm looking for a more desirable sound.

Is the secondary cat left untouched using the ACM/bypass method?

Again, I'll have to wait until I hear this in person to determine if this would be acceptable.

AMG_LAWL, that was one of my original questions, and yes, it can be done.

Reading about your situation...neighbours, leaving day/night etc., it's almost like my situation ,i work in 3 shifts !
So i think best thing for both of us is...keep the non/perf mod. thinking that ACM will be about 15/20 % louder and with cold/start cycle even louder !
About ACM method it's only the muffler mod and secondary cats left untouched,when removing the secondary cats your car will smell...the fuell you know ,same with test pipe & primary cats removal,car will sound than even louder and with Oem. exhaust very raspy !
And it's logic when driving slow/low rpm = less of noise or exhaust sound !
For me personal ACM sounds to much like a broken exhaust,but that is just my personal taste of sound !
Actualy it's like with colors...maybe you like red and i like blue !

[Ezio]

Originally Posted by CorrectoMan

Thanks for the pics.

My concern now is how loud this is under slow/low-rpm driving and cold-start as I don't want complaints from the neighbours as I start up and roll away. My work schedule has me returning and leaving at all hours of the day/night, and it is my daily driver.

The safer option for me is to remain with the non-perf mod, maybe remove the secondary cat... But I'm looking for a more desirable sound.

Is the secondary cat left untouched using the ACM/bypass method?

Again, I'll have to wait until I hear this in person to determine if this would be acceptable.

AMG_LAWL, that was one of my original questions, and yes, it can be done.

i have the two pipe method done like you. i removed the resonators. car got a decent amount louder, also there are more poping noises which i like. it also got deeper sounding at idle and lower RPMs. although its still overall a higher pitch exhaust.

i heard a muffler delete M3 in person. it had a much deeper sound. sounds more like a muslce car .the ACM would be something more like a muffler delete. i prefer the the deeper sound. but at the cost of more drone i passed.

i think either deleting resonator or 2nd cat is worth trying out.

[webninja]

Here's a vid comparing the ACM vs the OEM - ACM sounds way better to me.

[CorrectoMan]

It's a no-brainer in the videos. But having recorded a clip myself, I know that watching a video is not accurate.

Thanks for the help, I'll report back when I track down a local M3 with the ACM mod.

[Ezio]

idk why that vid was posted. it was a OEM and ACM. we all know either mod sounds better than stock lol

[AlpineE92M3]

Originally Posted by Ezio

idk why that vid was posted. it was a OEM and ACM. we all know either mod sounds better than stock lol

Truth

[webninja]

Originally Posted by Ezio

idk why that vid was posted. it was a OEM and ACM. we all know either mod sounds better than stock lol

My bad, I thought the video was ACM exhaust mod vs OEM exhaust mod - no wonder I thought the OEM exhaust mod didn't make any difference.