OEM Exhaust Mod

[SYT_Shadow]

Originally Posted by becausephilchow

What is the ACM Mod? Do they replace all the pipes with solid pipes, not just the perforated ones?

it's pretty much a muffler bypass. With stock xpipe it isn't very loud, but people's definitions of 'loud' vary greatly.

My definition of 'drone' does not vary. I've been in plenty of cars with ear-splitting drone whose owners proudly exclaimed 'no droneeeee'.

When I installed the oem exhaust mod muffler I started the engine with no back section and it doesn't sound louder than the ACM. It doesn't sound loud at all.
Now, when I started the engine after removing the Xpipe, straight out of the headers, holy DTM music batman!!! Way too loud of course

All this to say that regardless of what you do with the muffler it will never get truly loud.

[Iyzmi]

Originally Posted by SYT_Shadow

it's pretty much a muffler bypass. With stock xpipe it isn't very loud, but people's definitions of 'loud' vary greatly.

I agree, it isn't very loud at all other than during cold start (which sounds amazing). People talk about it like it's extreme when in reality it isn't even close to some of the louder systems I've heard. In my opinion, this is the best way to do the muffler mod and anything less wouldn't even be worthwhile if you're after increased volume.

[SYT_Shadow]

Originally Posted by Iyzmi

I agree, it isn't very loud at all other than during cold start (which sounds amazing). People talk about it like it's extreme when in reality it isn't even close to some of the louder systems I've heard. In my opinion, this is the best way to do the muffler mod and anything less wouldn't even be worthwhile if you're after increased volume.

Exactly. As long as you have a stock xpipe you can literally remove the muffler altogether and it still wouldn't be 'lookatme' loud

The E90M I bought now has a 2 perforated pipe/2 covered OEM exhaust most and I can't hear the thing

[M3ANMACHINE]

Can someone tell me how they hit the welds on the bottom sides of the pipe?

[SYT_Shadow]

Originally Posted by M3ANMACHINE

Can someone tell me how they hit the welds on the bottom sides of the pipe?

I do not think it's fully sealed

[vroooom]

I had the ACM mod done to my E92 DCT this morning. It sounds amazing. However, it does drone on the highway. From 2900-3100 rpm (75-80mph-ish) its pretty loud in the cabin. So if you have a long highway ride to work, ACM might not be for you. Otherwise though, it makes the car so much more a delight to drive through the gears. Downshifts sound so good I spent more time in S mode than I have since I bought the car!

[M3ANMACHINE]

Originally Posted by vroooom

I had the ACM mod done to my E92 DCT this morning. It sounds amazing. However, it does drone on the highway. From 2900-3100 rpm (75-80mph-ish) its pretty loud in the cabin. So if you have a long highway ride to work, ACM might not be for you. Otherwise though, it makes the car so much more a delight to drive through the gears. Downshifts sound so good I spent more time in S mode than I have since I bought the car!

I had it on my last 6MT E90 and it wasn't that bad IMO, but i'm used to pretty loud exhausts. Were you in 6th or 7th gear?

[M3ANMACHINE]

Originally Posted by SYT_Shadow

I do not think it's fully sealed

Thanks for the info. Can anyone else confirm this?

[vroooom]

Originally Posted by M3ANMACHINE

I had it on my last 6MT E90 and it wasn't that bad IMO, but i'm used to pretty loud exhausts. Were you in 6th or 7th gear?

7th. It's only during that specific rpm range that it's annoying. I'll just turn the radio louder on the highway.

[M3ANMACHINE]

Originally Posted by vroooom

7th. It's only during that specific rpm range that it's annoying. I'll just turn the radio louder on the highway.

Just leave it in 6th and it should help

[///M Power-Belgium]

Originally Posted by M3ANMACHINE

Thanks for the info. Can anyone else confirm this?

Positive !
It's not possible to weld under the full pipes ...I can know it,I have done this by myself .

But actually it's no problem because the Oem.pipes were completely perforated , so a small spot not weld under the pipe is not a problem .

Pic from the perforated Oem pipe and the full pipe for the replacement ...

[GOFAST M3]

Thanks to everyone for all your responses and information.

Sounds like the way to go for me would be the 4 pipe replacement as I need it to be louder for sure, and the 2 pipe sounds a bit tame for me.

Am I right in preparing myself for a little drone with the 4 pipe replacement? Seems drone is subjective, and I am very sensitive to drone so I may need to be prepared for some right? Seems the ACM version definitely has drone, so I will avoid that. Maybe I should try the 2.5 pipe option from the video above? The version that seems to wrap the large pipes completely, and only half of the little perforations on the small pipe. Seems that little bit of perforation should cut drone slightly from the 4 pipe version.

Thanks again!

[Powashiftin]

4 pipe. Make it easy and just have the shop cut a piece of stainless pipe in half and weld/wrap it over the perforated pipes. Sounds great, not loud at all.

I'm actually looking into getting resonated test pipes to open up the sound at the top.

[SYT_Shadow]

Originally Posted by GOFAST M3

Thanks to everyone for all your responses and information.

Sounds like the way to go for me would be the 4 pipe replacement as I need it to be louder for sure, and the 2 pipe sounds a bit tame for me.

Am I right in preparing myself for a little drone with the 4 pipe replacement? Seems drone is subjective, and I am very sensitive to drone so I may need to be prepared for some right? Seems the ACM version definitely has drone, so I will avoid that. Maybe I should try the 2.5 pipe option from the video above? The version that seems to wrap the large pipes completely, and only half of the little perforations on the small pipe. Seems that little bit of perforation should cut drone slightly from the 4 pipe version.

Thanks again!

I am very sensitive to drone. I believe that moving to an aftermarket xpipe or maybe test pipes will remove the drone from the 3k rpm range which is where it's annoying

My evolve muffler on 'loud' is a straight through system like the acm. With the ess hfc xpipe, it does not drone at 3k.

Before you think i'm crazy saying louder = less drone, it's a matter of moving the drone from 3k which is annoying to 2k which you never use.
At the track when I have the muffler on loud, at 2k it can split my brain in half during the cool down lap. Fortunately I never drive there on the street, so it's a perfect setup: real loud but without drone.

I strongly believe the acm exhaust will work exactly like the evolve on loud

[becausephilchow]

I can understand louder doesn't necessarily mean more drone.

I have a full iPE with headers on my W204 C63, and I don't think it really drones that much when the valves are open, it's just loud as all fucking hell.

Thanks for all the info everybody, looks like I'll probably go with the 2 Pipe Replacement.

[M3ANMACHINE]

Originally Posted by ///M Power-Belgium

Positive !
It's not possible to weld under the full pipes ...I can know it,I have done this by myself .

But actually it's no problem because the Oem.pipes were completely perforated , so a small spot not weld under the pipe is not a problem .

Pic from the perforated Oem pipe and the full pipe for the replacement ...

Thanks for the response. I'll be going with the ACM Bypass method as that's how I had it on my last e90 and enjoyed it.

Does anyone have experience with the differences between the full 4 pipe method and the straight thru bypass method? I imagine it would produce a pretty similar sound...

[///M Power-Belgium]

Originally Posted by M3ANMACHINE

Thanks for the response. I'll be going with the ACM Bypass method as that's how I had it on my last e90 and enjoyed it.

Does anyone have experience with the differences between the full 4 pipe method and the straight thru bypass method? I imagine it would produce a pretty similar sound...

No , they sound different ...
With the 4 pipe the Helmholtz chambers are still involved and works anti-drone .
With the ACM or straight through method you will hear drone , and it's the loudest method because the Helmholtz is actually deleted.

But it's also about sound quality , and for me personal the ACM method sounds like a broken exhaust .
The sound quality from the 2 big and all 4 sounds way better and refined , kinda racy sound .
And of course I know it's all about personal taste ..

[GOFAST M3]

Originally Posted by ///M Power-Belgium

No , they sound different ...
With the 4 pipe the Helmholtz chambers are still involved and works anti-drone .
With the ACM or straight through method you will hear drone , and it's the loudest method because the Helmholtz is actually deleted.

But it's also about sound quality , and for me personal the ACM method sounds like a broken exhaust .
The sound quality from the 2 big and all 4 sounds way better and refined , kinda racy sound .
And of course I know it's all about personal taste ..

Thank you very much for all your help and answers throughout the thread.

I have decided to go with the 2.5 version as shown at 3:07 in the video from post 8. I think that is the happiest median between as loud as OEM can go(ACM), and as drone free as it can be while modded(just 2 pipe). Seems people are reporting 'some' drone with the complete 4 pipe replacement.

I will report back and let you guys know what I think, and take videos if I can.

[///M Power-Belgium]

Originally Posted by GOFAST M3

Thank you very much for all your help and answers throughout the thread.

I have decided to go with the 2.5 version as shown at 3:07 in the video from post 8. I think that is the happiest median between as loud as OEM can go(ACM), and as drone free as it can be while modded(just 2 pipe). Seems people are reporting 'some' drone with the complete 4 pipe replacement.

I will report back and let you guys know what I think, and take videos if I can.

Awesome , and it's all my pleasure
For further questions I'm here , or just PM me at anytime...

[M3ANMACHINE]

Originally Posted by ///M Power-Belgium

No , they sound different ...
With the 4 pipe the Helmholtz chambers are still involved and works anti-drone .
With the ACM or straight through method you will hear drone , and it's the loudest method because the Helmholtz is actually deleted.

But it's also about sound quality , and for me personal the ACM method sounds like a broken exhaust .
The sound quality from the 2 big and all 4 sounds way better and refined , kinda racy sound .
And of course I know it's all about personal taste ..

Interesting, I felt like the ACM method was the most exotic I have heard on the e9x M3 when I had it. Here's an example of my friends car with the ACM method:

However it sounds identical to this video of the 4 pipe method.. hmm..

Now i'm starting to wonder if he was mistaken and actually had the 4 pipe method instead of the ACM method.. I'll have to double check somehow!

[L4ces]

Originally Posted by ///M Power-Belgium

No , they sound different ...
With the 4 pipe the Helmholtz chambers are still involved and works anti-drone .
With the ACM or straight through method you will hear drone , and it's the loudest method because the Helmholtz is actually deleted.

But it's also about sound quality , and for me personal the ACM method sounds like a broken exhaust .
The sound quality from the 2 big and all 4 sounds way better and refined , kinda racy sound .
And of course I know it's all about personal taste ..

And I also know it's all about personal taste. To me, the above in bold is accurate. It took me a long time to develop an ear for it. I compared my AA axle back to one of the OEM mods (which was as loud as my AA). What I recall was that the mod lost alot of refinement. It was no longer racey and elegant. It sounded more aftermarket. My AA also sounds after market but only because it is loud, but dammit it is elegantly loud but with quality as if its sound was carefully tuned.

If you can't hear your 2.5, 1.75 OEM mod in cabin as you like, trust me when I say this, it is very very audible and noticable outside and is sounding sweet. No offense folks but I don't believe this is in my head.

Here's one more thing (as if any gives a ish of my opinion). I like that sharp and quick blip when I down shift or simply let off the gas, when the sound decays slowly it makes the engine sound lazy and less responsive. I like that sharp and quick decay after the roar (hard to explain).

[///M Power-Belgium]

Originally Posted by L4ces

And I also know it's all about personal taste. To me, the above in bold is accurate. It took me a long time to develop an ear for it. I compared my AA axle back to one of the OEM mods (which was as loud as my AA). What I recall was that the mod lost alot of refinement. It was no longer racey and elegant. It sounded more aftermarket. My AA also sounds after market but only because it is loud, but dammit it is elegantly loud but with quality as if its sound was carefully tuned.

If you can't hear your 2.5, 1.75 OEM mod in cabin as you like, trust me when I say this, it is very very audible and noticable outside and is sounding sweet. No offense folks but I don't believe this is in my head.

Here's one more thing (as if any gives a ish of my opinion). I like that sharp and quick blip when I down shift or simply let off the gas, when the sound decays slowly it makes the engine sound lazy and less responsive. I like that sharp and quick decay after the roar (hard to explain).

Exactly ..
I could hear from the first seconds (even at start up) the difference in sound in cabin , not only because it was louder but I noticed also the great sound quality and honestly I was really surprised and happy what I heard after a whole day of work with the mod.

Yeah...Outside it's completely different as well , but hard to tell in cabin how it actually sounds outside, that's why I let someone drive with my car while I was along the road (road without other cars) and so I heard some pulls under load and DCT downshifts from my car , and I was like ....Holy shit , this sounds just perfect !