OEM Exhaust Mod: Bypass or Cover Perf Pipes?

[dagolfpro]

Just found an extra OEM Exhaust and planning on doing it this week at a local shop who has done this before.

Question is, which method is "better/preferred"?

AutoCouture's bypass/straight pipe method

http://www.m3post.com/forums/showthread.php?t=609687

or

Replace the perforated pipes in the middle chamber method.

Which one will drone less?

Pro's & Cons of each?

[Ateam]

This one is easy since I just debated this.

"original" cover the perf pipes mode-MUCH more quiet but NO drone whatsover. If you have the bug for more sound however I feel this would not satisfy you for long. If you really are happy with the OEM sound and literally want just a touch more and would be thrilled with that-this is your mod.


ACM-which is what I got. I actually "thought" I would have been happy with just a touch louder like the original. When I got this I did not know as many people had not done this. However I realized it is MUCH louder than the original method and sounds about as loud as in between eisenmann sport and race. VERY sweet tone to it and it also sounds just like the m performance exhaust.

It DOES have some drone if you are in the wrong gears/speed/rpm. Around town its real easy to stay in the right gear at cruising to have none. On the freeway its funny-at 70 mph in 7th there is NOTHINg. At 75 and above in 7th there is drone.

The answer to that-either cruise at 70mph which is better for tickets and mileage. If you cannot do that than put it in 6th to cruise at 75 or above and the drone is eliminated but mileage suffers a bit!

So if you want m-performance sound for 400 dollars with some drone that is modifiable to have no drone as long as you select the right gear-this is it.

If you don't want to bother with any drone and have a very subtle change than the original is for you.

If you have the 3500 to spend, than get the m performance and have best of both worlds.

I did not have 3500 to spend on an exhaust-I am starting a business and need all the cash I can get-otherwise if you have the dough its a great system. if you do not have the dough the ACM is unbeatable for sound

[dagolfpro]

Thanks Ateam for the write up. So, I'm guessing you're happy with your ACM version?

[Ateam]

I am really happy. It made me get the bug to have even further sound enhancement via x-pipe or something but I will hold off for now. It draws just enough attention as it is and do not need/want anymore!

Its so cheap you might as well go for it! I say try it, if you do not like it or its too much than you can use your other exhaust to do the other type of mod or go back to stock. That is the beauty of this being so cheap!

However I don't see how you would not like it-it sounds awesome!

[M3Power55]

I did the oem exhaust mod, and I love it. What I did was I cut out all the perforated pipes (4 of them) and had new pipes welded in with no holes and I stuffed all the packing back in and welded it shut. I must say I am realy surprised at the sound I got. it has no drone which was my main concern it's not to loud and around 3-4 rpm it sounds almost like a Ferrari and at lower rpms sounds like a finely tuned v8 all and all this thing is a awesome exhaust.
But I will tell u this much in the begging it sounds a good but after u drive it once it breaks in the sound gets better.

[smmmurf]

It depends on how loud you want it.

Replace 1 set of perforated pipes is loud but no drone.

It seems like the new bypass method is akin to a straight pipe going through a resonated chamber and for that reason people report it to be louder with a bit of drone.

[abugiacomo]

i replaced just the two larger perforated pipes with straight pipes and am extremely happy with the sound, and there's no drone whatsoever...i also have had the same experience as m3power55 in that the exhaust has gotten slightly louder after the first few hundred miles...

http://www.m3post.com/forums/showthread.php?t=618613

i can't speak to the acm mod as i've never heard it in person, but i did get a quote from them and it was *way more* than $400...

[BMW Fanatic]

Originally Posted by M3Power55

I did the oem exhaust mod, and I love it. What I did was I cut out all the perforated pipes (4 of them) and had new pipes welded in with no holes and I stuffed all the packing back in and welded it shut. I must say I am realy surprised at the sound I got. it has no drone which was my main concern it's not to loud and around 3-4 rpm it sounds almost like a Ferrari and at lower rpms sounds like a finely tuned v8 all and all this thing is a awesome exhaust.
But I will tell u this much in the begging it sounds a good but after u drive it once it breaks in the sound gets better.

OP I don't mean to thread jack but this is one of those time where I agree with Ateam, ACM mod all the way, haven't done it but if you want the loudness then that is the way to go!

Ferrari -

[stocksure]

I had the ACM style mod done by a local shop. I didn't shop around for exhausts since I didn't want to spend more than $500.

Regardless of the price, the "straight pipe" mod is loud and awesome.

[dagolfpro]

Originally Posted by smmmurf

It depends on how loud you want it.

Replace 1 set of perforated pipes is loud but no drone.

It seems like the new bypass method is akin to a straight pipe going through a resonated chamber and for that reason people report it to be louder with a bit of drone.

That's why I've been trying to hook up to hear yours. I'm suppose to goto the shop tomorrow but maybe I'll hold off until I can hear yours.

[dagolfpro]

Anyone who did the ACM think it's too loud?

[bigjae1976]

Why couldn't we do the ACM mod and stuff the outer chambers with the stuffing from the center chamber and add a couple of perforations? I would think that would quiet the exhaust down a tad while getting rid of the drone.

[Ateam]

Originally Posted by bigjae1976

Why couldn't we do the ACM mod and stuff the outer chambers with the stuffing from the center chamber and add a couple of perforations? I would think that would quiet the exhaust down a tad while getting rid of the drone.

I suggested that awhile back but to be honest you may has well do the traditional type of mod if you want a quieter version. No benefit to going to the trouble to do what you suggest when there is a proven way to do a quieter version in the original method.


I have realized there is one deal breaker for the bypass method-if you cruise at 74mph or more on a regular basis and you do not want drone than this is not an exhaust for you! As of now I do not go on the freeway all that much so its not a big deal to me, but if you did, you would be facing either drone, or to get rid of it you need to have it in 6th gear which cuts your mpg signifigantly.

Also it does NOT sound anything close to a ferrari boys! That may be a pipe dream! It sounds really great, aggressive and semi-exotic (in respect to not sounding like a deep american V8 at all). However its no ferrari!

If you want to get some exhaust noise, order one from Acm, pay 500 bucks or whatever and if you do not like it than swap your old one back in and sell it to recover a couple hundred bucks. At the VERY worst you lose 500 bucks in trying it out and atleast experience it to guage for yourself.

With all that said-it has brought 100 more smiles than it has annoyances to me. It sounds like a god damn tractor when you do a cold start in the AM! Driving off it howls loudly and really brings so much pleasure that any drone to me is worth it.

Unfortunately you really cannot have the best of both worlds in exhaust design. If you want a certain loudness, inevitibly there will be some drone at some rpms. This is slightly louder than the m performance exhaust with the same type of sound. The M performance sounds like the best combo between sound loudness and lack of drone, but outside that, all the exhausts with similar noise level have some drone- The difference is this one is 500 bucks and keeps stock appearence which I actually like with the can painted black.

[dagolfpro]

Dropped the exhaust at the shop this morning. The shop says he's done the perforated pipe replacement and has not tried the ACM version. I asked how hard it was to do and he said it shouldn't be a problem. So, I decided to do the ACM/Bypass version.

I also found a shop that does powder coating a few blocks away who is going to black out the tips for me. It's going to take about 5-7 days for it all to be completed. Will post pictures once it's all done.

[Mbauer]

I did mine the ACM way. Ive got an extra one Ive modded that Ill sell to someone for $500. Im in SoCal PM me. BTW its not super loud, its just right.

[dagolfpro]

After almost 3 weeks, I'm hoping to get mine back from the exhaust shop this week. It took much longer then I thought as I decided to powder coat the tips black and the two shops had a difficult time coordinating their schedules.

I'll post pics once I get it installed.

[MUFCbmwbear]

Debating this as well. Anyone in Chicagoland has this?

[Grail05]

i would not suggest a BYPASS unless you really want it loud.

ITS FREAKIN LOUD... AND YOU WILL GET PULLED OVER.

[reechar]

Originally Posted by Sean05

i would not suggest a BYPASS unless you really want it loud.

ITS FREAKIN LOUD... AND YOU WILL GET PULLED OVER.

I just got the bypass done. IT IS REALLY LOUD WOW. I'm going to see if I can DD this, but the second I get pulled over, I am probably swapping back to stock.

[Grail05]

Originally Posted by reechar

I just got the bypass done. IT IS REALLY LOUD WOW. I'm going to see if I can DD this, but the second I get pulled over, I am probably swapping back to stock.

yea most people here thinks its just nah it wont be too bad.... with my perforated oem pipe replaced it was already somewhat loud on a OWT....

Bypassing the entire exhaust is just freakin crazy...

BTW how bad is the DRONE....

[Ateam]

Loud when on it but sounds like a ferrari or race car-I love it!

Drone is there if you are at 3k. Keep it below or above and drone gone

[reechar]

Originally Posted by Sean05

yea most people here thinks its just nah it wont be too bad.... with my perforated oem pipe replaced it was already somewhat loud on a OWT....

Bypassing the entire exhaust is just freakin crazy...

BTW how bad is the DRONE....

It drones in 6th going 70. Not super bad. Goes away if I slow down to 60 or cruise at 80. I can also get away with down shifting and going 5th at 70. I might want to swap with someone with the older OEM mod...