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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Tue, Feb-14-2017, 06:44:07 PM   #1
HassanEido
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Default My custom exhaust journy begins

As some of you may know, I've been looking around for an exhaust system to complement the Cams and CF Airbox.
After some research, and looking at fellow members dyno sheets, those who had success gaining more power while regaining low end torque and those who lost bottom end torque, I came to the following conclusions,which might be common knowledge to some, but might be useful to mention those in one place. These might also be controversial to some, but I've seen enough dynos on similarly modified cars to know the following :
-2.25/2.36 stock tubing do become somewhat restrictive approaching 400 bhp, these pipes in theory become less optimized to the system past 370bhp.
-The fact that upgrading these tubes yielded more power on cammed cars proves this theory to an agreeable extent.
-2.5 inch dual tubing is sufficient in theory for ~460hp, so should suffice for my needs.
-3.5 inch will flow as much as a 2.5 dual, with less weight, and less drag on exhaust gasses.
-3.5 inch mid section does not lose bottom end torque when the merge is executed at about where the stock H pipe resides. BW Street /track mid pipe has the X merging further back near the mounting points, and I've seen dynos with it retaining bottom end, so will be going with that.
-MOST aftermarket exhaust mufflers, the ones that I've seen at least, neck down to less than 2.5/2.38 inch on their internals . Couple that with horrendous bends, and you'll know why many AM exhausts actually flow worse than the stock muffler (RE Eldiablo necks down to about 2.25 after the flanges and has cute 180 bends that can't be doing any good. My own scorpion muffler internals necked down to 2.25 after the flange, and 1.9 inch internally(inside the muffler), huge restriction.. This was also pointed out by Chris from HPF a few years back ,since flow rate effects become very apparent when boosting these cars. RE El Diablo street was found to lose some 40 whp, while the OE muffler seemed to be extremely efficient and making adequate power.Same car same dyno 30 minute difference. While this might not do much to a car making near or just above stock power, it's an area to be addressed as more flow is added thru cams and an airbox, and approaching 80 90 whp over stock
-Keeping a true dual 2.5", without having it neck down in the perforated core section, and using less bends, should in theory keep my exhaust flow rates the same after the mid 3.5, while retaining a civilized exhaust tone

So, not wanting to buy an off the shelf aftermarket part for the previously mentioned reasons.. I started to think about a design I can make the race shop that I work with fab for me. I looked at BW race which was a straight thru muffler, but the single tip thing isn't for me. The DRONE isn't either, since it's my daily, so that was out. Borla street had too many bends , a couple of which were a 180 turn inside each muffler, so that was out. Then I saw the SS race. What a beautiful piece that is. Essentially, it's two mufflers, one has two pipes going into it, then I assume an internal Y splits the first pipe into two tips out the first muffler bottom, the second pipe would make a 90 degree bend and exits the side of the muffler and into the second muffler, which is horizontally mounted, and then it Ys into two tips out the second mufflers bottom.
So the fabrication started:
Stainless steel sheet!
SS sheet.jpg
first muffler inside, the first pipe takes a gentle 90 degree out the side,2.5 inch tubing mandrel bent.
firstmuffler.jpg
Perforated 2.5 inch tubes
perforation.jpg
Cut to length and installed
internal bracing.jpg
I reused the scorpion Y tips as they were 2.5 inch and beautifully made, extended those to fit onto the mufflers
welds.jpg

The resulting mufflers are two 40 cm and 35 cm custom mufflers with SS wool inside.
EDIT:
Dyno results
http://www.m3forum.net/m3forum/showp...4&postcount=39

(11/9/2017 Edit): custom sec2 update:

So, decided to go ahead and fab up that custom section 2 to finish off my custom exhaust.
The stock section 2 is very good for what it is. Unles the tiny sec1 that keausres 2.15", sec2 is a 2.38 inch piece. But having a 2.5 inch dual muffler and a 2.5 inch sectin, I just had to get section 2 done too! Besides those low to mid range gains from sec1 suggested that a sec2 of the same diameter will in theory continue the trend to higher rpms.
Also I decided to go with an e9xM Xpipe as the cross over, it's just so well made and hav8ng used e9x resonators in sec1, I was gonna continue theme lol.
I decided go with V bands instead of flanges. Those bored out stock flanges were looking thin anyway. So I had the X pipe welded right up to the end of sec1,to match where the H used to be, and added vbands afterwards making sec1 larger.
Sec1 :
Attachment 207449
Added X pipe:
Attachment 207450
Then 2.5 inch stainless pipes were routed to the back:
Attachment 207451
Attachment 207452

Impressions:

Sound:Its a tad louder. Noticebly louder. But it was too quite before. still has zero drone, zero rasp, but has some grunt
Power: as far as I can tell, it has lost zero wtqs down low. Still pulls like a sideways train from 2k rpm to 6.5k. Right at that rpm is where things get interesting. Compared to before it now hauls ass, like a fastforward button has been pressed. I have a feeling that top end has gotten much stronger, them needle just drops to 8500 with much more urgency, but i'll let the dyno be the judge on that one soon
And video, I was peddaling in first and 3rd at about 6_7k rpm(spinning in 1st and going round a bend in 3rd):

Thanks guys! Here's another video,0-60 4.4 secs :
Before 4.6 secs:
Before and after comparison:
You can hear the differen e in shift points

Edit 12/11/2017:
Dyno results are in. 357.7 whp . http://m3forum.net/m3forum/showpost....&postcount=165


So all in all it was an 18 whp increase from a custom header back exhaust
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Mods:
-Custom CF airbox
-SSV2 catless headers, Custom 2.5" dual sec1, Custom sec2 2.5" dual with e9xM X pipe, SuperSprint Race inspired custom section 3..
-Cat Cams 280 272.
-Custom dyno tune
-Tms pulleys and electric fan conversion
364.1 whp 287.8 wtq

Custom exhaust thread and dyno http://m3forum.net/m3forum/showthread.php?t=569086
Cams thread and dyno http://m3forum.net/m3forum/showthread.php?t=554439
Custom cf airbox thread http://m3forum.net/m3forum/showthread.php?t=595180
Why not to use after market bearings with surfacetreatments and /or increased clearance
http://www.m3forum.net/m3forum/showp...4&postcount=10

Last edited by HassanEido; Mon, Dec-11-2017 at 04:24:39 PM.
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Old Tue, Feb-14-2017, 06:53:08 PM   #2
HassanEido
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Default Re: My custom exhaust journy begins

Section 3 Complete!

ss1.jpg

Painted the beautiful TIG welds
painted ss1.jpg
ss2.jpg

And it was time to see how this custom setup sounded, and to my absolute surprise it was very very tame at idle. No drone between 1 and 3.5 RPM. Just a hint of bass so you know something special is installed. But overall much quieter than my older restrictive scorpion muffler. Once I'm on it, it sounds glorious but very refined, no rasp whatsoever. My old setup sounded like a carrot juicer in comparison. Overall I'm super pleased that a straight thru dual system, with 2.5 inch cores, sounds this good, to my ears at least

Cold start and rev.

inside car start and rev

Mid pipe and S pipes to come But for now, it definitely feels much happier. The previous setup necked down to 55 mm(2.16") at the flange and 50 mm inside the muffler(1.9"). Now it just drops into 8200RPM with what seems like a lot less effort. Dyno will tell
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Mods:
-Custom CF airbox
-SSV2 catless headers, Custom 2.5" dual sec1, Custom sec2 2.5" dual with e9xM X pipe, SuperSprint Race inspired custom section 3..
-Cat Cams 280 272.
-Custom dyno tune
-Tms pulleys and electric fan conversion
364.1 whp 287.8 wtq

Custom exhaust thread and dyno http://m3forum.net/m3forum/showthread.php?t=569086
Cams thread and dyno http://m3forum.net/m3forum/showthread.php?t=554439
Custom cf airbox thread http://m3forum.net/m3forum/showthread.php?t=595180
Why not to use after market bearings with surfacetreatments and /or increased clearance
http://www.m3forum.net/m3forum/showp...4&postcount=10

Last edited by HassanEido; Tue, Feb-14-2017 at 10:17:58 PM.
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Old Tue, Feb-14-2017, 09:24:10 PM   #3
vwrado
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Default Re: My custom exhaust journy begins

Very impressive!
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Old Tue, Feb-14-2017, 10:22:44 PM   #4
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Default Re: My custom exhaust journy begins

Nice work Hassan, and the system sounds great too btw! It does look like an SS Race, but w/larger 'cans'. Really looking forward to your larger mid-pipe set up and results as well...for obvious reasons!
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Old Tue, Feb-14-2017, 10:38:44 PM   #5
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Default Re: My custom exhaust journy begins

Well done!! Great info here too. I knew some exhausts are worse than stock but i didn't realize some pinched down to such small diameters inside.
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Old Tue, Feb-14-2017, 10:43:43 PM   #6
HassanEido
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Default Re: My custom exhaust journy begins

Quote:
Originally Posted by vwrado View Post
Very impressive!
Thanks!

Quote:
Originally Posted by stash1
Nice work Hassan, and the system sounds great too btw! It does look like an SS Race, but w/larger 'cans'. Really looking forward to your larger mid-pipe set up and results as well...for obvious reasons!
Hey broo! Yeah Going thru with the plan like we discussed last time
The cans are bigger to attenuate more sound there's a baby girl on the way so volume needs to be more baby friendly , So I can tell the wifey that I did it for a good cause although I don't know what's gonna happen after I add that 3.5 inch mid
Planning to dyno before and after the pipes.. Just to know what each part changed individually

Quote:
Originally Posted by ramp1
Well done!! Great info here too. I knew some exhausts are worse than stock but i didn't realize some pinched down to such small diameters inside.
Thanks man! yeah it's really a shame that they even advertise more power when there's none to be had with these restrictions added. The stock piece is a real piece of art, able to flow well at 600 whp power levels. A friend of mine has a 367whp NA m3, with the stock muffler on no problem. It also deadens the sound very well, too well sometimes but it weighs a ton and that's the case for a good aftermarket /custom section 3 ..well that and more exhaust note volume
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Mods:
-Custom CF airbox
-SSV2 catless headers, Custom 2.5" dual sec1, Custom sec2 2.5" dual with e9xM X pipe, SuperSprint Race inspired custom section 3..
-Cat Cams 280 272.
-Custom dyno tune
-Tms pulleys and electric fan conversion
364.1 whp 287.8 wtq

Custom exhaust thread and dyno http://m3forum.net/m3forum/showthread.php?t=569086
Cams thread and dyno http://m3forum.net/m3forum/showthread.php?t=554439
Custom cf airbox thread http://m3forum.net/m3forum/showthread.php?t=595180
Why not to use after market bearings with surfacetreatments and /or increased clearance
http://www.m3forum.net/m3forum/showp...4&postcount=10

Last edited by HassanEido; Tue, Feb-14-2017 at 10:51:47 PM.
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Old Tue, Feb-14-2017, 10:58:50 PM   #7
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Default Re: My custom exhaust journy begins

How much to make another?
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Old Tue, Feb-14-2017, 11:44:54 PM   #8
Brian N
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Default Re: My custom exhaust journy begins

Quote:
Originally Posted by Tchleung View Post
How much to make another?
Seriously if it flows well and it is like a quieter drone free version of the SS race. I think you might have a serious winner. I love the sound of SS race it's just way too loud for my liking. So I went with the SS sport which sounds a little different IMO because of the way the muffler is constructed.
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Old Wed, Feb-15-2017, 01:49:16 AM   #9
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Default Re: My custom exhaust journy begins

I want one as well. I'll pay to ship it international, PM me. Please.
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Old Wed, Feb-15-2017, 02:17:31 AM   #10
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Default Re: My custom exhaust journy begins

good stuff here!
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Discussing My custom exhaust journy begins in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)