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      10-07-2012, 09:42 PM   #1
v3.2mc
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OEM ///M mufflers gutted

had a few extra hours today and so finally got around to doing this bit of surgery. i've been curious about what's inside of these for a long long time, so all youz guys that like to study why our cars are the way they are, you should like this...


passenger's side muffler. the cuts will be made from the bottom...

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after removing the tips...

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all cuts made, including the 6 spot welds for the baffles...

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guts revealed! (sans fiber packing)...

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      10-07-2012, 10:00 PM   #2
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Nice work Were there any insulation used?
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      10-07-2012, 10:16 PM   #3
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Nice work Were there any insulation used?
yes... lots!

i filled a kitchen-sized waste bag nearly past its limits. i was surprised that it is a long-strand fiberglass, and not a stainless steel wool. i have no idea how many miles were on it, but the fibers appeared to be in good shape. most were pure white in color, with the only discoloration appearing where it had been soaked in a carbon/water mix (completely understandable for a muffler in a combustion engine).

i will be taking it to work tomorrow for weight.
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      10-07-2012, 11:19 PM   #4
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That complete muffler should weight approximately 21.5lbs, if I recalled correctly from the last time that I weighed it on my bathroom scale.
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      10-07-2012, 11:48 PM   #5
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Once I added straight-thru exhaust (Diablos), I instantly noticed a power increase. Folks don't believe me, but I stand by it.

Also, is the junkyard they ONLY place we can dump these things if we want to make a buck? (if they'll even take them).
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      10-08-2012, 12:50 AM   #6
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Nice work, and my curiosity is satisfied regarding what's inside. Pretty much the same as E9x M3 (which has a stock exhaust that's way too quiet). And we can say this, they're ugly inside than outside.

The only stock exhaust on a BMW that I think they've got right is the E9x 335 (still a bit quiet, but a step in the right direction) and the 1M. The 1M sounds perfect IMO for a stock exhaust.
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      10-08-2012, 07:32 AM   #7
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I vaguely remember another thread on here where the OP did something similar. After welding it back up, he noticed little to no difference in sound. Hopefully I'm wrong.

Are you doing it for weight savings or sound?
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      10-08-2012, 08:33 AM   #8
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Any feedback on the sound change ?
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      10-08-2012, 08:55 AM   #9
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E36 M drivers do this alot, and the muffler sounds completely different.

Interested in new sound
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      10-08-2012, 09:12 AM   #10
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Quote:
Originally Posted by Kgolf31 View Post
E36 M drivers do this alot, and the muffler sounds completely different.

Interested in new sound
Same... Be a pretty cheap mod, and the stock mufflers do look very nice, if you don't go hunting around for aftermarket ones too often like so many of us do LOL
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      10-08-2012, 09:31 AM   #11
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One thing is true, once you put the oem up against a after market, you wonder if the BMW designer purposely went for the butt ugly look. The OEM's on the Z4m's are horrendous looking IMO. The tips are a joke
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      10-08-2012, 12:16 PM   #12
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no final plans have been made yet, but so far the idea is to make this as straight-through as possible while not purchasing any additional parts for the innards.

i'm thinking that both baffles will be completely removed. the "Y" will be moved closer to the outlet, and angled towards the inlet. the long perforated pipe will go directly from the inlet to the "Y". all of the fiberglass will be reinstalled. after a full weld it'll be ready for testing.
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      10-10-2012, 09:57 PM   #13
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I've seen the old thread about another member gutting his mufflers, and also remember him saying that the sound was the same.

You made a bigger cut though, and we can see the design better. It really looks like the Supersprint Powerloop muffler inside. Very beautiful curves, if you mask me. No wonder tuners say that replacing it doesn't add much power.

Plus, its located far back and very low. So in terms of replacing it for weight savings, its kinda the worst location to lose weight in terms of handling and weight distribution, I THINK. Especially since most weight saving mods already address the rear, leaving the stock front too heavy in return
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      10-10-2012, 10:56 PM   #14
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i've seen that thread before... the only thing modified was removal of the batting. this would not change anything performance-wise, and might actually increase backpressure due to a loss of gas guidance provided by the very tightly packed batting, effectively inducing eddying.

the batting and overall shape of the muffler helps to combat standing waves. my theory is: if i can modify to a straight-through design while keeping the batting and muffler shape the car will retain the OE sound and lack of drone while increasing volume. my guess is this will also add some popping noises which to me is a bit of a negative, but we'll just have to wait and see. the sheer size of the muffler should help keep the sound low and healthy and completely devoid of rasp.

and this is truely the best part of the experimenting... i do not yet know the outcome. i will absolutely post the results though, so stay tuned.

as far as the asthetics are concerned, i actually quite like the look of the OE cans. it adds a visual weight that seems more functional than pretty... idk... i'm probably alone in this thought. and i have something else planned that i believe will compliment the functional look, so now this is being co-developed with another project.

now... i am completely open to ideas as i haven't modified anything yet, so if anyone has anything to add in... do it! i'm all ears!
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      10-10-2012, 11:29 PM   #15
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I wouldn't say it's the worst place to lose weight, though certainly not the best. Beyond thinking about weight being low vs high, and static weight distribution across the wheels, there are also other types of mass distribution that manifest themselves in dynamic situations: polar inertia. Having mass at the ends of the car makes it less apt to rotating. I like the gym analogy- it's easier to rotate a 45 lb dumbell in your hand than a 45 lb barbell. A lot of us discovered this is a kid by spinning around on a swing... feet out, slow rotations... feet in, fast rotations. ANYWAY. I doubt that the savings would be noticeable.

I appreciate the pictures! I wonder how much effort the engineers put in to shaping the mufflers around cancelling certain frequencies. My inclination is that they added bends so the exhaust pipe has three passes through the muffler rather than just one.
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      10-11-2012, 08:03 AM   #16
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I appreciate the pictures! I wonder how much effort the engineers put in to shaping the mufflers around cancelling certain frequencies. My inclination is that they added bends so the exhaust pipe has three passes through the muffler rather than just one.
i'm treating the acoustics as similar to any other chamber. negligible parallel interior surfaces and an unusually defined volume extinguish nearly all standing waves. the back-and-forth wrapping of the pipes acts as a transmission line, which effectively lengthens the fundimental frequency of the chamber. basically, it's there for two reasons... one: to fool the box into thinking it's bigger than it really is... and two: to mitigate any "outliers", noises, that the average listener might perceive as harsh. the batting also helps fool the apparent size of the muffler by cutting out much of the high frequencies, and allowing the low frequencies to come to the surface.

again, this is all based in what i THINK... so it'll be interesting to see what really happens.
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      10-11-2012, 09:05 AM   #17
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Smart ass : )
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      10-11-2012, 10:27 AM   #18
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eeesh... not trying to be!

like i've said... i'm open to ideas!
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      10-11-2012, 12:17 PM   #19
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The mufflers are actually not that bad looking once you've painted them black One the look-wise, one thing I would change would be the tips. A slightly larger tip that better fills up the opening would make it perfect
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      10-11-2012, 12:38 PM   #20
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The mufflers are actually not that bad looking once you've painted them black One the look-wise, one thing I would change would be the tips. A slightly larger tip that better fills up the opening would make it perfect
agreed with rgds to the tips... i'm looking at the eurosportdesign option. imo, they look factory+.
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      10-11-2012, 11:08 PM   #21
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agreed with rgds to the tips... i'm looking at the eurosportdesign option. imo, they look factory+.
That's a great looking tip However, I still don't think those 76mm tips will fill in the opening well enough. Take a look at my Remus tips, which are 76mm and there are still plenty of room on either side. If I had a choice, I would go for at least something in the 80mm-83mm range tips, like those on the Eisenmann.
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      10-12-2012, 08:11 AM   #22
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76mm is the largest that will fit on the OE mufflers due to the outlets being too close together. i do not want to modify that aspect as that would be a lot of work that i'm not comfortable with doing myself.

i guess i could find tips of different sizes and set it up as an homage to RPI...?
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