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      04-14-2013, 08:52 PM   #20
RPM90
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Drives: 335i Msport w/sport AT
Join Date: Mar 2006
Location: Chicago


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Quote:
Originally Posted by dd1981 View Post
It's out in a shop getting welded. My friends dad is doing it he said the inside pipe will be very easy to weld since its steel. The canister is aluminum and is a PITA to weld aluminum so he quoted $200 for the gas used and his labor.
If its successful (I believe it will be) it will be a well worth $200 mod, as opposed to spending a grand on the m performance axle back.
If unsuccessful in what I'm trying to achieve, we'll I threw away $200 on an experiment and you guys got to see the interior of the muffler

Stay tuned
Just removing the damping material will change the sound, making it louder and perhaps even a bit deeper.

If you consider that low frequencies are also longer waves, then allowing that wave to travel through to the outlet without being broken up will result in a deeper sound. Long waves can also bend around corners like through the tubing. That's why in a house we can still hear the bass coming from the stereo even if we're in another room down the hall.
Your idea to close off those holes is a "sound" idea, as those holes are where the longer sound wave is being broken up.
That additional damping material further absorbs the broken wave energy to keep things quieter.

I think you're going to get a much louder and deeper tone, but will it sound pleasant? THAT is THE question.
If it does sound good I'll be surprised considering that manufacturers spend time tuning mufflers and exhausts systems not just for flow but sound quality. It'll be a very happy surprise if the louder sound is also a pleasant one. You may find that only closing half or one side of the holes will yield a better tone.
Maybe you should have done only one side at a time.
That way you would know if you're on the right track.
But, too late now. If the sound is ugly you could then try drilling some holes back in.

I had a Yamaha V-twin a few years back with a very anemic and very quiet exhaust due to the same type of design as our stock mufflers. People experimented and came up with some ideas. I used the recommendations and did the drilling. Yes, the sound was louder and deeper, but the quality of the sound sucked.
So, I opted for a set of low cost slip on mufflers made by Jardine. The result was louder, deeper, but a much better and mellower sound quality.
The best experimental experience I had was with my former Honda VFR750.
It's a V-4 engine. I had a nice though quiet Yoshimura slip on muffler.
One day I took off the slip on and fired up the V-4. WOW, man that engine had a cool sound and with just the headers the sound was glorious. But now way I could ride it around, it was just too freaking loud.
I've loved the sound of V4 engines ever since. Too bad they're not common. I'd love an auto maker to make a V4 for a car. That configuration yields great torque, and what a sound, think 2 V-Twins beating against each other.
I digress, sorry.

I want to hear your frankenmuff experiment. Let me know when it's done and I can come out and take a listen.
PM or email me.

Last edited by RPM90; 04-14-2013 at 09:05 PM.