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Thread: Quiet Race Exhaust Help

  1. #1
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    Quiet Race Exhaust Help (Update w/Sound Clips)

    My 95 M3 current set up includes schrick cams, intake and headers. Cat delete and UUC exhaust- standard duel pipe set set up. At Laguna Seca I am 95-96 db with down turns away from the sound station. I would like to go to a single pipe 3" exhaust to save weight and get it down to the required 90 db. Anyone have a good formula for a race muffler and or resonator? Thanks!
    Last edited by GOFASTT; 03-21-2019 at 02:25 AM.

  2. #2
    NeilM is offline Member BMW E36 M3 Expert
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    Maybe it's because single 3" setups are usually configured as full race exhausts anyway, but I've never heard one that wasn't substantially louder than dual pipes. Your UUC exhaust is also known for its loudness. (Years ago I reluctantly returned mine for that reason, and that was with cats.) Resonators with your current setup would help.

    Neil

  3. #3
    joenationwide's Avatar
    joenationwide is offline Makes Cars Dance BMW E36 M3 Expert
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    I had a custom 2.5" exhaust on my race car. It had a resonator and a muffler and it was so quiet sounded like a Prius compared to the other race cars.
    So yes get the largest/longest round muffler you can for a resonator, and the largest and longest rear muffler and it will be quiet.

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    90 dB, not even fun. Last time there, had to run a euro intake filter box, stock cat back exhaust. Open element intake and UCC TSE blew up the meter. Weather conditions will impact dB, and look out for the roving meter... it’s bad enough breathing it out of T5.

    "It's not the people who vote that count, it's the people who count the votes."
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  5. #5
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    No kidding and the reason I haven't been back in a couples of years, but it is nice cool place to hit in the summer when temperatures soar and well its Laguna Seca!

    The car has evolved into non-op dedicated track car- this being one of the last bits. I've already frankensteined the exhaust a bit with removing the cats, the twin oem resonators are still in place as well as the cross "X" section. Time to just pull and put in a proper exhaust. As mentioned above a new single 3" pipe with resonator, muffler and a tip that can accept a super trap or baffled down turn is the plan.

    Thanks everyone for your comments.
    Last edited by GOFASTT; 02-20-2019 at 07:12 PM.

  6. #6
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    Anyone have experience with either a Coast Fab (now PRO-FABrication) or Burns dual stage muffler? I feel like the largest version of these mufflers might be quiet, but I also don't want to experiment with a muffler that costs like $500 just to find out it's still very loud!

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    Quote Originally Posted by GOFASTT View Post
    My 95 M3 current set up includes schrick cams, intake and headers. Cat delete and UUC exhaust- standard duel pipe set set up. At Laguna Seca I am 95-96 db with down turns away from the sound station. I would like to go to a single pipe 3" exhaust to save weight and get it down to the required 90 db. Anyone have a good formula for a race muffler and or resonator? Thanks!
    My setup is similar to yours. '95 with Schrick cams, aFe intake, Supersprint header and a Supersprint catless midpipe that has a fairly large resonator. I have a Stromung catback which I believe is quieter than your UUC. I've passed with the Stromung and also blown 95db with it. Atmospheric conditions play a huge part at Laguna and they can change quickly if fog rolls in. I doubt a 3" single setup would go under 90 without stacking up at least 2-3 mufflers. Hate to say it, but the absolute safest way to stay under 90 for all weather conditions is to remain dual pipe and use a stock muffler section. Intakes can have a big effect too as badmonkey suggested. I used to keep a euro airbox with my spares just in case... but with the stock muffler I never had issues.

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    Thank you for your comments, you could very easily be right but going to give it a go and knowing additional parts may be required. Spoke with Magnaflow and they spec'd (best guess) Rear Muffler – Part # 14149 – 5x8x14” Straight though design – 3.00” Mid-muffler / Resonator – Part # 14419 x2 – 4x14” – 3.00”. Hopefully I will have it installed the next week or so and post a follow up.

    - - - Updated - - -

    Quote Originally Posted by FredK View Post
    Anyone have experience with either a Coast Fab (now PRO-FABrication) or Burns dual stage muffler? I feel like the largest version of these mufflers might be quiet, but I also don't want to experiment with a muffler that costs like $500 just to find out it's still very loud!
    I like the sound clip taken at Thunderhill with a 5dbl drop but agreed expensive for a maybe.

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    Update- final parts installed single 3" straight thru Magnaflow MPE-14419 resonator MPE-14219 muffler. Very happy with the results and sound, but a track day at LS will of course be the test.

    Existing UUC cat back

    Magnaflow Exhaust

  10. #10
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    From the sound tracks, that magnaflow setup sounds good for a straight-through, and noticably quieter than the UUC. But, you added a resonator, correct?
    I may have to look at that magnaflow muffler. I can probably save 10-15lbs compared to my 3" merge to 2x2" stromung.

  11. #11
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    I like the sound of the Magnaflow. It's difficult to predict on-track decibels from free revving the engine though. Volume goes up a lot under load at full throttle. Be sure to report back with results!

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    Quote Originally Posted by aeronaut View Post
    From the sound tracks, that magnaflow setup sounds good for a straight-through, and noticably quieter than the UUC. But, you added a resonator, correct?
    I may have to look at that magnaflow muffler. I can probably save 10-15lbs compared to my 3" merge to 2x2" stromung.
    Correct I added a 4"x16" round muffler/resonator about mid point. Same location as the oem resonators.

    - - - Updated - - -

    Quote Originally Posted by NoLastName View Post
    I like the sound of the Magnaflow. It's difficult to predict on-track decibels from free revving the engine though. Volume goes up a lot under load at full throttle. Be sure to report back with results!
    Agreed and will do. I attached the muffler tip with a v-band clamp anticipating either the possible addition of a supertrap or a more aggressive 90° tip away from the sound station.

  13. #13
    NeilM is offline Member BMW E36 M3 Expert
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    The UUC sounds just as rorty as I remember. Your custom 3" is much more civilized than expected — impressive!

  14. #14
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    We use that Magnaflow on our race cars … they do sound great at full sing! Note that they will get louder as they age … dunno why, guess they lose their packing? Also if you install too close to engine, they can crack/blow out. We had them in the resonator location, but will be moving to rear location.
    Check out the 8legs Racing page: https://www.facebook.com/8legsRacing/


  15. #15
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    Quote Originally Posted by NeilM View Post
    The UUC sounds just as rorty as I remember. Your custom 3" is much more civilized than expected — impressive!

    Thanks Neil! I can't wait run this on track

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    Quote Originally Posted by ScotcH View Post
    We use that Magnaflow on our race cars … they do sound great at full sing! Note that they will get louder as they age … dunno why, guess they lose their packing? Also if you install too close to engine, they can crack/blow out. We had them in the resonator location, but will be moving to rear location.
    Blow out? that's wild.. I wonder if your igniting unburnt fuel in the exhaust at throttle lift?

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