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Need help with exhaust noise!!

Discussion in 'Technical Q&A' started by solly, Jul 4, 2004.

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  1. solly

    solly Formula 3

    Jun 2, 2001
    1,148
    Westchester NY
    Full Name:
    Dr. Steven S.
    #1 solly, Jul 4, 2004
    I had a custom exhaust fitted to the 360 Challenge last week, and it ran great at Pocono. No cats, tiny muffler. Great sound, a little extra noticeable bhp. 4 pipe exhaust instead of the usual 2. Noise seems to be about 20-30% louder than stock 360CH (my guess), and about as loud as Bob Coates' 512BBLM or an F-40LM/333SP. BUT I'm going to Lime Rock this week, and was told it may be too loud for this track. Track has 89db noise limit.

    I have been searching for hours for a slip-in slip-on silencer on the Internet, and came up with only this: http://www.hksusa.com/categories/?id=1718

    Anyone have any ideas for a DIY device to quiet this thing down? Something i can get done by Thursday? Anyone have any experience with the device in the link? Unless I have my math wrong if I fit one silencer to each of the 4 exhausts i should reduce noise by about 28db, which would be ok for thre track. Any thoughts would be appreciated.
     
  2. don_xvi

    don_xvi F1 Rookie

    Nov 1, 2003
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    Don the 16th
    #2 don_xvi, Jul 4, 2004
    Well I'm not familiar with these products, but (1) you won't get 7dB+7dB+7dB+7dB, I don't think the math works out like that and (2) you can also give consideration to a turndown. I don't know what kind of tips you have, but if you can direct the exhaust away from the microphones you can help yourself. Just remember that turning them down into the track will only make it bounce back.
     
  3. solly

    solly Formula 3

    Jun 2, 2001
    1,148
    Westchester NY
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    Dr. Steven S.
    #3 solly, Jul 4, 2004
    Good idea. Now if I can only find out where their decibel meter is....
     
  4. Ricambi America

    Ricambi America F1 World Champ
    Sponsor Owner

    Dec 7, 2003
    16,474
    Winston Salem, NC
    #4 Ricambi America, Jul 5, 2004
    Don't laugh, but I think you can shove some steel wool into the tail pipe and it'll make a noticable difference in quieting the car down. Personally, I've never done this, but conceptually it makes sence. Unfortunately, it'll create extra pressue on the system so the "free flow" advantages you have right now will be minimized.

    Hints from Heloise -- YMMV

    -Daniel
     
  5. ferrarifixer

    ferrarifixer F1 Veteran
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    Jul 22, 2003
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    #5 ferrarifixer, Jul 5, 2004
    You're gonna struggle here solly.

    I've tried stuff like that and they just don't do the work properly.

    Best bet is to find the guy operating the meter and shove two rolled up 100's in his ears....works here anyway!

    Seriously, we've tried a few things but you need two small silencers where the cats used to be, and then another one or even two on the system at the back.
     
  6. Smiles

    Smiles F1 World Champ
    Lifetime Rossa Owner

    Nov 20, 2003
    16,675
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    Matt F
    #6 Smiles, Jul 5, 2004
    Right. For what it's worth, 90 db is actually TWICE as loud as 80 db.

    --Matt
     
  7. solly

    solly Formula 3

    Jun 2, 2001
    1,148
    Westchester NY
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    Dr. Steven S.
    #7 solly, Jul 6, 2004
  8. solly

    solly Formula 3

    Jun 2, 2001
    1,148
    Westchester NY
    Full Name:
    Dr. Steven S.
    #8 solly, Jul 6, 2004
    Last edited by a moderator: Sep 7, 2017
    Or I can try this-recommended by the NSX club for Lime Rock;


    DH] If possible, you should do the following:

    Buy big coffee cans, put them on your exhaust, cut half of the top, pull it up and deflect sound away from sound meter. Use big hose clamps and tighten them extremely tight. picture of example on www.nsxfiles.com, click on Laguna Seca 1998
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  9. rexrcr

    rexrcr Formula 3
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    Nov 27, 2002
    1,578
    Kalamazoo, MI
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    Rob Schermerhorn
    #9 rexrcr, Jul 6, 2004
    You'll need a stock exhaust for 89dB! Matt pointed out that the decibel scale is logarithmic, not linear.

    Fastest solution is a stock exhaust. Stock Challenge is probably okay, as 360 Challenge has run there, though I didn't look for dB readings, and the event may have had one of just a few exemptions Lime Rock gets each year.

    A can or two on the back of an otherwise open exhaust will not work and allow the engine to run properly.

    You're in for a headache solving this quickly.


    Rob
     
  10. solly

    solly Formula 3

    Jun 2, 2001
    1,148
    Westchester NY
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    Dr. Steven S.
    #10 solly, Jul 7, 2004
    I know. Friday and Saturday are unlimited noise days, but Thursday is limited to 89db. I no longer have my stock exhaust. But I made up removable silencer tips out of 3.5 inch turnouts with Vortex cone silencers inside. Tomorrow I will learn how to TIG weld tabs to these pipes and to the exhaust, then it's just bolt-on bolt-off. Tried it on my 360 spider with the TUBI and it was definitely quieter, although I had no one to read the noise meter at 30 feet.

    I'll take some pics and let you know how they work out.
     
  11. parkerfe

    parkerfe F1 World Champ

    Sep 4, 2001
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    #11 parkerfe, Jul 7, 2004
    Use a slip-on type Supertrapp. They're inexpensive, effective and adjustable so you can get it quite enough without being too quite. www.supertrapp.com
     
  12. ferrarifixer

    ferrarifixer F1 Veteran
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    #12 ferrarifixer, Jul 7, 2004
    I don't rate supertrap either I'm afraid. tried it, didn't work.

    STOP SOLLY. Before you tig weld your exhaust.....either remove it from the car or disconnect all 4 main ecu's.....2xengine 1x gbox, 1xabs, plus of course the battery.

    And don't trust one of those anti spkie products that are supposed to protect them......
     
  13. 4i2fly

    4i2fly Formula 3

    Apr 16, 2004
    1,333
    SF, Bay Area
    #13 4i2fly, Jul 8, 2004
    I doubt the 360C races are run with sound restrictions. A 360C running laps at Laguna Seca with 92db restriction was black flagged twice in one day during HPDE open track day. It also had the extenders deflecting the sound away from the mics.
     

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