92 db noise limit....Help!

Discussion in 'Competition Camaros' started by Zedzag, Dec 30, 2009.

  1. Zedzag

    Zedzag Veteran Member

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    I'm almost finished building my 81Z for autocross and one on the last problems I have is noise. My local autocross clubs are restricted to 92db measured from 50ft. I currently have a 2001 LQ4 with full 3" (tailpipes but no crossover pipe)dynomax ultraflows which is way too loud. Any way to get real quiet using cats or shorty mufflers in line or if I step down to 2 1/2" will it be quiet enough? Whos' measured their exhaust db's? I'd hate to dump a bunch of money into a new exhaust just to find out that I'm too loud and need to hack it up for another muffler inline, I'd rather do it to my current system.
     
  2. mrdragster1970

    mrdragster1970 Veteran Member Lifetime Gold Member

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    .

    Have you checked collector cones. My buddy runs a blown Dodge for S/C.
    He was pretty damn loud when that blower kicked in, and he passed nhra's tests.


    .
     
  3. chevy-stu

    chevy-stu Veteran Member

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    I've got a full custom 2.5" stainless exhaust on mine, as I need to pass strict noise limits for circuit track days her in the UK and Europe.

    92db at 50ft is pretty loud.. at what revs would that be, or is that a drive-by level ?

    My car is 102db, but this is measured as standard here at 1 metre (about 3 feet) from exhaust outlet at a 45 degree angle with the engine at 2/3 to 3/4 revs. most circuits also have drive by microphones too.
     
    Last edited: Dec 30, 2009
  4. Zedzag

    Zedzag Veteran Member

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    They measure the car at various stages of your timed run. The revs could be 3000 to redline and they measure it all.

    What mufflers are you using and how long are they?
     
  5. 77bigbumper

    77bigbumper Veteran Member

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    on my old glh omni i turned the exhaust tip in so on the track it was turned away from the sound meter . it worked.
     
  6. chevy-stu

    chevy-stu Veteran Member

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    So basically like a drive-by meter...

    My mufflers are made by the company that fitted the system, so they're own generic straight thru ones, but the biggest pair that would fit under the car, hence they are very visible from the rear..
    [​IMG]
     
  7. Turbo70Camaro

    Turbo70Camaro Veteran Member Gold Member

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    Sound Off in Quietest to Loudest (Decibels):

    1.Borla XS, 80db at idle, 90db at 2,000 rpm, 110db at WOT.
    2.Hooker Maxflow, 80db at idle, 90db at 2,000 rpm, 120db at WOT.
    3.Magnaflow, 82db at idle, 91 at 2,000 rpm, 114db at WOT.
    4.Flowmaster, 82db at idle, 93 at 2,000 rpm, 115db at WOT.
    5.Flowtech Warlock, 83db at idle, 92 at 2,000 rpm, 112db at WOT.
    6.Dynomax UltraFlo, 83db at idle, 94 at 2,000 rpm, 113db at WOT.
    7.Borla XR1, 83db at idle, 96db at 2,000 rpm, 118db at WOT.
    8.Bassani Street, 83db at idle, 96db at 2,000 rpm, 120db at WOT.
    9.Edelbrock RPM, 84db at idle, 93db at 2,000 rpm, 118db at WOT.
    10.Bassani Real Street, 84db at idle, 96db at 2,000 rpm, MAX. (120+db).
    11.Flowtech Afterburner, 86db at idle, 94db at 2,000 rpm, 115db at WOT.
    12.Flowtech Terminator, 86db at idle, 94db at 2,000 rpm, 119db at WOT.
    13.Hooker Aerochamber, 87db at idle, 94db at 2,000 rpm, 114db at WOT.
    14.SpinTech, 87db at idle, 97db at 2,000 rpm, 116db at WOT.
    15.MAC, 87db at idle, 98db at 2,000 rpm, 119db at WOT.
    16.No Muffler, 91db at idle, 103db at 2,000 rpm, MAX. (120+db).

    It was a few years ago from one of the muscle mags (do not remember), it had your basic h-pipe dual exhaust IIRC with tails.
     
  8. Skip Fix

    Skip Fix Veteran Member

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    An X pipe can make a big difference.
     
  9. muscl car

    muscl car Veteran Member Lifetime Gold Member

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    if they're testing the db's in tech inspection but not during racing just stuff some steel wool into the tail pipes or turndowns ,this is what we do with our dirt track cars and haven't been caught by the sound meter yet


    steel wool is your friend when you need to quiet it down for the officials
     
  10. chevy-stu

    chevy-stu Veteran Member

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    Yes, but when the burning steel wool comes flying out of your exhaust glowing red and on fire rolling across the track you tend to get in trouble with the track officials, as my friend did when he tried this..
     

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