What is the noise limit at various tracks?

Some racetracks impose noise limits on "amature" races, drivers schools, or open lapping days to satisfy those in the surrounding community who don’t want it to sound like cars are racing up and down their street while they try to eat breakfast and read the Sunday paper. These are restrictions are lifted for professional racing, but that doesn’t help most of us! Usually you will have to pass one to three noise meters, some of which may move around to different spots during the course of the day. You typically get one warning, then on your second offense you’re kicked off the track for the rest of the day with no refund. Here’s a listing of some popular tracks and their noise restrictions.

How loud is my car?

Here are tips about measuring the amount of noise your car is producing.First, you need a sound level meter. Sound level meters are available at your local Radio Shack, and other electronics or audio stores. Typically, the noise is measured by holding the sound level meter 50 feet from the car accelerating at full throttle at high RPM.

How can I make my car quieter?

Most stock NSXs are fine at just about any track, which is pretty good since some stock sports cars (like the Viper) are too loud to run at some tracks.. Many modified cars, especially those with aftermarket exhausts, headers, cat bypass pipes, or any type of forced induction can exceed the noise limits.

   

      

        
  Doug Hayashi's car with a V8 can.
        
 Note the angled bottom. 
      
    

[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...OR

 
Put your stock exhaust on for this event. I went to Laguna Seca last weekend, and      decided just to put my stock exhaust on instead of the Comptech exhaust, so I don't have      to deal with the 92 db requirement... OR

 
If you plan on going to this track a lot, maybe have a local muffler shop fabricate      something you can clamp onto the comptech exhaust tips and point the exhaust away from      where the sound stations are. I think I may go this route for NSXPO. I was three seconds      faster than Wayne at Willow Springs with the Comptech exhaust on, but only a half second      or so faster than him at Laguna with stock exhaust on last weekend. (true, it is an apples      to oranges comparison, but that's my excuse).

What setups have been tried at various tracks?

Laguna Seca

 

    

      
 OK 
      
 Too Loud 
    
    

      
 Stock Intake/Stock Exhaust 
      
 All broken or "blown" exhaust systems. 
    
    

      
 K&N Intake/Stock Exhaust 
      
 Supertrapp exhausts with too few disks. 
    
    

      
 Stock Intake/DC exhaust or HKS Exhaust or RM Exhaust or newstyle

        Comptech exhaust, with or without headers, must have cats. 
      
 Cars with the Bell Twin Turbo system installed, without cats. 
    
    

      
 K&N Intake/DC exhaust or HKS Exhaust or RM Exhaust or new style

        Comptech exhaust, with or without headers, must have cats. 
      
 Open exhausts. 
    
    

      
 Supercharged cars with the above exhaust modifications. 
      
 All Vipers