Exhaust dB

[Team SSR]

I'm having an exhaust system made for the 944 ITS race car. I plan to use the existing headers (for now). Everything past the O2 sensor will be replaced with 3" pipe and exit out the rear of the car. Will a muffler be required to meet the SCCA sound requirements?

[joeg]

Not a clue. Certain tracks have different limits.

My guess is that you will need something.

[RacerBill]

Originally posted by Team SSR@Oct 6 2005, 09:18 AM
I'm having an exhaust system made for the 944 ITS race car. I plan to use the existing headers (for now). Everything past the O2 sensor will be replaced with 3" pipe and exit out the rear of the car. Will a muffler be required to meet the SCCA sound requirements?

[snapback]61920[/snapback]

Probably. Ask other 944 owners. Advice - read the GCR, know where the Sound Control station is at each track, know the specific limits for the tracks you race at.

If you get black flagged for a sound violation, do not get an attitude. Being proactive as opposed to defensive will help your cause and perhaps get you thru the weekend in stead of a trailer ride home with nothing to show for your entry fee.

You don't say what part of the country you race in, but geography does matter. Sound travels better in dry weather, for instance, so in Arizona Formula Continentals sometimes have to run mufflers. But it is absolute humidity is what effects the sound, not relative humidity (what is reported on the radio and tv).

Know the tracks - some have super restrictive limits (Waterford and Blackhawk come to mind).

Know the tracks - GCR recommends taking readings from the same side of the track as the property line. That could be driver's left or right.

Know where the Sound station is - some sound crews are taking readings at locations that have not be certified by the either the Divisional or National Administrator of Sound Control.

Spend some time with the Sound Control crew, learn how they take readings. In order to get a sound reading on a single car, the cars have to be a certain distance apart (depending on the track).

I would suggest two things on your first practice session with the car: 1) make sure that you come by the sound control station in the clear (no other cars near you) 2) let the stewards know that it is a new car and you are not sure of the sound level. They can get the sound readings for you as they are recorded in most cases, and get that to your crew.

If you have pit-to-car radio, they may let someone from your pit stand at the sound control station and radio the readings to you. That will allow you to try going by in different gears, rpms, etc.

Remember that sound is effected by weather and can change from morning to afternoon, so don't try and 'tune' your sound to be just under the maximum.

BTW, at the Runoffs this year, the National office was taking readings from different parts of the track because the corner stations were complaining about excessive sound of some cars, even though the cars were below the legal limit (probably had the ends of the pipes directed away from the microphone).

I held a National Sound Control license for 18 years.

[Team SSR]

Thanks for the help.
I am in central NC. We will race at CMP (kershaw), VIR, Charlotte, Road Atlanta, Roebling Road, and maybe some others on the NASA 944 Cup tour.

[chuck baader]

IF you exit the exhaust under the car, that will attenuate some of the sound. Be certain that the end of the pipe is pointed driver's right with at least a 45 bend. Remember, the rule says behind and away from the driver. I used that setup with my ITA car with 2 1/2" tubing and consistantly measured 98-99db. BTW, I did use a 12" Dynomax bullet muffler just before the turnout. Good Luck, Chuck

[JLawton]

I ran a 944 for two years in ITS with a Borla. People used to make fun of me because it was so quite!! I think you could get away with no muffler. Use a turn down and exit under the car like the others have suggested.

[vwmann1]

This is also the time you can use to get to the dyno and tune your exhaust for what you need. Just a thought.

[latebrake]

Originally posted by Team SSR@Oct 6 2005, 09:18 AM
I'm having an exhaust system made for the 944 ITS race car. I plan to use the existing headers (for now). Everything past the O2 sensor will be replaced with 3" pipe and exit out the rear of the car. Will a muffler be required to meet the SCCA sound requirements?

[snapback]61920[/snapback]

Jon Milledge says to do this. Take a 6 inch tube/Howe racing muffler/truck muffler,depending on how much room you have in the tunnel of the car. Run a 2" tube 14" long from the header flange 7" inside the muffler and exit with 3".

I had the howe muffler but would have had to expand the tunnel to get the big thing in there (7.5") and off the gournd. I used the 6" tube 18" long route to get there. Hope this helps. So far all of Jons' tips have worked for me. Quite enough and no drop in HP.

Lawrence

[Team SSR]

Thanks to all.

The pipe's at the muffler shop now. I decided to run 3" from the header flange back to where the stock muffler would be. Instead of a muffler I will have a 45 deg. fitting that I can rotate to the best position. There will still be some room to add some type of muffler if required.

[latebrake]

Originally posted by Team SSR@Oct 7 2005, 01:46 PM
Thanks to all.

The pipe's at the muffler shop now. I decided to run 3" from the header flange back to where the stock muffler would be. Instead of a muffler I will have a 45 deg. fitting that I can rotate to the best position. There will still be some room to add some type of muffler if required.

[snapback]62048[/snapback]

your four banger is going to miss that back pressure off the corners