Muffler to pass noise limits at Lime Rock and other tracks
05-18-2019, 09:15 PM
#1
Intermediate
Thread Starter
Muffler to pass noise limits at Lime Rock and other tracks
Just moved to CT from IL. The tracks in New England are not as lenient on noise as the ones in the Midwest.
Currently running the OEM mufflers and it's way too loud to even come close to passing sound at these tracks. Any recommendations on quieter mufflers so I can have fun at tracks like Lime Rock & Palmer?
Currently running the OEM mufflers and it's way too loud to even come close to passing sound at these tracks. Any recommendations on quieter mufflers so I can have fun at tracks like Lime Rock & Palmer?
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circuswings (05-19-2019)
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circuswings (05-19-2019)
05-19-2019, 10:26 AM
#4
Burning Brakes
Back in the day before I did a full race build, my C5 Z06 had an LS-6 with about a .600 lift cam and made about 400 RWHP. I had a Borla exhaust (not the quiet one either) and the car sounded about as snotty as snotty gets for a street car. I went to Lime Rock, unaware of sound restrictions and to my surprise, I was fine but two Miatas testing there were bagged for being over. It appears that the higher pitched sounds from these vehicles is much louder than the deep low growl from that exhaust. I can’t see you having a problem with stock exhaust unless you are making a ton more HP than stock.
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circuswings (05-19-2019)
05-19-2019, 06:14 PM
#7
Melting Slicks
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Member Since: Nov 2013
Location: Ex DPRK, now just N of Medford, OR
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What is the limit?
Laguna days vary... last year was 91 most days, now some are 90.
My mostly stock C6Z was <91 with turndowns and the flaps closed, 94.5 with the flaps open (ooops).
Laguna days vary... last year was 91 most days, now some are 90.
My mostly stock C6Z was <91 with turndowns and the flaps closed, 94.5 with the flaps open (ooops).
05-19-2019, 07:10 PM
#8
Intermediate
Thread Starter
Looks like the limit depends on the day and the event being held, I was able to find the below list. Not sure how far off the track the sound station is, so dB limits without distances are kinda meaningless.
86 dB NASA DE
86 dB Audi Club DE
87 dB BMW Club DE
88 dB Porsche Club DE
88 dB SCDA DE
88 dB Lime Rock Drivers Club
105 dB Porsche Race Day
105 dB Tuesday Afternoon Test & Tune
86 dB NASA DE
86 dB Audi Club DE
87 dB BMW Club DE
88 dB Porsche Club DE
88 dB SCDA DE
88 dB Lime Rock Drivers Club
105 dB Porsche Race Day
105 dB Tuesday Afternoon Test & Tune
05-19-2019, 07:45 PM
#9
I was at LRP with my C5Z last week for 2 days. I have catless long tubes, x-pipe, and corsa extremes. I swapped one of the corsa with an oem muffler. Couldn’t wiggle the other one in so I tested my luck. I also just kept it in 4th most laps. I didn’t get black flagged somehow. Pretty sure it was due to low rpms over most of the track. Not an ideal strategy and I was a little lucky. It’s frustrating with the noise restrictions.
05-19-2019, 11:43 PM
#10
Melting Slicks
Pro Mechanic
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Location: Ex DPRK, now just N of Medford, OR
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Looks like the limit depends on the day and the event being held, I was able to find the below list. Not sure how far off the track the sound station is, so dB limits without distances are kinda meaningless.
86 dB NASA DE
86 dB Audi Club DE
87 dB BMW Club DE
88 dB Porsche Club DE
88 dB SCDA DE
88 dB Lime Rock Drivers Club
105 dB Porsche Race Day
105 dB Tuesday Afternoon Test & Tune
86 dB NASA DE
86 dB Audi Club DE
87 dB BMW Club DE
88 dB Porsche Club DE
88 dB SCDA DE
88 dB Lime Rock Drivers Club
105 dB Porsche Race Day
105 dB Tuesday Afternoon Test & Tune
05-20-2019, 06:34 AM
#11
They always did the sound readings just after the uphill when I was racing there. I got shut down during a Scca race weekend for being over 105 db with boom tubes on my 640 hp busch north car. I fixed the issue by exiting the exhaust out the left side.
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Racingswh (05-20-2019)
05-20-2019, 02:29 PM
#12
- The track seems to have gotten stricter @ the end of last year and so far this year in enforcing the db limit which is 86 for most groups (and by track I mean the neighbors complaints to the track)
- The distance is 50 feet
- The db meter is definitely moved around. Depends on the day. Most times it's near start/finish or after the uphill
- Running in 4th will solve the problem for a largely stock setup but that will kill your lap times. I don't do that until after I am black flagged the first time. You get a chance to "fix" the issue. If it fails the 2nd time, then you're done for the day
- There are several unmuffled HPDE events per year - usually mid-week though
- Cloud cover and wind direction seem to have a lot to do with it. I'm 100% stock and have been flagged but only on cloudy days with no wind
05-20-2019, 06:53 PM
#13
Race Director
find out where the meters are and run turn downs. Roebling is like this, with some creative use of turn downs....maybe even a lift/shift at just the right spot.
Fortunately I raced at Lime Rock during the pro weekends when they relaxed the limits.
Fortunately I raced at Lime Rock during the pro weekends when they relaxed the limits.
05-20-2019, 08:12 PM
#14
Intermediate
Thread Starter
Thanks for the detailed description. Don’t think I’ll meet those 86 dB @ 50’ limits. I’ll see about getting one of the burns systems on there just to quiet the thing down for my own well-being. Will try to get out there on a Tuesday when I don’t have to worry about getting blackflagged.
05-20-2019, 10:42 PM
#15
Lime Rock is really strict, a lot of racers put elbows on the exhaust tips to point the noise away from meters, my friend ended up pointing the exhaust up after trying different orientations,
05-21-2019, 08:56 AM
#16
Melting Slicks
When I was racing T1 in California in a C5Z with LT headers I switched to Burns Stainless 2 stage mufflers with turn downs off the ends I could turn/adjust away from sound machines. I never had problems at Laguna Seca or Thunderhill. I highly recommend them