Track Day decibel limits
#1
Team Owner
Thread Starter
Track Day decibel limits
I have an upcoming track day and the site has a 90dB limit. My '87 has this exhaust configuration: Hedman Elites with true 2-1/4" duals. There is an X-pipe about 12" after the collectors and I'm currently using Walker DynoMax Ultra-flo mufflers.
Last year (running the same exhaust configuration), the track noise limit was higher at 95dB and I got caught by the noise police at 97dB. That was in 3rd gear at 5000 RPM just before a shift into 4th on the main straight. For this year, I could simply shift into 4th prior to passing thru the area where the mike is located. That would probably take the fun out of the day. The penalty for exceeding the noise limit may be getting removed from the event with no refund This event will be at Portland International Raceway.
So any suggestions? I've thought about simply adding some 12" glasspacks where the exhaust pipes turn outwards behind the batwing.
Last year (running the same exhaust configuration), the track noise limit was higher at 95dB and I got caught by the noise police at 97dB. That was in 3rd gear at 5000 RPM just before a shift into 4th on the main straight. For this year, I could simply shift into 4th prior to passing thru the area where the mike is located. That would probably take the fun out of the day. The penalty for exceeding the noise limit may be getting removed from the event with no refund This event will be at Portland International Raceway.
So any suggestions? I've thought about simply adding some 12" glasspacks where the exhaust pipes turn outwards behind the batwing.
#3
Team Owner
Thread Starter
Thought about doing that but the area where the mic is located has 3' high jersey barriers on both sides of the straight. The mic is about 20' off the surface so it could be that any noise redirected by turndowns could echo off the barriers and upwards.
But it certainly can't hurt to try that!
But it certainly can't hurt to try that!
#4
Drifting
Member Since: Dec 2007
Location: Sumter South Carolina
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Thats pretty b.s. 90 decibels is nothing. I was at an orchestra concert and in the booth the decibles meter hit over 90 on big fortes. I have long tubes, 2.5, dual to magnaflow and I have electric cut outs under the batwing. When open ill hit 97 but closed I'm at about 91 or so. Short shifting is lame but if you know where the Mic is just shift at the mic. You will be lifting and short shifting. Or just move to a setup like Ihave.
I still think the 90 is rediculous for a "race track" usually you get a warning first. I doubt they would throw you out first time.
I still think the 90 is rediculous for a "race track" usually you get a warning first. I doubt they would throw you out first time.
#5
Team Owner
Thread Starter
Thats pretty b.s. 90 decibels is nothing. I was at an orchestra concert and in the booth the decibles meter hit over 90 on big fortes. I have long tubes, 2.5, dual to magnaflow and I have electric cut outs under the batwing. When open ill hit 97 but closed I'm at about 91 or so. Short shifting is lame but if you know where the Mic is just shift at the mic. You will be lifting and short shifting. Or just move to a setup like Ihave.
I still think the 90 is rediculous for a "race track" usually you get a warning first. I doubt they would throw you out first time.
I still think the 90 is rediculous for a "race track" usually you get a warning first. I doubt they would throw you out first time.
They do give warnings , but it's typically only if you are just 2-3 dB over the limit. Anything more (like straight exhaust) then you are asked to stop running. I could go slower, but I hate getting passed by Miata's on the straight.
#7
Burning Brakes
45 degree turn downs might work
Thought about doing that but the area where the mic is located has 3' high jersey barriers on both sides of the straight. The mic is about 20' off the surface so it could be that any noise redirected by turndowns could echo off the barriers and upwards.
But it certainly can't hurt to try that!
But it certainly can't hurt to try that!
A while ago, I received a 98 dB recording at Laguna Seca. Fortunately while I was putting on my turn downs, a track worker arrived by my side. I was about to point these so they would bounce off the pavement at about the 7:00 position. The worker explained that I should instead point them slightly up to about the 10:00 position and it worked! I never received another meat ball flag. Unfortunately, there are a lot of variables at play here. Some include wind,temperatures, humidity,topography and more. It's a real crap shoot.
Best of luck
#8
Tech Contributor
Member Since: Jun 2004
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Instead of the X-pipe how about a large resonator or an exhaust pulse termination box in the system. The (large) interior volume of these things will reduce the pressure amplitude peaks that the mufflers have to contend with. It won't restrict flow or weigh much either.
#10
How far away do most of the tracks you guys goto measure the sound in the test area? In my experience it's 50 feet, and the stock C6 Z06 rings in at 87db with baffles open, ~4000rpm blip. My Akras were 90db from the same distance.
#11
Drifting
You can buy devices to insert into the exhaust pipes that are advertised as reducing noise by as much as 10 dba.
I ran Atlanta Motorsports Park last year and with headers, small straight through mufflers and a X pipe i blew a 105 dba on a warm up lap. AMP has a strict limit of 98 dba. I bought a set of these vortex devices from an on-track shop and went out on a hot lap and blew a 103 dba at full throttle. That's not an apples to apples comparison since the warmup lap was nowhere near full throttle so I can't say how much they did reduce the noise level, but a lot of people swear by them.
It's not much fun having to short-shift and stay off the happy pedal all day.
Jim
I ran Atlanta Motorsports Park last year and with headers, small straight through mufflers and a X pipe i blew a 105 dba on a warm up lap. AMP has a strict limit of 98 dba. I bought a set of these vortex devices from an on-track shop and went out on a hot lap and blew a 103 dba at full throttle. That's not an apples to apples comparison since the warmup lap was nowhere near full throttle so I can't say how much they did reduce the noise level, but a lot of people swear by them.
It's not much fun having to short-shift and stay off the happy pedal all day.
Jim