c4cruiser

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.

andy3101

Put some turn downs (turn aways) at the end of the exhaust to point the sound away from the Mic.

c4cruiser

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!

rithsleeper

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.

c4cruiser

Unfortunately, this particular event is on a Monday and that's the only day that has the 90dB limit. But because of the noise limit, the entry fee is much cheaper. And Monday is a day off for me.

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.

BEZ06

Here are a couple good solutions.

Maybe you could rig something like that for your car!!

Bob

Dirk Miller

Man, I know how these low dB levels can really concern us.
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

69427

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.

db2xpert

Some tracks have 86 and 87 decibel limits.
Stock C6 Z06 with mufflers open is 98 Db from the factory.

Phoenix1911

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.

jlutherva

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