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Help? Exhaust noise restrictions (on my FC at Lime Rock)

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Help? Exhaust noise restrictions (on my FC at Lime Rock)

Old 09-24-12, 06:37 PM
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Help? Exhaust noise restrictions (on my FC at Lime Rock)

Not sure where to post this, I figured the "track people" would know more about this than anyone.
Next month I am looking to do an HPDE event in my turbo FC at Lime Rock park. This track has a strict 86db limit.
My car has a BNR stage 1 turbo upgrade, a racing beat 2.5inch downpipe and presilencer. The rest of my exhaust has generic stock sized pipes and mufflers. It's definitely quieter than other rotary cars, but still loud for a road car.
Does anyone have any idea how loud this car is going to be? Anyone know how/where do I test before hand? I'd hate to show up and not run (and not get a refund!) due to being too loud

I've seen other cars at previous HPDE events (on this course) that are obvious track cars; souped up and somewhat noisy, and they were able to run.
However, I've also seen some cars with the "beehives" sticking out the exhaust, or steel wool jammed in the pipes.

I haven't seen too many rotaries at this track: Only a 2nd gen NA track car (it had the beehives), and a 3rd gen. But this was two years ago and I can't recall the noise levels then.

If anyone has any advice and/or can help, I'd appreciate it.
Thanks
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Old 09-24-12, 11:15 PM
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There is an app for measuring decibels. You can also buy a decibel meter at Radio Shack also.

What's the limit up there?

Never had a problem there in my rotaries but last time I was there in a rotary was back in the late 90s.
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Old 09-25-12, 05:54 AM
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Limit is 86. I don't own an iphone or a droid, but plenty of people do. I'll see what I can do. Thanks.
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Old 09-25-12, 11:25 AM
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86db? thats quieter than laguna, and stock cars have trouble.... i've done some reading on noise/sound and its a really weird subject!

1. find out where the sound meter is.
1a. the last track event i did, i was flagged for sound, but if i lifted right before the sound booth, that fixed it.

2. to get it really quiet the intake matters also. stock airbox is quieter than a cone...

3. with the exhaust it does help to point it away from the sound meter, hence the weird pipe extensions and things you'll see. some people even run an extra muffler.

4. hope the weather is good! we got flagged for sound, over 103DB, and Jack went back the next weekend and it was under 103, the difference? a cloud! seriously.
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Old 09-25-12, 11:59 AM
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^i've read that weather has does effect it. End of October though I imagine cool, dense air. Maybe that will quiet things?

I was thinking of getting some cheap 90 degree elbows and putting them facing downward on the back of my car, that could help a little.
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Old 09-25-12, 12:23 PM
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Originally Posted by beefhole View Post
^i've read that weather has does effect it. End of October though I imagine cool, dense air. Maybe that will quiet things?

I was thinking of getting some cheap 90 degree elbows and putting them facing downward on the back of my car, that could help a little.
i don't know about cool dense air, but clouds will bounce the sound back down.

elbows are nice to have, get some good clamps too.
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Old 09-25-12, 01:23 PM
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Knowing where the sound meter is the key!
Sand bagging passed it is the only way. Because a tire sliding with sqeeling is over 90 db. If you do ellbows. Point them up and away, not down.
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Old 09-25-12, 04:13 PM
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Originally Posted by Gian View Post
Knowing where the sound meter is the key!
Sand bagging passed it is the only way. Because a tire sliding with sqeeling is over 90 db. If you do ellbows. Point them up and away, not down.
up and away doesn't always work, although it could.
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Old 09-25-12, 05:57 PM
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I think my best bet is to buy some elbows and stuff them with steel wool, do the lift off thing, and then pray...
I will get 2 warnings and then they park me
Maybe I will bring my civic as back up.
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Old 09-25-12, 11:49 PM
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Originally Posted by beefhole View Post
^i've read that weather has does effect it. End of October though I imagine cool, dense air. Maybe that will quiet things?

I was thinking of getting some cheap 90 degree elbows and putting them facing downward on the back of my car, that could help a little.
Cooler air actually makes it louder.

86 dB is very low, I would try a 90 elbow pointed in the other direction from the meter.
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Old 09-26-12, 12:21 PM
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86 is very low. Some performance vehicles STOCK will get flagged. When I was there in June one guy in my group was flagged and he had a stock Elise!

I wonder if the town ever complained about all those harleys...

In the mean time I've ordered a decibel meter from ebay. The **** I buy for this car...

thanks everyone!
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