Devens db limits

[dejcobra]

Just a heads up there are new sound restrictions in Devens. I was one of three cars from this weekend that was told to "adjust the volume of my exhaust". The limit was set at 52db and I was 59db...I am not sure how many feet away they were measuring from. I know inside the car I have 104db at 6000 rpm wot. Stock FFR side pipes 347FI 401rwhp. Time to get the sawzall and welder out.


Dana

[Cone Basher]

You are not that far above the limit. Before you take a sawzall to the complete system I would try a coupe of SS lap band clamps (JEGS has them) on each side. Just saw the exhaust section off of each pipe allowing room for the lap band clamp and this will enable you to point the exit down or even under the car and return to "'stock" set up by adjusting the clamps. I recently ran an Auto-X where a guy had a full on track car a BMW and all he did was add a 45 angle to his system pointed down and away for the "sound police". This kind of ticks me off because 99% of the Harleys in my area have straight pipes and they rip from stop light to stop light and you can hear them coming for 3 or 4 blocks.
If you want to change your entire system look at power sticks available at
www.classic chambered.com.
HTH
CB

[cobramd]

Dana was that with your new pipes or the stock ones that you were running earlier this year?
Sorry I've been missing the past few events, vacation and family commitments have been keeping me away. Hopefully I'll see you at the NESVT event on sept 9th

[MikeKelly]

Originally Posted by dejcobra

The limit was set at 52db and I was 59db...Time to get the sawzall and welder out.

I think you're probably mixed up on the dbs, 92db + 99db would be a lot more of a "normal" track sound restriction + sidepipe reading. 60db is the reading for "normal conversation".

Anyway, before you go for the sawzall you might want to check this thread out:

Flexible exhaust insert

HTH,

Mike

[dejcobra]

Thanks for the tips guys. The car is pretty loud and I had planned on putting new mufflers on anyway. Any recmondations on mufflers...if I recall there was some talk about lowbacks...I don't think my spelling is right. I will also check out the power sticks.

John it was a fun day but hot as hell. I'm getting closer to Garry on 2 seconds from him now. I don't think I will be at NESVT on Sept 9th because I will be heading down to the Watkins Glen . I am registerd for BSCC on Sept 2nd though. They usually have less cars.

Dana

[Cone Basher]

I typed it wrong its Classic Chambered Exhaust Inc. - Home Page or phone 248-889-4364. Worth a look, they offer chamber mufflers in different diameters with different packing (quiet or loud with the sameinrernal diameter). Similar to the side pipes that were offered on the big block Corvettes back in the day.
Got this info from the forum as I was looking to upgrade my Coupe exhaust for better flow. Burns Stainless also makes them but they are loud.
HTH
CB

[mmarshall]

The plus side of fixing the factory exhaust issues is you also pickup 60-70 HP. I am amazed how large of engines some folks try to make flow through those tiny exhaust tubes.

On my new engine I used shortie headers and 2.5" magnaflows. My engine made 50hp more than it was rated for from the factory and the car is much quieter than it was with the stock sidepipes. Also with the exhaust exit so far forward the horrible resonance you get while cruising at 2000-2500 rpm is completely gone. I can now do whatever I want for a cam and not worry if a bunch of duration/overlap will put me over the edge on sound. The only downside is you lose the classic twin sidepipe look.

Dana ask bstuke about the lowbaks as he runs them. I raced with him last year in Nashville and he was 6-8 DB quieter than I was with stock coupe sidepipes. I believe he was 86 or 88 DB and I was 94 DB. They are quite loud at idle, but don't really get much louder at redline. Plus they will never blow out and get louder like the factory pipes.

[smallblockhead]

Dana, I was taking some of those measurements on 28 July and 4 August , and the current standard "noise" limit is 10 dB over ambient at specific monitoring sites. The readings were taken at two places, at the far end of the runway on the main straight, and on Bishop Road near the entrance gate. As I remember, at the July event, "ambient" at Bishop Road was generally around 43 dB, and ambient at the end of the runway was around 50 dB. I think the 4 August ambient levels were similar. One of the problems however is that "ambient" typically varies by +/- 3 dB based on breeze, rustling leaves in the trees, distant traffic noise, etc. In most of the cases, the sound level from the autocross was considerably less than the level of passing cars, airplanes over head, wind noise, etc.

Gary

[MikeKelly]

Originally Posted by smallblockhead

I was taking some of those measurements on 28 July and 4 August , and the current standard "noise" limit is 10 dB over ambient at specific monitoring sites.

Interesting - The measurements I was referring to (elsewhere of course) are taken 50' from the side of the car in a straight (full throttle or close to it).

It can be aggravating, because if you stand behind some of the other stuff that is passing sound you can tell they are clearly louder than the sidepipe cars that are not passing sound due to the location of the sound meter...

Just a different method of achieving the same end I suppose. Maybe a better method (the Devens method)...

Thanks for the detail.

Mike

[bbk347]

The angle of the exhaust tip has alot to do with it also. The FFRs are pointed right at the listening police and could probably pass ok if they were just pointed downwards as mentioned before. Time for a "track day" set of pipes. The lowbacks work. I have used them in the past. Got them from Calif and could track down the contact info if interested.

[MikeKelly]

Originally Posted by bbk347

The angle of the exhaust tip has alot to do with it also. The FFRs are pointed right at the listening police and could probably pass ok if they were just pointed downwards as mentioned before.

Just FYI - We made the turnouts 360 degree indexable. In our *limited* sound meter testing we weren't getting any significant changes by pointing the turnouts...

YMMV

[bbk347]

I purchased my lowbacks (actually lobak) from Racing Products & Muffler Co., 941 West "A" St, Hayward, Calif 94541 510-783-3714 although it was a while ago. They have different lengths which can quiet the car down more the longer they are. I used a set of 18" ones on a challenge car (stock 302) and they worked well but anything with alot of power I would use longer ones.

[bstuke]

I have 26" lobaks. 86db at idle, 86db at WFO.

OK maybe not that loud at idle, but louder than stock, but never over 86dba any other time.

I am still the darling of the autocross scene, as it still sounds awesome.

And I turned the tips down some as well. That helped a lot.

[Wade Chamberlain]

Originally Posted by MikeKelly

Just FYI - We made the turnouts 360 degree indexable. In our *limited* sound meter testing we weren't getting any significant changes by pointing the turnouts...

YMMV

I got whacked on a saturday at a ProSolo in DC for 101db. I went home that night, and after several beers, cut the tips off with a sawzall and tacked them back in place pointing 45° down. It got me into the 97-98db range on Sunday, avoiding a DQ. I later ground the drunk-booger-welds off and used some stainless band clamps to hold the tips on...that allowed me full 360° adjustment and I could leave them pointed straight out most of the time. 2 bolts and 60 seconds to adjust at the event.

Point them under the car for even more noise reduction AND it blows the dust off in front of the rear tires.

[MikeKelly]

Originally Posted by Wade Chamberlain

AND it blows the dust off in front of the rear tires.

Heh,,,, BONUS!


It's funny how much readings vary from situation to situation.

The only thing I can guarantee is YMMV...


Mike

[Mark Reynolds]

Wondering if I will be under the sound limit at Devens tomorrow. I have a 302/340 Crate Engine, 1-1/2" shorty headers and stock FFR J-Pipes and Sidepipes.

If I'm over the limit is it instant black flag or continue to run and just quiet it down before the next event.

Any comments or words of wisdom?

[bstuke]

Wait a minute, you are asking us??? WTF? You are the expert!

Bottom line is if the glass is blown out of stock pipes, you will be at 100dba with a calibrated meter at 50 feet WFO. I had to put the cats back on to quiet it down until I got the Lobaks.

If they don't have a calibrated meter, they will have a hard time proving you broke sound.

If the pipes are pretty new and stuffed, you should be fine.

You won't be black flagged but you will be "warned" After two warnings you will be DQ'd.

HTH..

[Mark Reynolds]

Pipes are only about 700 miles old.

Last autocross I did was in 2001.

I've been so busy sending parts to people over the last 12 years there has not been so much time available to play with actual cars!

[mmarshall]

Mark just find out where the meter is and either lift or shift to 3rd in that area. Seriously it would be better to drive a momentum line in 3rd than to get black flagged. Until you get a warning just go fast and have fun.

Also I see you are running 3.27 gears so the rpm's won't be too high so that will help.

[bstuke]

Go have fun Mark!

[cobramd]

I did tje sound checks again this weekend at Devens. By far the loudest things were planes, helecopters and the wind Even Pat's coupe had lower sound at the perimeter than a moderate breeze blowing through the leaves

[Cobra 302]

Originally Posted by cobramd

I did tje sound checks again this weekend at Devens. By far the loudest things were planes, helecopters and the wind Even Pat's coupe had lower sound at the perimeter than a moderate breeze blowing through the leaves

Thats what you were doing all the way down there.
I thought you got off track and shut it down for the day.