Noise

[Jim T]

Hello everyone

I am considering entering the National Tour event, but need to know more about how the DB's are measured. Example 93 DB at 50 feet, 100 feet, or what distance? FYI I have 1971 MG Midget which would be entered in G Prepared.

Your advise is needed
Merry Christmas

[Jeff]

It's 93 db at 50 feet.

The details can be found here:

http://www.sdr-scca.com/solo2/docs/2009_Supp_Reg-R1.pdf

Page 19 (or 23 of the PDF).

[oinojo]

of course aim to be in the low 80s...

Weather plays some weird games, especially during the tour. Give yourself 7-9db allowance.

[nalbar]

Jim, if you can try to enter the small practice we have the Friday before the Tour. We call it the 'Mini Tour'. It gives you a chance to run by the sound meter and make adjustments if you are over.




nalbar

[STALKER L-67]

As mentioned before in another thread I HIGHLY recommend DYNOMAX mufflers. Their web site is the only one I have found which has the CFM and HP numbers before any measurable back pressure. Super Turbo mufflers are the quietest you can get with good flow.

Just my 2 cents.

[chapmanr]

To some, I'll sound like a broken record. But, I just hate the disappointment and stress that can go with a sound violation, especially for someone out of the area.

If you're a belt and suspenders kind of guy, I'd suggest reading our sound requirements, buy a cheap (less than $50) sound meter from Radio Shack, and doing a dry run at your next local event. This data won't help you if you are too loud down here, but it will give you an idea of where you're at and maybe some peace of mind.

Come prepared to make a change to the exhaust system if you need it. I've suggested Supertrapps before as the easiest, most painless way to make the visible change needed to make another run. If you have an adapter welded to the end of your exhaust, you should have no problem getting it on before your next run. Other people have suggested a prefitted ready to go turndown, but its arguable if that really changes the loudness or just redirects it. I wouldn't take a chance on the leanings of whatever lucky person is the sound chair for the event.

Just keep in mind that the event is run in an urban environment with homes less than 50 yards away, and the sound requirements makes sense.

[Jim T]

Thanks for the replies. I do not want the six hour tow, until I have been checked at a San Francisco event. Maybe sometime in the future.

[Sebastian R.]

I would not rely on a pass from SF region, I believe their limit is 95db at 100ft instead of 50ft. It's a big difference.

Put it this way: I've run 3 SF events with my ST Honda (loud) using no disks in my supertrapp, and been fine with sound. In SD, I run with 13 disks and have had a high reading of around 89db.
For some reason my Honda is a little quieter than others though, it might be partially due to my header which is somewhat unique.

Please don't be scared off though, please come for the tour, just be prepared to make changes for sound.

[STALKER L-67]

Dont you guys want some back pressure in the exhaust system for improved torque?

For you people with loud cars my question is, why?
What is the benifit?
Am I missing something?

[fd_racer]

Some guys are space limited and there is not enough room to quiet down a Race Car...

Kiesel

[RandyC]

And weight. Unfortunately going to smaller cans or lighter exhausts may mean a louder noise.

[chapmanr]

The sound rules are really no different than class rules. You have to engineer your car accordingly. You can stretch the rule set, but you suffer if you take it too far.

And, aside from keeping sites and being good neighbors, I think every event should have reasonable sound rules. At Atwater, the uncorked SM BMWs just hammered my ears when I had to work the course. So, they find 5 or 10 horsepower (in probably a 400 hp car) at the cost of everyone else's hearing. Lovely.

And, at one road race event, there was a Trans-Am car in my group which just assaulted everyone's hearing. I couldn't hear my own car (a fairly uncorked RX7) when he passed me. That was at an event where suddenly the region decided to enforce sound rules. I missed the memo (snoozing through the driver's meeting), was given sound warnings on three consecutive laps, and wound up being DQ'd. The analogy in autocross is to be told after all your runs that you were too loud and you are DQ'd with no opportunity to fix it.

The ironic thing: the Mustang knew where the sound meter was and lifted every lap. No DQ for him....and he probably had me by 15 db.