SS Race dB Level?

[fitchesbass]

It depends where the source is measured from. If you are measuring it right at the tailpipes vs. a number of meters away it would change your resulting power level. This can be seen via the sound wave equation. It becomes more complex than that.. but perhaps the moral of the story is unless they don't specify a reference measuring point, there is some 'grey area' and it may not be a specific SPL number. Keep in mind that every 3 dB is equal to twice the power.

Just an FYI: dB is not unit of measure - it's unitless. You want SPL (Sound Pressure Level) in dB relative to some reference point (often 20 micro Pascals). dB just means the measurement is in a logarithmic scale and is a ratio of the measured level relative to your reference point.

[fitchesbass]

Originally Posted by mfanatic325

So for 92dB Laguna Seca limit purposes, I'll attempt to capture sound close to redline from 60 ft. away. Of course, this may take some time, as I'll have to find a otherwise unoccupied length of quiet road. Luckily I have just the one in mind, up in the nearby mountain, where I can do this safely and won't jeopardize anyone else besides myself and a friend that will be helping me record.

As for street purposes, California 95dB rules say that testing procedures involve putting a microphone no more than 20 inches away from a tailpipe, and to have the car rev to half of its total capable RPM. For this case, it'd be approximately 4k rpm. This will be easier to capture, as I can just do it in my driveway. Will post up recordings as soon as I can.

Per California code:
What is the exhaust noise test specified in 13 CCR? Can this be used for enforcement?

Section 1030-1036, 13 CCR, were intended to be used by Licensed Muffler Certification Stations as a means of detection if an exhaust system met the requirements of the Muffler Certification Program (When those programs were operational) They specify testing procedures for motor vehicle exhaust noise alone (as opposed to total vehicle noise). This procedure specifies a limit of 95 dB measured 20 inches from the exhaust pipe outlet with the engine operating in neutral, typically at speed of 3000-5000 rpm. It applies only to passenger vehicles. It does not apply to motorcycles or to vehicles over 6000 pounds gross weight.

Sorry for the delay!

Just saw this - good info on how to measure.

[mfanatic325]

Hah yeah. Laguna Seca's sound check hut is located on the righthand side of the track between turns 5 and 6, approximately 60 ft. away.
Prior to headers, I could go WOT and make the 92dB cut. But after headers, I registered @ 96dB.
I then had to drive by and lift off nearby the hut on the lefthand side of that portion of track just to register a lower sound.

[mfanatic325]

Just an update. With the following setup, I registered at 102dB from about 60ft. away @ WOT on Laguna lol

- JVT headers
- SS uncatted section1
- OE section2
- SS Race mufflers

My SS section2 (x-pipe) is coming in a few days
So it'll probably bring me up to 105dB or something like that lolol..
I obviously hafta lift-off where the sound-hut is, otherwise I'd get meatball flagged all day long. 3-strikes and I'm out

[z4mnyc]

Reviving this thread.. what are your options when you are at Laguna and exceeding the sound limit? I may go to a track day there later this year but I am almost positive that the car will exceed the 90db limit.

[mfanatic325]

The limit there is 92dB. What are your exact mods in terms of sound? From your signature, I'm seeing euro headers and SS race mufflers. With those two, you might already be borderline. IIRC, my car ran 88dB when it was bone stock.

Some options available (for anyone that's interested):
1) drive to the left-most side of the track when passing by the sound hut [between turns 5 and 6]

2) let off throttle a bit when passing the sound check hut

3) upshift a gear temporarily while passing sound hut to bring the revs down

4) try to attach tin foil-type bent tubes in the exhaust tips to direct sound to the driver's side

orrr
5) all of the above lol...

I wouldn't recommend clutching out of gear just to bring the sound down and pass sound check, since being in-gear is more stable than being out-of-gear.

Also, I might recommend that when you do visit Laguna with whichever host you're running with, just ask the track marshall for a sound check.
Every car gets three strikes per day; three strikes and you're done for the day. But requesting for a "sound check" will not count as a strike against you. It is merely used as an FYI.
When you're on your free sound check run, just gun through right past the sound check hut. You could try one lap running closer to the sound hut (righthand side), then one lap in the middle of the track, then the third lap farthest away from the hut (lefthand side) and compare the dBs.

[mfanatic325]

By the way, my car with:
- JVT headers
- SS uncatted section1
- SS x-pipe
- SS race mufflers
Altogether registered 106dB last time I was @ Laguna. And the main track marshall was NOT happy

[z4mnyc]

- Euro catless headers
- SS uncatted section1
- SS x-pipe
- SS race mufflers

so... yeah..

[mfanatic325]

hahaha okay yeah, then you'll be at around 106dB as well if you don't use any of the above-mentioned options/methods lol
During my final lap of the final session of the last track day I went to, I blew by the sound hut, as close to the hut-side of the track as possible and was almost at redline. And that's how it registered 106dB and the main track marshal came to scold me in the paddock