> What does 18" at a 45 degree angle from the tip have to do with a number
> measured on a moving car at 100 feet?
Who said anything about a moving car at 100'? Tony was talking about
the legal limits for a street car. Which is not at all defined by what
a car sounds like when it's moving by 100' away. Specifically,
California VC 27151 states:
"27151. (a) No person shall modify the exhaust system of a motor
vehicle in a manner which will amplify or increase the noise emitted
by the motor of the vehicle so that the vehicle is not in compliance
with the provisions of Section 27150 or exceeds the noise limits
established for the type of vehicle in Article 2.5 (commencing with
Section 27200). No person shall operate a motor vehicle with an
exhaust system so modified.
(b) For the purposes of exhaust systems installed on motor vehicles
with a manufacturer's gross vehicle weight rating of less than 6,000
pounds, other than motorcycles, a sound level of 95 dbA or less, when
tested in accordance with Society of Automotive Engineers Standard
J1169 May 1998, complies with this section. Motor vehicle exhaust
systems or parts thereof include, but are not limited to, nonoriginal
exhaust equipment."
I believe the J1169 standard states that sound is to be measured by a
microphone placed 18" from the exhaust tip, 12" off the ground, at a
45-degree angle from the direction of the exhaust tip, with the engine
revving (in neutral I think) at 75% of the engine's stated maximum
horsepower RPM. It goes into a lot more detail than that but basically
that's how the state referee will measure your car's sound level to
determine if it complies with the limits set by the law.
--
Viet-Tam Luu (a.k.a. "Tam")
SFR-SCCA Solo2 #149 T1-CS, #149 EM
Sponsored by WORKS (www.WorksEvo.com)
On 5/30/06, Smokerbros@aol.com <Smokerbros@aol.com> wrote:
> In a message dated 5/30/2006 9:42:12 A.M. Pacific Standard Time,
> viettamluu@gmail.com writes:
>
> Realistically speaking though, I'd say an overwhelming majority of
> cars running in non-stock classes, and probably a significant portion
> of cars running in Stock, don't meet the legal sound limit, 95 dB(A)
> as measured by SAE standard J1169 (distance 18 inches at a 45 degree
> angle from the tip I think?).
>
>
>
> What does 18" at a 45 degree angle from the tip have to do with a number
> measured on a moving car at 100 feet?
>
> Charlie
>
> Your messages not reaching the list?
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