There have been a lot of questions on here concerning modified exhaust systems in the state of California. I am not an employee of any state agency, a lawyer, or anything else like that. I'm an engineer with WAY too much spare time on my hands, So I spent some time researching this on the 'net. Here's some of what I found.

Concerning noise levels of modified exhausts: Click Here

Concerning aftermarket parts: Click Here

For the CVC index: Click Here (Scroll down to "Exhaust Systems" for way too much info on the subject :')

If anyone else has some good links on this issue, please post them. I think that in the interest of accuracy and legitimacy, please keep links limited to "reputable" sites such as Air Resources Board, DMV, and SEMA.

 

"27151 if they emit no more than 95 dbA when tested in accordance with Society of Automotive Engineers Standard J1169 May 1998"

Does anyone know if that is at WOT or idle?

 

Here's a link from GReddy's website. Here

Here's my experience with "fix it" tickets... I've never gotten one. I have a 3 inch cat-back with a Magnaflow race series muffler (similar to the Turbo XS setup) on my WRX. In my opinion, it's quite loud. Loud enough to trigger the warn away on most alarms. From my experience, and the experience of my younger brother (he's had 6 fix-it tickets in about a year) you get a fix it ticket for basically annoying an officer. I have a stock appearing, but LOUD WRX, and have never gotten a fix it ticket. My brother has a lowered s-10 with full stereo system, flowmaster exhaust, clear lights, etc... and used to get fix it tickets all the time. the kicker here is: My car is much louder than his truck. How does that work out? We tried an experiment by putting his factory taillights back in and turning the stereo down. Now he only has one or two annoying things about his truck instead of 4 or 5. No more fix it tickets. I guess the moral of the story here is you can get away with a couple things, but once your car really stands out from the crowd, you're going to get noticed a lot more, by on-lookers AND police officers.

 

"They specify testing procedures for motor vehicle exhaust noise alone (as opposed to total vehicle noise). This procedure specifies a limit of 95 dB(A) measured 20 inches from the exhaust pipe outlet with the engine operating in neutral, typically at a speed of 3000-5000 rpm."