I understand the need but this is just plain California stupid. This new law starts 1/1/19 and fines are 1K and possibly a state ref to check exhaust.
California Vehicle Exhaust Noise Laws
Many car enthusiasts decide to modify their car’s exhaust system, but there are laws governing the noise limit your vehicle can produce. The section below outlines relevant laws and legislation pertaining to car exhaust noise laws in California.California Vehicle Code § 27150 – 27153 (2017)Vehicle Code 21750. Adequate muffler required27150
. (a) Every motor vehicle subject to registration shall at all times be equipped with an adequate muffler in constant operation and properly maintained to prevent any excessive or unusual noise, and no muffler or exhaust system shall be equipped with a cutout, bypass, or similar device.Vehicle Code 27151. Modification of exhaust systems
(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.
In summary all cars and other motor vehicles must be equipped with a muffler, and any exhaust modifications must not be designed to increase the exhaust noise above 95 dbA.
There are additional regulations as well so we recommend reviewing the California Vehicle Code for important sections related to exhaust noise levels. For example Section 2115.3 prohibits installing “whistle-tip” or similar devices which emit a high pitched or shrieking noise when the vehicle is in operation.
Furthermore certain vehicles can get special exemptions from these laws while participating in an organized racing or competitive events (27150.c). Additionally motorcycle exhaust noise levels depend on the year of manufacture, where motorcycles manufactured before 1970 can have up to 92 dbA, and after 1985 up to 80 dbA (full table in Section 27202 in Article 2.5 linked below).