When you are about to modify your car’s exhaust system, you must know the laws that limit the noise levels a vehicle can produce. The following section explains the California vehicle exhaust noise laws.

Vehicle Code 27150 – Adequate Muffler Needed

27150 (a) Every motor vehicle subject to registration at all times shall be provided with an adequate muffler in constant operation and properly maintained to prevent any strange or excessive noise, and no exhaust system or muffler shall be provided with a bypass, cutout, or similar device.

Vehicle Code 27151 – Modification of Exhaust Systems

  • An exhaust system of a motor vehicle shall not be modified by anyone in a method that will increase or amplify the noise discharged 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 set for the type of vehicle in Article 2.5 (commencing with section 27200). No one shall operate a motor vehicle with an exhaust system modified so.

  • For 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 by Society of Automotive Engineers Standard J1169 May 1998, complies with this section. Parts or exhaust systems of the motor vehicle thereof include, but are not limited to, non-original exhaust equipment.

The motor vehicles and all cars in California must be provided with a muffler, and the exhaust systems must not be modified in a method that will raise the exhaust noise levels above 95 dbA. Some vehicles, when participating in competitive events or organized racing, can get exemptions from these laws.

Also, vehicle exhaust noise levels vary depending on its year of manufacture. For vehicles that are manufactured before 1972 are allowed to have up to 92 dbA, and vehicles after 1985 can have up to 80 dbA.

California Vehicle Exhaust FAQs

How Do Police Officers Find Out Exhaust Noise Levels?

According to vehicle exhaust noise laws in California, the motor vehicles should have 95 dbA, which is legal. However, police officers will check your car and determine whether your noise level exceeds the actual limit. Sports cars that contain factory-installed exhaust systems do not go beyond 75 decibels.

How Loud Is 95 dbA?

95 decibels is an approximate sound of:

  • Car horn at 10 feet
  • A lawn mower
  • Food blender less than 3 feet
  • Plane flyover at 1000 feet
  • The inside of a subway car

Which Exhaust Modifications Are Illegal in California?
Exhaust modifications are illegal only if the noise levels produced by a vehicle exceeds 95 decibels. However, California smog laws or other regulations may make your custom exhaust modifications illegal. Exhaust systems of all the motor vehicles and cars must have mufflers. Any whistle tips, bypass, and cutouts are not allowed.

Contact us today to learn more about California vehicle exhaust noise laws. Our professionals will help you determine your vehicle’s noise level and check whether it is legal or not.