Rick's Free Auto Repair Advice

Muffler Delete

Why a muffler delete reduces engine performance

Stock engines are designed for a certain amount of exhaust backpressure to lower the effects of fuel scavenging during the valve overlap stage of engine performance. If you perform a muffler delete without making any other changes to your camshaft, valves, variable valve timing mechanics or software, you’ll actually experience lower performance and MPG. That’s because a portion of your fuel is being swept right out the exhaust port during valve overlap, thus robbing you of fuel during the following intake stroke.

Muffler delete gets you a citation in California and most other states

California Governor Gavin Newsom recently signed SB 112 legislation that immediately restores “fix-it” tickets for cars suspected of violating the state’s exhaust noise limit.

Here’s the bill’s language regarding exhaust noise:

“Existing law requires every motor vehicle subject to registration to be equipped with an adequate muffler in constant operation and properly maintained to prevent any excessive or unusual noise and prohibits a muffler or exhaust system from being equipped with a cutout, bypass, or similar device.

Existing law further prohibits the modification of an exhaust system of a motor vehicle in a manner that will amplify or increase the noise emitted by the motor of the vehicle so that the vehicle exceeds existing noise limits when tested in accordance with specified standards. Under existing law, if, after an arrest, accident investigation, or other law enforcement action, it appears that a violation has occurred involving, among other things, vehicle equipment, the arresting officer is required to permit the arrested person to execute a notice containing a promise to correct the violation and to deliver proof of correction to the issuing agency, unless a disqualifying condition exists. Under existing law, a violation of the noise requirements related to mufflers and exhaust systems is a disqualifying condition.

This bill would delete a violation of the noise requirements related to mufflers and exhaust systems from the list of disqualifying conditions, thereby making a person who is arrested for one of these offenses eligible to execute the notice described above, except if the violation consists of modifying the exhaust system of a motorcycle in a manner that will cause it to exceed noise limits. The bill would update the noise level testing standards described above to reflect a more recent standard.”

What does the muffler delete law really mean?

If you get caught with a muffler delete, cutout, bypass, or similar device on a vehicle with a manufacturer’s gross vehicle weight rating of less than 6,000 lbs. (other than motorcycles) that results in exhaust noise above 95 decibels, you will be ticketed and given 30-days to correct the vehicle to bring it into compliance.

©, 2019 Rick Muscoplat


Posted on by Rick Muscoplat


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