DIY

How Loud is Too Loud for an Exhaust System?

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Performance vehicles have always been associated with how beautiful their exhaust notes are. Muscle cars give off a loud and throaty V8 bellow while supercars give off a higher pitched, rich jet engine-like V12 roar. People who can’t afford the models which come with these unique exhaust notes can modify their cars to have similar or even grander sounding exhausts. Mufflers and resonators are mainly responsible for the volume of your engine’s noise. Starting 2019, you would have to be more mindful of your vehicle’s sound, especially if you’re from California. An assembly bill which controls modifications to a car’s exhaust noise may affect you even if you don’t live in the state.

The Dodge Challenger Hellcat can produce up to 105dB.

What does a Muffler and Resonator do?

The exhaust system of your car is comprised of interlinking pipes that stretch from the engine to the rear of the vehicle. Exhaust pipes need to run a long distance to be able to cool the exhaust gasses coming from the engine. This also gives the exhaust gasses an opportunity to run through the catalytic converter making it less toxic to the environment.

Situated after the catalytic converter is the muffler, which deadens the exhaust noise without stopping the flow of exhaust gas. The muffler achieves this by making the sound waves counteract each other, effectively softening the noise. A resonator is a secondary or substitute sound eliminator to the muffler. The resonator and muffler complement each other and have many combinations. Some lessen the noise while others are tailor made to be loud.

What exactly is too loud?

California state law has said that the absolute loudest a light vehicle can be is 95-decibels(dB) tested under the Society of Automotive Engineers (SAE) under test procedure J1169 (May 1998.) Vehicles with a gross weight less than 6,000 pounds and motorcycles are included in this state law. This has been part of California’s vehicle code for years. Vehicle Code 27150 states that all cars registered under the state of California are required to have an adequate muffler that is properly maintained and operating. Vehicle Code 27151 explains the parameters of the noise limit set for vehicles registered in the state of California.

California state law stipulates that the absolute loudest a light vehicle can be is 95-decibels(dB) tested under the Society of Automotive Engineers (SAE) under test procedure J1169 (May 1998.)

What is the fuss with California Assembly Bill 1824?

Many car enthusiasts have been making a big deal about AB 1824, which was signed into effect in January 2019 by then-California State Governor Jerry Brown. AB 1824 does not change the state’s vehicle code on how loud the exhaust noise can be on your car, but affects what happens when you get caught by the cops for an exhaust noise violation. Before 2019, when you get pulled over for an exhaust noise violation, you would receive a “Fix-it ticket” giving you 30 days to fix your vehicle’s exhaust system to the state’s regulation. Providing proof within the 20 day period will void you from paying fines.

Life after AB 1824 still allows for a modified exhaust pumping out all sorts of noise within the 95-dB limit. However, if you get caught for an exhaust noise violation, expect that you will be fined. Fine for this violation in the state of California can range upwards of $1000. The Specialty Equipment Market Association or SEMA issued a press release clarifying the concerns of car enthusiasts.

How loud is 95-dB?

According to the Centers for Disease Control Prevention (CDC), noise above 85dB over a prolonged period of time may start to damage your hearing. A leaf blower or a gas-powered lawn mower is already 85dB while a concert or a club can range from 105-110dB. 95dB is plenty loud, but some cars come out of the factory exceeding that limit. The Dodge Challenger Hellcat produces upwards of 105dB when pushed to the limit. Skirting the limit is the Ford Mustang Shelby GT350R which produces 92dB of exhaust noise.

A police officer has to use his best judgment to enforce the 95dB limit, which has people up in arms saying the rule is vague and that different people interpret sound differently.

How does this affect me?

California is just an example of what can happen to other states. There are existing exhaust noise laws across the United States that can be clarified using this map which SEMA organized. Some are saying this is a ploy to increase the income of the city while others claim it’s a step to fighting illegal street racing. Whatever the real reason behind it, there should be a clear method of determining what is too loud before issuing a ticket. For now, you should make sure that your vehicle is operating with a maintained and working muffler. If you have a modified exhaust system, make sure that it complies with SAE J1169. Have proof that your vehicle has been tested and is still within the law. This will be vital in escaping that $1000 fine when a cop accuses you of having a vehicle that’s “too loud.”

Make sure you comply with SAE J1169 if you have a modified exhaust system.
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In the Garage with CarParts.com is an online blog dedicated to bringing DIYers and devoted car enthusiasts up to date with topical automotive news and lifestyle content. Our writers live and breathe automotive, taking the guess work out of car repairs with how-to content that helps owners get back on the road and keep driving.

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