With the upcoming release of our new performance exhaust system for the 2017+ Civic SI sedan we have had an influx of FC1 and FC3 owners reach out to us to ask; how loud is our new exhaust system? More specifically a great deal of our California friends wanted to know if this new exhaust system is legal for them considering that recent law/fine changes that came into effect for 2019.

We decided to find out for you guys, but before we jump in with the numbers let’s first lay down some groundwork to understand how the new laws applies to your Honda Civic.

For this blog we are writing with consideration of the statutes and laws of California. These laws may or may not apply directly to your city, state, or country but we can safely say that where you live has some type of law regulating how much engine noise can be emitted from your car on public roads.

***Note the info in this blog is accurate and up to date to the best of our knowledge at the publishing of this blog. We are gearheads not attorneys so be sure to check with officials in your area for more details***

First off, it is not illegal to have an aftermarket exhaust on your car. You can in fact upgrade your front pipe and front-pipe back system on your SI, Type R, Sport Hatchback, or any car really. Swapping out your downpipe however follows a different set of rules because it houses your catalytic converters and those are emissions controlling devices. The California Air Resources Board (C.A.R.B.) have there own sets of rules for governing emissions but that goes beyond the scope of this write-up.

Second, the exhaust law in California did not change at all.

What did change is how you can be fined for an infraction of the unchanged exhaust law. Before 2019 if you were found to have broken this law then you were issued a “fix it” ticket. In this case, you would not be fined and instead given the opportunity to make a repair such as installing the OEM exhaust or a quieter aftermarket exhaust. After repairs, you could get the ticket dismissed by a police officer, DMV agent, or court clerk with a small dismissal fee.

The big change recently is that they no longer issue a “fix it” ticket but rather proceed to a straight fine and you still have to fix it. You can find more info on the protocol at the SEMA ACTION NETWORK

What exactly is the law as it is written in California?

“exhaust systems installed on motor vehicles with a manufacturer’s gross vehicle weight rating of less than 6,000 pounds, other than motorcycles, may not exceed a sound level of 95-decibels when tested under Society of Automotive Engineers (SAE) test procedure J1492 (formerly J1169).”

If you want the specifics of that test procedure you can find them here.

So the question you want answered is; Is the new 27WON SI exhaust for the 10th gen legal in Cali?

YES it is. Below are two graphs showing our recorded test results following SAE J1492 test standards.

This is the sound levels as recorded on a 100% stock 2017 Civic SI

This is the sound levels as recorded on a 100% stock 2017 Civic SI with only the addition of our front-pipe back exhaust system. Note this is on a stock downpipe and front pipe.

Lastly we can take at look at this graph plotting each test over the same period of time. You can see that while louder than the OEM the 27WON system falls below the required 95db maximum as imposed by California when installed on a stock down-pipe and front-pipe.

Do note this also applies to our exhaust system for the 2017+ Sport Hatchback. So if you are rocking an FK7 you need not worry.

Be sure to order yours up on April 17th.

Till next time,
-Vincent @27WON

Want to Avoid a Ticket? Check out our SI Exhaust Sound Test