Aftermarket Exhaust in California
Replacing the exhaust system is legal in California, but a muffler in good working order is required and cutouts or bypasses are prohibited. There is no statutory 'no louder than stock' rule — the standard is that the exhaust must not produce excessive or unusual noise.
Verified against primary sources · August 2026
What the law says
Replacing the exhaust system is legal in California, but a muffler in good working order is required and cutouts or bypasses are prohibited. There is no statutory 'no louder than stock' rule — the standard is that the exhaust must not produce excessive or unusual noise. Removing the catalytic converter is prohibited by federal law (Clean Air Act § 203) regardless of state rules. California adds a 95 dBA limit for vehicles under 6,000 lb and anti-tampering rules: emissions-affecting parts such as headers and catted downpipes need a CARB Executive Order number, while cat-back systems are exempt. Smog check enforces this.
Specific Limits
- Cutouts
- prohibited
- Muffler required
- Yes
- Louder than stock
- not addressed; excessive noise standard applies
- Catalytic converter
- removal prohibited by federal law
Frequently Asked Questions
Are aftermarket exhaust legal in California?
What are the exact aftermarket exhaust limits in California?
Street-legal aftermarket exhaust picks
Gear that helps you mod without a ticket in California.
Cat-back systems keep your emissions equipment intact — the compliance-friendly route.
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