The state of Texas doesn’t mandate a specific decibel level limit for how loud a vehicle’s exhaust system can be, but it does have laws on other exhaust system properties. It also regulates a vehicle’s emissions – some counties and vehicles require an emissions test in addition to an annual safety inspection.
How a Motor Vehicle’s Muffler Works
A motor vehicle’s muffler is part of its overall exhaust system. It is designed to reduce the amount of noise the engine produces by using a combination of baffles and resonators to dissipate and cancel sound waves. This results in a quieter exhaust output.
The muffler causes the engine’s exhaust gases to expand and release energy via sound, which is then absorbed and redirected by the muffler. This ultimately reduces the amount of noise that exits the vehicle’s tailpipe.
Muffler Laws in Texas
Motor vehicles on Texas roads must have a muffler in good working condition that continually operates to block excessive or unusual noise. The vehicle’s owner cannot use a muffler cutout, bypass or similar device. The Lone Star State does allow some aftermarket exhaust modifications, but those modifications cannot make the exhaust too loud.
Texas state laws do not include a well-defined exhaust noise law and do not specify a decibel limit when it comes to mufflers. Emissions tests do not check for noise levels, and vehicle owners can be cited for having a loud exhaust. Some cities in Texas have local ordinances regarding noise laws and mufflers.
Texas and Exhaust Modifications
A vehicle’s muffler in Texas must be fully intact without any perforations and look as close to new as possible. If a muffler has a hole in it, it must be replaced. If a vehicle has a patched-up muffler during a vehicle inspection, it will fail the inspection.
The vehicle’s owner will need to repair their exhaust system if any component of it, like a catalytic converter or resonator, leaks or has holes. A replacement muffler must look like, and perform similarly, to the original.
Installing a Dual Exhaust
Vehicle owners cannot change from single to dual exhaust or dual to single exhaust, but there are a few exceptions to this rule. They can install a dual exhaust if the vehicle's manufacturer has designed a particular make and model to fit it.
Even if an owner places two catalytic converters into the emissions system, they cannot place dual exhausts on the vehicle. If they do, and their car’s chassis is designed for only one catalytic converter, the vehicle may fail the emissions inspection.
Emissions Laws in Texas
Texas Transportation Code has additional requirements for a motor vehicle’s emission system that include:
- Engine and power mechanisms must be equipped and adjusted to stop excessive smoke or fumes from escaping. Vehicles or engines for model years after 1967 must be equipped to prevent crankcase emissions into the ambient atmosphere (air in the atmosphere in its natural state).
- Vehicles or their engines for model years after 1967 with an exhaust emission system must be maintained in good working condition and used when the vehicle or its engine is in constant operation.
- Vehicle owner or operator cannot remove all or part of the emissions system or otherwise intentionally make it inoperable unless they install another part or system that is equally effective in reducing emissions.
- Vehicle owner commits an offense if they operate or knowingly permit another to operate a vehicle that emits visible smoke for at least 10 seconds, or visible smoke that stays suspended in the air for a minimum of 10 seconds before dissipating fully. An exception is when travel conditions require the driver to downshift or use lower gears to keep momentum.
Procedures for Emissions Testing in Texas
All vehicles registered in Texas must be inspected annually for safety, and some vehicles and locations require an additional emissions test.
- Vehicles registered in Brazoria, Collin, Dallas, Denton, El Paso, Ellis, Fort Bend, Galveston, Harris, Johnson, Kaufman, Montgomery, Parker, Rockwall, Tarrant, Travis, and Williamson counties.
- Vehicles powered by gas with the exception of diesel powered vehicles and motorcycles.
- Vehicles that are two to 24 years old.
- Vehicles with an expired two-year initial inspection sticker.
Legal Vehicle Modifications in Texas
A motor vehicle owner can modify their car in other ways. For example, they can alter:
- Sound Systems: An owner can upgrade their sound system, provided it doesn’t exceed 68 decibels within 15 feet of the car.
- Frame and Suspension: There are no suspension limits and no limits on frame height, wheel or bumper alterations or adjustments to the steering system. Vehicle’s overall dimensions must not be more 102 inches wide; 13 feet, 6 inches tall; and 45 feet in length.
- Engine: Texas has no limits on engine exchange.
- Windows: Rear window tint can have any darkness level, but front and back-side windows must allow more than 25 percent of light to pass inside and must not be more 25 percent reflective. Texas allows non-reflective tint on the windshield above the manufacturer’s AS-1 line or at the top 5 inches. The driver must place a sticker on the driver’s side window identifying legal tint levels.
All vehicles in Texas must have working headlights and taillights. They can also have auxiliary driving lights, auxiliary passing lights, fog lights and spotlights.
Lights must have a DOT or SAE stamp. Lights used off-road or for show equipment cannot be used on roadways. Stop lamps and taillights must be red or amber, and Texas prohibits illuminated license plate frames.
- Texas Legislature: Chapter 547 Vehicle Equipment Subchapter A. General Provisions
- Able Tire and Brake: Automotive Q & A
- Midland Muffler and Brakes: Are Exhaust System Modifications Allowed in Texas?
- Texas DPS: Inspection Criteria for the Annual Safety Inspection
- Sun Auto Service: Legal Car Modifications You Can Do in Texas
Michelle Nati is an associate editor and writer who has reported on legal, criminal and government news for PasadenaNow.com and Complex Media. She holds a B.A. in Communications and English from Niagara University.