Undercar Digest

MD Publications, Inc.

Thank you for the question you faxed to us on August 19, 1991 concerning exhaust repairs. Below we have repeated the question and provided a response for your readers.

Question: Can I take off an original equipment muffler with a 3-inch inlet and 2-inch dual outlets and dual tailpipes and install a muffler with a 3-inch inlet and single 3-inch outlet and single exhaust 3-inch tailpipe?

Answer: Federal law prohibits any person from removing or rendering inoperative any emission control device or element of design installed on or in any motor vehicle or motor vehicle engine. The exhaust system configuration, including the location of the converters, and the exhaust pipe diameter and length, are items specified by the manufacturer during certification because engines and some of the associated emission systems are generally affected by the exhaust backpressure, which subsequently affects vehicle emissions. Thus, the backpressure and the exhaust system configuration are elements of design of the emission control system as certified by the vehicle manufacturers. Therefore, any change to that system could be considered a violation of federal law. Additionally, such an installation may also void the emission warranties afforded vehicle owners under section 207(a) and (b) of the Act.

While we would not recommend, encourage or endorse any exhaust modification that makes the vehicle different than the original system, EPA is currently not pursuing enforcement actions on these types of potential violations at the present time. Any such changes should be approached cautiously because of the potential to adversely affect emissions, performance, and warranty coverage.

EPA is currently not pursuing enforcement actions on potential violations that are down stream of the last converter in the system and downstream from where the exhaust system comes together as a single system.

Sincerely,

Steven K. Albrink

Acting Chief, Plans and Program

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