We're all aware of the legal difficulties in owning and driving a customized ride. All gearheads feel the heat of law enforcement, whose mission of "To Serve and Protect" seems to add the tag line of "from the automotive enthusiast" in matters pertaining to us, but none so much as the driver of a modified import. Ever been pulled over for rolling too low or sporting too loud of an exhaust? Ever had your car impounded on suspicion of a stolen engine or missing emissions equipment, simply because there's no way for you to immediately prove the contrary? This month, our friends at SEMA's SEMA Action Network (SAN) help us address five points of vehicle legality you need to know.
Your exhaust is probably legal.
The number-one reason owners of modified imports say they're pulled over is for the aftermarket exhaust installed on their car. The truth is that as long as an aftermarket exhaust doesn't compromise a car's emissions equipment (it's catalytic converter, for example), the federal government, via the U.S. Environmental Protection Agency (EPA), is cool with it.
State law is a different matter, and while no state bans replacement exhaust systems outright (since no stock system lasts forever), most stipulate that a replacement exhaust must remain "largely faithful" to the design of the original, and cannot be made or modified to increase output of engine noise.
Vehicle Noise Laws -- Reflects Past 10 Years
States colored red on the map to the right are those that have quantifiable noise standards on the books-a good thing, if not for the fact that many of these noise limits apply to vehicles in motion on a public road, and thus are difficult to measure and enforce. States in green have adopted SEMA's model legislation, establishing a standard 95dB maximum sound output for light car exhausts (which most of today's exhaust manufacturers strive to meet), along with a process by which exhaust output can be tested and verified.
But the vast majority of states, represented in yellow, have no objective standard for exhaust legality. Many times a police officer is given the sole authority to determine whether or not an exhaust emits what he/she considers to be "excessive or unusual noise".
Your engine swap could be illegal.
Like laws regarding aftermarket exhausts, the feds are generally straightforward in matters dealing with engine swaps (referred to as "engine switching" in legal circles). In a document titled "Engine Switching Fact Sheet", the EPA states that-aside from imported engines that can't be certified for any vehicle sold in this country (like that SR20DET engine in your 240SX)-it "will not consider any modification to a certified configuration to be a violation of federal law if there is a reasonable basis for knowing that emissions are not adversely affected."
Your state may make you jump through hoops, though. Take California, which has its own unique engine switching laws. The Bureau of Automotive Repair's (BAR) website stipulates that any engine switching must not change or degrade the effectiveness of a vehicle's emission control system, and that the engine and emission control configuration on exhaust-controlled vehicles must be certified to the year of the vehicle or newer, meeting the same or more stringent new vehicle certification standards.
Switching engines from different manufacturers, or to those with a different number of cylinders or that are aspirated differently than stock is expressly "not recommended", but isn't directly prohibited. As long at the installed engine and host chassis retain all of their original emission control equipment, the engine and chassis are from the same class of vehicle (light passenger, for example), can pass a complete smog inspection, and receive a BAR vehicle identification label, they can be made legal-provided the new engine and donor vehicle are properly registered with the state where necessary. If your swapped car doesn't meet all of these criteria, it's not technically legal for road use in California and possibly other states.