It’s a dirty job, but somebody’s got to do it.
If your vehicle was produced after 1975, chances are good that it came from the factory equipped with a catalytic converter (also know as a “cat”). Unlike a muffler whose primary function is to lessen exhaust noise, a catalytic converter employs some serious science to reduce the amount of harmful emissions your vehicle releases into the air.
Why do you need a catalytic converter? That’s easy: it’s the law. State and federal regulations require that if you’re traveling on public roads, you need one of these air fresheners as part of your exhaust system.
The way they work is pretty simple: exhaust gases flow through two ceramic honeycombs contained in the cat, each of which is usually coated with a combination of precious metals. When those exhaust gases come into contact with the coating, a chemical reaction is initiated that converts your vehicle’s emissions to nitrogen, carbon dioxide, oxygen, and water before releasing them into the atmosphere.
What and where you drive has everything to do with the type of catalytic converter you need. Some vehicles utilize an Air Injection Reaction (AIR) system to supplement the chemical reactions taking place inside the catalytic converter. For those vehicles, you’ll need to make sure that your converter is equipped with an AIR tube to channel that added oxygen into the cat.
Additionally, you need to consider displacement and vehicle weight when shopping for a universal cat. Exceeding a catalytic converter’s published specs will diminish its effectiveness, and that could get you in trouble when it comes time for a smog or emissions test. If your ride’s packing on the cubic inches or the pounds, a dual-cat setup might be just what you need to stay legal. Direct-replacement converters take all of these specifications into consideration and are essentially plug-and-play.
In the US, catalytic converter certification comes in two flavors: EPA and CARB. Any state outside of California falls under EPA emission requirements, so you’ll need an EPA-approved (49-state) converter. If you live in the Golden State, your vehicle falls under CARB (California Air Resources Board) jurisdiction, and you’ll need a special CARB-approved converter.
Remember, while aftermarket cats are generally less expensive than an OE replacement and can increase exhaust velocity and horsepower, according to federal EPA regulations, it’s only legal to replace your vehicle’s catalytic converter if it doesn’t pass a state or local inspection, it’s at least five years old or has more than 50,000 miles, or if it’s missing.