MUFFLERS & EXHAUSTS
The factory exhaust system on your vehicle is designed to muffle sound as much as possible. This also means it restricts the flow of exhaust gases out of your engine, creating what’s called back pressure. While most engines require some back pressure to operate properly, it also robs power. Essentially, the engine has to use some of the power it generates to cram exhaust gases out of the tailpipe instead of using that power to drive the vehicle.
If you’d like to steal some of that power back, you can replace that stock exhaust with less-restrictive performance exhaust components. In some upcoming posts, we’ll show you how to choose the right components—exhaust kits, headers, mufflers, etc.—for your vehicle. But let’s start with a quick review of exhaust systems and components and some of the upgrade options that are available.
The first exhaust components to handle spent exhaust gases from your engine, headers (also called exhaust manifolds in stock form) are bolted to the cylinder heads and scavenge exhaust gases from the combustion chambers.
Aftermarket headers are typically mandrel-bent to reduce exhaust restriction, allowing the exhaust gas to move freely from the engine. This reduces power-robbing back pressure and helps build up enough exhaust flow velocity to create energy pulses that actually pull, or scavenge, spent gases from the engine.
Headers are available in full-length and “shorty” dimensions and come in multiple configurations, including Tri-Y and 4-into-1. We’ll talk more about choosing the right design for your ride in a later post.
Also called head pipes, downpipes simply link the headers to the mufflers. Between these two points, a downpipe is often interrupted by the catalytic converter, depending on the application.
If your vehicle was produced after 1975, chances are good that it came from the factory-equipped with a catalytic converter (also known 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? It’s the law. State and federal regulations require you to have one of these air fresheners if you’re traveling on public roads.
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.
One of the most recognizable components of the exhaust system, the muffler is responsible for exhaust noise reduction. While the job description of a muffler sounds simple, the way in which a muffler performs its main task is varied and complicated.
Depending on the style, a muffler uses some combination of baffles, chambers, perforated tubes, and/or sound deadening material to achieve this goal. Muffler manufacturers configure these components in different ways to produce different exhaust tones. Ideally, an aftermarket muffler will provide a good performance exhaust tone without creating too much power-stealing back pressure.
Crossover pipes are designed to balance the exhaust flow on a dual exhaust system. Typically installed near the headers, crossover pipes reduce uneven exhaust flow from the two banks of engine cylinders by giving exhaust pulses an avenue to travel between the two sides of the dual exhaust system. This reduces back pressure by preventing an exhaust build-up on either side of the system.
The two most common types of crossover pipes are X-pipes and H-pipes. As their names suggest, X-pipes are shaped like the letter “X,” and H-pipes look similar to an “H.”
The tailpipe is often the last piece of the exhaust system puzzle. It runs from the muffler to the back or side of your vehicle. Many aftermarket manufacturers will finish off their tailpipes with a chrome or polished exhaust tip. You can also buy exhaust tips separately in your choice of finishes or shapes
Now that you know the basic anatomy of an automotive exhaust system, we’ll help you get to second base by showing you how to choose the right exhaust for your ride.