So, bottom line, headers, when properly tuned, help improve overall combustion efficiency. And that, ultimately, is interpreted as seat-of-the-pants performance. But there’s something else as well. Headers can lower the underhood temperature, and that can help extend engine life.
“Cat” Kits: For maximum performance, a complete head to toe aftermarket exhaust system--headers, catalytic converter, muffler, and tail pipe--is the way to go. A less-expensive option is to retain the stock manifolds, but go with a cat-back (catalytic converter to tailpipe) aftermarket exhaust system. Typically, cat-back systems consist of replacement mufflers and tailpipes designed to reduce back pressure. As a rule, aftermarket cat-back mufflers are a re-design of stock mufflers, and are usually found in kit form along with larger-than-stock tail pipes that are specially bent to eliminate kinks or other exhaust-flow restrictions.
Cat-back exhaust systems are designed as stock replacement parts. This is a real advantage for the do-it-yourselfer, as such systems are direct bolt-on equipment that usually retain the factory mounting locations and pipe routing.
A cat-back system is significantly cheaper than a header-to-tail pipe system. Though the rewards are less, the vehicle will still perform better than stock.
Noise Vs. Performance: The third and least expensive option is to replace only the muffler.
“As exhaust gas moves from the engine to the tailpipe, it carries a hitchhiker of sorts in the form of sound waves,” Anderson says. “The muffler is really a network of baffles that bounce the sound waves around. As they bounce, they cancel each other out; when the waves finally pass out through the tailpipe the sound level has been greatly reduced.”
But the price for reduced noise is reduced performance. The typical muffler restricts the flow of exhaust gas, which increases back pressure, which leads to a reduction in engine efficiency and fuel economy. (Note: For the purposes of this discussion, we are not including the catalytic converter, which is another obstacle in the path of exiting exhaust gases. However, Federal emissions laws require catalytic converters, so any modification you attempt needs to include the converter.)
“As a rule,” says Anderson, “there are three basic types of aftermarket mufflers. The first is intended solely as a stock replacement part. You’ll get no performance benefits here. Its obvious asset is its affordability. The second type typically incorporates some form of sound-deadening material--such as fiberglass or steel wool--and an exhaust gas route that is essentially direct or straight through from inlet to outlet. This results in reduced back pressure, which translates into performance gains.”
Since type two mufflers rely on the packing material to reduce the exhaust noise, the decibel levels can sometimes rise to annoying levels.
“The third type of aftermarket muffler uses no packing material to deaden exhaust noise,” Anderson says. “Rather, it takes advantage of specially placed baffles that have been precisely located to cancel out certain sound frequencies as the sound waves progress through the muffler. In addition, the flow path of the exhaust has been designed to minimize back pressure. Typically, these mufflers, such as those manufactured by