This story was part of Counterman’s annual Technical Sales Seminars, which was published in the April 2009 issue.
One of the best selling points about performance exhaust systems and mufflers is that they are not repair parts. In other words, you don’t have to wait for the original muffler and pipes to rot out to make a sale. There are a lot of people who will pull of the stock exhaust system on a brand new car so they can replace it with a performance aftermarket system. And why not? Stock mufflers are usually overly restrictive and overly quiet.
OEM exhaust systems have to meet strict noise regulations, so it is hard to optimize the system for maximum performance if the vehicle has to meet restrictive decibel limits. Though noise laws are not always strictly enforced, many states will ticket a motorist if their exhaust produces more than 95 decibels. Some cities and states have even stricter noise regulations, and won’t tolerate anything over 70 decibels at 35 mph, or 79 decibels at highway speeds. Even race cars are being fitted with mufflers these days to comply with local noise regulations.
AFTERMARKET TO THE RESCUE
Fortunately, aftermarket exhaust suppliers have developed cat-back replacement exhaust systems that can meet noise regulations and provide more horsepower (10 percent more power typically) and better fuel economy than the stock exhaust systems they replace. On diesel trucks, many of these performance exhaust systems also produce a significant drop in the exhaust temperature (up to 150 degrees cooler).
On the better systems, the baffles and sound absorption components inside the muffler are designed to minimize backpressure without sacrificing sound control. Exhaust pressure waves are used to cancel each other without having to use overly restrictive baffles. On some of the less expensive aftermarket performance mufflers and systems, however, this isn’t always true. Some mufflers are a straight-through design that provides minimal noise control. Even so, some people prefer a nice loud exhaust tone over no tone at all.
Muffler tuning is a real science, and the difference in tone quality from one brand of muffler to another can be significant. A properly-tuned performance muffler will sound great. One that is not so well refined may sound like a chain saw on steroids. The better mufflers and exhaust systems will produce a low powerful sound that doesn’t resonate or hiss. The cheaper performance mufflers typically do little to attenuate or dampen annoying sound frequencies, especially when they are installed on four-cylinder sport compact cars. Better to spend a few more bucks on a good, quality performance muffler or complete system that sounds great than to buy a cheap muffler that buzzes and resonates and grates on people’s nerves.
Exhaust flow is also improved by replacing the stock pipes with smooth, mandrel bent tubing. By keeping the diameter of the pipe consistent throughout the length of the pipe, changes in velocity that cause restrictions in many stock exhaust systems are eliminated. Pipes may also be larger in diameter to reduce backpressure and increase flow.
Many of these performance cat-back exhaust systems are available in stainless steel, so the vehicle owner doesn’t have to sacrifice anything in terms of long-term durability either. Stainless is expensive, but is essential if you want the system to last. Many aftermarket performance exhaust systems and mufflers are actually made from a higher grade of stainless steel (304) than the OEM systems they replace. But there are lesser quality grades of stainless that sell for less. A stainless performance muffler can retail for $200 to $300 or more, and a complete system can easily cost $500 to $800 or more plus installation depending on the make and model of the vehicle.
THE CERAMIC ROUTE
Ceramic coatings are another option. Various aftermarket companies can apply a wide range of ceramic-metallic coatings to exhaust pipes and headers. These coatings won’t flake off and retain their like-new appearance for years. Not only does this extend the life of the exhaust system, but it also keeps the heat in the exhaust.
That means lower temperatures under the hood and under the car, and higher exhaust velocity through the system for better scavenging, breathing and more power.
Most premium mufflers and systems are also plasma or TIG welded to maintain the strength and corrosion resistance of the stainless steel. Some manufacturers also use a process called “bulge forming” or “hydroforming” to form steel sheets into molded shapes using extremely high-fluid pressure.
Performance mufflers are available in both direct fit or universal configurations. You’ll find the greatest selection in universal mufflers, which can be adapted and made to custom fit almost any application. Installation may require some cutting and welding, as well as fabricating custom hangars.
