Skip Navigation LinksNorCal Cars > Articles > Automotive Maintenance and Repair > Aftermarket Exhaust System

Choosing an aftermarket exhaust system

Choosing the right aftermarket exhaust system is the single most effective action that will give a noticeable increase in the power and possibly the economy of your light truck, SUV, auto, Jeep, Hummer, or motorcycle. Consider that your vehicle comes from the factory with all the parts designed and assembled with an eye for profit, not high performance. A properly designed system such as a Magnaflow exhaust system will give a realistic expectation of 10% increase in horsepower.

What’s going on here?

A performance exhaust system allows the engine to breathe more freely by reducing back pressure. Your engine’s cylinders fire at different times, causing exhaust gases to build up in the manifold and exerting pressure against more gases entering the system. A performance exhaust system allows the gases to flow through more freely, reducing the back pressure and its resulting drag on efficiency, increasing horsepower and often economy.

This back pressure is one of the primary concerns of automotive engineers seeking to increase efficiency without sacrificing power. Reducing back pressure allows the cylinders to clear out the combustion by-products more quickly, thus allowing more fresh gasoline-air mixture into the cylinder.

“Before you select a system, take the time to make certain it’s legal in your state,” says Chris Grosso of PartsGeek LLC. “Some systems reduce back pressure by eliminating the catalytic converter, which is required in some areas by the EPA or state-level environmental protection agencies. You don’t want to discover after the installation is complete that your system won’t pass your state’s inspection.”

Also make certain the system is constructed entirely of stainless steel, with the manifold or header make of cast iron. Anything less won’t last.

“As an example of quality, look at a Magnaflow exhaust system,” says Grosso of PartsGeek. “They don’t skimp.”

Three major components

There are three major components that make up a high performance system. The factory exhaust manifold is replaced with headers, which funnel each cylinder’s exhaust individually and join them together into a single pipe. Usually a single outlet to a single converter and muffler gives a satisfactory increase in performance. However, if there has been a lot of conversion done on the engine then dual exhausts would more likely be an advantage. The design of these can be quite critical and when properly tuned to match the engine characteristics, will give a noticeable increase in performance. Also they’re a joy to behold when you lift the hood.

The second major component is the catalytic converter, which is largely credited with the improvement in air quality noticeable in larger cities. The three-way converters used in the United States reduce tailpipe emissions through a chemical reaction, converting toxic gases to more benign ones.

The third section of the system is the muffler. This is where there exists the greatest potential for back pressure and its reduction by experienced designers. Mufflers do more to affect your car’s sound than any other component in your vehicle. Generally speaking, the smaller units are louder more like a lion’s roar, whereas the bigger and longer mufflers can reduce the sound to a whisper. A word of caution here: louder does not always mean more powerful. It could mean being stopped more often by the law or irritating the neighbors with your high performance.

Performance, diesel, and truck exhaust systems

There are a number of companies that have recently developed advanced technology as applied to high performance exhaust systems. Corsa is a company that uses a noise cancellation principle, enabling them to build a straight through pipe in the muffler with specially designed baffles to cancel the noise. This design allows for virtually no back pressure.

Another company to consider is Borla. They are heavy into racing and competition events such as hot rodding. They also deal in off-roading equipment, which is a specialty quite different to street-legal everyday driving.

If you own a pickup truck or a large SUV then Gibson has just the right truck exhaust system for you. These larger engines have different design characteristics from the family auto. Gibson also can supply high performance systems for diesels, which have quite different operating parameters to gasoline-fueled vehicles.

Duramax is another brand specializing in diesel exhaust systems and they are ready to meet the new EPA emission standards going into effect in 2010. A big advantage in their EGR system is that it won’t need any change in driver or mechanic training or application, a big cost-saving feature during installation.