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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 convener.)
“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 Flowmaster, have come out of high-performance and racing environments, but are now beginning to gain wide acceptance among outdoorsmen, especially those who tow boats?’
As you can expect, type three mufflers cost more because they do more. And though some truck owners always opt for cost overfeatures, it’s best to balance cost, back pressure, and sound control. You may find that by shelling out only a few dollars more, you wifi get a remarkable Improvement in performance.
You may also see performance gains that you didn’t expect. “Trucks that are used to tow or haul heavy loads generally place a big strain on their engines,” says Anderson. “When these engines work hard, underhood and coolant temperatures rise, and the entire power train becomes more labored. In really bad instances, the temperature may rise high enough to burn spark plug wires.
“Generally, a chronic overheating problem is attacked through the use of oversized radiators, auxiliary transmission fluid coolers, and cooler-running thermostats. Fact is, the problem may be solved, or at least minimized, by a reduction of exhaust gas back pressure.A freer-flowing exhaust not only can help an engine run cooler but can also keep the exhaust gas from choking the engine, and that allows ihe engine to operate at higher efficiency, especially under towing loads.”
As you ponder your options, keep in mind that aftermarket mid- 11cr companies such as Flowmaster offer a choice of sounds from quiet to mild to more aggressive tones—all with the same perforounce gains. So, you can pick the sound you want, though some outdoorsmen—deer and turkey hunters in particular—probably would 1w better served by a muffler that has been designed to minimize exhaust noise.