High Performance Mufflers & Exhaust

High Performance Mufflers & Exhaust Systems

by Larry Carley c2008

performance mufflers reduce backpressure

High-performance mufflers and exhaust systems are as much about looks and sound as they are about horsepower. Most people who want these types of products want mufflers and exhaust systems that look and sound as good as they perform. It is all about personalizing their vehicle and projecting an image. Motorists who buy performance exhaust products are the same ones who buy aftermarket custom wheels, street performance tires, performance shocks, struts and suspension kits, aftermarket sound systems, spoilers, wings, aero kits and other bolt-on accessories.

Polished stainless-steel mufflers and free-flowing cat-back exhaust systems are hot bolt-on upgrade opportunities, and can be easily installed on most sport compact cars, larger cars, SUVs and trucks.

STAINLESS EXHAUST
Most premium-quality performance mufflers and pipes today are made of stainless steel (usually aircraft-quality T-304), but there are lesser quality grades of stainless that sell for less (and offer less corrosion resistance!). Aluminized steel is another option, but it does not have the durability of stainless. Even so, aluminized steel is much better than plain, uncoated or painted steel.

Most performance pipes are formed with mandrel bends which do not narrow the diameter of the pipe where it curves. This reduces unwanted restrictions and keeps the exhaust flowing freely. 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.

DIRECT FIT OR UNIVERSAL MUFFLERS?
Performance mufflers are available in both direct-fit or universal configurations. You will find the greatest selection in universal products, which can be adapted and made to fit almost any vehicle. But the main drawback of one-size-fits-all mufflers is that they sometimes require cutting and welding pipes, and fabricating hangers and mounts.

When the stock muffler is removed, the existing pipe may have to be cut, shortened or lengthened. If the pipes are getting weak, they may also have to be replaced to complete the installation. New hangers are often necessary to support the muffler, or existing hangers may have to be repositioned to provide proper support and keep the system from flexing or rattling. Clearance may be another issue, especially with large oversized muffler cans that are not the same size, shape or length as the original muffler.

Making modifications to a stock exhaust system raises another issue. It may complicate matters if you ever want to go back to a stock muffler. This may not seem like much of an issue when your are installing the muffler or exhaust system. But if and when you sell the vehicle, you may want to remove the parts you installed and replace them with the original parts. So the fewer modifications that have to be made to install a custom universal-fit muffler, the better.

Direct-fit mufflers usually do not require modifications or changes because they are designed to replace the stock muffler perfectly. Most are a simple bolt-in installation that connect to existing pipes and have mounts that line up with the stock hangers. The major drawback with direct-fit custom mufflers is limited availability for less popular models.

Sound quality is something that is harder to control with universal-fit mufflers than direct-fit mufflers, which have been engineered for a specific vehicle application. Different engines sound differently and produce different frequencies and harmonics in their exhaust systems. So don't expect a universal muffler to sound exactly the same on different vehicles.

At the same time, some performance mufflers are tunable in that they have removable baffles. You can change the sound by adjusting or removing the baffles.

COMPLETE PERFORMANCE EXHAUST SYSTEMS
Cat-back exhaust systems also are available in kits and are usually direct fit for easy installation. Pipes may be stainless steel, aluminized steel or plain steel and will be priced accordingly. Pipes may also be larger than the stock pipes to reduce backpressure and increase flow.

How much power a performance muffler and exhaust system will add to an engine depends on a lot of variables. A more restrictive stock system and more free-flowing replacement system equals a better gain in horsepower.

Most manufacturers claim power gains of 15 to 25 horsepower or more with their products. The larger the displacement of the engine, the more it usually benefits from upgrading to a free-flowing exhaust system. This is especially true with turbocharged engines. Reducing exhaust backpressure allows boost to come up more quickly and to reach a higher level. Throttle response is improved and the engine runs cooler and stronger.

One thing to keep in mind when installing a performance exhaust system is heat management. Exhaust systems reflect a lot of heat. That is why stock systems often have heat shields to keep heat away from the floor, fuel tank, brake lines and fuel lines. So reuse or fabricate heat shields where necessary to keep heat away from anything that might be heat-sensitive.

EXHAUST HEADERS
Exhaust headers also are available for many popular import engines. The free-flowing four-into-one or four-into-two-into-one welded tube headers are more efficient at routing exhaust out of the engine than the stock manifolds, and provide a boost in both power and torque for a couple hundred bucks.

Stainless-steel headers are the most durable, and the most expensive. Plain steel headers that have been coated with ceramic/metallic compounds will also retain their appearance and remain rust-free on street-driven vehicles much longer than plain steel-painted headers. Thermal coatings also help to retain heat in the pipes, which reduces underhood temperatures and increases exhaust velocity for better throttle response. They look good, too. Installing exhaust headers may be easy or difficult depending on accessibility and the age of the vehicle. Just make sure the headers have the required fittings for the oxygen sensor or other emission hookups that are required to be street legal.

When installing headers, do not use stock exhaust manifold gaskets. Use a premium type of gasket made of graphite or multi-layer steel (MLS). There is a tremendous amount of heat and motion between the cylinder head and headers, so use gaskets that can withstand both. On older vehicles that have a carburetor, changing the headers and exhaust system may require rejetting the carburetor to maintain the proper air/fuel ratio. This should not be necessary on fuel-injected engines with O2 sensors because the engine management system should compensate for changes in exhaust flow. Just make sure there are no air leaks between the cylinder head and headers that might confuse the O2 sensor.

STREET LEGAL EXHAUST?
Some companies make complete exhaust systems that run from the engine all the way back to the tailpipe, but eliminate the catalytic converter. These are great for racing but are not street-legal systems unless a vehicle is exempt due to its age (typically older pre-converter-equipped vehicles).

Low-restriction aftermarket performance converters are available and can be installed in place of the original converter if the OEM converter is out of warranty or has failed an emissions test. But the converter must meet the applicable EPA requirements to be street legal. On late-model vehicles with OBD II (1996 and up), a replacement converter must be OBD II-certified.

Noise is the other concern with some aftermarket performance mufflers and exhaust systems. Reducing backpressure with a straight-through muffler often allows more decibels to blow out of the tailpipe unabated. High-revving four-cylinder engines typically produce a high-pitched buzzsaw sound. A properly tuned system will dampen the higher frequencies and allow a lower, more powerful tone to emerge. Others seem to pass every exhaust pulse unabated, resulting in an ear-splitting racket that sounds like an open exhaust.

Many owners of street performance vehicles love the sound of a powerful exhaust system. But others may find the noise to be annoying. Many communities have sound regulations and will ticket a vehicle owner if their exhaust is deemed to be excessively loud. But such rules are typically enforced at the discretion of the local law enforcement officers who may or may not make it an issue depending on the driver's driving habits and previous encounters with the law. Noise regulations vary a great deal from one state to another, but generally speaking a muffler that makes more than 80 to 90 decibels of noise may be in violation of the law. For an example of California's Noise Regulations, Click Here.

Got an Exhaust or Muffler Question? Need help Now?

We have partnered with JustAnswer! to offer online email advice from expert automotive technicians who can answer questions for an affordable fee (typically $10 to $15). Answers usually come in 15 minutes or less, you can ask follow-up questions, and you pay nothing unless you accept the answer.

Need More Information on Performance Mufflers or Exhaust Systems? Try Google Search. Enter Keywords or a Phrase:

Be sure to visit our other websites:

AA1Car Automotive Diagnostic Help Center
Auto Repair Yourself
Carley Automotive Software
OBD2HELP
Random-Misfire
ScanToolCompanion
ScanToolHelp
TROUBLE-CODES

High Performance Mufflers & Exhaust Systems

More Exhaust Related Articles:

Got an Exhaust or Muffler Question? Need help Now?