High performance exhausts

[Chemical Darryl]

Exhaust systems on most vehicles are a compromise. Besides carrying the exhaust fumes away from the passenger compartment, they also have to reduce emissions, muffle the noise and also fit around the body, suspension and drivetrain components. Over the past several years, the auto manufacturers have paid a lot of attention to exhaust system design, as it is one way to improve fuel efficiency and power without adding stress to engine components. Even so, they have to keep manufacturing costs down. That is where the aftermarket manufacturers step in with performance exhaust systems.

In a typical exhaust system, the gases flow from the engine through exhaust manifolds. They are then fed into a catalytic converter (some vehicles with V6 or V8 engines use two converters) and then into a muffler. Most vehicles come with a single exhaust pipe that feeds a single muffler near the back of the vehicle. Dual exhaust outlets are a frequently seen styling feature on many vehicles, but usually both outlets come from a common muffler.

The most common type of aftermarket performance system is called a “cat-back” system. These systems replace the factory system after the catalytic converter. By leaving the converter in place, the vehicle still meets the emission standards. The cat-back system often uses larger diameter pipe that is routed to minimize bends. Where bends are required, a mandrel bender is used to create smooth curves in the pipe. A conventional exhaust tubing bender compresses the pipe on the inside of the bend. The pipe will be reduced in diameter and have several wrinkles on the inside radius that restricts gas flow. Smooth mandrel bends flow better and look better too when showing off your ride!

Cat-back systems also include the muffler. By increasing the size of the muffler, there is more room for the exhaust gases to expand and this increases flow. Large is good! The muffler may have different internal passages that also allow more exhaust flow. This can change the tone of the exhaust note and the volume, which some drivers prefer. A high-performance cat-back system doesn’t have to be noisy however, and if you drive a lot of highway miles you will appreciate a quieter exhaust system.

Catalytic converters get a bad rap and are blamed for restricting exhaust gas flow and reducing performance. This may have been true when converters were first introduced in the 1970’s, but modern converters are extremely free flowing. Some have as many as 900 passages per square inch to allow exhaust gases through. An exhaust back pressure gauge can be used to measure the restriction in an exhaust system. This gauge is a sensitive pressure gauge that will read in the zero to about five pound per square inch (PSI) range.

Not all manufacturers give a specification for maximum allowable backpressure, but of the ones that do, about three PSI is common. This is the maximum, and tests we have performed on vehicles show that the tailpipe must be almost completely blocked before back pressure reaches this level with the engine idling. Most vehicles will have less than one-half PSI backpressure when everything is in good shape. Measuring the backpressure before and after the converter shows almost no difference is readings, indicating the converter is not restricting exhaust flow. If you are looking to install a performance exhaust system, leaving the catalytic converter alone and bolting on a cat-back system is a good way to go.

For maximum performance, some drivers want to install tube headers. These replace the factory exhaust manifolds and the header pipes are more equal in length to extract the exhaust gases as efficiently as possible. Headers are great for performance but they do create problems. On the road, they “ring” like a bell continuously. You may not notice it at first, but it can cause fatigue and headaches on long drives. Most headers also route below the engine compartment and decrease ground clearance, so they are more easily damaged by road debris, speed bumps and pot holes.

Other disadvantages of headers are that the pipes are routed for the best flow and this can create interference with other engine compartment components. The best quality headers have better engineering and fit better, but every header system I have seen has created some interference. If you remove the catalytic converter when you install headers, in many parts of the country the vehicle is legal for “off-road” use only, so keep the converters in place to pass emissions testing.

Finally, if you think noisy is good, talk to the local stock car racers. Many tracks require mufflers on these race cars and guess what – the cars started going faster with the mufflers installed

From Canadian Driver

[Knight1]

Great post

[rainman]

Excellent post man!

[THE SYNDICATE]

great info.........

as always partner!

[ShIvAm]

i kno this kinda off topic, but how come a chrome muffler doh make noise wit a diesel engine

[legendkiller@1891]

great stuff there man!!!

[Knight1]

[VexXx Dogg]

so all those scoobys with decatted downpipes are wasting tme then....???

[Chemical Darryl]

Thanks guys, I take great pride sharing info I research off the net.

[legendkiller@1891]

thumbs up

[crazybalhead]

[Ignorant Ignis]

but they do get more restrictive over time ..... so it makes sense to remove them in older vehicles to gain power or replace them with a new one

[wagonrunner]

[VexXx Dogg]

[bushwakka]

note daryll.....u should copy the link u took articles from though

they prolly referring to vehicles like the TS which won't benefit much from a decat operation cuz the increase is prolly negligible

[mossman]

great info dude