If you're thinking about adding some performance to your vehicle, an exhaust system is a good way to go. For today's modern muscle cars, you'll be dealing with a few things that old school hot rodders don't have to worry about. Most OEM catalytic converters do not flow exhaust very well. Depending on your performance and sound requirements, you may choose several options. An exhaust system is made up of some or all of these parts: A set of exhaust manifolds or headers, Down Pipe (exhaust manifold to catalytic converter), catalytic converters, X-pipe or H-pipe, mufflers, muffler back pipe, and exhaust tips. You may have some of these exhaust parts or all of them. Most quality exhaust systems include pipes that are mandrel-bent so they are the same diameter throughout the pipe curve/bend and aren't collapsed.
Remember: You must comply with local, state, and national regulations on exhaust product upgrades and changes. Not all exhaust products are 50 state legal.
Headers Back Exhaust Kits
Many exhaust makers build complete exhaust systems that include the exhaust parts necessary from the headers all the way back to the exhaust tips. These systems are application-specific and made so it is an easy bolt up. You install the pieces with no guesswork. Kits that require catalytic converters usually include high flow catalytic converters, an X or H pipe, preformed exhaust pipes, mufflers, and tips. Older applications may include an X-pipe, H-pipe or formed pipes, mufflers, preformed exhaust pipes, and tips, depending on the system.
Cat-Back Exhaust Systems
Cat-back exhaust upgrades are very popular. You get a number of benefits from adding a cat-back system. By adding high flow aftermarket mufflers, you can gain some performance. You can also select a system for the sound you want. Different manufacturers build their mufflers and cat-back exhaust systems with a certain sound in mind. The loudness and pitch of exhaust sound will vary between manufacturers. Cat-Back Exhaust Systems vary in sound level and tone. Some exhaust makers have even gone high tech to use technology to cancel out more of the sound at low RPM and then leave the system louder as you get on it. Cat-back exhaust systems are available in steel, aluminized, stainless steel, and some other special materials.
Exhaust Pipe Diameter
"Bigger is Better" is something we all hear as hot rodders all the time, but is certainly not the case when selecting the correct exhaust pipe diameter. The only part that holds true to this mantra is that bigger is louder. Low-end performance requires back pressure in an exhaust system. This back pressure is created by the restrictions in the exhaust pipe itself and helps pull spent exhaust gasses instead of having the engine push them out. This trait is called scavenging. When you choose a pipe diameter that is too big or an exhaust system that is too free-flowing, often you will lose a noticeable amount of low-end performance since the exhaust system is no longer providing a scavenging effect. This is because the engine has to use the power that would normally go to the wheels to push these gasses out of the engine. Generally, gasoline V8 engines making less than 500 horsepower will perform best with a single 3" system or a dual 2.5" system. Gasoline engines producing over 500 horsepower will perform best with a single 3.5" or 4" pipe or a dual 3" exhaust system.
Diesel performance differs greatly when selecting the correct exhaust pipe size. The exhaust pipe size can be used to raise and/ or control the exhaust gas temperatures (EGT) of the engine which can lead to much more performance. Diesel exhaust systems will commonly be much larger, often up to 6" diameters for higher horsepower applications, but there is a ceiling in this arena as well. Generally speaking, with a larger exhaust pipe more fuel can be added to make more power. This mixture of fuel and exhaust flow helps maintain the EGTs but if the proper amount of fuel is not added with the increase in pipe size, severe engine damage may result.
Whether it be a gasoline or diesel application, it is never advantageous to run a straight pipe exhaust system without some sort of muffler. The only exception would be a high RPM race application.
H and X Pipes
H Pipes became known in the mid-80s most commonly on the Ford (fox chassis) Mustang. The problem with a dual exhaust system on a dual bank engine such as a V6 or V8 is that there was no way to balance the exhaust cylinder pulses that enter the H-pipe. This H-pipe is a short section of pipe installed perpendicularly into a dual exhaust system that connects the two pipes and helps balance the exhaust pulses from bank to bank. The scavenging effect mentioned earlier is also enhanced by an H pipe as the exhaust system now has twice as many cylinder pulses to work with. X-pipes are a later offshoot of the H-pipe concept and are often found to provide even better scavenging than a conventional H-Pipe. If you are thinking of installing one of these pipes, do it. They are a great addition to any exhaust system. H and X Pipes can be purchased by application, universally or built into many cat-back systems. Contrary to what you might think, both styles balance pipes will make the overall exhaust system quieter than without.
Mufflers are wide open! There are hundreds to choose from. Mufflers vary in loudness and tone so you can buy the mufflers you like. You can get steel, aluminized metal, stainless steel, and polished stainless steel mufflers. Stainless usually costs more but will outlast most other types of mufflers. Common muffler inlet and outlet diameters for V8 gas and small truck diesel engines are 2.25", 2.5", 3", 3.5", and 4". Most mufflers are specified by the inlet size and the outlet size. Mufflers may have one inlet pipe and 1 or 2 exit pipes to run dual tailpipes. Inlet and outlet positions can vary. A muffler that is labeled "Center In" or "Center Out" means the inlet or outlet pipe on the muffler is centered on the muffler body. A muffler labeled "Offset In" or "Offset Out" means the inlet or outlet pipe is offset on the muffler body. Some are cylindrical while others are more rectangular shaped. The physical dimensions of a muffler typically affect the sound and performance.
OEM catalytic converters aren't usually meant to flow exhaust as we would like them to. Step up to a high flow set of catalytic converters to relieve the back pressure on your system. If you want your exhaust to flow better, you can't have an exhaust system with any limitations in it. Many high flow cats are available in stainless steel for long-lasting performance.