Definitive Guide To Aftermarket Exhaust Systems 
Mon Aug 01 2022
Ever wonder how people make their car exhausts sound so different and thrilling? Well, all they do is modify, replace, or eliminate some of the components to make them sound however they desire. Other than pure glorious sound, performance gains are also a motive. But before we get to how aftermarket exhausts work, we need to understand the basics of a common exhaust system.
What is an exhaust system?
Historically in cars, the primary system that converts one or more energy sources to mechanical energy is the internal combustion engine. The combustion of a fuel, gasoline, or petrol depending on where you are from causes the rapid expansion and pressurization of the combustion chamber. This rapid expansion of the combustion products drives a piston which in return turns a crankshaft. The crankshaft is connected to a flywheel which is connected to the transmission. That’s enough about the drivetrain, let's focus on the exhaust. After combustion, the exhaust system delivers the burnt gasses, or exhaust gasses as they are called, from their source at the combustion chamber via a series of pipes to a desired and suitable point, usually away from the system that produces them. Unfortunately, in the case of electric cars, they use electric motors rather than internal combustion engines. This leaves them without need for an exhaust system.
What’s the purpose of the exhaust system?
Exhaust systems serve many purposes. They prevent exhaust gasses from entering the cabin by guiding them away, they reduce the noise the engine produces and they make the exhaust gasses cleaner for the environment.
In a typical vehicle, the following components are used for the aforementioned purposes: The exhaust manifold guides the exhaust gasses away from the engine into the catalytic converter. The exhaust gasses through the magic of science are converted into less harmful gasses there. The noise is primarily reduced in the muffler that follows the catalytic converter. However, there could be other components like resonators or secondary catalytic converters that aid in the muffling. After the muffler, they are finally let out via the tailpipes, which are usually at the back of the car. The majority of the time in a one exhaust tip manor but with higher performance cars you typically have more than one, often two or four.
Why do you need aftermarket exhaust components?
State and federal regulations require that your vehicle emit less noise and harmful gasses. For this, manufacturers use mufflers, resonators, and catalytic converters. While the intended regulatory purpose is achieved, these components mute the car's exhaust sound and to make things worse, there are some performance losses. All of these components are obstructive to the exhaust flow, creating backpressure. Backpressure increases the atmospheric pressure relative to the combustion chamber, making it harder for exhaust gasses to escape during the exhaust stroke. This saps the engine power because the next combustion reaction won’t be as efficient because there’s leftover combusted gas. This reduces the amount of cold fresh air you can intake, increases the heat of the chamber, and is just generally bad. To recover some of this power and improve exhaust sound, aftermarket exhaust systems are used.
Other than performance, some people will just want their vehicle to sound better. Since the original exhaust system has to regulate the noise level, it makes the car sound boring and oftentimes completely muted. Most of the time aftermarket exhausts involve removing parts and simplifying the exhaust system in terms of overall components. People can make the mistake of thinking it’s a simple process. Just delete the catalytic converters, mufflers, and resonators, right? The real effort honestly isn’t at the consumer level. The complexity of aftermarket exhausts derives from the many hours of engineering and research that goes into crafting the perfect tone and exhaust note.
For every make, model, and generation of a car, different aftermarket exhaust components are attached to the car in question and used to perfect the exhaust sound. Aftermarket exhaust companies use different materials, more pipes, less pipes, different diameters of pipe, different pipe angles, and different methods of bending the pipes to perfect their final aftermarket exhaust product. We will now take a look at the different aftermarket exhaust components and how they work together to maximize performance and produce distinctive exhaust notes.
Aftermarket Exhaust Components
Headers or Exhaust Manifolds:
The term "headers'' usually refers to aftermarket exhaust manifolds. They are the first components that handle exhaust gasses. Bolted directly onto the cylinder heads, they are much less restrictive than the original, making the exhaust flow easier and reducing backpressure. How the header pipes are bent matters a lot as well as the length of each individual header pipe. Traditional exhaust benders can cause deformation along the bend, leading to a non-ideal flow of exhaust. Mandrel-bent pipes are preferred for their freer flow as a result of the uniform bend.
Headers are also available in different dimensions, usually full-length or long tube headers and shorty or short tube headers. Short tube headers combine the individual pipes from the cylinders earlier and provide a reduction of back pressure and reversion. Meanwhile, long tube headers provide an even greater reduction of backpressure and reversion. In addition, due to the extra length of the long tube headers, you can achieve greater scavenging from cylinders and improved pulse tuning.
Another consideration is how the pipes from the cylinders are combined. Tri-Y and 4-into-1 are common configurations, but different configurations may be available depending on the type of engine.
The downpipes connect the headers or turbocharger to the rest of the exhaust. Here, the diameter is of great importance. The larger the diameter, the freer the exhaust. Downpipes are often found on turbocharged vehicles, connecting the turbochargers to the midpipe. Downpipes often contain the following component:
Catalytic converters are commonly referred to as Cats. Cats are the main exhaust component responsible for reducing harmful emissions. Due to the nature of emissions, many states as well as the federal government have made laws requiring them on your vehicle. In the past, they were quite restrictive but now, high-flow performance cats are becoming more and more popular, allowing for performance gains while keeping your car from smelling like exhaust fumes. Explore all of the positives of high-flow performance cats with our article, "Why buy High Flow Catalytic Converters". Catalytic converter theft is common because of the precious metals that are used in them.
Inside cats are ceramic honeycomb meshes coated with platinum, rhodium, or any other noble metals that react with exhaust gasses, converting them to less toxic hydrogen, nitrogen, water, and carbon dioxide. It’s impressive given it’s a completely passive process, science is amazing.
Oftentimes there are multiple catalytic converters throughout an exhaust system. For example, in the case of turbocharged vehicles, there is often a catalytic converter between the engine and the turbo, a front catalytic converter after the turbo within the downpipe and a rear catalytic converter within the midpipe section. Modern cars have oxygen and temperature sensors before and after each catalytic converter, allowing the car’s onboard computers to monitor the performance of the catalytic converters. With this information, the computers know when the catalytic converters are warm or if they’re faulty for regulatory purposes. This is why it’s oh so common to get a check engine light whenever you modify or remove your catalytic converters. Learn more about catalytic converters with our articles "What Are Catalytic Converters, How They Work, and Why Are They Stolen So Often?".
Depending on your car’s make and model, it may have mid-pipes. They are present between your car’s downpipe / headers and the rest of your exhaust, whether the next component is a resonator, muffler, etc. X-pipes, H-pipes, and Y-pipes are common types of mid-pipes only differing in shape. Again, the pipe diameter is enlarged to reduce back pressure.
A resonator does what a muffler cannot. It’s more refined and uses destructive wave interference to remove annoying hums and buzzes from the engine and makes the exhaust much more pleasing to the ears. Not all cars use a resonator, but you may need it if the purpose of your aftermarket exhaust system is the exhaust note.
In dual-exhaust vehicles, it is common practice to use crossover pipes to distribute the exhaust evenly. Two banks of engine cylinders may result in uneven exhaust buildup; therefore, the X or H shapes are used to provide a passage to make it even and reduce backpressure.
The most well-known part of the whole exhaust system is the muffler. Its job includes suppressing the exhaust noise. How this is done is more complex than it sounds. It uses a combination of chambers, perforated tubes, and/or sound-deadening material. Like the resonator, mufflers utilize destructive wave interference to alter the sound of the exhaust. Unlike the resonator, whose primary purpose is to remove unwanted sounds due to pitch or tone, the muffler's primary purpose is to reduce the overall volume of your exhaust. Aftermarket mufflers are designed in such a way that they reduce the backpressure while also not compromising peak noise levels and exhaust notes. Mufflers are often one of the components completely removed from many aftermarket exhausts.
What you see from the back of the vehicle are the exhaust tips connected to the tailpipes or muffler. The rear is the most common place of exit, but they are also found at the side, like the Dodge Viper, or on the top, like the fantastic-sounding Porsche 918. They are also available in different finishes and shapes. Their primary function is to look good.
How Aftermarket Exhaust components work
How they work depends on the type of modification you have done. Speaking of which, there are several of them. Find out what not to do with your car's exhaust with our article " 10 Things You Should Never Do To Your Car's Exhaust". The most common and popular aftermarket exhaust systems are as follows:
What is Header-back?
As the name indicates, this system involves the replacement or modification of the whole exhaust system, from headers to tailpipes. You can increase the diameter of the pipes and make them straighter for more unrestricted flow. At the same time, you can tune them to your desired exhaust note. Due to the scale of this system, it is expensive and more complicated to carry out. But it provides the most power gain and overall customizability when compared to any other aftermarket system.
What is Cat-back?
Similarly, a cat-back aftermarket exhaust replaces the exhaust system beginning from the catalytic converter to the tailpipes. It is a scaled-down version of Header-back. And since cat-back doesn’t disturb the catalytic converter, you are not at risk of illegal modification and don’t have to worry about the exhaust fumes that come with removing your catalytic converters.
A cat-back aftermarket system is the most sought-after because it has the best value for money. Being not as complex and expensive as the Header-back they still give more than enough power gains and exhaust note tuning. The same method of enlarged pipes replacing the original pipes is implemented, while additional modification may be done to the Mufflers and Mid-pipes.
What is Axle-back?
This aftermarket system just concerns the exhaust system that is after the rear axle. Again the pipes are enlarged to carry more exhaust and a resonator may be introduced if needed. The resonator simply creates a smoother exhaust note while retaining the original exhaust volume. The purpose of a resonator is acoustic and nothing more. Axle-backs are typically cheaper than the other types of systems and don’t offer as much in the performance gains department.
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