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Stock Vs. Aftermarket Exhaust Systems: the Notable Differences in Each Part

Aftermarket Exhaust System

Gearheads will find a thousand different topics to debate and argue on when it comes to cars, but they all agree that the best way to turn an everyday vehicle into a power machine is to upgrade its exhaust system. The fact is, most vehicles come with a restrictive stock exhaust system simply because manufacturers choose to put together a vehicle that will be sold at a more competitive price on the market, so they use lower quality materials and manufacturing techniques in the exhaust manufacturing process. But in order to get a better understanding of how and why aftermarket performance exhaust systems outperform stock exhaust systems, you need to take a look at all the exhaust system’s parts individually and see where the main differences lie.


Let’s start at the very first part of the exhaust system – the exhaust manifolds. Stock exhaust manifolds are usually made of cast iron in a block-like configuration. The purpose of these parts is to suck out the exhaust systems out of the engine that is a result of the combustion process. Stock manifolds are built using cast iron in a block-like configuration as that gives them longevity and sturdiness. Cast iron is quite thick so it performs quite well when under extreme heat. However, this also means that the thick walls of the manifolds offer very little space for the gases to pass through, and iron casting is rough, which further slows down the flow. This results in backpressure, which prevents the exhaust gases from flowing as efficiently, which ultimately results in reduced power.

Aftermarket headers, or extractors, as they’re commonly called in Australia, solve the aforementioned problem by using individual steel tubes for each of the engine’s cylinder. These tubes are connected to a collector pipe and are smooth and equal in length which ensures that the gases from the cylinder reach the collector pipe separately, thus avoiding the build-up of backpressure. However, keep in mind that this benefit will be lost if the exhaust pipes that follow the extractors are also not upgraded to wider diameter pipes that will allow the gases to flow more efficiently out of the entire system. Aftermarket headers have thinner walls but are typically made of quality steel. Due to the fact that they’re thinner, they don’t absorb sound as well as cast iron manifolds, which makes your vehicle louder.


The next major part of the exhaust system is the catalytic converters. Cat converters are responsible for converting the harmful exhaust gases that come out of your engine into less harmful ones. Stock catalytic converters are great at what they do, and you don’t always have to replace them to get more performance. However, aftermarket cat converters are far more efficient and are made of superior materials that make them last longer. Typically, when purchasing aftermarket exhaust systems, you’re also getting an aftermarket high-flow catalytic converter, but if you’re only replacing your catalytic converter, then make sure you get one that fits your specific model, make and year vehicle and complies with local emission regulations.

Cat converters feature dense honeycomb structures that are made from ceramic and are coated with precious metals. When the harmful exhaust gases come in contact with the precious metals they’re reduced into less harmful gases. The harmful exhaust gases are nitrogen oxide, carbon monoxide, and unburnt hydrocarbons. Once these three gases pass through the catalytic converter, they’re reduced into nitrogen and oxygen, carbon dioxide, and water in the form of steam. Here’s a blog that goes into detail about the operation method of catalytic converters.

After the catalytic converter, the gases pass through the muffler and eventually through the exhaust tip and off into the atmosphere. The muffler and exhaust tip don’t play a role in the performance of your system, but instead in its sound and looks. You’ll find exhaust systems with different types of mufflers and you can pick one depending on your personal preference. Some mufflers make your vehicle sound more aggressive, while others timider. The same goes for exhaust tips. Exhaust tips come in a wide range of shapes, forms, and finishes.


Lastly, aftermarket exhaust pipes can make a huge difference in how your vehicle performs. After all, the pipes are like the veins and arteries to your exhaust system. They’re responsible for transporting the exhaust gases from one part to the other, and eventually, out of the system. Aftermarket exhaust pipes usually feature a wider diameter than stock exhaust pipes, but you have to keep in mind that wider is not always better. If the pipes are too wide, they won’t be clamped well and they’ll cause rumbling when you drive, which will rob you of power.

Another reason why aftermarket exhaust pipes are superior to stock exhaust pipes is that they’re generally made using a special bending technique known as mandrel bending, whereas stock exhausts are made using crushed bending. The crush bending manufacturing process is more simplistic and affordable, which is why car manufacturers opt for it. On the other hand, mandrel bending is more expensive and more complex, and as a result, it doesn’t restrict the flow of gases throughout the system.

The mandrel that’s placed at the inner walls of the pipe holds the pipe diameter steady as the pipe sweeps through the backing shoes and die, resulting in pipes that are free of profile and diameter changes. The mandrel is also generally lubricated using lithium grease which promotes a smooth gliding action inside the pipes.

By Anthony Hendriks

The life of the party, Anthony is always up for spending some time with family and friends, when not blogging of course! Ever since a child, his love for books of mystery, race cars and travelling keeps on growing so it's difficult for him to single out that one all-time favourite hobby. If there's one thing he hates, though, it's having pictures taken but you already guessed that from his choice of plant photo for the blog.