Exhaust Tech 101


An aftermarket exhaust system is a bread and butter modification most car enthusiasts do to enliven their car’s performance and driving sensation. However, many don’t consider the important points of picking the right exhaust for their cars, which is mainly, sound, power and costs.  


More often than not, the standard factory exhaust is designed to muffle noise as much as possible. By restricting the flow of exhaust gasses out of the engine, it creates backpressure that robs some power, but provides useable torque for daily driving. Backpressure occurs when the engine is pumping out exhaust gasses faster than it can exit the tail pipe. While most engines are designed and tuned from factory to work with the backpressure, sometimes it is much better to have little to no back pressure, especially on cars with big capacity or turbocharged engines. Replacing the factory exhaust system with less restrictive, aftermarket items will restore some of the power loss, and give a great exhaust note too. We’ll go in depth on the components of exhaust system, and show you how to choose the right ones for your vehicle.  

Headers and Exhaust Manifolds

The headers and exhaust manifolds are bolted to the engine’s head, and are in charged with collecting the exhaust gasses and sent them on the way out of the car. Factory designed manifolds are great at scavenging exhaust gasses from combustion chambers at low to medium engine speeds, where the car spends 99% of its time. However, at high revs, the factory manifold becomes a restriction, dropping top end power. Aftermarket headers are designed to be more free flowing, allowing high amounts of exhaust gasses to quickly exit the combustion chambers. Most aftermarket exhaust manifolds are often mandrel bent to remove exhaust restrictions. Highly effective headers also have massive amounts of research and development, and are a critical component in the exhaust system in freeing up power. There are also different configurations of headers, such as Tri-Y, 4-1, and are available in different lengths and runner sizes. As a rule of thumb, 4-1 headers provide better mid range and top end power, while a Tri-Y configuration has better low and mid range response and power.    

Catalytic Convertor

The catalytic convertor (or popularly known as cat) removes harmful emissions from the exhaust gas emitted by your engine before allowing it to continue on its journey. Using special, honey comb filters coated with precious metals, it converts harmful gases to neutral chemicals before being released into the atmosphere. Factory catalytic convertors can be highly restrictive, and many race cars run without one. However, it is illegal to remove it from road cars. However, there are high flow cats that are not as restrictive as factory ones. Normally rated at 100 CELL to 300 CELL, the lower the number, the less restrictive it is. After installing a high flow cat, there is a high chance that the car may no longer meet its emissions rules, and is no longer road legal.


The most recognizable part of the car, the muffler is the key in reducing exhaust noise. Depending on style and size, the muffler uses sound deadening, multiple baffles and perforated tubes to achieve this. XForce's Varex mufflers also allow users to change the sound levels from quiet to loud, and anywhere in between with a click of a button. Watch out for badly designed mufflers that use cheap materials. As heat and exposure degrades the components, the cheap mufflers' exhaust tone can change over time. These mufflers can also be a restriction by using a smaller inner pipe to reduce noise to an acceptable level. A good aftermarket muffler will provide a great tone without the tinny drone while cruising. It should also be designed in a way that it will not generate excessive back pressure. The internal diameter of the muffler should also match the rest of the exhaust, and ideally should be larger than stock. XForce Performance Exhausts supply a full exhaust system, either for universal applications, or specific car models. Extensive research and development, alongside testing has gone into making XForce’s products to provide performance and satisfaction. To find your nearest authorised XForce dealer, visit www.xforce.com.au/where-to-buy  

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