Exhausts 101: Everything You Need to Know

If you’re considering car upgrades that offer the best bang for your buck, then an aftermarket exhaust should definitely be high on your shopping list. With wider tubing, better materials, and revised designs, a performance exhaust opens up a range of advantages over what comes with your car. Airflow is significantly improved with better-engineered parts and this is a prerequisite for more low-down torque and power. The sound leaving the tips will also be singing to a better exhaust tune. And improved durability also means the piping will hold its own no matter where or how you drive. 

Why Change Your Factory Exhaust?

Cars are the sum of their parts. And some of these parts are made to a better standard. Others go through cost-cutting measures, meaning that the performance they provide, while adequate, can be improved. This includes common components like car clutches [link], brake assemblies, and exhaust systems. There are way better parts to be found aftermarket, and not necessarily at a much higher price. Here the quality of materials is higher and the production methods are more complex. Exhaust builders additionally throw in a lot of R&D for a range of different vehicles, with the end goal of giving your car that little bit extra. 
When it comes to performance exhausts, this implies redesigning components (or the complete exhaust system) to allow for the best possible airflow. Your factory exhaust consists of too many unnecessary bends and twists and tubing that is too narrow and this kills airflow. Additionally, you’ll see backpressure buildup, with exhaust gas hindering the next combustion cycle, and possible ruptures in the tubing. An unwanted byproduct is increased stress on related engine parts, like pistons, exhaust valves, and camshafts. 

What do You get With an Aftermarket Exhaust? 

• Performance – Better airflow and higher exhaust velocity in performance exhausts greatly improve power and torque. With reduced obstructions in the piping, wider diameters, and revised layouts, the engine achieves more efficient combustion cycles. Faster airflow also helps the turbo spool faster and feeds the engine with new air. The most obvious changes are done to the most restrictive exhaust components, such as the downpipes, catalytic converters and mufflers.
• Sound – Better sound to completely transform your car is one of main the selling points of a performance exhaust. This is achieved with different layouts and tubing widths, but also with different muffler and resonator configurations. Brands will have their own distinctive sound and the choice of going for a really loud or more refined and muffled sound. 
• More durable materials – Factory exhausts are made of mild steel. This is prone to rust and needs to be optioned thicker, so also bumps up weight. Aftermarket versions step things up with longer-lasting corrosion-resistant stainless steel, or more exotic materials like titanium, with substantially higher strength and much lower weight, or Inconel with extreme hardness and exceptionally high heat resistance. There’s also more attention to detail and looks, especially with the inclusion of carbon fibre in the tips. The better the materials, the less the chance that the part or piping will succumb to cracks, deforming, rust, and general wear and tear. 
• Advanced production methods – Factory exhausts use crush bending as an inexpensive production method. This though doesn’t warrant uniform widths and materials are prone to kinking (deformation) from high temperatures and pressure. In addition, impact with rocks, gravel, and road debris will likely cause scratches, dents or cracks. Aftermarket systems not only use better materials but also deploy mandrel bending, a technique that uses solid steel rods to form the tubing and bends. This ensures that the pipes are strong and won’t wrinkle or break, and also produces a clean and neat look. 

Exhaust Options

While most systems today are of the modular type, meaning you can change individual parts, most car enthusiasts will choose between an axle-back, cat-back and header/turbo-back exhaust. These are regarded as complete systems. 
Axle-back exhausts change your car’s stock piping from the rear axle to the tips and emphasise the performance, design, and sound characteristics in the mufflers and resonators, and the look of the tips. The major divide here is between resonated and non-resonated exhausts (often with straight tubes) for louder sound. Valving is another popular option and allows drivers to modify exhaust sound and volume to suit. While axle-back systems do improve airflow, the power gains are minimal at most. 
Cat-back exhausts include the mods of an axle-back exhaust, along with wider mid-section tubes stemming from the catalytic converter (the part that burns off remaining toxic gases). Designs differ and depend on the engine. The major pro of a cat-back system is the much-improved airflow, so there are additional gains in power. 
For the best results, go with a header back exhaust on an aspirated engine, or a turbo-back unit on engines with forced induction. These replace all the parts in your factory variant. Major revisions include the design and widths of the downpipes and collector pipes and the inclusion of high-flow catalytic converters. These systems offer optimal exhaust flow, improved scavenging (replacing spent gases with new air), and considerably better sound. They’re also the easiest on the engine. 

Buying Considerations

The type and brand of exhaust you choose boils down to your budget. You can spend between a few hundred dollars for the cheapest stainless steel axle-back exhaust to anywhere north of ten thousand for a full header-back system optioned in lightweight titanium or Inconel. Of course, the exhaust also needs to be designed to work with the engine. This takes into account cylinder count, power output, fuel type, whether the engine has a turbo or supercharger, and if it’s been modified. 
Generally, all aftermarket systems will include tubing that is half to one inch wider, changed designs (like x-pipes) that speed up exhaust velocity, improved mounting points and gaskets between individual parts for reduced vibrations, better sound as is, and a superior overall build. The cost difference between different types lies mainly in the choice of materials, the layout and addition of various parts, and the promised performance gains.