Car upgrades can be subtle, from interior trim additions and new seat covers to more pronounced exterior additions, including upgraded alloys, bespoke body kits and full aftermarket exhausts. If generating more power is your end goal, then factory exhausts are often the first components to see a makeover. Swapping these out for an aftermarket system and engineered exhaust components provides the foundation for all subsequent engine and power additions.
The Limitations of Factory Exhausts
The main role of exhausts is to safely channel hot, spent gases from the combustion process away from the engine and cabin. Factory systems do this adequately, but current noise and emissions regulations impact overall pipe designs and widths, effectively causing airflow restrictions, such as backpressure. This causes gases to linger in the piping for longer, and negatively impacts engine performance. With slower airflow, the engine is limited at the opposite, intake end, and deprived of its next breath.
Another consideration is the cost-cutting measures manufacturers use to keep end vehicle prices low, meaning compromises in materials and layouts. Most production cars leave assembly lines with crush-bent mild steel exhaust systems, snaking through recesses in unnecessary bends. This has a huge say in overall durability, especially when the piping faces higher temperatures and pressure during higher engine loads. The material is prone to deformation, further hindering airflow and engine performance, as well as corrosion, puncturing and leakage from impact with road obstacles, debris and moisture. All rob the car and engine of potential power.
Why Choose a Performance Exhaust?
Aftermarket systems sourced from reputed builders address the numerous issues in factory piping. Choose engineered performance exhaust systems tailored to your vehicle and engine, and enjoy multiple benefits:
- Increased power and torque: Performance exhausts go with wider and straighter pipe and component configurations, increasing airflow efficiency, with gases leaving the tips faster. This results in lower backpressure (the resistance gases face when exiting the engine), improved power and torque with higher exhaust velocities (the speed gases leave the car), and more efficient scavenging (pulsating pressure waves that draw spent gases from the combustion chamber). Real-world benefits are engines more responsive to throttle input, with faster acceleration and more pulling power from low revs.
- Durability: High-grade stainless steel systems provide the basics for increased pipe strength and durability. These deploy modern shaping methods, such as mandrel bending for consistent widths along the entire piping, and reduce instances of metal fatigue. The material and production methods ensure performance exhausts last in spirited driving without succumbing to staining, thinning walls or punctures. Moving up to higher-end options such as nickel alloys, titanium and carbon-fibre further improves strength, while also shedding considerable weight, especially when compared to mild steel. All material options also perform much better against moisture, resisting rust buildup and corrosion.
- Personalised sound: A key difference in aftermarket exhaust is optioning mufflers, resonators and components in less restrictive designs. These parts do two things: increase airflow and change sound characteristics as spent gases move through the piping. Freer airflow produces louder, deeper exhaust sound, with volumes dependent on engine loads. Proprietary systems can also tailor the exhaust note by combining technologies like valving and different muffler and resonator combinations.
- Customisation: Performance exhaust systems are essentially modular designs, with separate parts either welded together or connected with flanges and gaskets to ensure a tight, leak-free fit. This allows a large degree of customisation, for instance, choosing revised headers for improved scavenging, extractors and downpipes for improved turbo spooling (in cars with forced induction), cat-less systems for track use, wider mid-pipes for optimised airflow, and parts to tune the sound.
- Reduced weight: High-end materials increase strength while cutting down weight. For full systems, such as dual header-back exhausts mated to larger 6 and 8-cylinder engines, the weight savings can exceed 20 kilos or more. A significant number if you’re looking for faster track times, or want to save on fuel.
Key Buying Considerations
Exhaust layouts, materials, widths and vehicle compatibility are the main buying considerations. Choose more affordable axle-back systems with new parts from the rear axle to the tips for improved sound and higher durability; cat-back and diesel-specific DPF-back systems with wider and straighter mid-pipes for reduced backpressure and tangible power increases; or header and turbo-back systems that rip out all factory parts and replace them with performance components from the engine exhaust or turbo manifold to the tips. These produce the highest power gains and are essential components in detailed tuning stages.
Heat, impact and corrosion-resistant 304 stainless steel is the baseline for extreme tunes and engine modifications. Exhausts in this material withstand extreme heat and pressure in bigger burns. A slightly cheaper, though less durable alternative is 409 stainless steel, often in mid-pipes and tail-pipes. Exotics like Inconel 625 are used in headers, and carbon fibre is common in tips for unique looks and superior strength. Materials can be used in separate components or in the whole system, and to a large degree affect the end price.
Lastly, consider going wider than the factory piping to reap all the benefits. Performance exhausts tend to go half an inch wider, with common widths and pipe diameters between 2.5″ and 3.5″ for most vehicles. Widths are dependent on engine layouts, cylinder count and fuel types, and whether you’re adding new piping to aspirated or turbocharged engines. Exhaust builders have pre-assembled configurations for specific car makes and models, making purchases, compatibility and installation simpler.