Upgrading your car? Start with basic power modifications. These are bolt-on parts, like cold air intakes and exhaust systems. They let the engine breathe better. Improved airflow and combustion efficiency bring multiple benefits. Expect increased power, low-end torque, snappier throttle response, and an engine that’s willing to rev. Pair these with essential extras like ECU tunes. Together, they set the groundwork for more serious engine upgrades.
Limitations of Factory Exhausts
Cars are produced to meet price points and strict noise and emissions standards. Exhausts are where most cost-cutting occurs, mainly because piping is out of sight and adequate for engine power. Problems arise when those few extra horses from fuelling or timing changes high-pressure injectors, new cams, or turbo boosts. These changes push more combusted gases out of the manifold and increase heat. Here, the crush-bent mild steel used in most production vehicles begins to toil. This starts as oxidation and rust, then progresses to metal fatigue, discolouration, and thinning pipe walls. The result is punctures and leaks, which reduce engine power.
Another shortfall is design complexity. Exhaust tubing is pushed through multiple bends and tight spaces, effectively slowing gases as they make their way out of the car. This produces several problems – increased backpressure in the piping that ultimately prevents subsequent combustion cycles (and effectively power to push the piston and turn the cranks) and excessive heat in key components such as exhaust valves and catalytic converters. In turbocharged engines, restrictive pipe designs impact turbo spooling, resulting in noticeable turbo lag.
What Aftermarket Systems Get Right
Simple design changes and the use of better materials go a long way. Straighter, wider piping throughout the length of a car performance exhaust range deals with factory airflow issues and reduces backpressure. And the mandrel-bent stainless steel sorts the metal fatigue, rust and tensile strength of inferior and thin-walled mild steel. Combined, these bring several benefits:
- Increased power and low-end torque: Gases freely exiting the engine and exhaust piping result in higher combustion efficiency. This translates to faster and cleaner combustion cycles with tangible power and torque increases. Real-world benefits are the snappier throttle for faster acceleration and overtaking, more low-end torque for towing and hauling and an engine that freely spins to higher redlines. Power gains vary depending on components and configurations, with figures ranging between 5 and 10 per cent of rated engine power in full systems.
- Improved durability: The use of high-tensile strength materials such as stainless steel, nickel alloys and carbon fibre allows for higher heat cycling and vastly improved impact resistance. The piping holds its own against potholes, rocks and other obstacles, and fares better against road debris, mud and water with higher corrosion resistance.
- Customisable sound profiles: Since performance exhausts are modular designs, parts can be purposely mixed and matched. If you’re tired of exhaust drone creeping into the cabin, want more character than the lacklustre sound most production exhausts, consider muffler and resonator combos and proprietary technology such as muffler valving. These vary exhaust volume and speed as gases exit the car to produce an exhaust ranging from whisper-quiet for street use to a full-bodied roar with additional straight piping and more fun on the track.
- Aesthetics: Rusted, punctured and faded pipes and tips are an eyesore. A well-appointed car performance exhaust goes with heat-treated, brushed or polished finishes that do double duty of boosting both durability and looks. Experimenting with tip layouts, shapes and finishes also provides more visual appeal.
Key Upgrade Paths
One of the reasons basic upgrades such as aftermarket exhausts, cold air intakes, brakes or alloy wheels are so common is affordability. Motorists don’t have to spend thousands to see real benefits. For exhausts, this can mean simple and effective axle-back systems to sort out the sound and prevent leaks in harsher driving environments. Or the addition of exhaust separates, such as high-flow cats and straight-tube mufflers, when tuning cars for the track.
Most drivers opt for cat-back or diesel-specific DPF systems, with wider mid-pipes and changes to muffler and resonator layouts for added power. The configuration eases built-up backpressure, helps reduce intake temperatures and balances performance and price. It won’t require any serious ECU remapping, so it keeps prices down.
If power is your main priority, consider header-back systems, aspirated engines and turbo-back systems in engines with forced induction. Here, revised headers and extractors draw more spent gases out of the manifold (known as exhaust scavenging), ensuring the engine can start the next combustion cycle. Remaining parts are often the same as those in cat-back and axle-back systems, but there’s also the choice of going with more efficient catalytic converters and DPFs, or splitting piping into X or H-pipe layouts to get more torque and power at specific engine loads. With completely new piping from the manifold to the tips, this is the most expensive configuration, but it provides all the benefits and is a must-have if you’re also considering upgrading the engine internals or bolting on bigger turbos.
