Exhausts: Does Louder Equal More Performance?

A loud car can be either exhilarating or annoying, depending on where you’re seated. However, some owners make the mistake of thinking that louder equals more performance.

Merely making an exhaust louder is easy enough, though that should never be your objective unless you want to embarrass yourself and lose the respect of your friends and family. Making your car sound objectively better might be a longer journey, but worth the effort in the end.

If you enjoy cars that make sound, we understand that how cars offered these days are pretty underwhelming in that respect. The bad news is that it’s only going to get worse as internal combustion engines are phased out in favour of electric motors for the majority of new vehicles, be it powered by batteries or a hydrogen fuel cell.

Cars Are Too Quiet?

These days, even cars that aren’t fully or partially electric tend to be pretty silent during normal operation. Unless you put your ear right up to the engine bay, you’re not too likely to hear all that much noise while it's idling. And the same applies to the exhaust pipes.

They might be large and pronounced, dressed in chrome finishers, and even have more exits than the engine has cylinders (such as the Proton X50 Flagship), but barely make their presence known outside of low burble.

This seeming shyness, this aversion to noise, is particularly frustrating for owners of cars that were engineered and promoted as something a little more sporty. It might sit low to the ground and have all the visual trappings of aggression, but none of the auditory presence.

Consequently, some of us look for ways to make our cars louder than they were when rolled out of the factory.

Not Loud And Proud

We’re currently living in a time where nearly all cars feature a variety of measures to make sure the characteristics of combustion engines (i.e explosions) are somehow non-existent on a sensory level.

Modern engines are extremely refined with very little vibration coming into the cabin, are fitted with fat catalytic converters, advanced de-pollution systems, and will even turn off if you’re sat stationary at a traffic light.

Turbochargers, which spin up on hot exhaust gases exiting the combustion chamber, are also prevalent across multiple classes of cars, which allows automakers to downsize engine displacements even more. Despite this having a positive effect on fuel economy, torque and horsepower, it’s a killer for engine noise.

However, even prior to this shift away from natural aspiration, exhaust upgrades were the most popular and most accessible path to a louder car. The main difference here is that, if fitted to a turbocharged engine, they have very little impact on performance.

Sound amplification takes a hit too as there as much of the intensity of the post-combustion air was used to spin those turbines, and that’s before it encounters even more obstructions from the catalytic converter, resonator, and muffler. Imagine trying to talk while blowing into a straw through a cigarette filter. There’s not going to be much noise coming out that other end.

Getting a modern turbocharged car to sound ‘good’ isn’t just about removing the catalytic converter or resonator (which is a legal grey area in Malaysia, but also unsafe) or installing a less restrictive ‘performance’ version of these components.

Other factors such as your exhaust diameter, pathing, length, material and overall resonance will play a role in how your car sounds. Since every car is different, this is why aftermarket exhaust makers (the good ones) spend many hours testing different combinations to balance flow characteristics with acoustic qualities before offering a kit for that specific vehicle. Even then, it’s not guaranteed that the noise they land upon will be to your taste.

Back To The Pressure

You might have heard about the term ‘back pressure’ when researching exhausts. A rough definition would be the measure of air pressure in the exhaust system and how much resistance it takes to discharge (push) into the atmosphere.  

In short, back pressure affects the rate at which the exhaust gases can be expelled into the atmosphere to make room for freshly combusted air to take its place. Sometimes, automakers or aftermarket tuners will deliberately throw in uncombusted petrol so that it'll ignite in your exhaust system for those pops and bangs. You're not driving in a rally car, you don't have anti-lag, and you're probably ruining your engine.

Though it is generally seen as a negative characteristic for an exhaust system to have since it makes it more difficult for the engine to effectively exhale, thereby reducing power. However, it’s particularly detrimental for turbocharged engines since their operational efficiency depends on a large volume of hot gases flowing quickly through its turbine blades, spinning it up and compressing more air into the induction system.

With excess back pressure, the turbocharger will bog down and become ineffective at low engine speeds where air volume is limited, creating ‘turbo lag’. Automakers spend a lot of time and energy designing an exhaust system that creates a minimal amount of back pressure while also complying with emissions standards and noise regulations.

Haphazardly undoing their finely tuned work by fitting a custom exhaust system that lacks the same level of testing and adjusting will likely result in a louder exhaust, but a worse performing vehicle.

You might get away with it on a car with a naturally aspirated engine, but the chances of taking a step backward in output and response with one that’s turbocharged are much higher.