Louder exhausts can sometimes increase engine power. Pictured: Polestar exhaust on a Volvo XC60.
Modifying your exhaust system to increase engine performance isn’t always straightforward.
De-catting your vehicle (illegal here in Singapore) or swopping the stock system for a louder exhaust is easy to do.
Your car may sound nicer (this is subjective, by the way), but louder exhausts don’t necessarily translate into more power.
Now, before we dive into this exhaust-ing topic…
What do exhaust systems do?
An exhaust system is responsible for extracting the gases that come from combustion.
The catalytic converters in the exhaust “clean” most of the harmful particles and emissions.
The O2 or oxygen sensors measure the amount of oxygen in the exhaust gases.
The date is then sent to the ECU (engine control unit) to fine tune the throttle and fuel injection to maintain optimum fuel efficiency.
The remaining exhaust gases are then sent into the muffler, which reduces the sound volume.
Finally, they exit the system via the tailpipes.
Okay, so how do louder exhausts create more power?
Louder exhausts are noisier than stock units because they are tuned to make “nicer” sounds.
They also have lower backpressure.
What is backpressure?
We all know that the natural movement of gas is from high-pressure to low-pressure.
The pressure in the engine cylinders or combustion chambers is higher than the pressure in the exhaust system.
However, exhaust systems have backpressure, or resistance.
These can be caused by too many turns, so the exhaust gases have to travel further before they can exit.
These turns also slow down the velocity of the gases.
Here’s an analogy. Imagine breathing in through your nose, but having to breathe out through a tube attached to your mouth.
If that tube had twists, turns and a filter (in a car, this would be the catalytic converter) to pass through, you’d need more effort to breathe out!
So louder exhausts + lower backpressure = more power?
In theory and on paper, yes.
However, swopping to the widest diameter exhaust pipe won’t enhance power, unless you’ve got a really powerful engine.
An exhaust pipe still needs to be narrow enough to enhance exhaust gas velocity.
Louder exhausts that are too wide for your make and model cannot increase gas velocity.
If you want to reap the benefits, our suggestion is to take your car to a qualified tuner/workshop.
They will be able to advise you on the right modifications and perhaps even tune your engine to complement the new system.
Beware of mods that claim to be an “aftermarket exhaust”.
There are many aftermarket louder exhausts that are just slip-on systems.
This means only the muffler and exhaust tip are replaced by “slipping them on”.
They can make a car sound louder, but depending on the brand/model, a slip-on system may not improve performance as much as a full exhaust system.
Especially if the headers and mid-pipes are still a bit narrow.
A full exhaust system, on the other hand, consists of many more components, which should include headers and a mid-pipe.
Performance exhaust systems, which can be made from titanium, are often lighter than stock units.
This means in addition to producing more power, you can reduce your car’s weight, too.
