Other than making it sound louder?
In: Technology
An internal combustion engine is basically a fancy air pump.
The amount of fuel put into an engine needs an accompanying amount of air in order to be fully burned, so the amount of ‘power’ a given engine can make is completely dependent on how much air can be sucked in, and then pushed out, and how easily. This is why putting a Supercharger or Turbocharger will usually increase the power of an engine, because it will cram more air into the engine that if it was “naturally asperated”.
This is why a smaller engine that can operate at a high RPM, can make an equivalent amount of power as a big low RPM ‘V8’. It spins faster to pump an equivalent amount of air.
If you address all of the airflow issues of the intake side, then the bottleneck becomes how easily your engine can shove the air out of it’s cylinders once combustion is complete. A dual exhaust, or bigger/high flow aftermarket exhaust will help with the bottleneck.
With that said, **the bottleneck of a given engine is almost always the intake side**, because in a *naturally asperated* engine there is ‘vacuum’ as your pistons try to suck in as much air as they can, whereas exhaust, because it’s already in the engine, has to go **somewhere** once the piston starts pushing it back out of the combustion chamber.
Getting air in is always harder than getting air out. Like blowing up a balloon.
This is why on engines that have an uneven number of valves in a cylinder (Like the Ford ‘Triton’ V8, or some Toyotas had 5 valves per cylinder) there are always more intake valves than exhaust valves. In an engine with 2 valves per cylinder (The most common configuration) the intake valve is almost always bigger than the exhaust valve.
This means that, unless you’ve increased the amount of air that can flow into an engine* **first**, dual exhaust or an aftermarket ‘fart can’ exhaust nets almost zero power gains, and just makes a tonne of extra noise.
*Manufacturers will sometimes release ‘high output’ versions of their engines that can flow more air, and thus need the bigger/dual exhaust.
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