Performance Exhaust Components Guide
While to a layman, a sports exhaust doesn’t seem complex, it’s actually a lot more complex than you would think.
Unlike many other performance car parts, sports exhausts do not have any moving parts, so from the aspect of mechanics, they are simpler in nature than other performance parts, but there is a precision to quality sports exhausts which can mean the difference between a standard exhaust and a performance exhaust system.
There are many types of exhaust systems available, for pretty much every make and model out there.
The basic function of an exhaust system is easy to understand, it touches into parallels found within nature on many levels. The purpose of an exhaust system is, put quite simply, to expel waste gasses from the engine.
But expelling gasses from the engine is not the only function of a performance exhaust system, they serve other important roles as well. They reduce noise emitted, improve fuel consumption and improve engine performance.
This guide is to help you in understanding the different aspects of a sports exhaust system parts and their function.
TURBO DOWN PIPES
On a turbo charged engine, the exhaust system part which arguably serves the most important function in a performance exhaust system, is located directly after the turbine outlet, it’s called the down pipe.
On most standard cars, the down pipe is restrictive and results in the turbo responding slower, holding back it’s power. A turbo charger is essentially a pump, it’s crucial for the pipes flowing in and out of the turbo to have unrestricted airflow.
Reducing this gas restriction allows for the turbocharger to spool up much faster., resulting in more power and being more economical.
BENDS
This component of exhaust systems can be considered a bit of an art. It should come as no surprise that gas will flow faster through a straight pipe than it would through bends. But as the chassis varies between each sports car make and model, this isn’t always possible and usually bends are inevitable.
Bends need to be as smooth and subtle as possible, and for cars which require a system with lots of mandrel bends, it is recommended to compensate for this with a larger bore than usual.
Each bend causes a restriction in the flow of gas, so to get the highest performance out of an exhaust system, any unnecessary bends should be avoided.
PIPE DIAMETER
The exhaust pipe diameter is an important component of any sports exhaust system. Calculating the correct diameter is a balancing act. An exhaust pipe which diameter is too small will not allow enough gas to escape. But this isn’t to say that smaller diameters are worse, as there are actually benefits of exhaust pipes with smaller diameters, which allows for faster gas speeds.
Smaller diameter pipes helps to reduce what is known as the ‘scavenging’ effect, which is when gas pulses when leaving the exhaust pipe. But too small of a pipe reduces overall performance.
So there is a sweet spot when it comes to exhaust pipe diameter.
The science behind this sweet spot is along the lines of…
- The mass of air which the engine sucks in + the mass of fuel = the mass of exhaust gases
- The volume of air that the engine sucks in is calculated by multiplying the displacement of the engine by the engine’s RPM, divided by 2. The volume is then converted into mass.
- Once you have calculated the mass of the exhaust puipe, you can easily figure out how much mass that would occupy (whilst adjusting for high temperature expansion)
MANIFOLDS
The manifold is an exhaust system component which serves a very important function. You could think of it as being the lungs of an engine, it inhales the gases from the engine during the combustion process, passing them through to the tailpipe, allowing for oxygen to make its way into each cylinder.
The manifold also ‘scavenges’ gas from the cylinders. While the force of the pressure inside the cylinder is strong enough to push out most gas, the final remnants of gas are sucked out by the sucking power of the manifold.
In a naturally aspirated engine, a good manifold is essential for high power output. On turbocharged engines, a good free-flowing manifold is not as important as the pressurized inlet air also effectively forces exhaust gas from the engine. So you can still get very high power output using a very basic manifold on a turbocharged engine.
MUFFLERS
Unsilenced exhausts are loud and cause a stir, you simply can’t go without a muffler. Driving around on Australian roads without a silenced exhaust will land you in trouble with Police and trying to register your spots car at the track without a silencer will be next to impossible.
Turbocharged sports cars are already very quiet, so it doesn’t take too much to silence them. You can generally get away with installing a single silencer. Naturally aspirated and supercharged engines are very loud and take a lot more to silence.
EXHAUST MATERIALS
There are only a few types of materials used for performance exhaust systems, these are steel, stainless steel, titanium and nickel alloys.
By far the most commonly used material in exhausts is steel. Carbon steel is far cheaper than stainless steel and you will find this to be the standard material for exhausts in most stock vehicles. Stainless steel is more expensive and offers much higher quality, most performance exhaust systems are made from stainless steel, it’s still relatively economical, doesn’t rust and has a much longer life span.
Titanium is also used in exhausts. It is incredibly light in weight, but can oxidize at higher temperatures, for this reason, Titanium needs to be welded in a non reactive gas atmosphere.
The most expensive material used in exhausts are nickel alloys. They are created to be substantially more resistant to corrosion and strength, withstanding much higher temperatures. These properties make it more suitable for very high demanding vehicles such touring cars Formula 1, etc.
EXHAUST COATINGS
This exhaust system component helps in keeping heat inside the exhaust. The hotter the gas inside the exhaust, the faster it moves, so concentrating this heat adds extra performance to the vehicle and allows the turbo to spool quicker.
TAIL PIPES
Tail pipes don’t actually increase a vehicles performance, they are purely an aesthetic upgrade. They are easy to install and give a nice boost to your vehicle image. They also change the noise produced by your exhaust, there are many shapes, sizes and variations, also making producing slightly different tones.
CATALYTIC CONVERTERS
A catalytic converter is a part within the exhaust system which converts harmful compounds into less harmful compounds. The three harmful compounds being; hydrocarbons, carbon monoxide and nitrogen oxides. This helps in converting carbon monoxide to carbon dioxide, hydrocarbons into carbon dioxide and water and nitrogen into oxygen.
While most vehicles have quite restrictive catalytic converters, sports cars are equipped with catalytic converters with much wider honeycomb cells, allowing for more gas flow than is standard.
