The job of an exhaust system is to move burnt air-fuel mixture out of the engine. But that’s not where it’s work ends. An exhaust system is also responsible to clean this emission and reduce unnecessary noise generated. This system also affects your cars overall performance so it actually matters how well designed it is. Keep reading to learn how the exhaust system works and why is it necessary.
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Parts Of An Exhaust System
As is the norm, we need to see what parts are used in an exhaust system before we can look into how they work.
The job of an exhaust manifold is to collect the exhaust gases and kite them into one single pipe. It is the first part of an exhaust system and is connected directly to the engine.
Two sensors are employed one after the manifold and another after the catalytic convertor. Their job is to sense the level of oxygen in the exhaust gas.
These serve as a connection to different parts of the exhaust system and are often designed keeping high pressure in mind.
The part after the exhaust manifold, its job is to remove harmful gases from the exhaust like NOx and CO.
Not present in all cars, the resonator is right after the catalytic converter. It is employed to reduce noise over a certain frequency.
As you might already know silencer is used to reduce noise. It is different than a resonator as it works for a wider range of sounds.
Its the endpoint of the exhaust system. It throws the exhaust gases out of the car.
Working Of An Exhaust System
After the 4th cycle of a combustion engine, exhaust gases are produced. The exhaust manifold is connected to the engine and is made in such a way that it has pipes going in all cylinder. It has only one output. The manifold collects all the exhaust gases from different chambers at the same time and push them through a single pipe. The opening and closing of the exhaust manifold are controlled by a poppet valve.
After the exhaust gases are collected they go through the catalytic converter through pipings. Stock pipings are made in such a way that they can cut the cost of the car so they have unnecessary tapers that affect the pressure of exhaust gas and can cause back pressure which leads to performance reduction. We will discuss this after we finish ‘working of the exhaust system’.
Oxygen sensors are used to check the amount of oxygen in the exhaust gas. Too much oxygen means the car is not using enough fuel and less oxygen means too much fuel is being used. This data is transferred to the TCU and it changes the fuel delivery accordingly.
The catalytic converter is a complex system that uses chemistry to reduce harmful NOx and CO into simple harmless gases. It breaks down the gases using two methods, reduction and oxidation. Reduction occurs when a NOx particle comes through the catalyst. The converter reduces the NOx particle into N and O which are both harmless. Thus its called reduction. Oxidation occurs when CO particle comes through. The catalyst adds another O in CO thus making it CO2 which is harmless compared to CO. In this way, the catalytic converter cleans the exhaust gases.
Another oxygen sensor is present after the catalytic converter for the same purpose. It ensures the gases leaving the catalytic convertor are indeed CO2 and O. If it finds otherwise it informs the ECU that there might be a fault in the catalytic converter.
Resonator albeit not used in all cars is employed because they can reduce some noise from the driving experience which can get irritating. It mainly cuts on noises like the droning sound by introducing the same frequency sound but in an opposite wavelength. This cancels out the frequency and removes the noise.
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Mufflers on the other hand are present in all cars. They are used to remove a wide variety of noises by absorbing as much as possible.
The exhaust system ends at the tailpipe whose entire job is to throw the air out of the car.
As we said earlier, correct pipe design is necessary as it can help increase or decrease the car performance lets see how.
Pipe Design Matters
This can be explained using basic physics. If there is a taper in the pipe there will be a pressure build-up. This buildup will not be cleared because of the taper and thus will force the exhaust gas to go backwards. This backwards movement known as the backpressure will go back into the cylinder and act as an opposing force to the piston movement. This reduces performance.
If you were to make the pipes too big there won’t be enough pressure to move the exhaust gas forward so they will start hanging around in the pipe and will only move when another batch of exhaust gas pushes them forward.
Another possible fix could be to remove tapers but removing them can result in exhaust gases going out not from the exhaust port but the intake port again reducing performance. Thus tapers need to be made so as to be as less opposing to the exhaust gas movement as possible while ensuring they don’t enter the intake manifold.
This covers the exhaust system. It is a necessary part of a car and its designing cannot be random and needs to be perfectly made to get the most performance.
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