How does a car exhaust system work?

By Juliet Onyeachonam
Publish on May 17, 2019

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In a car exhaust system, the catalytic converter converts harmful gases produced during combustion in a car engine to gases which are less harmful both to man and atmosphere. A car exhaust system also takes care of high sounding sound waves which are also harmful to man and the environment. If you are looking for information on how exhaust system works, stay with to find out how.

1. Overview of car exhaust system

When a car is in operation, small explosions in form of combustion happen in the engine. As power is produced to run the car, so are harmful gases also produced in the process. These potentially harmful gases need to be routed away from the engine and out into the atmosphere so they are not inhaled by passengers.

Modern day car exhaust systems do not just route harmful gases into the atmosphere because it could have an adverse effect on the environment and other people outside the vehicle. It is therefore fitted with modern technology that converts these harmful gases into harmless ones.

Also, the engine combustion produces high sound waves that are also harmful to humans and constitute a nuisance. Modern day exhaust systems have components to cater for all these issues.

Below are basic functions of a car exhaust system:

  • To minimize noise pollution by controlling the noise emanating from the vehicle
  •  To prevent the exhaust gases from harming the passengers by directing it away from the vehicle
  •  To improve engine performance
  •  To improve fuel economy of the vehicle


Badly maintained car exhaust systems will do great harm to the environment

In understanding how car exhaust system works, depending on a couple factors such as vehicle manufacturer, the number of engine valves and vehicle model, the configuration and schematics of the exhaust system may differ from vehicle to vehicle. However, all exhaust systems use the same principle to direct exhaust fumes from the point of formation (engine) to the point of expulsion (exhaust pipe).

The following gases are produced for emissions in every vehicle; they are harmful and pose a health risk to passengers and must therefore be expelled properly.

  • Carbon monoxide
  • Nitrogen oxide
  • Nitrogen monoxide

2. How car exhaust system works  

To answer the question of how does a car exhaust system work, hot gases along with sound waves are generated at the exhaust stroke and sent to the exhaust manifold through the exhaust valve. The exhaust manifold is metallic, usually made up of cast iron. It is the link between the engine and the rest of the exhaust system.
The exhaust manifold collects the exhaust gases in the engine cylinder head where it is produced. Acting as a funnel, the exhaust manifold separates the exhaust gases and prevents them from re-entering engine cylinders. It directs the gases to the front pipe.

Modern exhaust systems are fitted with an oxygen sensor in the exhaust manifold that measures the amount of oxygen in the harmful gases. In an ideal situation, there is supposed to be no oxygen but this is not the case. The engine would attempt to use the right amount of oxygen to burn the fuel in order to negate the possibility of leftover oxygen in the waste gases. In modern fuel-injected vehicles, the engine control unit reads the oxygen amounts in the waste gases and optimizes the fuel - oxygen mixture in the engine by injecting more fuel to balance out.


This is the schematic of a car exhaust system

These gases and sound waves then enter the catalytic converter. Due to partial combustion, gases entering the catalytic converter include carbon monoxide, nitrogen oxides and unburned hydrocarbons. All these gases have adverse effect on the humans and the environment.

>>> Don't ever underestimate the role of a catalytic converter! Check here 6 symptoms of a bad catalytic converter you can check easily

Meanwhile, the catalytic converters is made up of a two block honeycomb structure made up of platinum and rhodium in one block and platinum and palladium in the other block. These metals serve as catalyst for conversion. The nitrogen oxides is broken down by the catalyst into nitrogen and oxygen respectively. The carbon monoxide reacts with oxygen molecules in the second block and forms carbon dioxide. The unburned hydrocarbons react with oxygen to form water and carbon dioxide.

This converter cleans up the harmful gases into inert gases such as carbon dioxide, nitrogen and water.

The gases and sound waves are then transported into a silencer. Like the name suggests, it serves as a noise reducing mechanism in vehicle exhaust system.
When a car has a damaged silencer, that’s when you notice the increase in noise levels. The silencer has tubes of different sizes placed strategically within it that fine tune and cancel out sound waves, giving a noise canceling effect.

The loudest sound waves go into the resonator. Here the sound waves bounce off the walls of the resonator generating opposite waves of the same frequency. Additionally, sound absorbing materials are packed within the silencer to reduce excessive noise.
This enables the waves to cancel each other out. Excessive noise have been linked to a number of health implications such as heart problems.

Any damage to the structure of the silencer will lead to corrosion. This would disrupt the movement of sound waves through the tubes therefore preventing the noise cancelling effect. This leads to increase in noise.

After leaving the silencer, the exhaust fumes finally gets emitted through the tail pipe located at the rear of the vehicle where exhaust gases have no chance of entering the passenger compartment. Therefore, less harmful gases and low sound waves are released into the atmosphere at this point bringing the process of how exhaust system works to an end.

The component of the exhaust system are connected using clamps, hangers, flanges and caskets.

>>> Read more tips for Safe driving and Car maintenance on!

Juliet Onyeachonam

Juliet Onyeachonam is an enthusiastic car nut which is why she has turned that passion into a fantastic job by becoming a car blogger on Juliet's blogs are a wealthy resource for information on car maintenance, driving tips and also how things pertaining to cars work.

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