Home > Vehicle Safety > How Does an Exhaust System Work?

How Does an Exhaust System Work?

By: Kevin Watson MSc - Updated: 7 Aug 2013 | comments*Discuss
Exhaust System Tail Pipe Muffler

After combusting its mixture of fuel and air, an engine creates power, heat and exhaust. This exhaust is dangerous. It can poison and kill. An exhaust system draws the noxious gases from an engine, passes them through a series of units, and expels the gases from the vehicle.

Other Functions

An exhaust system has two other functions.

1. An engine discharges unused fuel. An exhaust system converts this into a spent and less toxic substance.

2. Engines can be noisy. An exhaust system helps to reduce this noise.


An exhaust system has an exhaust valve, a manifold, a flange, a catalytic converter, a muffler, system hangers, a heat shield, sensors, and various pipes.

Exhaust Valve

The exhaust valve is in the engine. It opens to release the exhaust gases created when the fuel/air mixture combusts.


The gases come from more than one source in the engine. This is because every engine cylinder releases exhaust. All these exhaust gases go into the manifold.

The manifold is therefore the device that collects the engine’s exhaust. It then transfers the exhaust to the first of the system’s pipes. The exhaust flange is the connection between the manifold and the pipe.

Catalytic Converter

The catalytic converter is the next part of the exhaust system. It plays a vital role in controlling emissions.

The catalyst element of the converter is a chemical. This heats up and burns any unspent fuel in the exhaust.

It’s worth noting that some catalytic converters are part of the exhaust manifold. Also, vehicles may have more than one catalytic converter to further reduce pollution.


After passing through a catalytic converter, the exhaust continues down another pipe. This takes the exhaust to the muffler.

The aim of the muffler is to reduce noise. A performance muffler, however, will create the gravelly sound associated with a sports car.

In a standard muffler, there are barriers. These reflect the noise of the engine back on itself. A muffler may also have packing material that quietens the noise.

Tail Pipe

After passing through a muffler, exhaust leaves a vehicle through a tail pipe.

The tail pipe is the most visible part of an exhaust system. A vehicle may have one or more tail pipes depending on the model.

System Hangers

In a car, the exhaust system runs from the engine at the front of the vehicle to the very back. The pipes, catalytic converter and muffler hang below the car’s floor. System hangers made of rubber and stretched between hooks hold the system in place. The rubber reduces noise and prevents friction with the rest of the vehicle.

Heat Shield

The steel or metal alloy of an exhaust system becomes very hot. A heat shield therefore runs beneath a vehicle between the system and the floor.

The heat shield is particularly important around the catalytic converter. This is the part of the system that can reach the highest temperature.


An exhaust system has oxygen sensors for fuel management. The main sensor may be in the manifold. Another sensor may be along the pipe that links the catalytic converter to the muffler.

The sensors monitor exhaust gas and send information to the computer that runs the engine’s control system.

You might also like...
Share Your Story, Join the Discussion or Seek Advice..
Why not be the first to leave a comment for discussion, ask for advice or share your story...

If you'd like to ask a question one of our experts (workload permitting) or a helpful reader hopefully can help you... We also love comments and interesting stories

(never shown)
(never shown)
(never shown)
(never shown)
Enter word:
Latest Comments