How the Exhaust System Works

How the Exhaust System Works

Your internal combustion engine is a source of exhaust gases that contain lots of harmful byproducts of burning fuel. Besides, it is extremely loud and can make your driving the worst experience you have ever had if the sound it produces is not managed. This is when and where your exhaust system comes into play. It does a couple of essential jobs at the same time, cutting the loud sound of your engine and reducing the amount of harmful byproducts in the exhaust gases, while routing them out of the engine and the vehicle.

The exhaust system is what makes your driving comfortable and free from an extremely loud sound and poisonous fumes inside the cabin. It starts doing its job as soon as exhaust gases leave the cylinders, gathering them together into one pipe with the help of the exhaust manifold and routing them to the rear end of the vehicle through an arrangement of pipes and other exhaust system components. While the gases are transferred through the exhaust system, it works hard to reduce the amount of harmful byproducts and to make your vehicle sound quieter.

An exhaust system of a modern vehicle consists of several essential components, each of which does its piece of job to give you a safe and pleasurable driving experience. A typical basic set of exhaust system parts and components includes an exhaust manifold, a catalytic converter, a resonator, a muffler and a tailpipe. Let’s describe them one by one.


A muffler is a cylindrical box placed underneath the rear end of a vehicle. It is connected to the rest of the exhaust system via an exhaust pipe and can be of a weld-on or bolt-on type. Usually made of steel or, rarely, stainless steel, it comes with internal tunes, baffles or another insulator that is used to cut the exhaust sound.

While at first sign a muffler may seem to be a simple cylinder with tubes or passages inside, its engineers should have spent a lot of time to create an ideal muffler for a specific vehicle that meets several important criteria and performs its job properly. It must be able to absorb sound waves produced by the engine of a specific vehicle, while still allowing for the best exhaust gas flow to keep the engine running safely and efficiently. At the same time, it must allow the engine to sound as nice as possible.


The main job of a resonator is to cancel or to absorb sound waves before they enter a muffler. It is placed somewhere between a catalytic converter and a muffler and features a straight-through design with either an insulator or perforated walls. As a general rule, it is smaller than a muffler, yet does a major part of the job when it comes to reducing exhaust sound. Working in tandem with a muffler, they make a vehicle run quieter without sacrificing its performance.

Catalytic converter

Also known as a cat, a catalytic converter is the most expensive part of an exhaust system because of precious metals such as platinum, palladium and rhodium that it contains. The presence of these metals is required to perform a chemical reaction, which allows for turning nitrogen oxides, carbon monoxide and hydrocarbons into less harmful to the environment and human gases. Before and after a catalytic converter, there is an oxygen sensor, each of which analyzes exhaust gases and sends signals to the engine control unit to make it aware of catalytic converter operation.

A catalytic converter can reach extreme temperatures during engine operation, which is why you should avoid any contacts with the catalytic converter as well as other exhaust system parts when the engine is running and some time after it has been shut down. 

Exhaust systems in sports cars

If you have ever heard the sound of a sports car, you might notice that it sounds more aggressively than a regular car at high RPM, while being relatively quiet when idling. This happens thanks to a special type of exhaust systems, called active exhaust systems. The main feature of such exhaust systems is a computer-operated or vacuum-operated valve placed before a muffler. When the engine is idling, the valve is closed allowing all exhaust gases to flow through the muffler. However, once the accelerator is depressed, the valve opens, allowing some exhaust gases to escape from the gap that appears. This makes the vehicle sound more sporty and aggressively. At the same time vehicle emissions are not affected since a muffler doesn’t take part in any chemical reactions.

Exhaust manifold

An exhaust manifold meets the top of an engine, connecting directly to its cylinder head with bolts. It features individual tubes or passages for each cylinder on one end and a collector on the other one where it is connected to the rest of the exhaust system. As a rule, it is made from durable steel to withstand high temperatures and pressure caused by exhaust gases.


Depending on the design of your vehicle, you may have either one or two tailpipes. The tailpipe is connected to the muffler with a clamp or welding, directing exhaust gases away from the exhaust system. It is the final piece of the system, so you can see the end of the tailpipe in the rear of the vehicle.

Other exhaust system parts and components

Different flanges, flexible joints, metal-to-metal joints and gaskets are no less important than the rest of the exhaust system. They keep main exhaust system components together, while preventing exhaust gas leaks. These exhaust system parts are also secured to the vehicle with the help of flexible, yet durable hangers. They allow for some movements of exhaust system components when you’re driving over bumps and other road imperfections.

Exhaust system troubleshooting

The majority of exhaust system parts and components are maintenance-free, which means there are no periodic inspections unless the other is mentioned in your owner’s manual.

The most common exhaust system failures are a rusted muffler or resonator, loose clamps, worn-out gaskets, and damaged mounting flanges or hangers. If any of them happens, we recommend you to use factory replacements or aftermarket parts of the same quality. Cheap low-quality replacements may lead to a premature failure of other exhaust system parts and components. Besides, factory replacements are usually covered with the manufacturer’s warranty.

While some exhaust system replacements and repairs can be done by just about any driver, more complex tasks may involve lots of labor, a specific knowledge and special equipment. If so, we recommend you to leave such jobs to a professional.