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Exhaust System Parts 101: The Basics (Diagram Included)

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The exhaust system is tucked away underneath your vehicle, out of sight and out of mind, making it easy to ignore. You may not even know which parts make up the exhaust system—but now’s the time to learn.

By becoming acquainted with the various exhaust system components, such as the muffler and catalytic converter, you’ll be more in tune with your car. You’ll also be better prepared to talk to your mechanic or select parts for repair if any problems should arise.

Car Exhaust System Components

Simplified Automotive Exhaust System Diagram showing different components
A typical exhaust system diagram with basic exhaust system parts 

The exhaust system routes exhaust gases away from the engine and out the vehicle’s tailpipe. A typical modern exhaust system contains the following components:

Exhaust Manifold

Exhaust gases leaving the engine first travel through the exhaust manifold. The manifold collects the exhaust gases from the individual ports in the engine’s cylinder head, then routes those gases to the rest of the exhaust system.

Engines with a ‘V’ or flat configuration have two exhaust manifolds (one for each bank of cylinders), whereas inline or straight engines have just one manifold.

exhaust manifold
The exhaust manifold collects the exhaust gases from the individual ports in the engine’s cylinder head, then routes those gases to the rest of the exhaust system.

Catalytic Converter

The catalytic converter is an emissions control device that converts harmful exhaust gases into water, carbon dioxide, and nitrogen. Some catalytic converters are integrated into the exhaust manifold, whereas others are attached to the vehicle’s exhaust pipe. It’s also worth noting that some cars have just one catalytic converter, while others have as many as four.

catalytic converter
The catalytic converter is an emissions control device that converts harmful exhaust gases into water, carbon dioxide, and nitrogen.

Oxygen Sensors

Oxygen sensors measure the amount of oxygen (or the concentration of combustibles) in the exhaust gases leaving the engine.

Modern vehicles have both an upstream and a downstream oxygen sensor. Upstream oxygen sensors are located before the catalytic converter, while downstream sensors are located after the converter. There is typically one upstream and one downstream sensor for each of the vehicle’s catalytic converters.

The engine computer, which is often referred to as the powertrain control module (PCM), uses data from the upstream oxygen sensor to regulate the engine’s fuel mixture. Meanwhile, the PCM primarily uses the signal from the downstream oxygen sensor for monitoring the health of the catalytic converter.

oxygen sensor
Oxygen sensors measure the amount of oxygen (or the concentration of combustibles) in the exhaust gases leaving the engine.

Exhaust Pipes

Various exhaust pipes connect the parts of the exhaust system together. The pipes are often made from aluminized or stainless steel to protect against rust and corrosion.

exhaust pipe
The exhaust pipes are often made from aluminized or stainless steel to protect against rust and corrosion.

Muffler and Resonator

As its name implies, the muffler reduces or “muffles” the noise created by the engine. The exhaust system also has a resonator, which cancels out engine noises of specific frequencies.

muffler and resonator
The muffler reduces or “muffles” the noise created by the engine while the resonator cancels out engine noises of specific frequencies.

Tailpipe

The tailpipe is the final link in the exhaust system—it routes the exhaust gases, which have been cleaned up by the catalytic converter, away from the vehicle and into the atmosphere.

tail pipe
The tailpipe routes the exhaust gases away from the vehicle and into the atmosphere.

Miscellaneous Exhaust System Components (Gaskets, Heat Shields, and Hangers)

Many people forget about the miscellaneous bits and pieces found throughout the exhaust system. For example, there are gaskets that seal the individual exhaust system components to one another.

There are also heat shields that protect the vehicle—and objects directly beneath it—against the heat from the exhaust system. Plus, there are hangers that serve as mounting points for the various exhaust components.

exhaust system heat shield
Many people forget about the miscellaneous bits and pieces found throughout the exhaust system such as the gaskets and heat shields.

Common Exhaust System Problems

Like any part of your vehicle, the exhaust system can eventually have issues. The most common problems include:

Leaks

Over time, the various components found within the exhaust system can develop leaks. An exhaust system leak is a serious problem because it can expose you to deadly carbon monoxide. Furthermore, a leaking exhaust system can cause the oxygen sensors to interpret a false lean condition, potentially leading to engine performance problems and an illuminated check engine light.

Obstruction

Parts of the exhaust system can become obstructed due to impact damage or upstream engine problems. When the system becomes clogged, it creates excessive back pressure, effectively choking the engine. As a result, the vehicle may exhibit problems, such as lack of acceleration, hard starting, and an illuminated check engine light.

Loose Components

The heat shields in an exhaust system can become loose due to impact damage or missing fasteners. When this happens, you’ll likely hear a metallic rattling noise coming from the undercarriage.

Also, the exhaust hangers can become worn, allowing the exhaust system components to move around and cause clunking or banging noises.

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