Motorcycle Exhausts 101: What You Need to Know

Your motorcycle's exhaust system is more than just a way to channel fumes away from the rider. It affects engine performance, noise control, and even the overall look of your bike. While all motorcycles come fitted with an exhaust system, most riders usually install aftermarket motorcycle exhaust for various reasons.

This guide will cover everything you need to know about motorcycle exhausts. Whether you are a new rider who wants to understand how motorcycle exhaust systems work or an experienced rider wondering whether to upgrade to aftermarket exhausts, this guide is for you. Read on to learn more.

How does a motorcycle exhaust work

The primary function of the exhaust system is to channel away the hot, burned gasses produced by the engine combustion process. These harmful gasses need to be expelled efficiently for the engine to run smoothly and avoid overheating. The exhaust system also muffles the loud noises from the engine's explosions. It does this through a series of chambers and passages that help dampen the sound waves before they exit the tailpipe.

Moreover, a good exhaust system will improve engine performance by helping to regulate exhaust flow. That said, how does it really work? The exhaust system comprises several components that enable it to function well. Here is a breakdown of these parts and their functions.

Exhaust headers

Motorcycle exhaust headers, also called pipe headers, enable the engine to push out exhaust gases and minimize back pressure. They connect directly to the engine block and collect the hot exhaust gases from each engine cylinder into a single channel.

Pipe headers are made of heat-resistant material and can be configured in various ways depending on the engine layout (e.g., 4-into-1 or 4-into-2). The length and diameter of the header pipes can be strategically designed to utilize the pressure pulses from combustion to improve scavenging (drawing fresh air into the cylinders) and overall engine performance.

Exhaust collector

In multi-cylinder engines, the individual header pipes converge into a larger chamber called the collector. This combines the exhaust flow from all cylinders into a single stream. The main function of an exhaust collector is to receive gases from the header and help convert toxic gasses into lower emissions to some extent.

Catalytic converter

The catalytic converter is situated within the exhaust collector. Its purpose is to reduce harmful emissions by converting pollutants like hydrocarbons, nitrogen oxides, and carbon monoxide into less toxic gases like carbon dioxide, nitrogen, and water vapor through a series of chemical reactions.

A catalytic converter is essential for motorcycles to meet EPA emission standards. While the EPA doesn't specifically require motorcycles to have one, like motor vehicles, the easiest way to meet this requirement is to have one. However, some bikes, especially classic ones, do not have catalytic converters.

Oxygen sensor (Lambda sensor)

The oxygen sensor is located in the collector, and its job is to monitor the oxygen content in the exhaust gases. What usually happens is the sensor generates a voltage signal based on the oxygen level. A high voltage indicates a lean fuel mixture (too much air), while a low voltage indicates a rich mixture (too much fuel). It provides crucial feedback to the engine control unit (ECU) to adjust the air-fuel mixture for optimal performance and emission control.

Butterfly valve

The butterfly valve is located behind the silencer and regulates backpressure (the resistance the exhaust encounters as it exits the engine). Adjusting the backpressure of the valve can influence performance and noise control. However, not all exhaust systems have a butterfly valve.

Muffler (Silencer)

The silencer is the workhorse of noise reduction. It uses a series of baffles and chambers to dampen sound waves. The design of these chambers and baffles can vary, affecting noise reduction and exhaust flow. You can add a DB killer to the muffler to reduce noise further.

Tailpipe

This is the final point where exhaust gases exit the motorcycle. The tip can influence both sound and appearance. Some tips are simple openings; others may have specific designs to enhance sound or style.

Types of motorcycle exhausts

There are many types of motorcycle exhausts available on the market, making it easy for beginner riders to get confused when shopping. However, motorcycle exhausts are generally categorized based on installation method or by the number of pipes.

By installation method

Stock exhaust

Stock exhaust is the most basic type of motorcycle exhaust available. This exhaust system comes pre-installed on your motorcycle from the factory or manufacturer. It is cheaper and prioritizes noise reduction and meeting emission standards. Because of the lower price tag, they only balance performance and legal requirements. However, the performance is enough for most riders, especially those on a budget.

Aftermarket exhaust

If you find stock exhausts too basic, consider upgrading to aftermarket exhausts. These are designed to replace the stock system and can offer a variety of benefits depending on the specific design, including:

• Increased power: Some aftermarket exhausts can improve horsepower and performance by reducing backpressure and allowing for better exhaust flow.
• Weight reduction: Certain aftermarket exhausts are made from lightweight materials like titanium, reducing the motorcycle's overall weight.
• Enhanced sound: Many riders enjoy a throatier exhaust note. Aftermarket exhausts can deliver a louder or more desirable sound. However, check noise regulations in your area before purchasing.
• Custom look: Aftermarket exhausts come in more styles and materials than stock options. This is important if you want to personalize the appearance of your motorcycle.

When shopping for aftermarket exhausts, you will likely encounter two different types: slip-on or full exhaust systems.

Slip-on exhaust

This type of exhaust replaces only the muffler section of the stock system. It is relatively easy to install and cheaper but offers only a milder performance or sound improvement.

Full exhaust system

This replaces the entire exhaust system, from the header pipes to the muffler and tip. Full exhaust systems offer the most significant performance gains but involve more complex installation because some may require adjustments to the fuel delivery system. Generally, the bike will gain higher performance, reduced weight, and better sound.

By number of pipes

The pipes are for the main exhaust body, not including the header pipes.

Single exhaust pipe

This setup has one main exhaust pipe running from the collector (in multi-cylinder engines) or directly from the header pipe (in single-cylinder engines) to the muffler and exhaust tip. This design is simpler and cheaper and still performs well on smaller engines. However, it's too basic compared to dual exhaust and offers limited performance gains.

Dual exhaust

This setup features two separate exhaust pipes, each with its own muffler and tip. It's often seen on larger motorcycles and cruisers and can add a more aggressive look and sound.

Maintaining your motorcycle exhaust system

Regular maintenance is crucial to keeping your exhaust system functioning correctly. Here are a few tips for maintaining your motorcycle exhaust system:

• Regularly inspect the exhaust system for leaks, cracks, or loose parts. Damaged exhausts can affect performance and pose safety risks.
• Clean the exhaust system periodically to prevent rust and corrosion buildup. Follow the manufacturer's recommendations for cleaning products and methods.
• Stick to your manufacturer's recommended maintenance schedule to ensure your exhaust system operates at its best.

Conclusion

A well-functioning exhaust system is vital for a smooth, enjoyable ride. It not only controls noise and emissions but also contributes to your motorcycle's performance. When you buy the right exhaust systems and follow proper maintenance practices, your bike will run clean, sound good, and perform at its peak. Remember, safety is paramount. Always be mindful of hot exhaust fumes and avoid touching the exhaust system when the engine is hot.

That said, you can't enjoy the rider's life if you don't have your own motorcycle. A motorcycle loan could help you buy your dream bike if you don't have the cash to pay for it outright.