Making the Right Performance Exhaust Upgrade: Cat-Back vs. Axle-Back Exhausts

Date Posted: 12 August 2024

If you are thinking of an exhaust upgrade for your vehicle, the choice between a cat-back vs. axle-back system is one of the most common ones. Yes, both options offer distinct advantages, but they also serve different purposes and vary in complexity.

This guide is meant to help you understand what each system entails, how they work, and which might be the best fit for your needs. Whether you're looking for performance enhancements or simply a new exhaust sound, this comparison will provide the insights you need to make an informed choice. In that context, let’s first explain what cat-backs and axle-backs are.

What Is a Cat-Back Exhaust System?

A cat-back exhaust is a special type of exhaust that goes from the catalytic converter to the rear of the vehicle. It typically includes the mid-pipe, muffler, and tailpipe; that’s where the term ‘cat-back’ comes from - the fact that this system replaces all the components ‘back’ of the catalytic converter. This also means that cat-back exhaust upgrades are fully legal as the cat converter has not been replaced.

The mid-pipe connects directly to the catalytic converter and runs towards the rear of the vehicle, leading into the muffler, which is responsible for reducing the noise produced by the engine's exhaust gases. Finally, the tailpipe directs the exhaust gases out of the vehicle, often finishing with a stylish exhaust tip.

How Does It Work?

An image of all of the parts of a cat-back exhaust.

A cat-back exhaust system works by optimising the flow of exhaust gases from the engine (as we mentioned, starting just after the catalytic converter). When your engine burns fuel, it produces exhaust gases that need to be expelled efficiently to maintain performance and reduce emissions. The catalytic converter first treats these gases to minimise harmful pollutants.

After the catalytic converter, the gases enter the mid-pipe of the cat-back system. The mid-pipe, which is often wider in diameter in a cat-back than stock pipes, allows for a smoother and quicker flow of exhaust gases. This reduced backpressure improves engine efficiency, giving you more horsepower and torque.

Then, the gases pass through the muffler - the muffler is designed to minimise sound without overly restricting the flow. Performance-oriented mufflers in cat-back systems often use straight-through designs or fewer baffles, allowing gases to exit more freely while still controlling noise levels.

Finally, the exhaust gases are expelled through the tailpipe. The entire system is structured to reduce resistance and maintain a steady flow, which can result in improved throttle response and a more aggressive exhaust note.

What Is an Axle-Back Exhaust System?

An axle-back exhaust system is the portion of the exhaust system that begins just behind the rear axle and extends to the tailpipe. This type of system typically includes the muffler and the exhaust tips, and sometimes a small section of piping - almost always, less than a cat-back upgrade.

The name ‘axle-back’ comes from the fact that this system replaces all components of the exhaust system ‘back’ of the rear axle. The muffler in an axle-back system is designed to manage the sound levels of the exhaust gases, while the exhaust tips are often styled for a more customised appearance.

The piping in an axle-back system is usually similar in diameter to stock, focusing more on sound and appearance than on altering exhaust flow significantly. The structure of an axle-back exhaust system is simpler compared to other types of exhaust systems, including cat-backs, as it only affects the rear section of the vehicle's exhaust pathway.

How Does It Work?

The muffler in an axle-back system is crucial for controlling the sound of the exhaust. By using different internal designs, like chambers, baffles, or straight-through configurations, it modifies how sound waves from the engine are managed before being released. This can result in a more aggressive exhaust note or a deeper tone, depending on the design.

However, since the axle-back system primarily focuses on the muffler and tailpipe, it doesn't significantly change the exhaust flow or backpressure, unlike the cat-back (or turbo-back setups). The modified muffler can slightly alter the exhaust flow characteristics, which might have a minor impact on engine performance, though the effect is generally less than with other exhaust upgrades.

Overall, when comparing cat-back vs. axle-back systems, the axle-back system functions by enhancing the sound and appearance of the vehicle’s exhaust without making major changes to the exhaust flow dynamics or the engine’s performance characteristics, so this is mostly a performance upgrade for a louder exhaust sound.

The Pros and Cons of Cat-Back vs. Axle-Back Upgrades

When you are choosing between a cat-back vs. axle-back upgrade, think about what you want to get. Cat-back systems improve the exhaust flow, resulting in increased horsepower and torque. They also provide a more aggressive sound, plus, they can enhance fuel efficiency. However, they are more expensive and complex to install than axle-back systems.

Axle-back systems, on the other hand, are more affordable and easier to install, making them a great choice if you are primarily seeking an upgrade in exhaust sound and appearance. However, they offer minimal performance improvements compared to cat-back systems.

Cat-Back vs. Axle-Back Simplified

Cat-Back	Axle-Back
Significant performance upgrades	Minimal performance upgrades
Significant exhaust sound upgrades	Significant exhaust sound upgrades
Can be costly	Cheaper than cat-back upgrades
Somewhat complex to install	Easy to install

DIY vs. Professional Installation

A mechanic checking the undercarriage wondering about the pros and cons of cat-back vs. axle-back exhausts.

When deciding between DIY and professional installation for exhaust upgrades, consider your skill level and the complexity of the system. Axle-back exhausts are generally simpler to install, often requiring basic tools and minimal modifications, making them more than suitable for DIY projects.

Cat-backs are more complex and involve the replacement of more components and, potentially, require cutting or welding. If you don’t have some experience with DIY car projects, professional installation is likely the best course of action to ensure proper fitment and avoid issues like exhaust leaks. That being said, installing a cat-back system by yourself is still more than feasible.

After You’ve Made a Decision Between Cat-Back vs. Axle-Back

We hope this article has helped you make a choice between axle-back vs. cat-back exhaust systems. If it has, the only thing left is to find a place where you can get high-quality exhaust upgrades. At Perfrom-Ex Auto, we have many kinds of standard replacement and performance exhaust you can choose from.

You can also find any other exhaust parts you are looking for, from DPFs to exhaust accessories. Once you’ve found something you like, all you need to do is place your order online and we will ship the parts to your chosen address. And know that all the parts come with a genuine warranty. In case you need any help or wish to consult with experts before you make a purchase, please contact us and we will respond as soon as possible.