Cat Back Exhaust Systems

A cat back exhaust system replaces everything behind the catalytic converter, from the cat to the tip. The converter itself is not touched, which is what separates a cat back from the systems that start further forward. It is a common first exhaust upgrade and is usually fitted without a tune.

Cat back, axle back or turbo back

These three names describe how much of the exhaust gets replaced.

An axle back is the smallest change, replacing only the section behind the rear axle. It alters the note and the tips without touching the middle of the car.

A cat back replaces the mid and rear sections together, everything from the catalytic converter back, so it changes more pipework and gives a bigger change in tone than an axle back. On a diesel the same idea is a particulate filter back system, which starts behind the particulate filter and leaves everything forward of it in place.

A turbo back goes further forward again. It starts at the turbo outlet and takes in the down pipe and the catalytic converter, so it is the only one of the three that replaces emissions hardware. Those systems are in the full exhaust range rather than on this page.

If you want a note change on an otherwise standard car, cat back is usually the right level.

Fixed or valved

A standard cat back gives one note, set by the muffler and pipe design. A valved system gives you two, with a valve in the rear muffler that opens for a louder note and closes for something far closer to stock, switched from a key fob. An optional controller adds app control over Bluetooth for finer adjustment. Valved systems suit a car that does daily duty and needs to leave home quietly.

Race versions are the loudest option in this range and are worth reading carefully before ordering.

Construction

Systems here are stainless steel, most commonly 304 grade, with some of the older fitments built in 409. Pipework is mandrel bent, which keeps the internal diameter consistent through the bends rather than pinching at each corner. Finishes vary by system, from raw through brushed to polished, and tip options include polished, gloss black, gold and burnt blue.

Fitment

Subaru has the deepest coverage by a wide margin, followed by Volkswagen, then Toyota and Hyundai. Audi, BMW, Cupra, Chevrolet, Kia and Lexus are also covered, among others. Systems are built for a specific chassis and often a specific body style, so a sedan and a wagon of the same model can take different parts. Check the code on the listing against your car before ordering.

Where this sits in the range

This page covers cat back systems only. Turbo back systems, particulate filter back systems for diesels, headers, down pipes, dump pipes and tips sit in the full exhaust range. If you are shopping by brand, the Xforce range is collected in one place.

FAQ

What does a cat back exhaust system include? Everything behind the catalytic converter, which usually means the mid pipe, any resonator, the rear muffler and the tips. The exact contents are listed on each product page.

What is the difference between cat back and axle back? An axle back replaces only the section behind the rear axle. A cat back replaces that plus the mid section, starting at the catalytic converter, so it changes more pipework and gives a bigger change in tone.

Does a cat back system remove the catalytic converter? No. A cat back starts behind the converter and leaves it in place. Systems that replace or remove emissions hardware sit further forward and are listed separately.

Will it be too loud for daily driving? That depends on the system. A fixed system has one note, so read the description before ordering, and note that Race versions are the loudest here. A valved system can be quietened from the driver seat.

Do I need a tune? A cat back on its own does not usually require one, because it sits behind the catalytic converter and the oxygen sensors the engine fuels from. Changes that start at the turbo often do.

Is an aftermarket exhaust legal in Australia? Noise and emissions requirements are set by each state and territory and depend on the vehicle and the system fitted. Check what applies where you drive before fitting, and tell your insurer about any change to the exhaust. We are not able to confirm compliance for your vehicle.