All About Cat-Back Exhaust Systems

A cat-back exhaust refers to the section of the exhaust system that is downstream of catalytic converters. It is legal to replace everything behind the cats, which are typically located just behind the engine. A cat-back upgrade leaves the emissions equipment untouched, so it won’t trigger a check engine light or affect emissions.

After the exhaust passes through the catalytic converters, the vital work of controlling emissions is done. So, you can configure the cat-back exhaust system to produce the desired sound and flow. Smoother bends, larger-diameter pipes, and less restrictive mufflers can enhance the exhaust flow and make a louder exhaust note.

Most cat-back systems are designed as bolt-on upgrades, making them a relatively simple DIY job for garage mechanics.

What Are the Benefits of a Cat-Back Exhaust?

There are two primary reasons to upgrade with a cat-back system: increased power and enhanced rumble. In nearly all cases, you will gain both, along with better fuel economy. What you want to achieve with the system will help steer you to the right kit.

A Borla Atak cat-back exhaust system for the Chevrolet Camaro ZL1

As an engine runs, it pushes the burned fuel and air charge—the exhaust—through a manifold or header. Each pulse of the exhaust pushes the previous pulse down the line through the pipes. As the gases stack up, you get backpressure. Too much backpressure makes it harder for the engine to breathe.

A cat-back system reduces backpressure and increases exhaust flow, helping the engine breathe more freely. It also enhances what’s known as the scavenging effect—the process where the momentum of exiting exhaust gases creates a low-pressure zone behind each pulse. That vacuum helps draw the next pulse out more efficiently, which in turn allows more fresh air and fuel into the combustion chamber. The better the scavenging, the more power the engine can make. Scavenging is your friend.

In most cases, a cat-back exhaust will make your car louder. It may also change the tone of the exhaust, often to a lower, throaty rumble. It depends on the specific system you buy. Mufflers and resonators come in many variations. Every brand of exhaust has its own tone. We recommend researching a kit’s sound profile before purchasing it.

Is a Cat-Back Exhaust Easy to Install?

Cat-back exhaust systems are one of the easiest exhaust upgrades you can make. They are designed to replace the factory system, using the same routing and locations. Cat-back systems use the same retainers and have the same tailpipe outlet position. (Single-to-dual kits might have an extra pipe.)

Sometimes you need to cut the stock pipe to remove the OE exhaust from the vehicle.

In most cases, there are no modifications to the vehicle. However, some kits require drilling holes or minor cutting. Most cat-back kits can be installed in a single afternoon without special equipment.

To install a cat-back system on some vehicles, you only need to replace a few feet of pipe and mufflers. Older vehicles, as well as most SUVs and trucks, have significantly more pipes to replace. Many high-performance cat-back systems convert a single to a hybrid dual exhaust. Others maintain the factory style.

The installation utilizes band clamps like this to achieve a leak-free seal. These are the best types of clamps for an exhaust system.

The number of catalytic converters on your vehicle varies based on year, make, and model. Here are a few things to consider:

• Most vehicles that are 20 years old or older have one or two catalytic converters.
• Many modern vehicles have multiple cats, as many as six.
• Some vehicles use a single exhaust with one tailpipe.
• Cars with V-6 and V-8 engines typically feature true dual exhaust, which has two separate tailpipes. That means a pair of everything—mufflers, cats, resonators, and pipes.
• If the car has four cats, there will be a second pair a few feet behind the first set.
• There is a hybrid system with a single exhaust system located at the front of the vehicle, which then splits near the rear axle into two pipes, often with separate mufflers, and exits out the back with two tailpipes, giving the appearance of a true dual exhaust.

What Are the Most Popular Exhaust Brands?

The world of custom exhaust is divided into various genres and subgenres. There are universal companies, such as Borla, Flowmaster, Hooker, and Magnaflow, that manufacture kits for all types of vehicles. Then, you have niche brands like GReddy, Invidia, and Megan Racing that focus on Asian and European imports.

A Pypes Pype-Bomb cat-back exhaust kit

The brand matters because the brand’s style determines the sound. Pypes exhaust produces a rowdy muscle car note. Meanwhile, Borla offers a softer, gentler exhaust note but with more rumble than the factory system. Flowmaster has a bit of both. The 40 Series muffler is obnoxiously loud, while the 70 Series is just slightly louder than stock.

A cat-back will wake up your ride, give it more tone, and add some rumble. Nothing puts a smile on your face quite like firing up your engine after you have given it the exhaust note you love.

What Tools Do You Need to Install a Cat-Back Exhaust?

Safety first. Always use a floor jack to raise the vehicle, and jack stands to support any vehicle you get under. Never use cinder blocks, bricks, stacked items, or a jack alone to support a car. Always work on a solid surface.

Tools required for most cat-back systems:

• Floor jack and jack stands
• Ratchet and sockets
• Wrenches
• Dead-blow hammer
• Welder (optional)
• Reciprocating saw or cutting wheel (optional)

Important Considerations

Will a Cat-Back Exhaust Affect Your Car’s Emissions?

The primary purpose of a cat-back exhaust is to ensure that your emissions system remains unaffected. That’s why cat-back exhaust systems are legal. However, exhaust noise regulations vary by state, city, and even by local housing authorities, such as homeowners’ associations. Check federal and local laws regarding exhaust noise.

Does Your Engine Need to Be Tuned After Installation?

Most cat-back systems do not require any tuning; however, having the engine tuned after installing all the performance parts you plan to run will yield the most performance from the new engine setup.

Will a Cat-Back Exhaust Affect My Car’s Resale Value?

It depends. In most cases, a cat-back exhaust won’t hurt the value and may even slightly increase it. How much depends on the kit. If you use a cheap kit, you won’t get much of a bump. But if you install a premium stainless steel or titanium kit, you are likely to increase your vehicle’s resale value.

What Is the Difference Between a Cat-Back and an Axle-Back Exhaust?

While essentially the same thing, an axle-back exhaust strictly replaces the exhaust from behind the rear axle. On the other hand, a cat-back replaces everything behind the catalytic converter.

In most cases, a cat-back is positioned directly behind the catalytic converters. Most axle-back kits, which only replace the mufflers and tailpipes, are designed to enhance sound. Performance gains are typically lower.