What Is A Cat-Back Exhaust And Is It Worth Adding To A HEMI Engine?

Installing an aftermarket exhaust kit is an easy and cost-effective way to enhance the performance and sound of any HEMI engine. Mopar fans have two choices: Cat-back and axle-back. A cat-back exhaust refers to all the exhaust outlets from the back of the vehicle's catalytic converters, hence the "cat-back" name. It comprises larger diameter piping, mid-pipes, freer-flowing mufflers, tailpipes, and exhaust tips.

The benefits are a louder, more aggressive exhaust bark, reduced backpressure, more horsepower, and less weight. Cat-back exhausts are more expensive with their plethora of parts, but they have the potential to improve on-track performance with a simple bolt-on installation.

On the other hand, an axle-back exhaust refers to all the exhaust components after the rear axle and consists of mufflers, tailpipes, and exhaust tips. Unlike cat-back exhaust kits that could yield significant power gains, axle-backs are for improving the flow and exhaust sound with little to no improvements in horsepower. However, axle-back exhausts would enable your muscle car or truck to bark louder than stock.

Combined with other go-fast mods like a cold air intake, a ported intake manifold, and a pedal controller, a cat-back exhaust could deliver a 15 to 20-horsepower boost while making your ride sound more muscular when starting, idling or revving your HEMI V8 motor.

Depending on the application, most cat-back exhausts will delete the restrictive stock resonator and replace it with an X or H pipe to deliver better flow. Opening up the exhaust flow yields a better sound, but adhering to local noise regulations is critical when considering a HEMI exhaust upgrade. The cat-back and axle-back won't affect your HEMI's emissions, since all the mods would still incorporate the stock catalytic converters.

Unleashing more power and performance from your HEMI truck or muscle car is possible by combining cat-back exhausts with higher-flow catalytic converters and an aftermarket intake manifold. Doing so unleashes 30 to 35 more horsepower if done right, but you'll need to spend more.

For reference, a stainless steel cat-back exhaust kit for a 2008 to 2014 Dodge Challenger with a 5.4L, 6.1L, or 6.4L HEMI V8 starts at around $1,700, while a set of headers with high-flow cats and mid-pipes adds $2,200 to the bill.