Blog

Cat-Back vs Axle-Back Exhaust: What Actually Fits

Apexsupplydirects writes these notes from the workshop floor, so the advice you get here comes from parts we have actually fitted, measured and returned. Nothing below is theory pulled off a spec sheet. If a torque figure or a wear limit looks wrong for your car, ring us and we will check it against the manual before you spend a cent.

Ask the team All articles
Cat-back and axle-back get spoken about as if they are interchangeable. They aren't, and the difference matters more for a daily driver stuck in traffic than for a weekend car that only sees open road. An axle-back replaces the rear muffler and tailpipe only. It's cheaper and faster to fit, and because the factory centre section stays, you get a slightly deeper note without much change in volume at cruise. The compromise is that the factory pipe diameter remains. If the car left the line with a restrictive centre section, an axle-back won't fix that flow restriction however good the muffler is. A cat-back replaces everything from the catalytic converter back, including the resonator and rear muffler. That lets you choose the pipe diameter, which is where the real decisions live. On a 2.0-litre turbo, 2.5 inches is usually right. Go bigger and the exhaust pulses slow down at low revs, so you lose torque exactly where you spend the day. An NA V8 moves more gas, and there 3 inches starts to make sense. Pipe size should come from the engine, not from a forum post written by someone with a different cam. Drone is the part most people underestimate. A cheap system with no resonator sounds great for the first week, then becomes tiresome at 2,300 rpm on the motorway. A centre resonator costs a little more and cuts that band without touching the top-end note. Before you commit, ask for recordings on the same engine and pipe size. If a seller can't produce that, they are guessing about what will land in your driveway. We keep three recorded samples of the engines we see most often, and the car goes back on the ground for a clearance check before you take the keys.
Daniel Mercer

Daniel Mercer

Workshop lead at Apexsupplydirects. Fifteen years under everything from a Corolla to a LandCruiser, and still happy to crawl under a car on a Saturday.

Spotted something in this article that does not match your car? Email apexsupplydirects@gmail.com with the model, year and engine code. We will check the part number and tell you straight whether it fits.

Keep reading

More from the workshop

Two more articles that cover the questions we get asked most often on the phone.

Brake pads inspected on a workshop bench

Brakes, 6 min read

How to tell your brake pads are done

Squeal, grind or a soft pedal each point at a different fault. Here is how to work out which one you have before you book anything.

Read the article
Coilover suspension being adjusted

Suspension, 8 min read

Coilover setup without the guesswork

Ride height, preload and damping all pull against each other. We explain what each adjuster actually does and the order to change them in.

Read the article

Stuck on a part number?

Send us the model, year and engine code and we will come back with the right fitment, the price and how long it takes to land in Brisbane.

Send an enquiry Back to the blog