How to Install a Cat-Back Exhaust on a 2015-2023 Mustang
"Step-by-Step Directions for Installing Cat-Back Kits Whether You've Got Active Exhaust or Not"Last Updated December 19, 2022 | Hamilton Schutt
Cat-back exhaust kits improve your Mustang's performance, appearance, and sound all in one go. That probably explains why nearly half of our S550 customers choose cat-backs over other exhaust mods.
If you're considering buying a cat-back kit for your 2015-2023 Mustang, or you're on the fence about installing it yourself, we've got good news. Installing a cat-back exhaust is straightforward and simple. There's no need to spend $300 to have a shop do it for you.
Check out our video and step-by-step instructions below to learn how to install a cat-back exhaust kit on your S550 Mustang. We detail the processes for S550's with or without Active Exhaust. Click on whichever type of exhaust you have below to jump to the correct install.
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Before You Get Started
Before you begin your cat-back installation, read through some commonly asked questions about the process:
- Should you replace the hangers? If your exhaust is hanging lower than normal or the tips look uneven, pick up a new set of hanger insulators. Worn-out hangers put stress on the exhaust pipes which could lead to cracks. This might end up costing you power and acceleration capabilities if the fumes are escaping before they get used.
- Can you add Active Exhaust if your Mustang didn't come with it from the factory? Ford's Active Exhaust feature is very popular, and adding it through aftermarket mods is an option. However, most kits that add active exhaust are axle-backs instead of cat-backs, so the power gains will be limited.
- What is the best way to lift your Mustang for a cat-back exhaust install? While having a lift would make your exhaust swap much easier, it isn't a necessity. Backing your Mustang up onto a set of ramps and chocking the front wheels gives you plenty of room to work. You could also use a jack and jack stands to lift your S550, but you'll have less room underneath the car.
Install Instructions: Cat-Back Exhaust without Active Exhaust
For this installation, we used the Ford Performance Stainless Steel Sport 2-1/2" Cat-Back Exhaust System with Chrome Tips. This system is a direct-fit replacement, so the install process shown should be the same for any aftermarket kit. Expect an installation time of around one hour.
- ⅜” Ratchet
- 13 mm Deep Socket
- 15 mm Deep Socket
- 6” Extension
- Safety Glasses
Step 1: Free Mid-Pipe Clamps
Unscrew the bolts on the two clamps holding the mid-pipe to the catalytic converter pipes. Then, slide the clamps towards the resonator.
If the clamps won't budge, you may need to pull the retention tabs out a little to allow them to move easier.
Step 2: Remove Factory Tailpipe Hanger Bolts
Remove the bolts holding the tailpipe hangers in place on the hanger bracket.
Step 3: Pull Factory Exhaust Out
Disconnect the mid-pipe from the catalytic converter by pulling the exhaust towards the rear of the car. Then, push the exhaust forward until the muffler hanger arms come out of the factory hangers.
We recommend finding a friend to help you with this step as the factory exhaust weighs around 70 pounds.
Step 4: Retrieve Factory Clamps and Hangers
Collect the mid-pipe clamps and main hangers from the factory exhaust system. Now is the time to switch the hangers if you plan to replace them.
Step 5: Install New Mid-Pipe
Slide the factory clamps onto the new mid-pipe and insert the mid-pipe into the cat pipes.
Step 6: Tighten Mid-Pipe Clamps
Position the clamp where the tailpipe and mid-pipe overlap. Tighten the bolts, but not all the way yet.
Step 7: Reinstall Factory Hangers
Press the hangers onto the hanger arms on the tailpipes. Be sure the hooks on the hangers are facing towards the body of the car. If they're facing towards the exhaust tips, they won't be able to hang on the exhaust hanger bracket.
Step 8: Install Tailpipe
Add a clamp to the end of the tailpipe that connects to the mid-pipe. Then, slide the tailpipe into the mid-pipe and hook the hanger onto the slot in the exhaust hanger bracket.
Repeat this step for the other tailpipe.
Note: If you're using the same kit as we are, the tailpipes will be labeled as Left and Right for your convenience.
Step 9: Reinstall Hanger Bolts
Reinstall the factory hanger bolts to secure the main hangers in place.
Step 10: Tighten Tailpipe Clamps
Position the clamp where the tailpipe and mid-pipe overlap. Tighten the bolts a bit, but not all the way yet.
Step 11: Position Muffler
Add a clamp to the muffler. Then, press the muffler hanger arm into the hanger that is still connected to the body of your Mustang. Make sure you position the muffler so the exhaust tips sit level.
Step 12: Secure Muffler
Feed the tailpipe into the muffler pipe and position the clamp where the two pipes overlap. Check again to make sure the tip is level. If it is, you're ready to tighten the clamp.
Step 13: Repeat Process on Other Side
Repeat Steps 8-12 on the opposite side.
Step 14: Tighten All Clamps and Bolts
Tighten down the loose clamps and hardware. Once everything is secure, you should be good to hit the road and sample your new exhaust note.
Install Instructions: Cat-Back Exhaust with Active Exhaust
We chose to go with the Borla Stainless Steel Cat-Back Exhaust System with Black Tips for our install. This kit is a direct-fit design, so the process should be pretty straightforward. Give yourself around three hours to complete the swap from start to finish.
- ¼” Ratchet
- ⅜” Ratchet
- 10 mm Socket
- 13 mm Socket
- 15 mm Socket
- 10 mm Wrench
- Flathead Screwdriver
- Panel Removal Tool
Step 1: Disconnect the Battery
Be sure to disconnect the battery before you start the installation. You'll be unplugging a couple of wiring harnesses and you don't want to get shocked in the process.
Step 2: Disconnect Active Exhaust Motors
Pop the active exhaust harnesses' pegs out of the brackets. Then, find the white tabs on the plugs at the top of the exhaust tips. Push the white tabs down and pull the plug to disconnect the harnesses.
Step 3: Remove Rear Hangers
Remove the two bolts holding the hangers in place and remove the hangers from the exhaust hanger bracket.
Step 4: Loosen Clamps
Loosen the bolts on each of the 2 clamps holding the cat pipes to the resonator. Then, slide the clamps back towards the resonator.
Step 5: Remove Exhaust System
We recommend doing this step with a friend so the pipes don't fall to the ground and get damaged.
Separate the resonator from the cat pipes while your extra pair of hands is holding up the tailpipes. Push the whole system forward towards the front of the car until the pipes drop out of place. Once you have the exhaust free from the car, set it safely aside.
You could technically do this step with a pole jack instead of a friend. But, in the words of resident Mustang expert Bill Tumas, "it wasn't pretty and I would not recommend it."
Pro Tip: If the tubes are refusing to budge, take a mallet to the clamps and hit them towards the resonator until the exhaust shakes loose.
Step 6: Retrieve Factory Exhaust Motors
Locate the active exhaust door motors situated above the exhaust tips. Then, remove the motor retention nuts. Pull the exhaust motors out of place and set them aside.
Step 7: Remove Factory Hangers
Using a hanger removal tool, remove the factory hangers from the stock exhaust and set them aside.
Step 8: Remove Factory Clamps
Pull the clamps that connect to the cat pipes off of the factory exhaust and set them aside.
Step 9: Reinstall Factory Clamps
Slide the factory clamps back onto the cat pipes.
Step 10: Install Mid-Pipe
Slide the new mid-pipe into the cat pipes and position the factory clamps on the pipe overlap. Then, tighten the clamps to secure the mid-pipe in place.
Note: Our kit included adapters to connect the aftermarket mid-pipe to the factory catalytic converter. If your kit has an adapter, be sure to use the manufacturer's instructions for proper installation.
Step 11: Prep First Tailpipe Assembly
Install the hanger onto the tailpipe hanger arm. Make sure the hook at the top of the hanger is facing the front of the car. Then, attach a clamp to the end of the tailpipe that will attach to the mid-pipe.
Step 12: Install First Tailpipe Assembly
Hook the hanger into the slot on the exhaust hanger bracket and slide the tailpipe onto the mid-pipe. Lightly tighten the clamp attached in the previous step to secure the tailpipe to the mid-pipe.
Step 13: Install Factory Active Exhaust Motor
Position the active exhaust motor's spring into the two slots on the valve located in the exhaust tip. Just make sure the door's in the open position (it should automatically open when the power from the battery is cut).
If you're unsure of whether the motor is seated, test it! With the motor installed, reach into the tailpipe and try to move the door open and closed by hand. If you feel resistance and the door is difficult to move, the motor is good to go. If the door moves freely and has no resistance, the motor is probably not in place.
Note: If you don't properly seat the motor, you'll get a check engine light and the exhaust door will not open.
Step 14: Tighten Down Factory Motor
Secure the seated motor with two of the original nuts on the bolts opposite the hanger arm. Before you thread the final nut, set the bracket for the harness on the remaining bolt. Then, thread the final nut in place and tighten it down.
Step 15: Install Muffler Assembly
Add a clamp to the muffler assembly and slide the muffler hanger arm into the rear hanger. Next, insert the muffler's pipe into the tailpipe, position the clamp at the overlap, and tighten the clamp.
Step 16: Reinstall Hanger Bolt
Thread the hanger bolt back into the hanger and tighten it down.
Step 17: Reconnect Wiring Harness
Fish the harness up to the top of the muffler and plug the motor back in. Then, clip the harness' peg into the bracket that we installed in Step 14 to keep the wires safe and out of the way.
Step 18: Install Second Side's Piping
Repeat Steps 11-17 on the remaining side.
Step 19: Tighten Up Remaining Nuts
Now is the time to hit each nut again to make sure your new exhaust system is secure and ready to go. It wouldn't hurt to revisit the clamps that were already tightened to ensure nothing is loose or hanging.
A Sound Improvement
With your installation complete, you should notice a difference in the sound emanating from your exhaust as soon as you hit the ignition. If you have active exhaust, switch through the different modes to be sure the motors are in place.
This article was researched, written, edited, and reviewed following the steps outlined in our editorial process. Learn more about CJ's editorial standards and guidelines.
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