Changing the exhaust system on your Mustang is not only a matter of improving the car’s performance but also a very personal decision for owners. Exhaust impacts how your car sounds to you in the cabin, and to others as you drive by. Do you want to be intimidating or stealthy? What if you could tune your exhaust as much for the mood you’re in, or as the situation dictates?

With the sixth-generation Mustang, Roush Performance developed an active exhaust system, which is available both on all serialized Roush vehicles, and via Roush Performance dealers. Roush vehicles can be sold by the dealer with a system that is prepped for active exhaust, and install the active system post-sale. Such was the case with our own RS1, Project 5-liter-Eater.

We decided to see what all the hype behind the active exhaust system is, and how it sounds on a 2015 Mustang EcoBoost. So, we had Roush send us the active exhaust package for our project car.

New Technology

Since Roush becomes the manufacturer of record, it is responsible for cars meeting all Federal standards, including those for noise. To avoid any potential challenges in having its cars continue to meet these noise standards, or even coming close to violating them, Roush chose to offer the active exhaust system as an after-purchase install.

Installation begins by removing the inner exhaust tips on both sides. These tips simply unbolt from the muffler. If the Roush block-off plates are still installed, those will be removed as well. With the tip removed, the small section of pipe that the tip attaches to can also be removed. The mechanical actuator and butterfly valve will install in place of the original small piece of pipe, and the tip will go back on over that. The actuator motor will go on top; it will take some finessing to get it into position and the muffler hangers may even need to be loosened or dropped to get things fully in place.

This is more than a switch, or a button on the dash, the Roush active exhaust system is actually a smart system. “This is a new patented technology developed in-house by Roush,” says Roush’s Justin Schroeder. Schroeder says the focus of the system is to allow for customization at the user level.

“The Roush exhaust is a modular system, allowing owners to customize it in multiple ways. Owners can remove the plates from the mufflers and run the system fully open, or install the Roush active exhaust components and use our active exhaust control system,” says Schroeder.

Going Active

The active system, (PN 421926) is comprised of a few key components. A bolt-on electronic actuator takes the place of the block-off plate on each muffler. That actuator contains a butterfly valve and a control motor. There’s also a control module, switch, and WiFi dongle.

Like many other Roush components, the entire package is designed to have OEM level fit and finish. Roush uses existing holes, hardware, and cavities within the Mustang to route the wiring harness for the system. The install is almost 100 percent plug and play with the exception of modifying the center console for the control switch.

The harness for the active control system is routed through the car from the trunk to the front. Top Row Left: There is an existing plug in the spare wheelwell that is easily removed to route the harness through. Center Right and Right: After removing the trim from the trunk, this hole located in the driver side of the bulkhead between the rear seat and trunk is used to insert the clip-nut and install the control module. Bottom Row Left: The rear seat bottom needs to be removed as does the driver's side quarter-panel interior trim. Left Side: The harness is routed through this existing passage beneath the driver's front door sill.

“We developed this system from the start to be an upgrade that an enthusiast could install on their own or have installed by a dealer or shop after purchasing the car and the parts,” says Schroeder. “Roush engineers spent a great deal of time packaging the components so that they fit without the need to drill, cut,or splice into the car.”

Bringing The Noise — Or Not

The beauty of this system is that it is 100 percent user controllable in terms of sound level and tone. The console-mounted switch contains four modes:

• Touring: The quietest setting, the butterfly valve is completely closed on the muffler directing all exhaust through the baffles for nearly stock volume and tone.
• Sport: Baffles remain open at idle allowing for some rumble, then run through an opening and closing cycle to give the system a quiet nature while cruising town and an open sound on the highway or under hard acceleration.
• Race: This setting keeps the butterfly open at all times. The system is wide-open and is the loudest in this mode.
• Custom: Owners can use the Roush application on their iOS device to custom tune sound profiles based on vehicle speed and throttle input. The system can open in varying percentages as set by the owner.

Left: The Roush Active control system gets power from an existing source located in the fuse panel. Roush outlines which fuse to pull and tap into for this source in the instructions. Center Left: The final piece of wiring is to route the harness for the control switch into the console and modify a connector there. Again, Roush provides detailed instructions on exactly how to do this. Center Right: Even using the supplied template, drilling holes in the console cover is a bit nerve wracking. Patience is a virtue here, and this is the only cutting, drilling, or modifying that's not plug and play in the entire installation. Far Right: The switch installed on our console, the control knob is held in position using an Allen head screw.

Future Updates

Roush is constantly working to refine and further develop its active exhaust technology. As updates are released the Roush app is updated via the Apple App Store. All currently installed Roush systems will be compatible with any updates. “If we release an update six months from now, all Roush vehicles with this system will be able to utilize the features of that update,” Schroeder says.

On the street and the track we’ve had some fun playing with our Roush active exhaust system. The app has allowed us to tailor a custom profile we use for autocross to keep our car within acceptable noise regulations while still maximizing performance.

Unless you're on the ground looking for the parts, the finished product is very stealthy, looking like just another quad-tip exhaust. Pictured left is the final product with the butterfly open, and right is the butterfly closed.

Driving around town, we sometimes flip the switch to race mode just so we can get a few blank stares from unsuspecting brand X owners, especially other four-cylinder models. Coming in to the house late in the evening, or leaving early in the morning, touring mode lets us get through the neighborhood, and in or out of the garage without waking the kids, or drawing unwanted attention.

We’ve been quite pleased with our Roush active exhaust system, and for an upgrade that takes just over an hour to install, we have to say the technology, as well as the fitment of the parts is superb. We’re looking forward to seeing how it sounds as we perform further upgrades on our car.