In the aftermarket world of Mustang performance parts, one of our favorite bolt-on components to upgrade to right off the bat is the exhaust system, and for good reason. Upgrading an exhaust system on a Mustang brings the sound and the grunt of a musclecar, and provides us with a few additional ponies in the process.

But with the Mustang market being saturated with endless exhaust system options, where does one even start when considering an exhaust upgrade? Fear not, as we hit up our friends at X-Force Exhaust USA out of Rancho Cucamonga, California, for what many enthusiasts refer to as ‘the last exhaust you’ll ever need to purchase.’

We examine the functionality, construction, and the sound benefits of our X-Force Varex Cat-Back Exhaust System for the 2015 Mustang GT and provide an easy installation process.

What Makes A X-Force Varex Muffler?

While relatively fresh to the U.S. aftermarket performance parts world, X-Force has been around for more than a decade in the Australian market. The company has built a strong following through it’s reputation for quality components with many Ford and GM enthusiasts. In the U.S. market, the company’s bread-and-butter component which is the Varex series exhaust mufflers system, has put X-Force on the map with enthusiasts who are considering a new exhaust system.

What exactly is an X-Force Varex series exhaust? This is a question that Marty Staggs, at X-Force Exhaust USA hears quite a lot. Staggs defines the technology incorporated into the Varex series mufflers, and explains how the system differs from the average aftermarket exhaust.

Staggs says, “The X-Force has basically incorporated two different muffler technologies into a single muffler, utilizing the patented Varxex valve assembly. When the muffler is in the closed position, the exhaust is routed through a conventional baffling type system within the muffler, using channels and packing material. When the muffler is in the open position, the exhaust has a straight path through the muffler which maximizes flow while still having a small amount of ‘muffling’ effect via the perforated core. It is important to note that these mufflers can be operated in many positions. They are not simply closed or open; you can set them to your preference.”

How The Varex Exhaust Works

The company’s Varex series mufflers have become popular with many enthusiasts, and for good reason. The Varex series exhaust system incorporates some particularly beneficial technology that can be quite favorable in everyday driving situations.

The X-Force Varex Cat-Back Exhaust System (PN XF-ES-FM15VMK-CBS) is constructed entirely out of 304 grade stainless steel and features the company’s Varex rear mufflers incorporated into the system. The main feature of this exhaust system is that enthusiasts have the ability to change the sound and the volume of their vehicle’s exhaust system. The Varex series exhaust system is able to achieve this by using an electronic exhaust actuator which controls the position of the electronic butterfly valve’s position inside of the mufflers.

Positioning of the butterfly valve is seamlessly controlled using a wireless remote controlled key fob that is provided with the kit. The kit includes two key fobs; however, if you happen to lose one of them, Staggs says, “If for some reason both are lost, replacement parts are available quite economically.”

The purpose of this exhaust technology is to allow enthusiasts to have an infinite amount of adjustability. Enthusiasts can choose to either open or close the exhaust valve, putting them in control of the amount of volume and the level of sound they want to hear.

Stages illustrates some of the benefits of this technology, and said, “The benefit is that this allows the end user to adjust to their particular preference. Many guys love a loud and aggressive exhaust. However, when they go to work at 5 a.m. (just one example), their neighbors may now particularly appreciate that. You simply press the remote control button and close them off while you tip-toe out of the neighborhood, and then open them up when you get to the highway. The performance benefits shine when they are wide open.”

Unlike electric cutouts which many of us may be accustomed to, the technology incorporated in a Varex muffler uses a wireless remote controlled key fob to adjust the butterfly valves located in the mufflers, which is achieved using an electronic exhaust actuator. Speaking of the actuator, Staggs says, “The actuator can really be in any location. It operates the same no matter where it is. Orienting the muffler with them on top simply makes for a ‘cleaner’ looking installation.”

Install Notes

Installing the new Varex cat-back system was extremely easy and straightforward. Throughout the entire process, we did not need to pry or bend any of the components to ensure fitment. We headed to London Chassis Dyno for the installation of the system.

The mufflers have adjustable hangers which utilize bolt-on polished tips. The hangers ensure the mufflers can be properly centered, which in our experience, was extremely easy to accomplish.

During the installation, we reused the OEM clamps which connect the factory mid-pipe to the factory cat-pipe. Be sure you don’t accidentally destroy them during the disassembly, as they’re a little tough to get open and remove in the first place. A little patience will go a long way with this removal. The new Varex mid-pipe/resonator combo weighs significantly lighter than the OEM components. We think this can be attributed to the new exhaust system’s smaller resonator and overall construction.

First up on the list was to disconnect the battery to prevent any possible electrical issues during the install. Next, we lifted the vehicle using a two-post stationary lift. We started the disassembly by removing the factory clamps which connect the OEM cat-back to the OEM H-pipe. Remember to save these clamps, as we will need to reuse them for the installation of the X-Force cat-back system.

We recommend having a friend to assist you in the removal and the installation process, as the system is quite heavy in weight. Once the clamps have been removed, remove the middle exhaust hangers holding the factory cat-back. Ask them hold the factory cat-back, as the last two hangers are located on the factory rear mufflers.

The easiest way to remove the entire exhaust assembly is to slide the exhaust backwards towards the rear of the car to release it from the OEM H-pipe, then slide the exhaust forward towards the front of the car to release the rear exhaust hangers on the OEM mufflers.

After removing the entire OEM cat-back assembly, make sure to keep both factory rear exhaust hanger brackets as well, as we had to reuse these components. To start the installation, begin by installing the factory cat-back adapters provided by X-Force. Next, reinstall the clamps onto the OEM H-pipe, then slide the new X-Force cat-back into the OEM clamps. Hand tighten the bolts on the clamps to ensure they hold while you install the rest of the exhaust system. Next, install the differential pipes by hand tightening the bolts as well.

Reinstall the factory exhaust hangers onto the differential pipes and ensure the 'hooks' are facing the correct direction. Hand-tighten the clamp here as well, making sure not to fully tighten it for adjustment later. Once the new X-pipe and differential pipes have been installed, install the new Varex mufflers by sliding the provided clamp over the muffler side of the piping. The adjustable hangers that X-Force provides will enable you to adjust the height and get a perfect center before tightening down everything.

Part of the X-Force Varex cat-back system’s charm is that the Varex mufflers are a complete plug-and-play installation. This requires no wiring whatsoever, so installation is a piece of cake here. We recommend installing the included control module in the center console, as this unit requires a 12-volt power source to operate.

• 

We ran the included wiring harness from the Varex muffler, through the rear of the trunk and to the control module. Bolt everything back up into place and let the new exhaust be heard. We recommend trying out the 'Race Mode' first!

Roaring To Life, Or Whispering If Need Be

The system sounds almost identical to stock when the butterfly valves on the actuators are fully closed. However, open the valves fully, and the fun begins. The car sounds mean, deep, and aggressive, like a proper V8 musclecar. With the system closed we couldn’t log a decibel reading above stock.

Opened, and sitting in the driver’s seat, you can tell there’ s lower frequency exhaust tone, but with the windows up the sound level is easily comfortable, and not much above stock. Outside the car however, if the system is open, everyone will know there’s a V8 under the hood.

Many enthusiasts want the performance of a larger diameter exhaust, but do not always want to constant level of sound. This is where the Varex series exhaust system shines. The exhaust allows enthusiasts full control over the volume of their exhaust system at the push of a button, enabling the vehicle to go from loud to quiet in a matter of only seconds.

Staggs gives us a few tips as well saying, “The current consumer market is more supportive of simple-to-install products. This kit is designed with that mentality taken into account. It can also be quite easily hard-wired in for those that wish to go that route — it’s quite simple. It is important to note that we do not recommend dyno pulls or racing with the mufflers in the closed position, simply due to the fact that the engine performance will not be ideal with the exhaust restricted.”

Check out X-Force’s website for a full line of products for your Mustang!