What are Active Exhaust Valves (AEV) in Ford Mustang S550? How do they work?

WHAT IS ACTIVE EXHAUST?

Active valve exhaust systems allow drivers to vary the loudness of their exhaust systems to suit their needs. Ford’s active exhaust system is now available as an option on all 2019 Mustangs, including the EcoBoost.

The Mustang’s active valve exhaust has four settings: Quiet, Normal, Sport, and Track. Quiet is still around 72 decibels, so it’s louder than normal conversation but quiet enough that it’s unlikely to bother your neighbors. On the other hand, Track can get as loud as you would expect a Mustang to be capable of.

WHAT IS QUIET START?

Quiet Mode helps drivers be better neighbors, and it is an incredibly useful feature for Mustang owners that live in neighborhoods or who keep unusual hours. If you have a Mustang that doesn’t have an active exhaust, you can install an aftermarket one to get some of these benefits, though scheduling Quiet Start in advance is a factory-only option.

To access Quiet Start, press the Mustang button on the steering wheel and go to the “MyMode” settings menu. “Exhaust Mode” will be one of the options. From there, select “Quiet Mode” and then turn Quiet Start on. You’ll have the opportunity then to select the start and end times for your Quiet Start. Thanks to the scheduling option, even if you tend to be a little forgetful in the morning you don’t need to worry about forgetting to select Quiet Start.

THE CREATION OF QUIET START

Ford’s active exhaust system has a pretty awful origin story. Steve Von Foerster, who was employed as Ford’s head of engineering, started up his Shelby GT350R and had the police called on him. Neighbors complained that his exhaust was simply “too loud.”

Foerster is certainly in good company; many auto enthusiasts find themselves on the wrong side of the law due to the volume of their vehicles. It’s no secret that big, powerful engines tend to have big powerful roars as well, and though everyone loves the sound when it’s coming from their vehicle, few enjoy being unexpectedly awoken by the noise.

Instead of getting angry, Foerster got innovative and designed the Mustang’s new active exhaust system. By using a variable valve that can be partially open or closed, the active exhaust is able to control the amount of sound a vehicle’s exhaust emits while still ensuring that poisonous gases don’t put a car’s passengers in danger. The valves know how open or closed to be based on mode and throttle input.

Active exhausts have been available for some time, but Ford’s is unique in a few key ways. The exhaust is controlled through buttons on the console, and the mode can be changed easily. The exhaust can even be programmed in advance so that during certain hours it will start up in “Quiet Start.”

Quiet Start has been nicknamed “Good Neighbor Mode” which is both informative in terms of what it’s useful for and also a nod to the development of Quiet Start.

DECIBEL RATINGS

Typically, sounds don’t start to bother people till their decibel rating is in the upper 70s. Quiet Start allows a Mustang to start up at 72 decibels. Once on the highway though, the driver can pick from Normal, Sport, and Track exhaust settings, each with its own deep-throated rumble.

Track mode is the loudest and has been tested at 86 decibels. For those who still want a little extra rumble and want to install aftermarket exhaust parts, that is still an option. As long as the installed aftermarket parts are geared for Mustangs with active exhausts they’ll only increase the decibel rating in Sport and Track modes.

Drivers should be careful; eight hours of 86 decibel sound can cause permanent hearing loss. At 110 decibels, even an hour can cause hearing loss. Many local governments are also becoming more aggressive about ticketing for overly loud exhausts.

MUSTANG EXHAUST SOUND

Sound is about more than just decibel rating though. A live rock concert and a chainsaw have about the same decibel rating, but they definitely don’t have the same sound quality. The nice thing about Ford’s active exhaust is that they worked hard to reach a “note” rather than a particular decibel rating.

What that means for you is that even in its stock form, the exhaust sounds the way Mustang enthusiasts expect it to sound. It’s less chainsaw, more rock concert.

Of course, aftermarket parts can be added to alter the sound if it’s not quite the way you prefer. Whether you’re a Roush or a MagnaFlow fan, as more Mustangs are available with these options, more companies will rise to the challenge of making parts that are compatible with them.

AFTERMARKET ACTIVE EXHAUST SYSTEMS

If you want an active exhaust system but don’t want to buy a new Mustang, there are a lot of aftermarket active valve exhaust systems available. Some even opt for these choices over the factory options because they offer customization options that are beyond the scope of what Ford offers.

Roush offers an upgraded active exhaust option that allows for customized configuration of multiple sound profiles through an IOS app. Though there are four pre-programmed options, users are free to use the app to create different exhaust tone configurations to suit their exhaust sound needs. It’s essentially like getting active valve exhaust and a massive exhaust upgrade at the same time.

For those with simpler tastes or who are just trying to get nosy neighbors off of their backs Roush also offers a more minimal active exhaust addition that allows you to easily toggle your exhaust valves between open and closed based on how much noise you want to make. This is still a great exhaust upgrade, and for people who prefer to just let their exhaust notes rumble out unaltered, it’s a great solution that allows Mustang owners to both be a good neighbor and enjoy the deep rumble of a good exhaust on the highway.

BORLA Performance Industries has developed its own patented Pocket Valve technology to allow its exhaust systems to retain the vehicle’s factory dual-mode or active valve functionality without restricting the flow of exhaust gases leaving the engine.

Many new cars feature some kind of exhaust system valve technology. These valves are generally designed to operate at different engine speeds to attenuate sound levels. Most manufacturers employ selectable or active systems. These allow the driver to choose the noise level. The purpose is to provide a quiet car until the opportunity presents itself to hit the loud pedal. At this point, the valves open to allow the allow the vehicle to produce a louder, sportier exhaust note.

While developing its performance exhaust applications for new vehicles, BORLA engineers need to understand how the stock exhaust valves systems operate so they can ensure the BORLA systems function in the same way. The video posted below was filmed during a test session using the 2018 Ford Mustang GT. The BORLA engineers removed the Ford valves from the stock exhaust and placed them inside the car so they could study the activation in the Mustang’s different driving modes.