Ford’s new Active Valve Performance Exhaust, found as an option on the new Mustang, can produce some absolutely amazing exhaust tones. It doesn’t really sound like any Mustang before, but boy howdy is it loud. So loud that the company has had to offer up a cool new quiet mode. Set the timer through the dash and the car quiets down when you fire it up in the morning. It might be less fun, but your neighbours will appreciate it. So how does the active valve exhaust work?

Variable exhaust tech has been around for decades. Automakers have used various forms of the idea in an effort to make cars both loud when you’re on it and quiet when you’re not. Pleasing drivers and pedestrians.

Those systems are usually simple, though there are a couple of ways to do it.

If you’re going for an all-out track mode, you simply add a mechanical valve that bypasses the muffler. It’s called an exhaust cutout or exhaust dump. All the exhaust takes the easy route when the valve is open. It gives maximum airflow, maximum noise, and probably maximum tickets if you get pulled over. These days it’d even get you booted from most tracks.

The second is a vacuum-operated system. Also common on cars with a sporting intent. There’s a second chamber in the muffler or even a second muffler. That second one has less sound isolation. But it’s blocked by a vacuum-operated valve.

The valve has a spring on one side and a vacuum line on the other. Floor the gas and the vacuum goes away. Then the spring pulls the valve open. That diverts the exhaust to the loud side and the car breathes more freely and more conspicuously. Lift the throttle and the valve closes again as vacuum returns. It’s simple, and as many late 1990s BMW 3 series owners have discovered, simply blocking off the vacuum line leaves the exhaust in open-mode all the time.

But this new Ford system is much more involved. It needs to be, since it has four different modes ranging from quiet to menace to society.

Instead of a simple dump valve or even something vacuum-operated, the Mustang uses electronically actuated valves. Two on each muffler for a total of four on the GT Performance Pack.

It’s fairly straightforward. When the car is in quiet mode, the valves stay mostly closed. They never open more than about 25 percent. This restricts flow and lets the exhaust spend more time being muffled. More muffling equals less noise.

In track mode, the valves all want to party all the time, party all the time, party all the time. Staying wide open, making all the noise, and making you feel a little more conspicuous than maybe you really wanted to. Especially when you’re driving through small quiet hamlets on the way to the racetrack. You know, in theory.

It’s the middle modes that are the most interesting, though. In normal mode, they open wider than in quiet. Eventually. They start out actually closing a bit, but then come on at around 3,000 rpm. Lift off the throttle, letting the car coast down, and the valves open wider. But since the engine isn’t making power, things don’t get rowdy. You just get to enjoy a little more rasp and burble.

In Sport mode, again they stay mostly closed until around 3,000 rpm. They’re actually more closed at 2,900 rpm than at idle. Then at 3,000 rpm they snap open. Opening to about 75 percent. Lift off and they go wide open. But when you’re driving, the butterfly valves dance like, well butterflies. Tailoring their position to make just the right amount of noise.

Tailgate a 2018 Performance Pack car and you’ll be able to see the active exhaust at work. Though we don’t recommend tailgating anybody. It’s dangerous. So don’t do it. Instead, watch this video from Borla where they cut off a stock Mustang’s tailpipes and rigged them up for you to visualize the active valve exhausts more easily.

So that’s how the new Mustang can go from not exactly quiet to HOA-complaint loud with the push of a couple of buttons. And it shows just how far automakers like Ford are prepared to go to make sure that enthusiast cars are more appealing than ever to enthusiasts.

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