It’s one thing to understand a concept, it’s another entirely to see exactly how it works. Thankfully, Borla set up a rig to let us see just how the Mustang GT’s stock exhaust valves work.
Ford gave the Mustang a couple of drive modes that change the Mustang’s volume pretty substantially. This is effectively accomplished by turning a butterfly valve at the exhaust tips.
The system does more than just that, though, and it’s pretty interesting to see the valves flutter through the rev range.
To show us how it works, Borla cut off the exhaust pipes just after the mufflers and attached them to a piece of steel that sits inside the car. They then rerouted the valve motor wiring and just let the Mustang do its thing.
As you’d expect, in quiet mode the valves are all but closed, while in track mode they’re pretty much wide open. The really interesting sound engineering happens in normal and sport mode when the valves are really doing a lot of work to manage the sound coming out of that 5.0.
With the valves inside the car (and not actually attached to the exhaust system), you can’t hear the difference, unfortunately, but the video below gives you an idea of what the different drive modes sound like.