While the powertrain team defined output targets that would yield an ideal balance with the chassis, another team made sure the car made the kind of sounds owners and enthusiasts would expect from a Mustang Boss.
Up front, a Boss-specific intake system is tuned to feed the engine with minimum restrictions. A retuned induction sound tube provides concrete aural evidence of what's occurring under the hood. And, in the Boss exhaust system engineers really had some fun.
"With an exhaust system, we have to consider three constraints: legal noise restrictions; backpressure, which can rob power; and ground clearance," explains Shawn Carney, Mustang NVH engineer. "Since the 2011 Mustang GT exhaust is already so free-flowing - it came in way under our backpressure targets - we already had excellent performance; we were able to tune the exhaust system for a unique sound. Combined with the rush of the intake, the exhaust system really envelops the driver in V8 sound.
Every Boss features a unique quad exhaust system: Two outlets exit in the rear similar to a standard Mustang GT. The other two outlets exit to either side of the exhaust crossover, sending exhaust through a set of metal discs that act as tuning elements before the pipes terminate just ahead of the rear wheel opening. Visually subtle, the side pipes flow very little exhaust but a lot of exhaust sound, providing a sonic experience unlike any other Mustang - and giving home tuners an additional avenue for modification.
"We added the attenuation discs to meet legal regulations, but we knew buyers might operate these cars in situations where noise regulations weren't an issue," Carney said. "The disc is removable and includes a spacer plate sized to match aftermarket exhaust dump valves. If an owner wants to add a set of electric valves, they just undo two bolts on either side; the disc and spacer slide out and the valve will slide right in. And the side pipes are tuned so that drivers can run wide-open and the sound levels are comfortable - very aggressive but livable for an all-day track outing."
Carney further explains the thinking behind the unusual step of an OEM easing aftermarket component installation. "We're Ford engineers, but we're also enthusiasts," he says. "We understand owner mods are part of the Mustang experience, so we try to help where we can."
In keeping with the Boss mandate to provide the best-handling Mustang ever, the already strong Mustang GT suspension system has been further refined. Higher-rate coil springs on all four corners, stiffer suspension bushings and a larger-diameter rear stabilizer bar all contribute to the road racing mission, and Boss models are lowered by 11 millimeters at the front and 1 millimeter at the rear versus the Mustang GT. The real key to handling, though, is in the adjustable shocks and struts, standard on all Boss Mustang models.
"We've given drivers five settings for their shocks," says Brent Clark, supervisor of the Mustang vehicle dynamics team. "One is the softest, two is the factory setting and five is the firmest, and we've provided a wide range of adjustment. A customer can drive to the track on setting two, crank it up to five for improved response on the track, then dial down to one for a more relaxed ride home. What's unique is that drivers will find - thanks to the way the suspension works as a complete system - the softest setting isn't too loose and the firmest setting isn't too controlled; each step just provides additional levels of control."
Also unique is the method of shock adjustment. Ditching the weight and complexity of electronic wizardry, the Mustang team opted for traditional race-style hands-on adjustability - similar to the Gabriel shocks available on the original Boss 302.
"The shock adjustment is right at the top of the shock tower, built into the rod and easily accessible from under the hood or inside the trunk," says Clark. "You just take a small flat-head screwdriver, turn the adjustment screw between one and five, and head back out onto the track."