2015 Mustang: Tradition Meets Technology
The sixth-generation Mustang is so fundamentally different from the fifth that other than the carryover powertrains, just a handful of fasteners and other small items are common between the two cars. A notable change is the switch to an independent rear suspension from the traditional live axle, though a large number of less-conspicuous parts received significant updates and revisions. The result is a Mustang that is more focused and capable, and that has a higher technology content than any of its predecessors.
An increase in the amount of high- and ultra-high strength steel, hydroforming and laser welding makes the coupe’s body-in-white lighter, 28% stiffer in torsion (the convertible model is 15% stiffer), and improves crash performance. According to Mustang chief engineer Dave Pericak, “The base EcoBoost fastback is pretty light at 3,524 lb., and the weight increases for the V6 and V8 models are just 6 and 87 lb., respectively, despite the addition of a more complex rear suspension, a doubling of the number of airbags, increased crash protection, and more standard equipment.” Aluminum content also has increased, and includes the independent rear suspension’s knuckles and control arms, the rear axle housing on automatic transmission-equipped cars, front brake calipers, and the front fenders and hood. In addition, replacing the individual front cross members of the previous car with a single, non-isolated front subframe not only reduces weight, it provides a more stable base for the new dual lower ball joint MacPherson strut front suspension while reducing mass.
Says Mustang vehicle engineering manager Tom Barnes, “The stiffer structure means it’s much less likely that the suspension mounting points are going to move in relation to one another under load, which has allowed us to tweak a number of things.” Anti-squat, anti-lift and anti-dive resistance has been doubled on each axle, and the suspension bushings and spring and damper rates have been revised to take advantage of the stiffer mountings. New steering rack mounts work in unison with the double lower ball joint front suspension to increase steering precision, and allowed engineers to make more nuanced boost level changes in the electric power steering system’s driver-selectable settings. “The front suspension design,” says Barnes, “reduced the offset that would have been necessary to clear the larger front brakes with the old suspension design.” Plus, the increased number of ball joints improves the suspension’s freedom of movement in multiple planes of travel without increasing ride harshness.
The brake packages have been significantly upgraded, says Pericak, to the point that “the standard brake set on the Mustang GT is equivalent to the last car’s Track Package brakes, while the new GT Performance Package brake system is the same one found on the 2014 Shelby GT500.” That car had 662 hp, 227 more than the 2015 GT. Both the Mustang V6 and EcoBoost start out with 320-mm vented front rotors clamped by two-piston 43-mm floating calipers, and 320-mm rear rotors with single-piston 45 mm calipers in the rear. The EcoBoost Performance Pack shares the base Mustang GT’s 352 mm vented front rotors and 46 mm fixed aluminum calipers, and 330 mm rear rotors with single-piston 45 mm iron calipers out back. Mustang GT Performance Pack cars retain the same rear brake setup, but swap for 38 mm vented front rotors with six-piston 36 mm aluminum Brembo calipers. “The fade resistance of these brakes is incredible,” says Pericak, “and we designed them to stand up to track days as well as everyday use.”
The 5.0-liter V8 has been modified to produce 435 hp and 400 lb.-ft. of torque, and has a redline of 7,000 rpm. It pulled forward many of the lessons learned with the Boss 302 motor and features: larger intake and exhaust valves, revised intake and exhaust cams, stiffer valve springs, modified ports with straighter paths, new combustion chambers, sinter-forged connecting rods, redesigned pistons with deeper cutouts for the larger valves, a rebalanced forged crankshaft, a new intake manifold with charge motion control valves, and a greater range of adjustment for the variable valve timing system. Not bad for a motor that, when it was in front of former Global Product Development vice president Derrick Kuzak for production approval, only was expected to produced 380 horsepower.
Though there are no changes to the base model’s V6 engine, a new 2.3-liter EcoBoost four cylinder that produces 310 hp and 320 lb.-ft. of torque has been added to the mix. It’s the first turbocharged four offered in a Mustang since the ill-fated 1984-1986 SVO Mustang. That iron block engine also was a 2.3-liter, produced 170 to 205 hp (a lot for the time), but was not in keeping with customer expectations for a performance Mustang. Ford hopes that this time around buyers will be more accepting of a small displacement performance motor that, according to the EPA, returns 32 mpg on the highway. Certainly it won’t be for lack of technology. The new engine has an exhaust manifold integrated into the aluminum cylinder head, a 9.5:1 compression ratio, forged steel connecting rods with full floating pins, a high-pressure die-cast aluminum engine block with integrated main bearing caps, a structural ladder frame, balance shafts, and a forged steel crankshaft. It’s also the first Ford production engine to use a twin-scroll turbo for optimum boost at all engine speeds.
Inside the car, the ergonomics have been significantly revised, the controls updated, and the materials significantly upgraded. One of the more trick items is the glove box door knee airbag. “The idea came from the design staff,” says Doyle Letson, Ford’s global interior design chief, “as we were looking for ways to increase front seat leg room. Putting the knee bag in the glove box door would let us pull the lower edge of the instrument panel back to increase front seat passenger comfort, but it was up to the engineers to make the idea work.”
An inflatable injection-molded plastic bladder is integrated into the glove box door, and forces the door’s outer surface straight out from the instrument panel. Because it distributes the crash loads over a broader area and is closer to the occupant, it can operate at a lower inflation pressure, and use an inflator that is 75% smaller. It is helped by seatbelt pre-tensioners added to the anchor side of the belt to hold the passengers more securely in a crash, and an increase in the number of crash sensors used around the car.
As important as styling is for Ford’s halo automobile, aerodynamics ran a close second. With an electronically limited top speed of 155 mph, and as the first generation Mustang to be sold globally, it was necessary to make sure it stays stuck to the ground, especially at autobahn speeds. “Thank God we didn’t have to resort to a teardrop shape to get what we needed,” comments Pericak. “It would have destroyed the car.” By adding vertical slots in the outer ends of the front fascia and wheel wells, aerodynamicists were able to form air curtains that create a wall of air that flows around the outer edge of the front wheels. In addition, each engine family gets a unique grille that only allows in the air the engine will need, thus reducing parasitic drag in the engine compartment. EcoBoost models adds active grille shutters that can completely close the grille opening during high speed/low load situations for even greater aero efficiency. The Mustang GT gets a unique hood with leading edge vents that evacuate engine compartment air, and reduce front end lift. However, the trick piece is the under-bumper splitter. The basic horizontal panel is the same for each car, but each powertrain option uses different locating points and channels for their unique front spoilers. Allied with the underbody aero panels fitted to each car, the 2015 Mustang has a lower drag coefficient than its predecessor, and produces about three percent less drag. “That drag reduction gets us about one percent better fuel efficiency,” says Barnes, “and it’s basically free.”
Fifty years after the launch of the Ford Falcon-based original, the Mustang finally has all of the things the original’s sporty styling promised. Finally available globally direct from Ford—“the often small differences between regulations and requirements around the world were enough to drive a sane person crazy,” says Barnes—the 2015 Mustang will be sourced from a single facility, Ford’s plant in Flat Rock, MI.
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