Rated at a combined output of 478-horsepower and 575-pound-feet of torque, the big SUV uses a twin-turbo 4.4-liter V-8 engine and a nickel-metal hydride hybrid powerpack to claim the title of the world's most powerful gasoline-electric hybrid passenger vehicle. That's no mean feat, with contenders like Mercedes-Benz, Lexus and Cadillac in the space. The two electric synchronous motors contribute 91-horsepower/192-pound-feet and 86-horsepower/206-pound-feet, respectively.
Accordingly, it's no wimp at the stoplight strip, sprinting to 60 mph in just 5.4 seconds, and on to an electronically limited top speed of 130 mph. And it does it all while eking out about 20% better efficiency than the standard V-8's ratings. The improvement is due largely to the hybrid system's ability to run on electricity alone up to 37 mph, though the hybrid-specifc automatic stop-start function also helps reduce wasted fuel at idle.
The EPA rates the six-cylinder X6 at 16 mpg city / 20 mpg highway, while the potent ActiveHybrid nearly matches that at 17 mpg city /19 mpg highway.
Like its big, brawny brother the X6 M (read our first drive of the X6 M here), however, the ActiveHybrid X6's main problem is a very American one--weight. Racking up 400-pounds for the hybrid drivetrain in addition to the standard vehicle's 5,000-pound curb weight, it's impressive that the X6 Hybrid gets the fuel efficiency it does.
Prototypes of the vehicle were spotted frequently throughout its development sporting a huge domed hood where the electronics and diagnostics equipment lived. That's been mostly solved for the retail version, with BMW packaging it all away tidily, though you'll still know the hybrid version from a distance.
The hybrid system employed by the ActiveHybrid X6 is a version of the Daimler-Chrysler-GM Two-Mode system that uses twin electric motors that can alternately provide extra power, charge the batteries at a 50 kilowatt regeneration rate, or trade power between each other as necessary. Tying the electrical side to the gasoline engine is a two-mode active transmission based on an electrical CVT and a standard seven-speed automatic transmission.
The two-mode active transmission provides the ideal combination of the two sources of drive power required for an even higher level of both efficiency and driving dynamics. Through the two electric motors, three planetary gearsets and four multiple-plate clutches, drive power is conveyed in the same way as with a seven-speed automatic transmission. Standard xDrive all-wheel-drive spreads out the power of the engine variably between the front and rear wheels.
The electric motors draw their energy from an NiMH high-performance battery fitted beneath the floor of the luggage compartment and supplying electric power also to the car’s on-board network. When applying the brakes or taking back the throttle, kinetic energy is converted into electrical energy and saved in the high-performance battery.