With a performance-oriented M version, two gasoline-powered models (with diesel options in Europe) and now the addition of the ActiveHybrid, the is 's first "full-line" vehicle. While we could question the marketing decision that led to a hybrid crossover coupe, instead we'll focus on how well the hybrid system works in this big vehicle.
For starters, the ActiveHybrid utilizes many of the same parts as the "regular" X6 xDrive50i. Externally, subtle ActiveHybrid badges on the sides and trunklid, as well as the Aero wheels, are the only telltale indicators. Inside, the doorsills carry ActiveHybrid badging and the center-console LCD display features hybrid-specific screens, while the instrument panel sports a unique analog battery gauge and a 4-segment bar graph showing the power output by the motors.
BMW engineers optimized the suspension and center-differential tuning to compensate for the additional weight (a claimed 5688 lb., up 419 lb. from the xDrive50i) of the 2-mode transmission and trunk-mounted 187-lb. battery pack. (And if the term "2-mode" sounds familiar, yes, it's the system jointly developed by , BMW and .) Absent from the powertrain is BMW's all-conquering torque-vectoring system. The intended city-based application made it unnecessary.
Its two synchronous electric motors, three planetary gearsets and four sets of multiplate clutches make the 7-speed transmission the heart of the hybrid system. One motor exclusively provides locomotive force to the wheels, while the other handles engine-start and power regeneration duties. Altogether, the system provides an additional 80 hp and 125 lb.-ft. of torque and seamlessly blends the power from the internal combustion engine and electric motors.
The hybrid's 4.4-liter direct-injected twin-turbo V-8 is the same as the xDrive50i's, but loses the alternator, starter, air conditioning compressor and power-steering pump. The last two, the vacuum assist for the brakes, are powered via an electric motor. Functionally, this increases efficiency by reducing parasitic engine load and allows the engine to shut down and restart based on drivetrain demands rather than ancillary needs.
At full song, the entire power system can produce 480 hp and 575 lb.-ft. of torque. At less rage-filled power levels, the ActiveHybrid can operate in full electric mode at speeds approaching 37 mph. During our quick drive, we achieved a consistent maximum speed of 34 mph with a fully charged battery on flat asphalt, but a light foot is needed to keep the car in electric mode. In normal driving, the electric motor will kick in when your foot is to the floor to provide additional boost.
During full electric running, we achieved stints of about a mile in light city traffic before the gas engine would activate. Regardless of engine load or speed, the transition from electric to gas was seamless. The 312-volt nickel-metal hydride battery pack is liquid cooled and at full throttle can deliver 57 kilowatts to the motors. The battery's cooling system dumps heat into either the air conditioning system (the a/c system can energize on its own) or the power steering cooling loop.
Like other electrically motivated vehicles, the ActiveHybrid charges the battery pack primarily during braking. The brake-by-wire system blends regenerative and hydraulic braking systems excellently, but pedal feel is spongy and vague. There was an almost imperceptible "clunk" sound at very low speeds that lets you know the transmission is shifting modes. When in either Sport or Manual mode, the engine will not auto-stop and will instead charge the batteries at idle.
BMW claims that the ActiveHybrid is 20 percent more efficient than the gas version, with a similar emissions reduction to boot. We achieved 19.6 mpg (versus 14 mpg) during our mixed-mode drive. And while some may criticize the X6's overall concept, it's hard to fault its seamless hybrid system. You just don't notice it. We only hope BMW's trickle-down approach to a performance hybrid begins with this car, which starts at a healthy $89,725.