The Specs
The Ultimate Driving Machine should be, well, ultimate. The watered-down, disconnected driving experience conveyed by some hybrids would be inappropriate in a BMW, right? That's why BMW has tuned its first execution of the two-mode hybrid transmission for responsive performance first, while only modestly boosting fuel economy.
The crossover's two-mode hybrid system was developed in partnership with General Motors, Chrysler and Mercedes-Benz (when the latter two were still on the same team), and the others have already launched their versions of the technology. BMW has used the extra time to develop more sophisticated control software for its version of the transmission, reports project leader Peter Tunnermann. While the other companies use only the four physical gears inside the transmission, BMW exploits the hybrid-electric drive's CVT capability to add three virtual gears, so the X6 ActiveHybrid displays seven distinct gear ratios. There is actually an eighth gear that is not apparent because it is only used on deceleration to maximize the generation of electricity while braking.
The ActiveHybrid announces its status with a bulging "power dome" in the hood. Hot rods of the past may have needed such humps in the hood to clear high-rise intake manifolds or superchargers, but the X6 may be the first of the coming wave of power domes stamped into hood sheet metal to provide clearance for an electric- drive electronics box that is mounted atop the engine.
Oh, the engine. That's right, there is a gasoline engine in there too, and it is a good one, though that is easy to overlook when there is some rather impressive electric-drive technology on hand. The 400-hp twin-turbo direct-injection V8 that debuted in the X6 xDrive50i nestles its two turbines in the valley of the engine's vee for a shorter path to the turbos and improved throttle response. In this hybrid configuration the engine is stripped of all its conventional accessories, with all ancillary systems converted to electric power rather than using drive belts that depend on the engine spinning.
The combined gas and electric systems crank out an impressive peak of 480 hp and a diesel-like 575 lb-ft of torque. BMW opted for the complexity, weight and cost of liquid cooling for the ActiveHybrid's battery pack, because it permits the battery to be charged and discharged more quickly than would otherwise be possible, according to the company.
The Drive
The ActiveHybrid's sprightly acceleration disguises its extra 419 pounds of batteries and electric motors well. And twisting the X6's thick-rimmed steering wheel produces the same kind of taut, communicative response drivers expect from BMW. This despite the hybrid's use of electric power steering, a feature that is frequently maligned, but can be done well.
Step on the gas pedal and the X6 whooshes effortlessly to Miami freeway speed—80 mph—and beyond with no indication of any exertion. Off the line, the hybrid is quicker than the xDrive50i thanks to the torque from its electric motors, but within a few seconds the gas version would reel in the hybrid, courtesy of the gas version's lower mass, according to Tunnermann.
Some hybrids are intrusive when decelerating, as the vehicle attempts to capture every last watt of kinetic energy for storage and reuse when the light turns green. Their electric generators cause the braking to be erratic and disconcerting. The X6 ActiveHybrid's system is expertly calibrated so that the regeneration is rarely noticeable. In most circumstances the energy recovery is invisible.
But when driving at a low enough speed that the BMW is running on electric drive only, there are two drive speeds for the electric motor. When it downshifts as the car slows, there is a slight lurch as the engine braking increases. It isn't terribly bothersome, just noteworthy as the only time the regeneration is apparent to the driver. BMW boasts that it is possible to drive the X6 ActiveHybrid at speeds up to 60 kilometers per hour (37.5 mph) and distances up to 2.5 km (1.56 miles) in electric-only mode. But this state proved to be elusive on our test drive, as the gas engine hummed to life at lower speeds with very little throttle application. The explanation by engineers on hand was that while the battery could deliver as much as 60 kilowatts (80 hp) of power to the electric motors, the system only taps half that for durability reasons, so requests for more than 40 hp are filled by the gas engine.
The Bottom Line
The X6 ActiveHybrid lists for $89,775. That's 22 grand more than the X6 xDrive50i, for an improvement in combined fuel economy of about a mile and a half per gallon. The ActiveHybrid scores 17 mpg city and 19 highway on the EPA test cycle, compared to 15 city and 18 highway for the twin-turbo V8 version. Over the Miami driving route we took, the BMW returned 18.5 mpg. There is no point in breaking out the accountant's eye shade here; these numbers are never going to work, so forget trying to rationalize the ActiveHybrid for a lower gas bill.
The ActiveHybrid will be the vehicle of choice for people who want to play with new technology and who don't mind paying for it. BMW's version of the jointly developed two-mode hybrid system is impressive, both on paper and in the metal. The effortless way the X6 ActiveHybrid surges forward can't be duplicated by other drivetrains, making BMW's hybridization of gas and electric power as appealing, if not affordable.
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