BMW ActiveHybrid X6

VEHICLE TYPE: front-engine, 4-wheel-drive, 4-passenger, 5-door wagon

BASE PRICE: $89,775

ENGINE TYPE: twin-turbocharged and intercooled DOHC 32-valve V-8, 400 hp, 450 lb-ft; AC synchronous electric motors, 91 and 86 hp, 192 and 206 lb-ft; combined power rating, 480 hp, 575 lb-ft

TRANSMISSION: continuously variable automatic with 4 fixed ratios and manumatic shifting

DIMENSIONS:
Wheelbase: 115.5 in Length: 192.0 in
Width: 78.1 in Height: 66.5 in
Curb weight (C/D est): 5700 lb

PERFORMANCE (C/D EST):
Zero to 60 mph: 5.2 sec
Standing ¼-mile: 14.0 sec
Top speed (governor limited): 130 mph

FUEL ECONOMY:
EPA city/highway driving: 17/19 mpg

Both models share ActiveHybrid badging and fall in the contradictory performance-hybrid segment, but their similarities end there. The 7 is a mild hybrid that uses an electric motor in its eight-speed automatic gearbox and a compact lithium-ion battery mounted in the trunk to assist acceleration and run the accessories; the X6 is a far more complex full hybrid. The latter’s pair of motors and advanced electronic continuously variable transmission allow it to waft up to 1.6 miles and at speeds of up to 37 mph on electric current alone. Forget about Prius-like fuel economy, though, because the ActiveHybrid X6 is the most powerful hybrid yet produced, with the electric bits combining with a 400-hp, 4.4-liter twin-turbocharged V-8 to produce a total output of 480 hp and 575 lb-ft of torque. (When pressed on why it didn’t choose to pair the hybrid system with the X6 xDrive35i’s twin-turbo six-cylinder, BMW simply says that using the V-8 made for the largest jump in efficiency. Plus, the company added, the resulting vehicle would be slower.)

Two Modes and Lots of Explaining

Based around the two-mode CVT BMW co-developed with General Motors and the old DaimlerChrysler, the X6 hybrid is similar in concept to hybrid versions of GM’s full-size SUVs and pickups, as well as the short-lived Dodge Durango and Chrysler Aspen hybrids and the upcoming Mercedes-Benz ML450 hybrid. That concept in a nutshell: Take a big vehicle with a relatively inefficient, large-displacement engine and pair it with an electrified transmission that keeps the powertrain at maximum efficiency no matter what the speed to improve city fuel economy without sacrificing highway efficiency.

Compared with the GM and Chrysler examples, which blend CVT operation with two electric motors and three planetary gearsets for a total of four fixed gear ratios, the X6’s unit stirs in three additional, “virtual” ratios, effectively making the transmission a seven-speed for better dynamic performance. As with the normal X6, manumatic shifting is performed via the console shifter or wheel-mounted paddles. The two electric motors within the gearbox—rated at 91 and 86 hp and 192 and 206 lb-ft of torque, respectively—assist with high- and low-speed mobility while also helping to recapture wasted energy through regenerative braking. The juice, stored in a 2.4-kWh nickel-metal hydride battery pack under the floor of the X6’s cargo hold (it lives where conventional X6 models keep their spare tires; run-flats are standard on the hybrid), is then fed back into the system and on to the drive wheels