BMW set to launch the world’s most powerful hybrid
BY TERRY MARTIN | 17th Aug 2009
Frankfurt is shaping up as the greenest show ever for the German prestige car-maker, having announced earlier this month that it would use the event to launch a “comprehensive sustainability campaign” which, as GoAuto reported last week, involves a new green sub-brand and the forthcoming Megacity all-electric compact car.
The two new large hybrids are being marketed under a now-confirmed ‘ActiveHybrid’ label, and both combine electric propulsion with BMW’s 4.4-litre twin-turbocharged V8 petrol engine.
However, the 7 Series uses a single electric motor while the X6 heralds the Munich marque’s first application of the two-mode (twin electric motor) powertrain developed in partnership with General Motors, Daimler and Chrysler.
As is the case with Mercedes-Benz’s first petrol-electric model to spring from the alliance – the V6-powered ML450 Hybrid (which is sold overseas alongside the ‘mild’ S400 Hybrid) – BMW has not engineered the X6 ActiveHybrid for right-hand drive, and the Australian division has this week ruled out both the wild one and the mild one for sale here.
“At this stage the ActiveHybrid X6 and 7 Series will be manufactured as left-hand drive only,” a spokesman told GoAuto. “If it becomes available in right-hand drive it would be considered for the Australian market. No timing can be provided as there are no indications whether or not a right-hand drive version will be available.”In the X6 ActiveHybrid, which was previewed as a concept at the 2007 Frankfurt show, the familiar 300kW/600Nm V8 used in the current X6 xDrive50i teams with two electric synchronous motors delivering 67kW and 63kW respectively, for a maximum system output of 357kW. Peak torque is 780Nm.
As seen in other applications, one electric motor is used for setting off and driving at low speeds while the other chimes in at higher speeds. With the two electric motors, three planetary gearsets and four multi-plate clutches, drive power is transmitted to all four wheels through a seven-step continuously variable transmission.
Electrical energy is stored in a 2.4 kWh nickel-metal hydride battery pack under the luggage compartment floor.
Full-electric performance is possible up to 60km/h for a maximum 2.5km, although the internal combustion engine will cut in as required as a function of load conditions. The system has a fuel-conserving idle-stop function, and offers regenerative braking, but BMW has not followed GM’s lead with its all-new 2011 Buick SUV in offering plug-in recharging.
According to BMW, the ActiveHybrid X6 can accelerate from 0-100km/h in 5.6 seconds on its way to an electronically limited 236km/h top speed, and still manage to cut fuel consumption and emissions by about 20 per cent – to 9.9L/100km on the combined cycle, and to 231g/km of CO2. Not bad considering the vehicle reportedly tips the scales at 2450kg, some 260kg more than the regular 4.4 V8 X6.
By comparison, the X6 xDrive50i hits 100km/h in 5.4 seconds, and returns 13.8L/100km and 329g/km.
In visual terms, the X6 has a ‘powerdome’ on the bonnet, ActiveHybrid decals and a new ‘Bluewater’ metallic paint.
This paintwork and similar model designations also appear on the 7 Series-based ActiveHybrid 7, which was first seen as a concept at the 2008 Paris motor show and uses a single three-phase synchronous electric motor that enables a maximum output of 342kW and 700Nm.
Power is transmitted via an eight-speed automatic transmission, with energy supplied by a lithium-ion battery pack. The technology is similar to that employed on Mercedes’ S400 Hybrid, with the two rival marques having collaborated on this hybrid system as well.
BMW claims the circa-two-tonne ActiveHybrid 7 can sprint from 0-100km/h in 4.9 seconds, with average fuel consumption kept to 9.4L/100km and CO2 emissions restricted to 219g/km.
By comparison, the non-hybrid 1980kg 750Li sedan, which uses the same 300kW/600Nm 4.4 twin-turbo V8, reaches 100km/h in 5.3 seconds and returns 11.4L/100km and 266g/km.
