BMW X6 ActiveHybrid (2009) CAR review

BMW doesn't do things by halves. This is their first full hybrid model, the ActiveHybrid X6, and it's the most powerful hybrid in the world. It combines a 407bhp 4.4-litre twin-turbocharged V8 engine with a fiendishly complicated gearbox that contains two electric motors, one optimised for low-speed running, one to boost power at higher speeds. 

The X6 ActiveHybrid's electric motors can produce 91bhp and 86bhp, respectively, but the total combined output is pegged at 485bhp and 575lb ft – lessening the load on the V8 petrol engine and further reducing emissions.

So the BMW X6 ActiveHybrid is a Prius in big, bad SUV wolf disguise?

Hardly, but the X6 plays all the usual hybrid tricks. The motors act as generators under braking (electricity is stored in a nickel metal hydride battery with a capacity of 2.4kWh located underneath the boot floor), which is then used to power the motors when driving under electric power alone or when supplementing the V8.

BMW claims the ActiveHybrid X6 will accelerate from 0-62mph in 5.6-seconds and hit 155mph, despite weighing a frankly absurd 2525kg – 260kg more than the conventional xDrive50i fitted with the very same V8 engine.

Woooah. So this is one lumbering, big fat beast?

Oh yes. But the tech does its damnedest to offset the weight to some extent. The incredibly complicated gearbox is at the heart of the Active Hybrid: It has elements of a continuously variable transmission with seven 'virtual' gears, but at higher speeds runs through more conventional planetary gearsets with multi-plate clutches, all the time supplemented by the two electric motors.

Developed by GM, Mercedes and BMW in partnership it occupied 150 engineers for a full three years. I can't begin to do justice to its inner workings (indeed, BMW admitted that the press material deliberately doesn't try to explain how the 'box works because it simply can't be put into layman's terms) so perhaps I should just describe how it feels from behind the steering wheel...

Tricky that, as such is the refinement of BMW's application of the hybrid system that it feels freakishly like the xDrive50i. Sure, there are some striking differences – for example when you press the 'Start' button the V8 doesn't fire-up at all, rather a little blue needle underneath the main rev counter flicks from 'Off' to 'Ready'.

Select D in the same way that you would with any other X6, brush the accelerator and the big SUV glides silently away on pure electric power. On light throttle openings the X6 can propel itself to 37mph without the help of the V8, after which it kicks into life with the merest hint of shunt. The range of electric drive is just 1.6-miles, however.

>> Click 'Next' for the rest of our BMW X6 ActiveHybrid first drive review