A hybrid system can make a car more efficient. And efficient car mean the same performance on less fuel, or more performance on the same fuel. Lexus pioneered the second route. Now BMW has taken the idea and gone ever so slightly berserk. BMW ActiveHybrid 7 is a two-and-a-bit tonne luxo-barge that gets to 60mph in 4.7 seconds.

When you drive it like that, the hybrid system isn't doing much. It's only a mild hybrid, which means the electric motor, sandwiched between the engine and transmission and turning always at engine speed, is relatively small and incapable of driving the car unaided. Instead, what it does is fill the gaps when the V8 isn't working very efficiently, so when you're driving gently you're using less throttle.

The electric car system also recuperates energy when you lift off the throttle and coast. This powers the aircon and operates a stop-start system that shuts off the engine when you come to rest and instantly restarts when you release the brakes. These things are common in manuals, but not autos. And most of them can't keep the aircon going, but this one can.

The system was co-developed with Mercedes and uses the same motor and battery as the Benz S400 BlueHybrid, but for the S-Class it is hooked to a V6 and tuned for economy, whereas for the 7-Series it's hooked to a 449bhp twin-turbo V8 and tuned for epic performance.

Net result is a car as economical as the six-cylinder 740i in gentle running, but will go like the V12 760i when you decide to forget it's a hybrid and just drive it like you stole it. It's not just the sheer kick on the back when the turbos spool up, it's the instant response of the electric torque that does it for me. Not to mention the noise transition - from civilised near-silence to a delicious V8 chorus. Result is not just a limo that's almost wickedly quick, but one that feels even quicker than it is.

But you won't be able to buy it in Britain. Some of the vital electrical bits are mounted where the steering column would need to go for RHD.

So don't go bugging your local showroom. Anyway, at £5k above a similarly equipped 750i in countries where they're both sold, it's also super expensive. But it does show how hybrids needn't be boring, and the sooner that idea catches on, the better.

source:
Paul Horrell
http://www.topgear.com/