2010 BMW ActiveHybrid 7: Clenched fist in green glove

Sedan proves worthy of its elite badge

Nov 06, 2009

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Munich–There are two basic things BMW is well known for: building vehicles that focus on performance and the driving experience, and the use of often cutting-edge technology to do so.

Since consciously adopting an internal policy in the 1990s of what it now calls "efficient dynamics", BMW's conundrum has been how to keep true to its "ultimate driving machine" credos while reducing the environmental impact of its products.

Although the company has pioneered the use of a variety of technologies such as variable valve lift (eliminating the need for a throttle) and direct fuel injection – both of which improve not only performance, but fuel efficiency – it has not until now used its considerable engineering prowess to create hybrid models.

That changes this year, when the German automaker will introduce not one, but two seemingly similar, yet distinctly different, hybrid vehicles: the X6 ActiveHybrid, which goes on sale in December, and the ActiveHybrid 7, set for launch next spring.

The result of a technology development agreement with Daimler that also produced the Mercedes S400 Hybrid, the 750Li-based ActiveHybrid 7 is a "mild" hybrid – the electric motor cannot propel the vehicle on its own.

While there is some commonality in a few components, BMW's execution and goals differed from Daimler's.

The Mercedes system helps a V6 to perform like a V8. The BMW's adds extra punch to the already very robust, 400-hp twin-turbo V8 used in the 750i family, while improving its overall efficiency.

BMW suggests that a reduction in consumption of about 15 per cent can be expected; it's 30 per cent on the EU Urban test cycle.

Key to the system is a three-phase AC motor that's bolted to the crankshaft immediately in front of the ZF-made eight-speed automatic transmission's torque converter.

Except for a few hybrid-specific additions, it's essentially the same gearbox used in other 5- and 7-series models.

Consequently, it operates conventionally, too – no weird rubber-band feeling as in most full hybrid vehicles.

Downshifts are prompt, and all shifts occur smoothly.

Only BMW's oddball returns-to-centre shifter (common to several BMW models) muddles the process for the uninitiated.

To say that the ActiveHybrid 7 (henceforth the AH7) has excellent overtaking power is a gross understatement. The combined output of the roughly 20 hp electric motor and the enhanced gasoline engine is a maximum of 455 hp and 516 lb.-ft. of torque.

The additional gasoline engine output (it's rated 440 hp solo) occurs without noticeable turbo lag because electric motors offer their maximum torque at zero rpm. The AH7's electric motors can mask the delay in low r.p.m. boost because they rev at a low output.

In fact, my biggest gripe after a few hours behind the wheel had to do with the AH7's idle stop system, a feature common to most hybrids.

In normal use, it shuts the gasoline engine down the moment that you come to a stop in the name of fuel savings. Releasing the brake immediately restarts the gasoline engine.

My tester had just enough delay between brake release and response to accelerator pressure that I became hesitant when making turns from a stop to shoot for gaps in the traffic that I'd normally take.

In fairness, I've experienced similar but lesser delays – which in this case was probably only fractions of a second long – in every hybrid I've driven, and I suspect that BMW has a little more fine tuning left before customer cars see the road.

The only other immediately obvious drawback to the hybrid version is the loss of about 40 litres of capacity in the left rear of the trunk, home of the system's 120-volt lithium-ion battery.

That location minimizes its effect on balance and handling, and protects it best in a collision. BMW says that four normal sets of golf clubs will still fit.

In all other ways, fitting a hybrid powertrain to the 7 Series has left the rest of the experience unchanged, which is a good thing.

Other than xDrive all-wheel drive, all of the veritable boatload of standard and available features that can be enjoyed in other 7's are available in the AH7.

Still, in spite of the claimed fuel consumption reductions, this is not a hybrid that buyers are likely to opt for in an attempt to recoup their investment in fuel savings.

The final price of an ActiveHybrid 7 has yet to be determined, but I'd expect to see a $5,000 to $10,000 premium over the $113,200 750Li – making a virtual tie with the $119,950 Lexus LS 600h L.

No, this is a clenched fist in a green velvet glove – a large, luxurious, and very, very quick sedan in the best tradition of such things – that allows its owners to feel a little better about their carbon footprint.

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