2007 BMW 7-Series - Review

 

 

 

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Blasting by on the Autobahn, you might never notice anything unusual about the 7-Series sedan BMW rolled out in Berlin last week. Indeed, even sitting behind the wheel, you might not sense anything unusual, despite the glowing amber “H” in the instrument panel.

 

Not until you stop to fuel up, that is, at the Total station on the outskirts of the German capital. Hit the filler release and a motorized door on the right rear pillar whirs open, revealing a stainless steel contraption definitely not for use with your everyday gasoline pump. It is, in fact, the most visible piece of the complex, bi-fuel powertrain that powers the most unique version of the BMW 7-Series to roll off the automaker’s Munich assembly line.

 

“We’ve reached an important milestone on our way to an era of sustainable mobility,” declared Klaus Draeger, BMW’s board member in charge of research, during the media preview of the Hydrogen 7, which can run on either petrol or hydrogen.     

 

A different hydrogen tack

 

BMW is by no means the only automaker looking to the lightweight gas as the clean fuel of the future, but where most competitors are emphasizing space-tech fuel cells, the Bavarian manufacturer is taking a decidedly different approach with the Hydrogen 7 sedan.

 

What starts out as a relatively conventional 760Li — including the sedan’s 6.0-liter V-12 engine — undergoes significant modifications before it rolls off the line. That starts with the cryogenic fuel tank tucked neatly between back seat and trunk. Bucking the general industry trend towards using compressed hydrogen, BMW engineers chose to maximize range by using the cryogenic form of the fuel — in liquid form, it must be supercooled to -253 degrees C, or just barely above absolute zero.

 

Sophisticated engine control software makes the car feel just like a conventional 760Li. Indeed, pressing the “H” button on the steering wheel to switch between fuels, a passenger might not even notice. Engine output has been detuned to 260 bhp. But despite its bulk, the sedan is still reasonably quick, in either mode launching from 0-100 km/h (0-62 mph) in just 9.5 seconds, with a limited top speed of 230 km/h, or roughly 145 mph.

 

Impossible to tell

 

During a day of driving around Berlin, we found it almost impossible to tell what fuel you were using without checking the instrument panel. There’s only the slightest shudder switching back and forth between gasoline and hydrogen, far smoother than even the silky smooth BMW six-speed automatic.

 

Under hard acceleration, there’s a slight bit more engine noise when running on hydrogen, more like a BMW diesel, but a bit more brittle-sounding, due to the way the gaseous fuel detonates.

 

The Hydrogen 7 only can hold about six kilograms of the fuel in its cryogenic tank — which swallows up half the sedan’s trunk space and four inches of rear legroom. That’s enough to get you just 125 miles — if you’re not too aggressive with the throttle. During our fast morning drive, we found ourselves getting about a third less mileage than promised.

 

After that, you’ll need to switch to gasoline power or find one of the rare liquid hydrogen pumps, like the one at a Total station a few minutes outside downtown Berlin. After hooking up the hefty refueling apparatus to the thermos-like H2 filler port, it took eight minutes to top off and get running again. (We hadn’t used enough gasoline to draw a refill for that tank.)

 

Cost killer

 

All-in-all, we’d have no problems using the Hydrogen 7 as our daily driver — if we had a ready supply of hydrogen, of course, and didn’t have to pay for all that added hardware. BMW officials won’t reveal how much it costs, though Timm Kehler, marketing manager for BMW’s so-called “Innovations” unit, conceded it’s substantial.

 

Still, he asserted, “Our customers are willing to pay for innovations. It’s part of the brand philosophy.” Actually, most drivers likely will pay little to nothing, as BMW is using the Hydrogen 7 as a combined research and marketing program.

 

In all, BMW intends to produce just 100 Hydrogen 7 sedans, nearly half earmarked for Berlin, most of the rest for Los Angeles. A few more will go to other parts of Europe, the U.S. and Asia. For markets with no ready sources of liquid hydrogen — which means most of the world — the automaker is readying a support fleet of mobile H2 tankers.

 

Despite all the hype about hydrogen, it’s unclear what the fuel’s future holds. On the positive side, it burns cleaner than anything else available. Burned in the Hydrogen 7’s V-12, it turns into little more than water vapor, with minute trace amounts of smog-forming nitrogen oxides and hydrocarbons from the oil used to lubricate the engine’s pistons.

 

Skeptics would contend that there’s an even cleaner alternative, the hydrogen-powered fuel cell favored by most other manufacturers. But Hydrogen 7 program director Frank Ochmann is quick to note that fuel-cell technology is a long way from production-ready, while BMW’s approach could quickly be scaled up for the mass market.

 

That’s assuming you could get hydrogen at the corner pump, of course. In reality, an H2 production and distribution network is, at best, years away. That is why, said Ochmann, “For now, the bi-fuel approach is needed.”

 

BMW researchers suggest there’s a lot of room to keep improving the hydrogen-powered internal combustion engine. A one-cylinder prototype, now being tested in the automaker’s Munich labs, nearly triples the power output of the Hydrogen 7’s V-12, using techniques like turbocharging and direct injection of liquid hydrogen.

 

BMW has often followed its own approach to technology, and has earned a strong reputation and solid sales in the process. Whether it will succeed with its hydrogen strategy remains to be seen, but the Hydrogen 7 should provide a clear indication.