Sunday, January 27, 2008

Alpina BMW B7

Alpina Create a New High Performance 7-Series Model

By selecting as the basis for the B7 the BMW 750i, with its V-8 engine and regular-wheelbase platform, Alpina could achieve a vehicle weight some 400 pounds lighter than that of the 760Li – a benefit in terms of agility and maneuverability. Then, to attain a power target of 500 hp, Alpina added a supercharger to the V-8 engine, which adds little weight but lots of horses.

The Supercharged Engine

At the time Alpina began development of the B7 engine, BMW’s V-8 engine with Valvetronic – the unique system that regulates power output by varying intake-valve lift – was at 4.4-liter displacement, not the 4.8 liters of today’s 750i. From this basis, which delivered 325 bhp at 6100 rpm and 330 lb-ft of torque at 3600 rpm, Alpina took on the challenge of supercharging a Valvetronic engine, something that had never been done before. To tell something of the ending before the story, the achievement is impressive: 500 bhp at 5500 rpm and 516 lb-ft at 4250 rpm. In German, such figures qualify as bullig and no translation is necessary to get the meaning.

Both supercharging (in German, a supercharger is a Kompressor) and turbocharging have their attractions as power-enhancers for combustion engines. A supercharger is mechanically driven by the engine; a turbocharger is driven by streaming exhaust gas. In this case the supercharger’s salient points include lag-free response, relative quietness, low exhaust back pressure and the ability to run the engine at part load (i.e. most of the time) just as it runs without the supercharger: with Valvetronic regulating its output. These last two factors speak for good efficiency and reasonable fuel economy in everyday driving.

The supercharger is a new development. It’s of the Radial or Nautilus type, not a brand-new concept as such but now appearing on an automotive engine for the first time. It had been patented by ZF in the 1980s, but only recently have metallurgical advances made this actual vehicle application possible. (In connection with the B7, Alpina has several patents pending.) At full boost, the supercharger delivers a positive induction pressure of 0.8 bar.

There is a clear subjective difference between an M-type exhaust note and that of the B7. Being high-revving, M engines emit a relatively high-pitched exhaust sound. The Alpina B7 engine, with its lower-rpm range and emphasis on big torque, just as naturally – and despite the measures to keep low-frequency sound in check – puts out a lower-pitched sound. Commenting on this sound in everyday driving, the April 4, ’04 issue of Germany’s auto motor und sport magazine called it “Gently murmuring, acoustically not unlike a costly Riva boat, the V-8 pulls away and shows with great refinement that there’s also driving pleasure at less than 500 bhp.”

Fine-tuning the 7 Series Chassis

Using the already advanced and sharp-handling 7 Series chassis, Alpina fine-tuned the hardware to the B7’s higher performance level. While retaining the regular models’ Active Roll Stabilization – which counters body roll or “lean” in corners via electronics and hydraulics – Alpina’s engineers, working with BMW and tire supplier Michelin, adopted a firmer calibration of springs and shock absorbers. They also chose the European 760i’s brakes, which have larger dimensions than those of the 750i.

And, where the rubber meets the road, Alpina topped even the 2006 BMW 760i’s standard 20-in. wheels and tires. Right from the days of its participation in developing the lightweight BMW 3.0 CS of the early 1970s, Alpina has a long tradition of radial-spoke wheels; this carries on in the B7’s massive 21-in. wheels of 9.0-in. front/10.5-in. rear width with the traditional count of 20 slender spokes. These provide for outstanding ventilation of the big brake rotors, and carry Z-rated performance tires of 245/35 front / 285/30 rear dimensions.

Exterior Features: The Alpina Touch

Through the years, Alpina’s exterior modifications have always stated “performance” but never screamed it. So it is with the B7, whose Alpina exterior is distinguished from that of a regular-production 750i by:

A special front bumper/spoiler ensemble
The 20-spoke Alpina wheels and their low-profile tires
Standard high-gloss Shadowline trim on the side-window framing
A special rear bumper ensemble
A rear spoiler that integrates perfectly with the 7 Series’ body lines
Availability of the traditional Alpina Blue metallic paint color
Alpina B7 badging
The effect is one of subtle performance emphasis, fully appropriate to the 7 Series’ elegant and substantial presence but leaving no doubt that this is a special performance 7.

Inside the B7: Special Instrumentation and Controls

Any 7 Series BMW offers its driver and passengers lavish luxury, fine materials and tasteful design. To this sumptuous ambiance, Alpina adds its own touches, both ergonomic and esthetic; the level of regular-production BMW standard equipment has been raised considerably as well.

Special Alpina features. First and foremost, it’s performance that characterizes the B7. And once seated behind the special Alpina steering wheel, the B7 driver is quickly and keenly aware of this emphasis.

Upon stepping in over the handsome B7 doorsill trims and setting his or her foot on the fine floormat with its Alpina logo, the driver can assess an instrument cluster with the traditional Alpina Blue as its background color and Alpina lettering at bottom right. Four readings from the iDrive system’s On-board Computer can be called up conveniently via a button on the turn-signal stalk: remaining fuel in tank, range on fuel, distance to destination and a digital display of current vehicle speed.

The steering wheel itself presents distinctive visual character and function: in its center, the Alpina logo; on its rim Lavalina leather and special stitching, plus symbols for the SWITCH-TRONIC transmission’s upshift and downshift buttons. These “+” and “-“ inscriptions are in Alpina Blue, and denote the actual locations of the shift buttons on the wheel’s forward side (away from the driver).