Until recently, engine outputs of around 500bhp were reserved for just a handful of Italian exotics - even the legendary Ferrari F40 had to get by on just 478bhp. Yet right now there's not one but two 5-series saloons hovering in the vicinity of that magic figure. We've already experienced BMW M Division's 500bhp M5 (073). Now meet the 492bhp B5 super-saloon from the BMW-Alpina works in Buchloe. The Alpina comes with a heavily revised version of the Valvetronic 4.4-litre V8 you might might once have found in a cooking 545i. But once Alpina has had its wicked way with it in its fabulous engine shop, the V8 ends up completely re-built, sporting a very special, super-efficient supercharger strapped to one side and an enormous intercooler sandwiched between water and air conditioning radiators in the nose. The addition of the blower results in the aforementioned wedge of power combined with a massive 516lb ft of torque. That's an extraordinary 133lb ft more than the M5 can muster and it's developed at a user-friendly 4250rpm rather than the giddy 6100rpm of the M5's short-stroke V10. And it's that chunky torque figure that makes this new Alpina B5 redefine our super-saloon expectations. When you first drive the Alpina you soon realise it represents a very different interpretation of the imaginary rules governing the super-fast saloon division. Compared with the rev-hungry, stiff-riding M5, the B5 delivers a much more relaxed approach to life in the fast lane. In fact, this easy-going nature is woven into the whole Alpina ethos by its wine-loving founder, Burkard Bovensiepen, who reckons the key to enjoyment in a car is less about absolute power and more to do with the manner in which that performance potential unfolds. In the B5's case it unfolds with gusto, posting a 0-62mph time of just 4.6sec (BMW claims 4.7 for the M5), with 100mph arriving in 9.5 and 125mph in 14.9; the B5 eventually fluffs into an aerodynamic brick wall at 195mph. These aren't computer-based guestimates either, but very real figures measured independently by German journalists. Frankly, I'm shocked by these numbers as the B5 seems to do everything in its power to disguise this illicit performance potential. For a start, in normal driving the six-speed ZF auto gearbox refuses to select first gear from a standstill (unless you select manual mode), pulling away in second gear in 'Drive' to give a more relaxing getaway for the occupants. Odd, but impressive all the same. As is the way all this power is delivered by the silky V8 engine. You could drive this car and convince yourself that there wasn't a supercharger force-feeding the cylinders with air. There's no whistle from the Nautilus-type compressor, despite it spinning at 105,000rpm at a crank speed of 6000rpm, nor is there a Jaguar-esque whine from the belt-driven epicyclic gear-set that multiplies the drive to this mini turbine. Power delivery is completely seamless throughout the rev-range and the car is utterly docile at low revs, too. It sets you wondering why BMW doesn't develop this sort of technology for itself. Even fuel economy hardly seems to suffer (it's in the mid-20s) thanks partly to the highly efficient Valvetronic technology that limits valve lift during cruising, and the miserly power consumption of the compressor - just 20bhp at full boost compared with 100bhp for the Jaguar XJR's Rootes-type 'charger. Some things never change at Alpina, though, namely the dreadful pinstripe graphics that run around the front splitter's edge and along the flanks of our test car; they're so naff, yet, having been around for so long, they're in danger of becoming cool again. Meanwhile, our test car's interior was surprisingly restrained, with perforated black leather seats, each sporting an Alpina badge on the backrest, together with an embossed metal badge on each floor mat, lest you forget the car's pedigree. The steering wheel is re-upholstered in special ultra-soft leather and gains two discreet 'nipples' behind the horizontal spokes that are the manual controls for the Switch-tronic gearbox. Alpina logoed blue dials and various high-gloss wood veneer inserts complete the interior makeover. It's a very subtle interior as well as being a superbly comfortable one. Your sense of well-being is helped along by Alpina's trademark suspension settings that cleverly combine a feeling of sportiness with long-distance comfort. It's an amazing achievement when you consider that the chunky Michelin Pilot Sport 2 tyres, specially developed for the B5, are 245/40 ZR19 specification at the front and 275/35 ZR9 at the rear - there are no runflats here, Alpina claiming the technology has a long way to go. The company places great store on achieving the optimum ride quality, and it tests extensively at various Michelin test tracks and on the roads around the factory. At least 36 months is set aside for this sort of development work before any Alpina is ready for market. And to accommodate the whims of a sportier clientele, the B5 also offers the option of 35-profile front and 30-profile rear versions of those Pilot Sport 2s. Alpina also does a lot of work on the DSC system so that, in the default setting, it spots how quickly traction is actually being lost once the rear wheels start to spin on a slippery surface. If it's very quickly, the computer presumes there's been a sudden loss of grip and immediately closes down engine power, allowing only 1.5 per cent slip until full grip returns. If, on the other hand, grip is slowly ebbing away it presumes the driver is actually still in control, balancing the throttle to the available grip and allows up to four per cent slip before intervening, permitting the driver to steer on the throttle without switching the DSC off. All clever stuff. Brakes are standard BMW items, cherry-picked from the parts catalogue to keep costs down. The anchors on the B5 are from a Middle East spec 760i, which has the biggest brake disc area of any model in the BMW range. This arrangement happens throughout the B5; it comprises one-third standard 5-series parts, one-third parts from other BMW cars and the final third unique Alpina parts. Recently, however, the flow of parts went the other way. Alpina started to develop its own diff to cope with the B5's prodigious torque, then got a call from BMW to see if the factory could use it for its V8 turbodiesels. Behind the wheel the B5 is distinctly softer than I imagined it was going to be. The steering seems a little slow but that's a direct consequence of Alpina's refusal to use BMW's Active steering technology, deeming it unsuitable on a sporting saloon like this. (There's also the small matter of super-direct steering being somewhat undesirable when you're thundering along at the B5's mighty 195mph top speed.) Turn-in doesn't have the snappiness of BMW's M-Power cars, but then it doesn't have their tense feeling when asked to cruise. The B5 pulls off the remarkable feat of being both an immensely relaxing car to drive and a ridiculously quick one. Then there's the added bonus of its rapturous exhaust note that builds from a silky burble to a howling snarl, never too loud but unmistakable from the cabin all the same; it's perfectly judged and you'd buy the car on the strength of the noise it makes alone. At the end of the day comparisons with BMW's in-house rival are inevitable. They cost almost the same - £61,755 for the M5 compared with £62,850 for the B5. On the face of it, the M5 seems the sportier choice. Yet to access its performance you really have to cane the V10; the B5 simply digs into its massive torque reserves and will happily hang onto the M5's quad tailpipes, before disappearing into the distance once the M5 clatters into its nannying 155mph speed limiter. The further you look into what the B5 has to offer, the less it seems the oddball choice. For a start it comes with the full three-year BMW warranty intact (and so it should given that it comes down the same production line at BMW that every other 5-series does and is fitted with its Alpina bits there); it's bespoke in a way that the M5 could never be, and it's a true automatic so you don't have to suffer the M5's occasionally irritating SMG gearbox. Yet BMW-Alpina reckons it's only worth bringing 150-200 cars a year to the UK. If there was any justice Alpina would sell at least double that, especially if rival AMG's recent sales are anything to go by. The understated B5 deserves a wider audience.
|Engine||V8, 4398cc, supercharged|
|Max power||492bhp @ 5500rpm|
|Max torque||516lb ft @ 4250rpm|