Alpina B5: test di Autocar

[Omphalos]

Minus six degrees centigrade. The orange glow from the information readout brings two things to the front of my mind. First, that I really should have checked the weather forecast before I packed, and second, something the man from Alpina said which is now brought into crisp focus.

Clocking my persistent gaze at the B5’s headline figures of 493bhp and 516lb ft of torque in the bumf, he let slip that those numbers were achieved while hot-weather testing in Dubai: ‘those are a minimum’. Today, with dense, freezing air feeding the forced-induction engine, it should easily improve on them.

It’s not been the easiest of times for Alpina recently. There was a risk of it being outgunned in the extraordinary power race between Germany’s prestige marques: Alpina’s finely crafted driver’s cars have struggled against a succession of monstrously torquey AMG Mercedes. Take the B10 (this car’s predecessor): like the old BMW M5, it had a normally aspirated V8, but with slightly less power. It offered a subtly different driving experience to the M5, but few people realised that. In order to better define itself, Alpina has decided to offer something else: where the new M5 has 10 cylinders, the B5 sticks with eight.

The B5 is meant to offer a more civilised take on the new M5. It’s been tailored mainly for the North American market, where the majority of AMG and M-division cars are sold, and where its conventional automatic gearbox will be most appreciated.

The B5 really is a proper BMW: the Alpina engineers do all their testing alongside their BMW counterparts, and the car is assembled on the same Dingolfing production line as any 520i or M5 (its special mechanicals are brought to the factory), before returning to the small Alpina factory in Buchloe for finishing.

Lift the bonnet and you’ll find a work of art. The B5’s engine takes star billing. Based on the V8 block from the 745i, Alpina uses its own internals but keeps the BMW top-end and Vanos variable cam-timing system. Each motor is built by one engineer. The clever bit is the addition of a radial compressor – a form of supercharger and effectively the intake half of a turbo – driven by an advanced planetary gear system with a 15:1 offset (which makes the supercharger more efficient). Alpina keeps the BMW throttle body, and installs one of its own ‘upstream’. This can be closed almost totally at low revs and loads, whereupon the supercharger impeller is just spinning enough to keep going, to help reduce fuel consumption. And a very efficient bespoke intercooler keeps the air intake temperature down (not that it’s necessary today).

The V8 fires up with a deep murmur, and the car will trickle around with effortless energy to a cultured soundtrack. But snap open the throttle and the B5 is slung forward with absolute disregard for its 1720kg kerbweight. Throttle response is sharp and wonderfully dependent on the angle of the accelerator pedal.

The Alpina will hit 62mph in 4.7sec, but beyond 100mph it seems to dig in again, the numbers flashing up on the head-up display (borrowed from the M5, it projects information onto the windscreen) as fast as the electronics can show them. The whole experience is utterly addictive and overlaid with a pure V8 howl, devoid of any annoying supercharger whine.

The B5 is a supreme overtaker, gobbling whole chains of slower traffic with a single burst in third gear. It’s the massive 516lb ft of torque that makes the difference: an M5 driver (with ‘only’ 384lb ft at their disposal) would have to be ragging their car to within an inch of its life to keep up.

The ZF six-speed auto ’box gets strengthened first and second gears, a new torque converter and reprogrammed software. It’s ideal in a car like this, never caught in the wrong gear and shifting smoothly. And with Alpina’s switchtronic function you can change gear using the precise buttons on the back of the thin, elegant steering wheel. Like the Aston DB9’s auto, the B5’s does a remarkable impersonation of a manual when required.

Smooth, icy roads make judging the Alpina’s chassis tricky. Nevertheless, the B5 feels like it makes the most of the 5-series’ talented underpinnings. Using M-Power springs with modified BMW dampers, the suspension is slightly softer than an M5’s (like the M-car it avoids run-flat tyres), but body control is excellent and the steering – a touch lighter than the M’s – wonderfully precise: the B5 immediately puts you at ease. After the endless fiddling with settings in the M5 (the gearbox alone offers 11 shift modes), it’s great just to jump in and drive a well set-up car.

Road noise is remarkably low, considering the wide low-profile tyres, and on the few sections of rough Tarmac on our test route the B5 seems pleasingly absorbent. There’s no limited-slip diff at the moment, so it tends to spin a single rear wheel rather than drift, but one will probably be offered as an option.

If you’re contemplating buying a super-saloon next year, it’s imperative you try a B5. Alpina expects it to be priced close to the M5 at just over £60k. Given the choice, I’d rather have the B5. It’s more comfortable, its power is more accessible, and the 5-series has never looked better than when adorned with Alpina’s retro-cool graphics.

Adam Towler

http://www.autocar.co.uk/FirstDrive_Summary.asp?RT_ID=212865