Alpina celebrates 50th with 200mph B6

Birthdays in the car industry are good. Rather than cut a dishevelled cake into measly slices before serving them on a greasy napkin, carmakers give us special editions to buy. And Alpina is no exception.

Everyone's favourite BMW tuner has hit the big five-zero, and it's marking the occasion with ‘Bi-Turbo Edition 50' versions of its B5 and B6. And they're the most powerful cars it's yet cranked out.

If you need bringing up to speed, the clues are in their names: the B5 is based on the 5-Series saloon and Touring, the B6 uses the 6-Series coupe as its starting point.

Both already come with Bi-Turbo variants, a retuned version of the BMW M5's 4.4-litre petrol V8 powering them. Alpina swaps BMW's pair of turbochargers for its own, though, as well as tweaking the cooling system and fitting lighter pistons. It also fits its own automatic gearbox and gives the cars a slightly calmer, though still fun character.

For the Edition 50, further spanners have been wielded. Tweaks for the induction and fuel systems have freed 60bhp and 52lb ft, taking the B5 and B6's totals to 592bhp and 590lb ft.

Despite neither car being light or small, that's enough for a 4.2-second 0-62mph time and a 204mph top speed, a 6mph improvement. Yep, Alpina even does away with BMW's spoilsport speed limiter.

The alloy wheels ape a classic Alpina design while shedding over 15 kilos with their forged construction. There's an Akrapovic-sourced titanium exhaust system to ensure plenty of eight-cylinder goodness, while a limited-slip differential should ensure they handle well for barges, too.

Inside, there's leather trim and commemorative plaques aplenty, as well as what's described as ‘luxurious Forest Green quilting' on the seats. Given the dictionary defines a luxury as ‘a delicacy rather than a necessity', we can't disagree. At least Alpina's trademark blue dials remain intact.

Alpina is officially affiliated with BMW, so you get a proper warranty despite some fairly significant mechanical tuning. There will be 50 of each made, with your choice of blue, green or sepia paint.

Prices start at £86,850, which ain't bad when you consider a 40bhp-lighter and far less exclusive M5 kicks the V8 M Car range off at a smidge under £74,000. Want one?