GENEVA MOTOR SHOW: Alpina creates more powerful B3 and B4 Biturbos

Legendary BMW tuner, Alpina, has announced it will launch a more powerful S version of its 3 Series-based twin-turbo B3 and B4 at the Geneva motor show.

Available on the B3 sedan, wagon and B4 coupe and convertible, the new S model is said to raise the power of both car's standard twin-turbo 3.0-litre straight-six from 301kW/600Nm to a more muscular 324kW/660Nm.

The bump in power has a dramatic effect on performance. Against the clock, the B4 Biturbo S is now capable of hitting 100km/h, from standstill, in just 4.2 seconds - 0.4 seconds quicker than the standard car.

The all-wheel drive B4 S, meanwhile, is faster still and can now reach 100km/h in an incredible 3.9 seconds.

Top speed has also risen from 278km/h (for the coupe) to a supercar-bothering 306km/h.

Alpina hasn't revealed how exactly it's extracted the extra power and torque but says the new S model is identified over the standard car thanks to a tweaked front and rear bumpers, new LED head- and fog lamps and redesigned LED rear tail lamps.

Inside, the B3 and B4S is said to come with higher-grade materials and, curiously, split folding rear seats.

Alpina was only launched late last year in Australia with the first batch of cars arriving in customer's hands last month.

It's likely we'll get the option of the power upgrade on the cars we get although it's not known how much of a premium Alpina will levy over the $155,900 it charges for the standard B3 and the $160,900 it currently costs for a B4 Coupe.