Although the powerhouse is based on the N55 engine fitted to PH's new 435i long-termer, Alpina's engineers have reverted back to twin-turbocharging rather than following BMW in its switch to a single blower, instead preferring the instant spool up that comes with a pair of smaller turbos. ZF's superb eight-speed auto switches gears while power is sent rearwards to an open differential. A limited-slip differential is optional, which, as we'll find out, is just as well.
What would be the point of an Alpina if it didn't ride? In typical fashion the B3 Bi-Turbo is wonderfully supple in Comfort mode, soaking up lumps and bumps with cushioned control. Despite the 20-inch wheels and 30-profile rubber, the ride quality really is right out of the top drawer. Even when knocked into Sport or Sport+ - the 3 Series' optional adaptive damping is standard fit here - there's enough compliance for daily use.
In Comfort mode the steering is spookily light. Around the straight-ahead position there's often a sense that the steering column has been disconnected entirely from the wheels. The Sport modes address this with added weight, but never do you have total faith in the steering and nor is there any degree of feedback.
On a twisting, narrow road that can become an issue because you find yourself unable to place the car with total accuracy. Allied to a chassis that, even in one of the Sport modes, feels a little blunt you do find yourself having to second guess your steering inputs and correct your lines. The B3 soon feels uncomfortable being hustled down a demanding stretch of blacktop for there isn't the precision and iron-fisted body control to make such a thing enjoyable. On open, flowing roads the B3 feels much more at home and is monstrously quick.
As ever, the ZF gearbox can't be praised too highly. Alpina's curious nipple buttons on the back of the steering wheel are certainly unique, but when pressing on a larger paddle would be easier to locate and therefore more effective.
F30-based M3/M4 will be like. It's much more idiosyncratic and cosseting than a typical M-car. For the quality of the ride, cabin, engine and transmission it is difficult to express just how brilliant a B3 Bi-Turbo, particularly in Touring guise, would be as a daily ride, but it doesn't back up that appeal with genuine sports car tactility.
Ultimately, the Alpina is ready to dissect a continent rather than destroy your favourite B-road or blitz lap times on a certain German race track.
ALPINA B3 BI-TURBO
Engine: 2,979cc, six-cylinder, twin-turbo
Transmission: 8-speed ZF automatic, rear-wheel drive
Power (hp): 410hp@5,500rpm
Torque (lb ft): 443lb ft@3,000rpm
Top speed: 190mph
MPG: 37.2mpg (claimed)