The B4 Bi-Turbo – which is available as a coupé for £58,950 or as a convertible for £62,950 – has undergone a two-year development programme. Alpina's team of 50 development engineers worked with specialist suppliers to enhance the engine, gearbox, cooling system, body structure, wheels, tyres, aerodynamics, steering, suspension and interior.
At the heart of both cars is an extensively re-engineered version of BMW’s 3.0-litre straight-six from the 335i. That engine’s twin-scroll single turbocharger is replaced by a twin-turbo system to provide very fast throttle response and the many bespoke components include a sophisticated cooling system and a new, forged steel crankshaft. In the Alpina, the engine produces 404bhp and 443lb ft.
The manufacturer claims that the B4 Bi-Turbo coupé – which comes with an eight-speed automatic transmission as standard – will sprint from 0-62mph in just 4.2sec and go on to a top speed of 190mph. Four-wheel-drive versions are only available in left-hand-drive markets and can reach 62mph from a standstill in 4.0sec.
The new model is said to return 37mpg on the combined cycle and emits 177g/km of CO2.
Standard equipment includes adaptive M Sport suspension, leather upholstery, electrically adjustable heated sports seats, climate control and bi-xenon headlights.
The B4 Bi-Turbo also benefits from myriad upgrades, including Alpina's trademark front and rear spoilers – additions that are reputed to increase the car's high-speed stability.