Alpina looks set to launch the BMW 4-series-based B4 Bi-Turbo as both a coupe and convertible at next weeks Goodwood Festival of Speed. Alpina will also be bringing the D3 Bi-Turbo saloon and estate pair to Goodwood,

The Alpina B4 Bi-Turbo convertible sports a three litre straight six found in the 335i coupe. The B4 Bi-Turbo is the result of a two-year development programme and the work of 50 engineers that looked at every part of the vehicle to increase performance, comfort, efficiency and style. This includes the gearbox, cooling, body structure, wheels, tyres, aero, steering, suspension and interior.

The coupe can reach 62mph from zero in 4.2 seconds (4.5 for the Convertible). As with normal BMWs, the B4 variants also deliver fuel economy of 37 mpg and CO2 emissions of just 177g/km.

In the B4, the modified 3.0-litre twin-turbo straight six produces 404hp and 600 Nm  of torque, up from the 435i’s 302hp and 400Nm.

Alpina has also overhauled the brakes and suspension for the B4 Bi-Turbo, fitting its own adaptive suspension and altering the aerodynamics a tad with a spoiler and a restyled front bumper.

“Alpina customers value the finely-honed feel of a bespoke car and the easily accessible performance that comes with substantial torque available at almost any engine speed,” said Alpina GB sales manager Matthew Stripling.

“We are not trying to compete with cars that must also perform well on a track. An Alpina is often described as ‘the best performance car for the real world’ and that’s something we are very proud of.”

The BMW Alpina B4 Bi-Turbo is available in the UK as a Coupe for £58,950 or as a Convertible for £62,950, with a long list of standard equipment that includes an eight-speed automatic gearbox, Adaptive M Sport Suspension, leather upholstery, electrically adjustable heated sports seats, climate control and Bi-Xenon headlights.