2014 Alpina B4 Biturbo: Alpina works its German magic on the BMW 4 Series

Legendary BMW tuner Alpina has already gotten its hands on the 4 Series coupe. The 2014 Alpina B4 Biturbo debuted at the 2013 Tokyo Motor Show.

The B4 Biturbo is based on the BMW 435i, and retains its 3.0-liter, twin-turbocharged inline-six. However, Alpina replaces the stock turbos with ones of its own design, adds a freer-flowing exhaust system, and modifies the engine internals.

The result is a substantial increase in power, from 300 horsepower and 300 pound-feet of torque to 410 hp and 442 lb-ft.

Equipped with an eight-speed automatic transmission, the B4 Biturbo will do 0-62 mph in 4.2 seconds, and reach a top speed of 189 mph.

Alpina also reinforced the suspension and brakes to make the B4 Biturbo more than just a dragster. The car also gets 20-inch wheels with Alpina’s signature multi-spoke design.

Unlike other tuners, Alpina has always preferred subtlety to loudness, and that’s apparent in the tasteful visual modifications seen here. Instead of flared fenders and acres of louvers, the B4 Biturbo gets a restrained body kit and trunk lid spoiler, plus quad exhaust outlets to hint at the power under the hood.

Alpina caters to a different crowd, which is why its cars traditionally have turbochargers and automatic transmissions, two things that (used to be) anathema to the in-house tuners at BMW M.

This impulse to do what M won’t has also led Alpina to build performance versions of cars the factory doesn’t want to touch, including diesels and the 7 Series full-size luxury sedan.

As with the regular 4 Series, the B4 Biturbo will be offered with either rear-wheel drive or all-wheel drive. It goes on sale in Europe in May 2014, but may not make it to the U.S.