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M4 who? The new Alpina B4 Bi-turbo tries to improve on the ultimate driving machine

Alpina’s new B4 Biturbo may wear the blue and white logo of BMW, but the M4-based two-door has been re-engineered under Alpina’s supervision from the near ground up.

The aerodynamics, 20-inch signature wheels, and eight-speed automatic transmission are all new for the B4 coupe and convertible. Perhaps the biggest difference, though, is the engine: the Bi-turbo uses a revamped version of the 335i’s N44 straight-six, rather than the S55 B30 from the new M4. 

The re-jiggered 3.0-liter straight-six yields 410 horsepower and 443 pound-feet of torque, 20 fewer hp but 38 more torques than the M4 can muster. Alpina manages this by moving from a single turbo system to a twin, which improves throttle response. Engine internals, like the crankshaft, are now forged steel, and there’s a new cooling system to keep everything under the hood tidy.

As far as acceleration goes, the M4 is a bit quicker to 60 mph: 3.9 seconds with the six-speed manual and 4.1 for the 7-speed dual-clutch. The B4 Coupe needs 4.2 seconds to reach 60 with the automatic. And as with all Alpinas, the auto is the only transmission offered. However, for left-hand drive markets, the Alpina will be available in all-wheel drive mode that’ll get the job done in 4.0 seconds flat.

The B4 may be a tad slower, but it has the Bimmer beat in fuel efficiency : the M4 gets approximately 25 mpg on the highway, while the Bi-turbo can manage a stunning 37.2 mpg in coupe layout. The Alpina is pricier, though. The coupe starts $78,452, a noticeable jump over the M4 Coupe’s $64,200 base price. The convertible will run $85,542.

The Alpina will debut at the Goodwood Festival of Speed next week, and it will do so with some extraordinary company: The Bentley Continental GT3, Elemental RP1, 2015 Range Rover Sport, a new, track-focused McLaren, and many more are all expected to make appearances at the event.

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