Alpina’s new B4 Gran Coupe packs more torque than the M4, and adds two doors.
Alpina has filled the gap between the BMW 4 Series and BMW M4 Competition with the second-generation B4, which gains a pair of rear doors for the first time.
Based on the BMW 4 Series Gran Coupé, the new Alpina B4 Gran Coupe arrives just weeks after the Buchloe-based tuning brand was acquired by BMW and is thus officially named the BMW Alpina B4.
It’s expected to be the final addition to the marque’s current-generation line-up of modified BMW models.
As with the firm’s take on the BMW 3 Series, the Alpina B3, the new B4 uses a tuned version of the ‘S58’ twin-turbocharged 3.0-litre straight-six petrol engine, sending 360kW and 730Nm through an eight-speed automatic transmission to both axles – only slightly less power and 80Nm more torque than the 370kW M4 Competition.
Despite the power deficit and weighing 240kg more than the two-door M4 Competition, the B4 is actually 0.1sec quicker than the more hardcore car from 0-100km/h, needing just 3.7sec for the sprint, and it just pips it for top speed, too, topping out at 300km/h.
Modifications to the engine include bespoke turbine housings that “convert exhaust gas energy into boost pressure” at low engine speeds, a larger intercooler, an upsised air filter system and an optimised cooling system.
The transmission has been reinforced, too, to cope with the substantially boosted torque output and is configured to send the bulk of the engine’s power rearwards, “as befits the athletic character” of the car.
Unlike the M4, the B4 is geared towards providing not only “high-level driving dynamics but also lots of comfort for relaxed touring”. The chassis has therefore been extensively modified in keeping with this billing.
Alpina lists upgrades including new bulkhead reinforcement struts, stiffer bushings and mounts, bespoke front anti-roll bars and a unique spring-and-damper configuration among the hardware changes that give the B4 a distinct character. Variable dampers are said to give “noticeable differentiation between the various driving modes”, while three different modes of steering response are available.
The brakes have been upgraded, too, with four-piston callipers gripping 395mm discs at the front and floating callipers paired with 345mm discs at the rear. Drilled, lightweight composite discs are optionally available.
As is customary for an Alpina car, the styling differences over the standard 4 Series are much more subtle than those of the M4. Unique bumpers, spoilers, exhaust exits, side skirts and badging are the obvious tells, plus there’s a new interpretation of the brand’s hallmark 20-spoke alloy wheel design.
Alpina says a new manufacturing process means these 20-inch wheels tip the scales at just 12kg each.
They’re wrapped in high-performance Pirelli P-Zero tyres designed especially for Alpina.
The B4 is yet to be detailed for Australia, although deliveries begin in Europe from July.
Felix Page