What is it?
If you’re in the market for a fast, luxurious coupé with more than 400bhp, you’ve likely considered the Mercedes-AMG C63, Audi RS5 and BMW M4. But for a touch of added exclusivity, you might want to consider an Alpina B4 S Biturbo.
The B4 S, which supersedes the old B4, is based on the same straight-six-powered platform as the M4, which has undergone extensive technical and aesthetic adjustments, as per Alpina’s traditions. It means the car is a more potent but less focused alternative to its BMW counterpart.
Under its svelte bonnet is a 3.0-litre six based on the N55 block of cooking 3 Series and 4 Series models, but it uses twin turbochargers that are 10% larger, a water-cooling system that’s 20% bigger and an uprated oil cooler with 35% more capacity. The engine spins a lighter crank that’s made from forged steel.
Maximum power output for the Alpina-fettled N55 peaks at 434bhp at 5500-6250rpm and torque reaches 487lb ft at 3000rpm. Those figures are 9bhp and 81lb ft more than the M4, although the B4 S, which only comes with an eight-speed automatic, is 90kg heavier than the auto BMW. Still, that added torque helps the Alpina to accelerate from zero to 62mph in 4.2sec, a tenth quicker than the M4.
Under the bonnet is where the technical improvements for the B4 S over the B4 end, though: Alpina has stuck with the same suspension settings, meaning it sits on slightly less aggressive springs and dampers than its cousin from BMW's M division.
As before, the B4 S gets BMW Professional infotainment as standard, which adds a widescreen sat-nav and all-round parking sensors. The car’s seats also come wrapped in Dakota leather at no extra cost, although the car you see here features Merino leather, a £1285 option.