​​Alpina sports coupé is something a bit different

On the road in the new Alpina B4 S Biturbo

Alpina’s B4 S Biturbo has joined the fast luxury coupe race, alongside more mainstream contenders including the Mercedes-AMG C63, Audi RS5 and BMW M4. The newcomer, which replaces the old B4, is based on the M4’s straight-six-engined platform, but boasts a raft of visual and performance upgrades.

Most headline worthy is its 434bhp from its N55-based 3.0-litre six-cylinder engine. This begins life as the regular unit used in the 3 Series and 4 Series, but boasts a pair of 10% larger turbos, a 20% more efficient cooling set-up, a 35% larger oil cooler and a forged, lighter crank. It’s all teamed with an eight-speed automatic gearbox, which can be manually shifted via buttons on the wheel.

The B4 S’s peak power now comes at 5500-6250rpm, while 487lb ft of torque surges in at 3000rpm. The figures are a 9bhp and 81lb ft boost over those of the M4, and while the 1690kg Alpina is 90kg heavier than the equivalent BMW, it’s 4.2sec 0-62mph sprint time is 0.1sec quicker.

Slightly softer suspension settings than the M4 are carried over from the B4. Also, the retained BMW Professional infotainment system adds widescreen sat-nav and all-round parking sensors, and Dakota leather is fitted as standard. Our test car’s Merino leather costs £1285 more.

The Akrapovič exhaust system emits a more subtle tone than the M4’s guttural growl, and in day-to-day driving in default Comfort mode you’ll get only a hint of the car’s performance potential. Its responses impress, nonetheless, and the ‘box changes up at 2000rpm in normal city driving.

It’s a different story in Sport, however. Low-down response is excellent, and is enhanced by a defined, great-sounding kick-on at 3000rpm and a boost of muscle on each upchange. The Alpina exhibits different characteristics when it comes to putting power down to the ground as well; the M4 has a more abrupt, traction-challenging style, while the B4 S’s delivery boasts more useable elasticity that makes it friendlier when exiting corners at full chat.

While the BMW’s low stance and weight advantage give more effective turning and stopping ability, its responses on slippery roads can be a little unpredictable. In contrast, the Alpina’s softer approach makes it a more comfortable companion over broken surfaces, despite the large 20in Alpina Classic alloy rims. It hustles along fast B-roads more easily than the M4, thanks especially to its compliance, superbly weighted steering and super-responsive transmission. The ease and reward of the driving experience becomes even easier in Comfort mode; whether this makes the car more flexible than the M4, or merely less focused, depends on your viewpoint.

Elsewhere, and in common with the BMW, the infotainment feels less hi-tech than the Virtual Cockpit of the equivalent Audi RS5. Still, it has a classic simplicity thanks to analogue dials that nicely fit its character. We like that the Alpina is refreshingly subtle compared with the more ‘in your face’ M offerings. There are plenty of hard-edged options on the market if that’s what you’re looking for; for a focused yet still relaxing drive, however, we’d definitely consider the B4 S.

Alpina B4 S Biturbo

Price £63,000
Engine 2993cc, 6cyls, petrol
Power 434bhp at 5500rpm
Torque 486lb ft at 3000rpm
Gearbox 8-spd automatic
Kerbweight 1690kg
Top speed 190mph
0-60mph 4.2sec
Fuel economy 35.8mpg
CO2 rating 180g/km
Rivals BMW M4, Mercedes-AMG C63, Audi RS5

Sarah Bradley is a writer for WhatCar.