Alpina B4 S 2017 first drive

At its heart, this is a more powerful Alpina B4, available as a coupé or convertible and as a B3 S with saloon or Touring bodywork.

For a tuning house keen to make clear that its job is not to tread on the toes of BMW’s M Division, the figures make for interesting reading.

But before that, a quick look as what’s been done. These new S models are not additional to the B3 and B4 range, but replace them. That said, the chassis has been left unchanged - because Alpina says it didn’t need changing - so what we’re looking at here essentially is a powertrain job.

As before, the host unit is BMW’s N55 motor but with its block recast to accept Alpina’s twin-turbo application. It has a forged steel crank, 10% bigger turbos, 20% more cooling capacity for the water and 35% more capacity for the oil. And again, the sound of the motor is spat out through Akrapovič exhausts. The automatic transmission is strengthened, has a bigger step between Drive and Sport modes and offers quicker shifts.

This work raises power by 30bhp to 434bhp and torque by more than 10% up to 486lb ft. So, Alpina’s hot 3 Series and 4 Series-based models are now more powerful than BMW M’s equivalent propositions, and offer a stack more torque. BMW Yes, the M cars are lighter (78kg for a two-pedal M4), which means they just manage to hold a fractional power-to-weight ratio advantage, but in terms of the arguably more important torque-to-weight ratio, the Alpinas are a distance ahead. The Alpina is more expensive, but by less than £2000. It should also be mentioned here that while the Alpinas are automatic-only, unlike their M car equivalents, they are available with rear or four-wheel drive.

The unchanged chassis retains Alpina springs, dampers and bars and comes with additional front camber relative to the BMW M3 and M4.

Forget that the figures point to a mere 0.1sec improvement in 0-62mph time, as traction limitations render such news worse than meaningless. Whereas the B4 always felt undeniably rapid, the rear-wheel-drive B4 S coupé we're driving here is a serious high-performance machine.

And it’s not difficult to see why: it’s not the power but that additional torque in the middle of the rev range that provides real-world performance a clear step ahead of its predecessor. The motor’s throttle response is almost as good as a normally aspirated unit and its unadulterated sound is actually better than most.