First drive: Alpina B4 Biturbo

What is it?

Alpina's attempt to out-BMW M4 the BMW M4. The B4 is, in essence, a heavily-pimped 435i, though the German tuning firm's pimping has proved so successful that the humble Alpina now looks a mighty compelling alternative to the M-division's own offering.

The B4 - largely through the addition of a second blower to the 435i's single-turbo straight six - makes 406bhp, which falls just short of the M4's 425bhp (also, of course, generated by a blown 3.0-litre six), but trumps the M-car on torque.

0-62mph takes 4.2 seconds - within a blink of the DCT-equipped M4 - with top speed standing at a not-so-shabby 188mph.

So this is more than a bodykit and ECU flash, then?

Much more. We've always been mightily impressed with the thoroughness of Alpina's conversion jobs, and the B4 is no exception. As well as the reworked engine, the B4 gets fresh suspension, a new Akrapovic exhaust, Alpina's lovely wheels, and heavy modification to the eight-speed ZF transmission (no manual is offered, sadly). And, of course, plenty of Alpina badging and those bodywork ‘upgrades', most noticeably a Jay Leno-esque chin spoiler.

How does it drive, then?

Interesting one, this. See, our first experiences of the M4 have been something of a mixed bag, with factions of the TG office suggesting it feels less like a standalone, halo-ringed product of the M-division, and more like, well, a bumped-up 435i.

The B4, of course, is a bumped-up 435i and, sure enough, feels very, very closely matched to the M4. Like the M4, it's a properly comfortable cruiser, buttering through commuter traffic with consummate ease. And, like the M4, it has a truly ballistic turn of pace when you wind it out.

Get those turbos blowing and the B4 flicks itself into the middle distance with an effortless swat, sounding every inch the classic M-car as it does so.

But, like the M4, the Alpina doesn't feel the most razor-edged companion on a twisty road. Yes, it's more than happy holding grand, daft skids - at least with the £1890 limited-slip differential fitted - but doesn't communicate a whole lot from the rear end as it does so, trading in seat-of-yer-pants feedback for a more relaxed day-to-day experience.

We didn't get a chance to test the B4 on circuit, but we'd suspect that, like the M4, it might feel a little woolly round the edges when given die bohnen on a track.

Does it feel exactly like an M4?

Tough to say without testing the two cars back-to-back. The B4's steering felt rather sweeter than the M4's, though that likely has as much to do with the Alpina's slimmer, firmer wheel - the M4 uses a strangely overplumped rim - as any mechanical differences.

Even on those vast wheels, the Alpina's ride quality is generally more than decent, but the B4 does get a little upset by sharp-edged potholes, a symptom we don't remember the M4 suffering to quite the same extent. The Alpina's seven-speed auto, on the other hand, is so good that you wonder why BMW went to all the effort of fixing a DCT for the new M4.

So which should I buy?

The Alpina costs almost exactly the same as the BMW M4 (£58,950 against £59,145) and offers all but identical performance.

The B4 seems truer to its stated brief as a road-and-track all-rounder than the newly civilised M4, but which one you prefer will, we suspect, come down to whether you prefer the idea of a BMW badge or something a little more left-field on the back of your super-coupe.

And, of course, whether you can get on board with the B4's visuals, particularly that chinny front clip. Another quality effort from the Alpina team either way.