In Sport, this same switch alters the speed of gearshifts and the level of automatic throttle blipping, and also provides an additional launch mode.
What’s it like?
Complicated, at first, and quick, of course. Once you’re in third you’ll be struck by how rangey the car feels in its middle bunch of gears because the engine revs so far, peak power arriving at 8300rpm.
But the most noticeable thing of all, if you’ve experienced BMW SMG transmissions of the past, is that the annoying head nod you involuntarily perform every time there’s a gearchange, has largely been banished. Largely, because in its most aggressive setting there is still a brief surge as you upshift on hard acceleration.
With the M3’s roof folded, you enjoy a new level of aural entertainment from the engine, whose creamily frenetic warble comes at you all the more clearly from the quartet of exhausts.
Apart from the obvious sunny-day advantages of a convertible, this has to be one of the major benefits of buying a drop-top M3. The trade-off, apart from the £4135 price premium, is its weight, which would doubtless be detectable back-to-back on a track, the additional mass fractionally diminishing the car’s agility.
But in isolation this M3 Convertible is a highly athletic beast, changing direction without hesitation and flaunting a cross-country fluency that is a pleasure to exploit. That pleasure is only faintly marred by the odd structural quake and quiver, with the removal of the M3’s roof inevitably weakening its shell.
That said, this M3 Convertible is 30 per cent stiffer with its metal roof closed than the previous fabric-roofed model. A question mark still dances over the M3’s steering, which ought to be more feelsome around the straightahead.
And the transmission? The surprise is that despite the potential for seamless shifts that a double clutch transmission provides, this is not always a jerk-free, quirk-free gearbox, even though it’s a huge improvement on the SMG boxes.
In fact, it has deliberately been configured to create a driveline thump in the sportiest modes, and more seriously, it is quite often slow on the uptake when you’re moving off from rest.
At times you’ll think you’re driving a car with an automated single plate clutch. And the descent through the gears as you stop at traffic lights, say, is not completely smooth.
But on the positive side, the speed of its gearswitches, the extra ratio and its magnificent downshift blips in the sportiest settings are major appeals, as is the convenience of paddle-shifting when you’re rushing a tightly twisty road.
Should I buy one?
Yes. The pleasures of hearing that V8 in all its high octane, warbling glory are not be dismissed lightly, and you lose little of the M3's real-world performance as a result of the added weight. Undoubtedly, though, those who want the ultimate in dynamics will go for the closed roof option.
And the transmission? The performance-obsessed should note that it makes the M3 a quicker car, that you get an extra gear (making it more economical, too) and that it provides another intriguing dimension of adjustment and fine-tuning.
But this is a sometimes quirky transmission, one that does not always do what you want it to – especially from rest – that sometimes jerks, shudders and displays less finesse than a master of the manual gearshift would muster.
It’s very likely a transmission whose appeal grows with familiarity, but some will prefer the simple purity of your classic manual transmission.