The optional Driver's Package gives you treble-top

That’s two-hundred and ninety kilometres an hour. And even that is still electronically limited. Unfettered, and on the right tyres, it’d go faster still. That’s what’s possible when the hp figure begins with a 5.

It's not a 'loud' button, it's a 'quiet button'

There are two settings for engine sound. They vary both actual exhaust sound – by opening or closing flaps in the system at certain revs and throttle openings – but the louder setting augments it through the speakers.

This is not some way of muting the engine to get through noise pollution rules: it always complies even in the loud mode. The engineers say most drivers will keep it raucous. But select ‘quiet’ for early-morning starts (pleasing the neighbours) or long trips.

The cylinder head uses 3D printing

That’s because its water passages are so intricate they couldn’t be produced by conventional casting. It uses a valvetrain that’s similar to the regular BMW straight-six, but apart from that almost every part in the M engine is different.

This straight-six is also all-new versus the previous M3/M4, and this time it’s closely related to the one in the X3M/X4M. But not quite the same. Both the car engine and the crossover engine have forged crankshafts, but the one in the car is lighter, to make it more responsive especially at high revs. The red-line remains at 7,200rpm.

The M guys make a great play of the fact the engine was developed ‘alongside’ the one for the M4 GT3 car. Which, they point out, goes up against Ferraris and Porsches. So certain main parts of the engine need to be ready to tackle the heat of high-level competition.

It's an automatic

Well, the Competition is. The regular one can be had with a manual, but that car isn’t sold in the UK.

And by ‘automatic’ we mean a conventional automatic, with eight ratios, not a twin-clutch box (aka DCT). The old one, the F3x, was a DCT. So was the V8-engined E8x before that. Prior to this, the E46 and E36 had the clunky single-clutch SMG.

This means it’ll be smooth in town. And we don’t expect the shifts will be slushy when you’re in a hurry: there are multiple configuration options to ask for them to bang through snappily. And it’s not like BMW doesn’t have experience in this area – see the current M5’s autobox.

It'll steer itself. Backwards

The M3 and M4 can be outfitted with all the driver assistance of any other 3 or 4. That includes the little-known reversing assistant.

It goes like this. When you go into R, you’re given the option to have the car’s steering take over and trace the exact same path in reverse as your last 50 metres going forward. So if you’ve driven a tricky course between walls and obstacles into a parking space, you know the car will get you out again. Provided the obstacles haven’t moved.

Pedals, of course, remain your responsibility in all this.

Wheel diameters are different front and back

The RWD Competition model has 9.5x18s at the front and 10.5x19s behind, in forged alloy. Tyres are 275/40 at the front and 285/35 behind.

The xDrive version will get 19 and 20.

The Touring should feel like the others

Actual prototype driving of the Touring version has only just started. But Carsten Wolf, in charge of the M3 and M4 ‘vehicle characteristics’, tells Top Gear the aim is to make it feel just like the sedan.

And he says the sedan feels just like the coupe. Subtle changes in suspension setups help compensate for slightly different weight distributions and body stiffnesses, you see.

A convertible is also in the plan

Yup, we’ve had it confirmed by Hagen Franke, head of product management for the cars. What he didn’t say – but we know because thinly disguised prototypes of the regular 4 Series cabrio are chugging around Munich – is that it returns this time to a soft top not a folding hardtop. That means less weight, less complication, sleeker styling and a bigger boot.

STORY Paul Horrell