This is a car for those who like going really, really fast. There's an option to unshackle it from the speed-limiter, taking the top end from 155mph (a 640d can do that) to a big-league 190mph. It'll go to 62mph in 4.2 seconds, meaning, in all probability, a 0-60 time nicely discounted to 3.99. It'll break the traction of its 295-section rear tyres as soon as look at you.
It's got the technology to back up the power. The twin-turbo V8 has a cat's cradle of a patented ‘Cross-Bank' induction system (the turbos are in the vee, and each one is driven by cylinders two and three of its own bank and one and four of the opposite one, since you asked) to feed evenly spaced pulses of exhaust gas to the twin-scroll blowers, which send the induction air via close-coupled intercoolers. That's all in the name of cutting lag. It's not entirely successful, but it's close. The V8 also has Valvetronic variable lift, VANOS variable timing and direct injection, all to take care of efficiency at everyday speeds. The transmission is a seven-speed dual-clutch, and the degree of diff locking is controlled by the ESP brain. The dampers are adaptive; the brakes, optionally carbon-composite.
You can separately configure the steering weight, the dampers, the transmission aggression, the accelerator map, the degree of ESP and even the lay-out of the head-up display (nav arrows or a huge tacho). Handily, you can store your favourite combos on steering-wheel shortcuts.
Impressive facts and stats. So it must be sensational to drive, eh?
Well, no. Sensation is exactly what's lacking. Oh, yes, your internal accelerometers are being spiked by the lateral and longitudinal forces, and the scenery blurs through the windows while other traffic becomes a near-stationary chicane. But there's little feedback from the controls, and the noise isn't very interesting. The car doesn't feel or sound alive - it doesn't report enough on what it's up to. Even when making huge efforts, it seems effortless. Is that your idea of a sports car - rapid transit, speed that you barely notice until your world fills with flashing blue lights? Me, I crave more of an experience. This isn't a sports car, because it doesn't make you tingle.
The M6 shares its powertrain, suspension and most of its other technologies with the M5. For a saloon, it makes some kind of sense that it all feels so subdued, but, with a coupe, I want a different calibration. And, by the way, I definitely enjoyed the M6 cabrio more than the coupe, driving on the same roads. The extra exhaust noise and the speeding rush of air brought the M6 - and its driver - to life.
4395cc, V8, RWD, 552bhp, 502lb ft, 28.5mpg, 232g/km CO2, 0-62 in 4.2secs, 190mph, 1925kg
Vastly quick and entirely capable, but it serves up its speed with a strange diffidence and sense of detachment. It pains - and surprises - us to report that the drop-top version is more fun. Not one of the great M legends.