In-Depth Photos of the 2020 BMW M850i xDrive Convertible

If the 8 isn't more than the 6 in size, though, it is more in several important ways. The first of those is design. In any form other than the Gran Coupe, the 6 was too conservative.

But the 8-series has more sculpting in its flanks, more sinew in its hood, and those great, gaping air intakes in the front fascia. Taillights inspired by the wild i8 hybrid never would have looked at home on the 6-series, but they work here.

And inside, where the 6-series was constructed from large forms and sharp angles, there's more art and nuance in the 8, which relies on more organic curvatures and shapes.

More important, the 8 is more than the 6 in terms of performance. The M850i's twin-turbo V-8 still displaces 4.4 liters, but the engine has been redesigned from the crankcase up and now makes 523 horsepower and 553 lb-ft of torque.

Not only is that up 78 and 73 units, respectively, over the old 650i, it's down only 37 horsepower from the old M6's engine and actually up 53 lb-ft of torque. We know there's an M8 on the horizon, and this has us awfully excited.

Not that the M850i isn't plenty exciting. With a launch-control program that effectively neutral slams the ZF eight-speed on the all-wheel-drive system, it hits 60 mph from rest in just 3.5 seconds and rips through the quarter-mile in 11.8 at 119 mph.

Remember when the Nissan GT-R democratized 11-second quarter-miles for sub-$150,000 cars? Now, here's a paunchy four-seat BMW convertible that can do so without the warranty-voiding woe that hung a big asterisk on the GT-R's accomplishment.

And the soundtrack is an improvement even on the current M5. The M car's exhaust note is a high-pitched whir that doesn't necessarily even sound like an internal-combustion engine. The M850i's twin-turbo, on the other hand, bellows out a bassy old-school V-8 beat that recalls Detroit's best muscle cars at idle, rocking like boats on the high seas.

There's no rocking from the 850i in motion, though, not even over rough roads. For a vehicle with such a big hole in its structure, the 8-series convertible is remarkably solid.

At a base price of $122,395, the 2019 M850i xDrive convertible is more than $20K more expensive than was the equivalent 2018 650i xDrive droptop. We guess that, if you're going to pull that one over on your buyers, a name change makes sense.