This next-generation 8 will be more modestly cylindered than BMW’s first: There will be an 840i with a turbocharged 3.0-liter inline-six and an 850i powered by a twin-turbo 4.4-liter V-8—though even the six, which makes up to 335 horsepower in today’s BMWs, will surpass the output of the original 850i’s 12-cylinder.