Most of the BMW 6-Series lineup isn't seeking recognition as a purebred sports car, or record lap times; as a rather large, hefty touring Coupe or Convertible, its specialty is devouring long stretches of interstate--or autobahn--while staying limber enough to take on mountain roads without breaking a sweat.
Throughout the 6-Series lineup, and whether you're talking Coupe or Convertible, there are two non-M models: 640i and 650i. At a time when BMW names correspond to virtual, not actual engine size, and turbochargers are part and parcel to the lineup, the 640i uses a 3.0-liter TwinPower turbocharged six-cylinder engine rated at 315 horsepower, while the 650i gets a 4.4-liter twin-turbocharged V-8 engine rated at 400 horsepower.
Both engines are willing performers, but we do tend to think that the larger, more laid-back character of the V-8, and its easy, smooth power, better suits the 6-Series' own personality. Handling is confident, and the 6-Series models track well, and while they steer and maneuver as lighter cars we do wish that the steering had a more natural feel, or some feedback. These are cars that can cruise effortlessly at well above 100 mph, so you'll need to take some extra measures if you're already a chronic speeder.
In either the 640i or 650i models, you get an eight-speed automatic transmission that shifts smoothly and seamlessly, and rises to the task of more aggressive driving surprisingly well. A six-speed manual transmission that had been a no-cost option, offered only on rear-wheel-drive V-8 models, has been deleted. You can get xDrive (all-wheel drive) on Coupe, Gran Coupe, and Convertible models, making them one of the few drop-tops with AWD.
All of these models are highly adjustable and customizable, through a system called Driving Dynamics Control. Through Comfort, Sport, and Sport+ modes available at the press of a console-mounted button, you can change throttle response, transmission behavior, and suspension settings, to best suit the type of road you're on, or the kind of company you have in the passenger seat. The range of performance can be astounding: steering goes from light and very quick to incredibly hefty, transmission shifts become rapid-fire or slow down to a mellow pace, ride quality makes road imperfections disappear or it seizes control with a steely grip but still without harshness, something BMW's done well in its transition to electronically controlled performance. The 6-Series' bulk and its hulking demeanor have even lightened up in this generation; it's noticeably less bunker-like, more involved with the road.
New again this year is the M6. It was introduced as a Convertible late in the 2012 model year, in 2013 as a Coupe, and this year it adds its ultimate expression in the form of the M6 Gran Coupe. Just as the latest M5 did, the M6 dumps the thirsty former V-10 in favor of a 560-hp BMW M twin-turbo V-8 with 500 pound-feet of torque. The transmission choices are either a special seven-speed M Double Clutch gearbox--it offers automatic and manual driving modes with three settings each, a launch-control function, and exceptionally fast shifts--or new this year, a six-speed manual transmission with three driving modes, rev-matching and a light pedal effort. The manual's shift modes--Efficiency, Sport, and Sport+--govern gear changes in the dual-clutch gearbox, and rev-matching in the manual, with Sport+ in the manual dropping the rev-matching entirely for complete human control.
With either transmission, the power's shifted between the rear wheels with an active differential that's in cahoots with the throttle and stability control, so that power can be used passive-aggressively, to tighten corners or to lower slip. And no matter which gearbox or bod gets the nod, the M6 is a rear-drive rocket ride: even in the long-wheelbase Gran Coupe, the M6 can shoot to 60 mph in 4.1 seconds, and charge up to a limited 155-mph top speed.
The M drivetrain is matched with an M-specific chassis with lighter construction, upgraded brakes (carbon-ceramics are a new option), special sport seats, and extensive M Drive controls over suspension, steering, powertrain, and stability controls--graded in Comfort, Sport, and Sports Plus settings. The M6 even includes two customizable setting buttons to quickly dial in a different character for a certain kind of driving, accessible like radio-station "favorites" with a simple tap.
That tap needs to be simple, and quick. The M6 builds speed with incredible swiftness, and most owners will want to exercise it any time even a small window opens in the road ahead. The range of driving feel has only grown since the previous M6, and BMW's gotten better at synthesizing more natural driving responses out of its electronically controlled systems. Steering responses are more progressive, still without feedback until you've dialed out almost all of the assist in Sports Plus; only in the same notch will the taut ride turn too tight for even the BMW diehards. The plush curb weights, even with the Gran Coupe, don't detract as much as they once did from the M6, and the frantic steering and throttle responses have calmed down, too.