Spied: BMW 8 Series Gran Coupe

BMW's revived 8 Series will sprout two extra doors.

BMW's upcoming 8 Series Gran Coupe has been spotted undergoing shakedown testing in Munich, Germany. The 8 Series Gran coupe follows the previously introduced 8 Series coupe and convertible.

The 8 Series Gran Coupe was hard for engineers to hide thanks to its enormous length. The 8 Series is believed to stretch more than 16.5-feet, placing it within spitting distance of the 7 Series sedan.

As with most of BMW's Gran Coupe models, the 8 Series features a low-slung roofline that tapers at the back. The rest of the Gran Coupe's styling largely mirrors that of the 8 Series two-door models.

The model spotted today is believed to be the M850i. The M treatment is given away by the car's blue brakes and quad exhaust outlets. Under hood the M850i will use a 4.4L twin-turbocharged V8 tuned to deliver 530 horsepower and 550 lb-ft of torque.

The M850i is expected to sit in the middle of the 8 Series Gran Coupe line; below it will be the six-cylinder-powered 840i and above will be the fire breathing M8. The 8 Series Gran Coupe range will give buyers an alternative to vehicles like the Porsche Panamera and Mercedes-AMG GT sedan.

Look for the BMW 8 Series Gran Coupe to make its official debut sometime next year.