2009 BMW X6Enlarge Photo
Currently, M engines are a 4.0-liter V-8 in the M3 and a 5.0-liter V-10 in the M5 and M6. Both engines favor very high RPM horsepower over big torque numbers, consuming plenty of gas along the way to their peak outputs. According to Autocar, the newest M model, the xDrive M, based on the BMW X6, will have a twin-turbo V-8 that should match the M5's V-10 at 500 hp, while making considerably more torque than the V-10 (rumored at up to 516 pound-feet). This should give the newest M model, even with its considerable heft, a 0-60 mph run of under five seconds.
A BMW official said that the new turbocharged engines should match or exceed current M performance, while delivering "much better consumption." The M division is also testing stop/start functionality, regenerative braking, and a gas/electric hybrid drivetrain for installment on future models.--Colin Mathews