What's the Difference Between a BMW 645 & BMW 650?

Updated February 26, 2018

The 645i and 650i automobiles from Bavarian Motor Works (BMW) represent two recent versions of its 6-series performance coupe. The 645i debuted in 2004 and the 650i replaced it in 2006. Both cars share similar size and styling, and have been made in both hardtop and convertible variants. Though the 6-series from 1977 through 1989 was powered by six-cylinder engines, the 645i and 650i have aluminium V-8s.

Engine and Transmission

The engine in the 650i is a 4.8-litre, 360-horsepower V-8, a slightly larger version of the 645i's 4.4-litre V-8 that produced 325 horsepower. Both cars have either a six-speed manual transmission or six-speed paddle-shifted transmission with manual and automatic modes. With this, you upshift and downshift by pressing paddles on either side of the steering wheel. The 645i was also offered with a traditional automatic transmission.


BMW's iDrive, used in both the 645i and 650i, has been enhanced for the later model. Intended to replace a console and dash full of buttons for climate control, radio and other functions, the iDrive system consolidates these into a single turn-and-push knob and dash display screen. The 650i received an iDrive based on a hard-disk based system instead of the older DVD-based system. Among other advantages, BMW set aside eight gigabytes of the hard disk space for music filed from compact discs and other sources.

Brake Energy Regeneration

New for the 2010 650i is a system called Brake Energy Regeneration. This engages the alternator to charge the battery when the car is coasting or decelerating. Under acceleration, the car disengages the alternator, running the electrical system on battery power. This reduces engine loading and saves fuel.

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About the Author

Chicago native John Papiewski has a physics degree and has been writing since 1991. He has contributed to "Foresight Update," a nanotechnology newsletter from the Foresight Institute. He also contributed to the book, "Nanotechnology: Molecular Speculations on Global Abundance."