E9, 3.0CSL, 1971-1975: While it doesn’t have an M6 badge on it, you could make a strong argument for the 3.0CSL being the very first M6. Like the M3 and M1, it was a homologation special, built to satisfy the standards of the European Touring Car Championship. It was essentially a road-going racer, with thinner sheetmetal for the body, along with aluminum doors, hoods, and trunks. Its side windows were Perspex. Sound deadening and other “unnecessary” features (power windows and such) were removed. It was powered by a 3.0-liter, six-cylinder engine, that was eventually bumped up to 3.2-liters. Finally, an aero kit was fitted for improved aerodynamics. It may not have been called an M6, but it certainly had a lot of the traits that make an M car.
E24, M6/M635CSi, 1983-1989: Although the E24 6-Series had been on sale since 1976, BMW didn’t offer an M-tuned version until 1983. When it did, it was 1983 and that car was called the M635CSi. Power came from a version of the inline six-cylinder engine from the M1 supercar, and produced 282 horsepower and 246 pound-feet of torque. That thrust was delivered to the rear wheels by a five-speed manual gearbox. In 1987, BMW finally shipped the M635CSi across the pond, where it was rechristened as the M6. Unfortunately (and as often happens) the M6 lost something in its translation to North American. Due to mechanical and emission changes, our M6 only developed 256 horsepower. The M6/M635CSi was M's first car after the M1 was discontinued, predating the M5 by two years
E63/64, M6, 2007-2010: At the end of 1989, the 6-Series, and the M6 with it, went on an extended hiatus. In 2005, the 6-Series badge returned, and it was a mere two years before we got another M6. This was a very different M6 than the 1980s car. It was a big, heavy GT, more in line with the 8-Series of the 1990s. It rode on a modified 5-Series platform (the E60 5er, hence the internal model names of E63/64, denoting coupe and convertible), and can trace its roots directly back to the E60 M5, on which it shares much of its technology. The V-10 engine is derived from BMW’s Formula 1 V-10, and displaces 5.0 liters. It nails the 100-horsepower-liter mark, with a total of 500 ponies and 380 pound-feet of torque. Power was sent to the rear wheels by way of a sequential manual gearbox. The second-generation M6 was also available in coupe and convertible.
F12/13, M6, 2012: There’s a lot to like about the new M6. For a start, it’s arguably prettier than the last car. Like the E63/64, it’s based heavily on the upcoming M5. That means a modified 4.4-liter, biturbocharged V-8 under that long hood, with 560 horsepower going to the rear wheels by way of an M dual-clutch transmission. That power should be good for a 60-mile-per-hour sprint in about 4.2 seconds. Like the previous M6, this one’s driving character can be heavily adjusted on the fly. The transmission, differential, and dampers all have independent settings to deliver max performance, max comfort, and everything in between. Look for the full write-up of the new BMW M6 soon.