BMW’s pure M and M-performance are currently being offered with six- and eight-cylinder turbocharged engines. But while German premium rival Mercedes-Benz offers – through its AMG division – a line of performance models (with 45 badge) powered by four-cylinder mills, BMW is adamant in not pursuing such power options unless some issues are addressed promptly and properly.
BMW isn't likely to employ four-cylinder engine due to power concerns, this was disclosed to the media by Frank Van Meel, chief executive of BMW’s high M Division. According to Van Meel, BMW and BMW W have been happy with its six-cylinder engines because they consider this mill as their heritage engine. He noted that six-cylinder engines have a long history with BMW, since it was the mill that first powered the M1, and that was in 1978. He also noted that a six-cylinder is an iconic engine, and BMW is a six-cylinder inline company.
As for a four-cylinder engine powering an M car, Van Meel shrugs off such possibility. He remarked that four-cylinder engines don’t have the characteristics or attributes necessary for an M car, even if it is a turbocharged four-cylinder mill. Van Meel has a valid point here, since four-cylinder engines – even those boosted by turbochargers don’t develop enough torque at low engine revs, which should affect performance especially during standstill accelerations. He noted that the typical attributes and overall drivability of an M car would be lost if it is powered by a four-cylinder engine.
However, Van Meel isn't totally against the idea of having a four-cylinder engine powering an M car. Engines that couldn’t provide the needed low-end torque—like a four-cylinder mill – could be complemented by a propulsion unit that could deliver high amount of torque instantly and immediately. Definitely, an electric motor is surefire way to get the needed torque instantly and even Van Meel is aware of this fact.
Complementing a turbocharged four-cylinder engine with an electric motor seems to be the right solution. However, these are still different powerplants even when working as a single hybrid drive unit. Adding an electric motor comes with the installation of a corresponding battery pack. As Van Meel noted, opting for electric motors would mean the addition of extra weight into the vehicle, thereby making an M car heavier than planned. In the end, this would tip the power-to-ratio to the negative side, affecting the motorsport capabilities inherent in M cars.
Van Meel remarked that as of now, four-cylinder engines won't find their way into M cars. Future innovations of battery cells – in terms of weight, power, range and density – might change the M Division’s position towards four-cylinder engines. For the meantime, six- and eight-cylinder engines are doing their job well and are providing the right solutions for BMW M.