German automaker Mercedes-Benz introduced their proprietary Active Cylinder Control concept to help boast the fuel efficacy of their flagship 12-cylinder engines.
All 12-cylinder cars burn an excessive amount of gasoline because they are strictly designed for performance. Wasting gasoline is an expected trade-off should a person want a car to drive with as much power as possible. Though most drivers, including owners of very high-end sportcars, rarely maximize the potential of their vehicle or ever put its engine to full use.
Active Cylinder Control (ACC) is a simple but effective system that will turn off some of an engine's cylinders if they aren't needed at a given time. ACC allows the car's computer to determine the number of cylinders required for the best possible performance, and can temporarily cut fuel to only these cylinders. ACC then greatly helps a 12-cylinder engine to operate through common traffic and driving conditions while consuming the least amount of fuel.
ACC was only applied toward Mercedes' 12-cylinder engines, and was discontinued in 2002.
