Stop-start systems essentially shut down an engine to save fuel when a car is sitting in idle traffic, and then almost instantly kick it back into life once the accelerator is depressed or the clutch is engaged. By doing this, stop-start systems offer the greatest fuel savings around town, where high cycle stop-and-go driving is common. The savings can be substantial, with four-cylinder models regularly returning savings of around 4-6% in fuel consumption. The fuel savings are expected to be higher in the six-cylinder models.
However, because of their complex mechanisms current systems only work with manual transmissions. While gearbox manufacturers like ZF have developed new versions that work with automatics, their market roll-out is still several years away for BMW.
As most six-cylinder BMW models are sold with automatics, the carmaker has been reluctant to add stop-start systems to these cars, according to BusinessCar. There’s been no mention in which markets BMW will first offer the option and in which models it will be available.