Reducing the fuel consumption of conventional ICE vehicles are usually achieved from reducing vehicle running resistance, improving engine efficiency, save the idle energy, and recycling the waste energy. About 5-10% of fuel consumption can be saved by engine idle-stop, which strongly depends on fuel cut-off schedule before the vehicle completely stop. However, engine shut-off during vehicle coasting-down always exist strong concerns of safety and drivability issues.
Fuel cut-off before vehicle completely stop creates the risk that the driver might change-of-mind (CoM). The driver could request the engine restart during engine running down period, when engine speed between 200-500rpm. With convention starter, the pinion gear is actuated simultaneously with the starter motor energizing. There will be no chance to engage the pinion gear with crankshaft gear when the engine is not still. That realizes idle-stop function activated before vehicle completely stop is unachievable by using conventional starter.