Development of a Stop & Start Sailing Activation Strategy for a Real-World Driving

Stop and Start (S&S) systems have been favorably accepted by OEMs lately as they offer significant fuel economy improvements at minimal cost. According to upcoming homologation cycles and due to more stringent Corporate Aggregate Fuel Economy (CAFE) targets, S&S should be further improved by operating it also at vehicle in motion. This feature is known as Sailing: it decouples the engine from the driveline during coasting, extending the distance covered by the vehicle, and shuts the engine off. The automation of transmissions paves the way for the introduction of this feature. In order to evaluate the opportunity for a sailing event over real-driving conditions, an innovative control strategy has been developed and assessed. This paper assesses, through numerical simulations and experimental testing on a C-segment vehicle powered by mid-sized EU6 diesel engine, the fuel economy potential of S&S Sailing over several schedules, i.e. FTP-75, US06, WLTP, Real Driving Emission (RDE). The simulation and experimental data over the new WLTP cycle highlight significant fuel economy benefits without significant engine emission drawbacks.