DEVELOPMENT OF A STOP & START SAILING STRATEGY FOR NEXT GENERATION POWERTRAINS

Nowadays OEMs (Original Equipment Manufacturer) are facing the challenge of producing vehicles that meet future fuel economy and emissions requirements at an affordable price to satisfy the desired customer value. Stop & Start (S&S) system has been favourably accepted by OEMs lately, as it offers significant fuel economy improvements at minimal cost. S&S system removes the engine’s drag torque, when no traction is required, preventing from burning extra fuel. According to upcoming homologation cycles and due to more stringent CAFE (Corporate Average Fuel Economy) targets, S&S should be further improved, by operating it even with vehicle in motion. This new operating mode is known as Sailing: it decouples the engine from the driveline during coasting, extending the distance covered by the vehicle, and shutting the engine off. The automation of transmissions paves the way to the introduction of this feature. Consequently, the aim of this work is the definition of the main characteristics of this new feature and its evaluation: in order to assess the benefits of the sailing feature over real-driving conditions, an innovative control strategy has been developed and implemented into a simulation tool for the preliminary quantification of the benefits. Starting from the lesson learned numerically a prototype vehicle has been built and implemented with a proper logic for the autonomous management of the clutch during the activation of the feature. Then, through an experimental test campaign on a C-segment vehicle powered by mid-sized EU6 diesel engine, the fuel economy potential and the impact on diesel emissions of S&S Sailing over real-world driving cycles, has been quantified. Finally a clinic survey was performed in order to study the phenomenon with normal drivers and investigate the level of acceptance of the actual prototype vehicle.