On the Fuel Economy Benefits of “Coasting”, Realized by an Electronic Clutch System

Anyone who already had the opportunity to ride a bike has experienced the benefits of a system operating at coasting: As soon as a certain velocity is reached, the biker stops pedaling and just coasts down, administering the kinetic energy to minimize his own energy consumption. The idea, inspired by biking, that it is possible to improve fuel economy just by adopting clever coasting strategies suggests also a very promising perspective in the automotive world and, as a matter of fact, is not a really “new” thing: It has already been explored in the past on several different vehicle models. Unfortunately it has not been able to establish itself “de facto” in the market, probably due to the difficulty in conciliating the available technical solutions of the time to the extensive list of requirements imposed by automotive industry. With the growing pressure of modern society for more energy efficient systems and with the technological advances in the last decades in the field of mechanics and mainly in electronics the original idea regains its interest and may be revisited in a modern technological framework where the barriers that once turned it inviable do not exist anymore. This paper presents a proposal for a clutch system equipped with a system capable of implementing the coasting functionality and discusses its benefits with focus on fuel economy. The system is electronically controlled and manages all the opening and closing operations of the clutch. The clutch pedal becomes electronic and, depending on the system configuration, may be completely dismissed. The driver has no direct interference on the clutch anymore. A prototype vehicle was assembled to demonstrate system’s capabilities. It has been submitted to different routes around the city of Campinas adopting typical urban and highway usage profiles. For each of them the coasting functionality was activated / deactivated and the mean fuel consumption was measured. The results confirm that there is a significant potential for reducing fuel consumption in real usage conditions by means of an electronic clutch system able to explore vehicle’s kinetic energy in a simple, efficient and safe way.