Browse Publications Technical Papers 2018-32-0079
2018-10-30

Study of a charged engine for motorbike application 2018-32-0079

Legislation bodies are increasingly pushing vehicles manufacturers all over the world towards the reduction of emissions and fuel consumption of new developed vehicles. These strict requirements applied to motorbikes manufacturers present them with a big challenge, since the efficiency improvement must be achieved without affecting the performance, in terms of torque and power first, and throttle response and drivability, which are significantly important to a motorbike owner. In order to meet the stringent consumption targets, in the recent years, the strategy of “downsizing” has become widespread in the automotive field. The reduction of engine displacement together with the adoption of turbocharging allows shifting the engine operating points in an area of higher efficiency with obvious advantages in terms of fuel consumption. At the beginning of 1980, many motorbike manufacturers attempted to apply the turbocharging technology to their motorbikes, with the aim of reducing the engines displacement and increasing the specific performance. The success of this attempt was limited because at that time the technology was not mature enough and the consequent poor throttle response and low reliability limited acceptance from customers. The technology is nowadays at an advanced stage and modern electronic control systems are so highly-developed and effective in managing high power outputs, that an application of turbocharging to motorbike engines could be meaningful. Nevertheless some important challenges must be faced: packaging, weight and cost, customer acceptance. The objective of this work is to provide a detailed analysis about the feasibility of the application of a supercharged engine to a motorbike: in a first stage, several engine architectures (In-line, V-configuration, Boxer) and charging concepts (centrifugal or volumetric compressor, with mechanical or fluid-dynamic connection to the engine) have been analyzed from the point of view of packaging and in terms of cost and weight. In a second part, a V4 engine architecture has been selected and optimized for a patrol motorcycle application. This kind of employment leads to specific requirements for the engine: high maneuverability especially at low engine speeds and part load conditions, smooth torque curve over the speed range, high maximum power target and an impressive exhaust sound. These performance requirements have been analyzed via 1D gas-exchange simulations and a charging strategy together with optimized intake manifold, exhaust manifold and valve timing has been found out. Finally, the conceptual investigation of the base engine design has been carried out with the development target of lowest possible weight and size. Several concepts of cylinder head, crankcase and valve train, type of lubrication and cooling systems, type and position of the gearbox have been investigated.

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