The adaptability of a basic motorcycle engine to different domains of application often requires the tuning of the torque characteristic or a modified topography of the maps for specific fuel consumption and pollutant emissions. Such adaptations are feasible by tuning the intake and the exhaust pipe, by changing the movement characteristics of the intake and the exhaust valves or by modifications of bore and stroke. The numerical simulation of the process stages in a motorcycle engine - from scavenging and mixture formation up to combustion and exhaust gas flow - in base on a one-dimensional model demonstrates a sufficient accuracy but a higher efficiency than a three-dimensional model, when applied for the adaptation of torque characteristic to different engine applications. In the same way the maps for specific fuel consumption or pollutant emissions can be modified as well. Determining factors for such adaptation in respect to the engine speed are the design of the intake and exhaust ducts in relationship with the control of the intake and exhaust valve movement: the generated pressure waves at intake and exhaust in relationship with the opening/closing timing of the valves determine the scavenging quality and therefore - for an homogeneous air/fuel mixture - the engine performances in terms of torque, consumption and pollution. Furthermore, modifications of bore and stroke allow the successful adaptation of a basic engine for tasks which require a different torque characteristic. When using a carburetor, its location in the intake duct influences the speed-related performances, because of the air pressure waves within the duct. The intake duct design and the carburetor location allow the adaptation of performances to the required engine function.
Optimization of motorcycle engine characteristics by simulation of the fluid dynamic process stages
Optimierung der Kennwerte von Motorradmotoren durch Simulation der strömungsdynamischen Prozessstadien
Development Trends of Motorcycles III, International Conference Development Trends of Motorcycles, 4 ; 28-48
2007
21 Seiten, 24 Bilder, 4 Quellen
Conference paper
English