Layout of a Charged Power Sport Engine

The main target for the development of power sport engines is and will be in future the increase of the power-to-weight ratio. However, the reduction of carbon dioxide emissions is getting more and more important as future legislation and increasing customer demands ask for lower fuel consumption. One possible technology for CO₂ reduction which is widely used in automotive applications is downsizing by reducing the engine capacity and increasing the specific power by charging strategies. Focusing on power sport applications, like motorcycles, the automotive downsizing technologies cannot be transferred without major modifications. The essential difference to automotive applications is the extraordinary response behavior of today's motorcycles, as well as the large engine speed spread. Additionally, packaging and cost reasons exclude the direct transfer of highly complex automotive technology, like two-stage charging, cam-phasing, etc., to motorcycle applications.
This publication treats the conceptual design and layout of a charged 800 cm₃ two-cylinder motorcycle engine with the demand of excellent driveability, power and response. In detail, the paper deals with the layout of an exhaust turbocharging system for an inline two-cylinder engine where the achievement of an appropriate response behavior is of particular importance. As reference for the transient behavior a turbocharged automotive engine has been chosen. The benchmarks for the transient behavior have been a state-of-the-art naturally aspirated motorcycle on one hand and an automotive TC engine on the other hand. Based on these targets, a previously presented simulation strategy for the selection of the different hardware components has been applied. Stationary and transient 1DCFD simulations as well as 3D-CFD and coupled simulations have been performed and various modifications on the engine and the periphery have been carried out for prototyping.