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Investigation on the Transient Behavior of a High Compression Two-Wheeler Single Cylinder Engine Close to Idling
Abstract:
The introduction of stricter emission legislation and the demand of increased power for small two-wheelers lead to an increase of technical requirements. Especially the introduction of liquid-cooling over air-cooling allows the introduction of higher compression ratios, which improves power output as well as thermodynamic efficiencies and thereby fuel consumption.
But an increase in compression ratio also introduces further challenges during transient behavior especially close to idling. In order to keep the two-wheeler specific responsiveness of the vehicle, the overall rotational inertia of the engine must be kept low. But the combination of low inertia and high compression ratio can lead to a stalling of the engine if the throttle is opened and closed very quickly in idle operation. The fast opening and closing of the throttle is called a throttle blip.
This paper describes the development of a procedure to apply reproducible blipping events to a vehicle in order to derive a deeper physical understanding of the stalling events. Goal is to identify influencing factors that determine whether a blip will lead to a stalling of the engine or not. These factors contain e.g. the timing of the blip within the working cycle or calibration parameters like average idle speed and ignition timing.
The investigations are carried out on a motorcycle with a water-cooled 400cc single cylinder engine from the performance segment with high compression ratio and an engine management system with port fuel injection. Several thousand blipping events are automatically applied and evaluated with the focus on the stalling probability.