Investigation on the Transient Behavior of a Two-Wheeler Single Cylinder Engine Close to Idling with Electronic Throttle Control 2018-32-0074
The introduction of new emission legislation and the demand of increased power for small two-wheelers lead to an increase of technical requirements. Especially for single cylinder engines with high compression ratio the transient behavior close to idling is challenging.
The demand for two-wheeler specific responsiveness of the vehicle requires low overall rotational inertia as well as small intake manifold volumes. The combination with high compression ratio can lead to a stalling of the engine if the throttle opens and closes very quickly in idle operation. The fast opening and closing of the throttle is called a throttle blip. Fast, in this context, means that the blipping event can occur in one to two working cycles.
Previous work was focused on 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. The corresponding investigations were performed on a motorcycle with a mechanical throttle body. Based on this the present paper is focused on a comparison to a motorcycle with the same base engine and boundary conditions but with electronic throttle control. The main targets are to reproduce the blip events based on the previous work and to evaluate whether any differences can be observed in the physical root causes, which can lead to a stalling of the engine.
In the course of the examination process, the previously introduced systematic of blip stall mechanisms is refined. Therefore, thousands of blip events with defined start position within the working cycle are applied, automatically evaluated and categorized.
The previous work showed a significant influence of the idle speed on the probability of a stall occurrence for a throttle blip. It was shown that a single retarded combustion process or misfire could lead to a stalling of the engine at a sudden throttle opening. The only counter measure in that case for a system with mechanical throttle body is an increased idle speed. Furthermore, it was shown that the additional pressure build-up caused by early ignition angles is increasing the stall probability. All measured stall events have been grouped into different stall modes, which are described by typical patterns of engine speed and intake pressure during and after the blip event.
Henning Heikes, Alexander Pelkmann, Alrik Barton
Robert Bosch GmbH
SAE/JSAE Small Engine Technology Conference