Online Engine Speed based Adaptation of Combustion Phasing and Air-Fuel Ratio 2014-32-0076
Equipping low cost two-wheelers with engine management systems (EMS) enables not only a reduction of emissions but also an improvement in fuel consumption and system robustness. These benefits are accompanied by initially higher system costs compared to carburetor systems. Therefore, intelligent software solutions are developed by Bosch, which enable a reduction of the necessary sensors for a port fuel injection system (PFI) and furthermore provide new possibilities for combustion control.
One example for these intelligent software solutions is a model based evaluation of the engine speed. By use of the information contained in the engine speed signal, characteristic features like air charge, indicated mean effective pressure (imep) and combustion phasing are derivable. The present paper illustrates how these features could be used to reduce the system costs and to improve fuel consumption and system robustness. Especially in the low cost segment there are significant bike-to-bike variations e.g. compression ratio or valve timing deviations. These deviations which are increased by ageing effects have a significant influence on the combustion process. For instance a variation in the valve timing, causing a different amount of residual gas to be left in the combustion chamber, might lead to deviations in the pre-defined combustion phasing. As a result either fuel consumption or emissions could deteriorate. After analyzing the potential benefits of the introduced features, two applications for model based engine speed evaluation are presented. One uses a rotational speed based estimation of the combustion phasing for a closed loop ignition angle adaptation, the second is able to adapt the air-fuel-ratio by estimating imep.