Improved cylinder air charge estimation for transient air fuel ratio control

Modern automobile engines require precise regulation of air-fuel ratio (A/F) to attain high catalytic converter efficiency and minimize tailpipe emissions. During engine transients, good A/F control requires, in turn, accurate estimation of the air charge entering the cylinders during each induction event. This paper describes the development and validation of a nonlinear, open-loop air charge estimator. A key feature is the inclusion of the dynamics of the mass air flow meter. The estimator was implemented on a V8 engine in a dynamometer test cell. Experimental results confirm the improved A/F control predicted by simulation. The prototype implementation was accomplished using an automatically generated high-level language control code executing in a dedicated PC and communicating via a shared memory board with the production microprocessor-based controller.