Patent ID: 8511154

Claim:
Method for estimating a cylinder air charge for an internal combustion engine, comprising: determining a first volumetric efficiency corresponding to engine operation with an open exhaust gas recirculation valve; determining a second volumetric efficiency corresponding to engine operation with a closed exhaust gas recirculation valve; and determining a cylinder air charge using a selected one of the first and second volumetric efficiencies; wherein determining the first volumetric efficiency comprises: determining a proportion of an intake air charge that is recirculated exhaust gas; and determining the first volumetric efficiency as a function of an engine speed and the proportion of the intake air charge that is recirculated exhaust gas; wherein determining the proportion of the intake air charge that is recirculated exhaust gas comprises: determining an effective flow area of the exhaust gas recirculation valve as a function of a position of the exhaust gas recirculation valve and a ratio of an exhaust manifold pressure to an intake manifold pressure; determining an exhaust gas recirculation flowrate corresponding to the effective flow area of the exhaust gas recirculation valve; and determining the proportion of the intake air charge as a ratio of the exhaust gas recirculation flowrate to the sum of the exhaust gas recirculation flowrate and an intake air flowrate.