Closed loop mass airflow determination via throttle position
 Mass air flow into an internal combustion engine is measured as a function of throttle opening. The mass air flow rate is expressed as an idle offset constant and the product of gain and effective air intake area which is a function of throttle position. During idle, the idle offset term is updated in response to an exhaust oxygen sensor feedback and during part throttle operation the gain is similarly updated to achieve stoichiometry. For subsonic air flow the mass air flow is further modified as a function of the ratio of manifold pressure to the pressure upstream of the throttle. At the same time the manifold dilution is controlled via an EGR valve to a predetermined schedule. 
General Motors Corporation
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William H. Wei-Ming
Holl Wang