| 摘要 |
An engine control method for improving air-fuel ratio control controls airflow when fuel injector limits are reached. The method includes a transient fuel model to calculate a required fuel injection amount based on actual cylinder air charge and feedback from an exhaust sensor. When the required fuel injection amount is outside an operable range, for example, less than zero, airflow is controlled to prevent deviations of exhaust air-fuel ratio. Otherwise, airflow is controlled to provide a desired engine torque. Alternatively, a minimum allowable airflow is determined based on a minimum achievable fuel flow. Then, airflow is prevented from falling below this minimum allowable airflow. The method is particularly useful in preventing rich excursions during rapid decreases in desired engine torque, such as during a driver tip-out.
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