A method of determining throttle flow in a fuel delivery system is disclosed. First, a time-efficient throttle flow data collection method is described. The collection method uses a sonic nozzle flow bench to measure airflow as a function of throttle angle and pressure in a manner analogous to on-engine dynamometer throttle flow characterization. Opening each sonic nozzle combination, then recording throttle downstream pressure and computed nozzle flow allows data to be taken in a fraction of the time normally needed. In conventional methods, the estimated airflow rate as a function of throttle angle differs from the measured airflow rate because the leak area is incorrect. The method of the invention correctly determines the estimated throttle airflow rate by using a low pass filtering technique to adjust the estimated airflow rate to eventually equal the measured airflow rate, particularly at small throttle angles.