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Motorized throttle valves on conventional spark-ignited engines are designed to have a default position such that when unpowered they go to a fixed position which is between closed-in-bore and wide open. This position allows some, albeit limited, vehicle function in the event of a throttle positioning fault. Described here is a new default positioning mechanism attained by rotating the valve past the conventional operating arc (between closed-in-bore and wide open) through wide open to a partially open position. This default throttle position concept eliminates control difficulties and an undesirable failure mode. The advantages and disadvantages are discussed. Further, the required valve geometry is derived.

A time-efficient throttle flow data collection method is described. It uses a sonic nozzle flow bench to measure air flow 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. Throttle flow modeling considerations are then discussed.