Control method for a direct injection gas engine with fuel vapor purging

摘要

A control method for a direct injection gasoline engine operable in stratified or homogenous combustion modes and having a fuel vapor purge system estimates the hydrocarbon concentration of purge vapor during open loop fuel control in the stratified combustion mode, and controls the fuel injection quantity and the combustion mode based on the estimated concentration. The hydrocarbon concentration of the purge vapor is estimated during open-loop fuel control by measuring the air/fuel ratio error during steady state operation with no fuel vapor purging, and using such air/fuel ratio error to normalize the air/fuel error observed during steady state operation with purge control. The fuel injection quantity is compensated for the estimated purge vapor concentration, and engine combustion mode is determined in part based on a comparison of the estimated concentration with a calibrated threshold.