Exhaust gas control using a spark plug ionization signal

摘要

This feature of the present invention comprises a method and apparatus to reduce NOx emissions in an internal combustion engine. This feature of the present invention uses a closed loop control of the exhaust gas re-circulation to provide the engine with the either EGR MBT timing or a knock limited timing to yield the minimum NOx emission with maximum fuel economy benefits associated with exhaust gas re-circulation. When the exhaust gas re-circulation rate is not knock limited, the engine sets its exhaust gas re-circulation rate to an optimal rate at which the engine runs at the exhaust gas re-circulation minimum best time for best torque spark timing limit. When the exhaust gas re-circulation rate is knock limited, the engine sets its exhaust gas re-circulation rate to a knock limited rate at which the engine runs at a retarded MBT spark timing limit. The engine uses calibratable MBT timing criteria to determine the retarded MBT spark timing limit.