Methodology to compensate the effect of humidity and altitude on HCCI combustion

1. Method for controlling combustion in a spark-ignition direct-injection internal combustion engine, comprising:

monitoring an engine operating mode and an ambient parameter;

determining a deviation of the ambient parameter relative to a nominal ambient parameter;

determining a nominal desired engine operation parameter based on engine speed and load, wherein said nominal engine operation parameter comprises one of a nominal desired oxygen concentration and a nominal desired air/fuel ratio;

determining an adjusted desired engine operation parameter based on said nominal desired engine operation parameter and said deviation of the ambient parameter, wherein said adjusted desired engine operation parameter comprises one of an adjusted desired oxygen concentration and an adjusted desired air/fuel ratio; and

controlling the engine based on the engine operating mode and one of said nominal desired engine operation parameter and adjusted desired engine operation parameter, comprising one of:

when the engine operating mode is stoichiometric, controlling external exhaust gas recirculation entering the engine based on the adjusted desired oxygen concentration when the monitored ambient parameter comprises altitude, and

when the engine operating mode is stoichiometric, controlling external exhaust gas recirculation entering the engine based on the nominal desired oxygen concentration when the monitored ambient parameter comprises humidity.

2. The method of claim 1 wherein:

said ambient parameter comprises humidity;

said nominal desired engine operation parameter comprises the nominal desired air/fuel ratio; and

controlling the engine is based on the adjusted desired air/fuel ratio when said engine operating mode is lean of stoichiometric.

3. The method of claim 1 wherein:

said ambient parameter comprises altitude;

said nominal desired engine operation parameter comprises the nominal desired air/fuel ratio; and

controlling the engine is based on the adjusted desired air/fuel ratio when said engine operating mode is lean of stoichiometric.

4. Method for controlling combustion in a spark-ignition direct-injection internal combustion engine, comprising:

monitoring an engine operating mode and humidity

determining a deviation of the humidity relative to a nominal humidity;

determining a desired nominal air/fuel ratio based on engine speed and load;

determining an adjusted desired air/fuel ratio based on said nominal desired air/fuel ratio and said deviation of the humidity; and

controlling a negative valve overlap of the engine based on the adjusted air/fuel ratio when said engine operating mode is lean of stoichiometric.

5. Method for controlling combustion in a spark-ignition direct-injection internal combustion engine, comprising:

monitoring an engine operating mode and altitude;

determining a deviation of the altitude relative to a nominal altitude;

determining a nominal desired air/fuel ratio based on engine speed and load;

determining and adjusted desired air/fuel ratio based on said nominal desired air/fuel ratio and said deviation of the altitude; and

controlling a negative valve overlap of the engine based on the adjusted air/fuel ratio when the engine operating mode is lean of stoichiometric.

6. Method for controlling combustion in a spark-ignition direct-injection internal combustion engine, comprising:

monitoring an engine operating mode and altitude;

determining a deviation of the altitude relative to a nominal altitude;

determining a nominal desired oxygen concentration based on engine speed and load;

determining an adjusted desired oxygen concentration based on said nominal desired engine operation parameter and said deviation of the altitude; and

controlling the engine based on the adjusted desired oxygen concentration when said engine operating mode is stoichiometric.

7. The method of claim 6 wherein:

controlling the engine comprises controlling an external exhaust gas recirculation based on the adjusted desired oxygen concentration.

8. Method for controlling combustion in a spark-ignition direct-injection internal combustion engine, comprising:

monitoring engine operating mode, ambient humidity and ambient pressure;

controlling in-cylinder oxygen mass for maintaining a desired combustion phasing based on engine speed and load, comprising:

determining a nominal externally recirculated exhaust gas setting for maintaining a desired in-cylinder oxygen mass at nominal humidity and nominal pressure;

determining a nominal in-cylinder air-fuel ratio setting for maintaining the desired in-cylinder oxygen mass at the nominal humidity and nominal pressure;

when the engine operating mode is stoichiometric and the ambient pressure deviates from the nominal pressure, controlling the externally recirculated exhaust gas from said nominal externally recirculated exhaust setting; and

when the engine operating mode is lean of stoichiometric and at least one of the ambient pressure deviates from the nominal pressure and the ambient humidity deviates from the nominal humidity, controlling the in-cylinder air-fuel ratio from said nominal in-cylinder air-fuel ratio setting.

9. The method of claim 8 wherein controlling the externally recirculated exhaust gas comprises decreasing the externally recirculated exhaust gas from the nominal externally recirculated exhaust gas setting when the ambient pressure is greater than the nominal pressure, and increasing the externally recirculated exhaust gas from the nominal externally recirculated exhaust gas setting when the ambient pressure is less than the nominal pressure.

10. The method of claim 8 wherein controlling the in-cylinder air-fuel ratio comprises decreasing the in-cylinder air-fuel ratio from the nominal in-cylinder air-fuel ratio setting when the ambient pressure is greater than the nominal pressure, and increasing the in-cylinder air-fuel ratio from the nominal in-cylinder air-fuel ratio setting when the ambient pressure is less than the nominal pressure.

11. The method of claim 8 wherein controlling the in-cylinder air-fuel ratio comprises decreasing the in-cylinder air-fuel ratio from the nominal in-cylinder air-fuel ratio setting when the ambient humidity is greater than the nominal humidity, and increasing the in-cylinder air-fuel ratio from the nominal in-cylinder air-fuel ratio setting when the ambient humidity is less than the nominal humidity.

12. Apparatus for controlling a multi-cylinder spark-ignition direct-injection internal combustion engine, comprising:

an external exhaust gas recirculation valve;

a variable cam phasing mechanism to control phasing of engine intake and exhaust valves;

a control module:

monitoring engine operating mode, ambient humidity and ambient pressure;

determining a nominal externally recirculated exhaust gas setting for the external exhaust gas recirculation valve to maintain a desired in-cylinder oxygen mass at nominal humidity and nominal pressure;

determining a nominal negative valve overlap setting for the variable cam phasing mechanism to maintain a maintaining the desired in-cylinder oxygen mass at the nominal humidity and nominal pressure;

when the engine operating mode is stoichiometric and the ambient pressure deviates from the nominal pressure, controlling the external exhaust gas recirculation valve from said nominal externally recirculated exhaust setting; and

when the engine operating mode is lean of stoichiometric and at least one of the ambient pressure deviates from the nominal pressure and the ambient humidity deviates from the nominal humidity, controlling the variable cam phasing mechanism from said nominal negative valve overlap setting.