Combustion control system for changing between homogeneous and stratified charge modes in a direct-injection, spark-ignition i.c. engine

摘要

In an in-cylinder fuel injection engine capable of selectively switching a combustion strategy from a stratified charge combustion to a homogeneous charge combustion and vice versa, when a coolant temperature at engine start is lower than a specified temperature, the combustion strategy is established to be a homogeneous charge combustion mode and this homogeneous charge combustion mode is held until the coolant temperature reaches the specified temperature. While the coolant temperature is higher than the specified temperature and lower than a warm-up completion temperature, the combustion strategy is switched from homogeneous to stratified by lowering the engine load from a high load area to a low load area so as to improve emissions and fuel economy. On the other hand, when the engine is restarted at the coolant temperature higher than the specified temperature, the combustion strategy is established to be homogeneous until the fuel pressure reaches a specified value and is switched from homogeneous to stratified after the fuel pressure reaches the specified value.