• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.6
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• pp.82-89
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• 2011

Ultra lean combustion with stratified air-fuel mixture is one of the methods that can improve fuel economy of gasoline engines. The aim of this study is to show that how much fuel economy is improved and what are differences in engine control of the ultra lean combustion compared with stoichiometric combustion. In this study, the BMW N53 GDI engine, which is one of ultra lean combustion GDI engines introduced in the market recently, was tested at various engine operating conditions. Results indicated that fuel consumption rates were improved by 11.9~25.8% by the ultra lean combustion compared with stoichiometric combustion. It was also found that multiple fuel injection, multiple spark, early intake valve opening, and large vlave overlap duration were the features of the ultra lean combustion for combustion stability and emission improvement.