Importance

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Abstract

A method of operating a spark ignition direct injection engine having two groups of cylinders supplied with air by separate manifolds controlled by separate throttles includes: (1) in a lower range of engine output, operating both groups of cylinders in a stratified charge mode with essentially unthrottled intake air; (2) in a higher range of engine output, operating both groups of cylinders in a homogeneous charge mode with partially throttled to unthrottled air flow; and (3) in an intermediate range of engine output, operating one cylinder group in a homogeneous charge mode near maximum output with lightly to essentially unthrottled intake air while operating the other cylinder group in a stratified charge mode with essentially unthrottled air intake, whereby the engine is operated over a major portion of the engine output range in unthrottled condition and with substantial throttling only in a portion of the higher range of engine output.

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First Claim