SPARK-IGNITION FOUR-CYCLE LEAN BURN ENGINE

摘要

PROBLEM TO BE SOLVED: To reduce cooling loss of a high-compression ratio spark-ignition four-cycle lean burn engine.

SOLUTION: In a controller 100, an air excess ratio λ is set at 2.5 or more and the G/F is set at 35 or more under an operation condition of an engine body (a lean burn engine 1) having a geometric compression ratio ε of 18≤ε≤40 is in the low-load region, and valve closing timing of an intake valve 21 is set in or after the middle period of a compression stroke.

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