CARBON ACCUMULATION DETERMINATION METHOD AND CARBON REMOVING METHOD AND SPARK-IGNITED DIRECT-INJECTION ENGINE

PROBLEM TO BE SOLVED: To easily determine carbon accumulation in a heat insulating layer 6 of a combustion chamber wall surface part.SOLUTION: Before the carbon is accumulated on the heat insulating layer 6, in a predetermined engine operation state, at least one of mean temperature during one burning cycle of the combustion chamber wall surface section, and, the maximum temperature during the one burning cycle of the combustion chamber wall surface section is detected as an initial value. The initial value detected is stored in a storage means. In the same engine operation state as when the initial value is detected, at least one of the mean temperature during the one burning cycle of the combustion chamber wall surface section, and, the maximum temperature during the one burning cycle of the combustion chamber wall surface section is detected. When at least one of the following conditions is satisfied, the carbon accumulation on the heat insulating layer 6 is determined: a condition in which the detected mean temperature increases to the first predetermined temperature or higher with respect to the initial value of the mean temperature; and a condition in which the maximum temperature detected in the temperature detection step decreases to the second predetermined temperature or lower with respect to the initial value of the maximum temperature.