Patent ID: 6976936

Claim:
A control apparatus for a multi-cylinder engine capable of performing compression ignition combustion, or selecting either the compression ignition combustion or spark ignition combustion, comprising: a cylinder-specific combustion state estimating means for estimating a combustion state for each cylinder; and a combustion state control means for controlling the combustion state for each cylinder; wherein the combustion state control means controls, during an engine operation in a compression ignition combustion mode, the combustion state for each cylinder based on the combustion state estimated by the cylinder-specific combustion state estimating means during the engine operation in the compression ignition combustion mode and the transmission so as to change the gear ratio, thereby decreasing an engine speed when it is estimated that the peak value of cylinder pressure of at least one of the plurality of cylinders is lower than a predetermined value, or the peak timing of cylinder pressure is retarded in relation to predetermined timing, based on the estimation made by the cylinder-specific combustion state estimating means, wherein the cylinder-specific combustion state estimating means estimates the combustion state based on a signal provided by a cylinder pressure sensor disposed in at least one cylinder of the multi-cylinder engine.