To considerably improve starting performance by preventing too early ignition caused by self-ignition immediately after the start of cranking, and performing combustion well from the middle of cranking.

This spark-ignition engine for an automobile comprises an effective compression ratio adjusting means, a fuel injection valve 32, an operating state discriminating means 101, a temperature state discriminating means 102 and a control means 103. The control means 103 controls to make an effective compression ratio lower in a light load region in the low speed region of the engine than in a high load region while making the effective compression ratio higher during cranking when starting the engine than in the light load region in the low speed region of the engine, and to stop fuel supply until engine speed rises to predetermined engine speed where intake pressure is lowered to a predetermined pressure in a cranking period in warm starting and to supply fuel to each cylinder from the fuel injection valve 32 to carry out combustion when the engine speed rises to the predetermined engine speed or higher.

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