Internal combustion engine driven with change-over of compression ratio, air-fuel ratio, and boost status

The engine has a control area (B), with torques higher than control area (A), to control torque output with settings of a high compression ratio, a lean air-fuel ratio, and a boosting state. A fourth control area (D) with torques higher than a third control area (C) controls the torque output with settings of the low compression ratio, the stoichiometric air-fuel ratio, and the boosting state. The third control area with torques higher than the former area controls the torque output. An independent claim is also included for a control method of an internal combustion engine.