An apparatus has a turbulence generator valve which is arranged in an intake air passage. The valve generates turbulence in a cylinder of an engine. The valve receives an intake flow torque TA by flow of intake air. The valve is driven by an electric motor in an electric actuator. Reverse transmission torque TB is necessary to rotate the electric motor in the electric actuator when the electric motor is not activated. A cancel spring is provided to apply a cancel torque TC to the valve. The torques are set to satisfy |TA+TC|