CONTROL SYSTEM FOR MULTIFUEL INTERNAL COMBUSTION ENGINE

An object of the present invention is to reduce the difference between the torque generated by an internal combustion engine and a required torque in a control system for a multifuel internal combustion engine that can use CNG and liquid fuel. To achieve the object, the control system for an internal combustion engine according to the present invention causes the internal combustion engine to operate in a first operation mode in which only CNG is used, when the required torque of the internal combustion engine is equal to or lower than a threshold and to operate in a second operation mode in which at least liquid fuel among CNG and liquid fuel is used, when the required torque of the internal combustion engine is higher than the threshold and changes the magnitude of the threshold in conjunction with the concentration of inert gases contained in CNG.