Engine control system

An engine control system configured to selectively switch between a first fuel and a second fuel and perform an operation control of a single engine, the engine control system comprising:

• a sensor configured to detect an oxygen concentration of an exhaust gas that is exhausted from the engine;
• and
• a control device configured to perform an air-fuel ratio feedback control such that an air-fuel ratio becomes a target air-fuel ratio based on an output signal of the sensor, wherein
• the control device comprises:
• a correction device configured to calculate a correction coefficient of an air-fuel ratio feedback control during an operation with the second fuel and further correct a difference between the calculated correction coefficient and a targeted correction coefficient arising from a change in composition of the second fuel;
• a storage device configured to store a fuel composition correction coefficient that is a value in a predetermined range;
• and
• a limiting device configured to set a limit to a changing range when the fuel composition correction coefficient is stored.