Dual fuel engine control unit

A multi-mode engine system comprising an engine adapted to operate in a plurality of different modes including a first mode in which the engine is fuelled substantially entirely by a first fuel, and a second mode in which the engine is fuelled substantially entirely by a second fuel, or by a mixture of the first and second fuels, the engine comprising:

• a first engine control unit (ECU) for controlling the flow of the first fuel into the engine when the engine is operating in the first mode;
• a plurality of first sensors operatively connected to the first ECU, each of which first sensors is adapted to sense a first variable, and to emit a first input signal dependent on a value of the sensed first variable;
• and
• a second ECU operatively connected to the first ECU;
• wherein the first ECU comprises:
• a signal receiver for receiving the first input signals, and an output for emitting a first output signal dependent on the first input signals, which first output signal determines the amount of first fuel supplied to the engine,
• the second ECU being adapted to modify the first output signal when the engine is running in the second mode to produce a first modified signal and a second calculated signal;
• the first modified signal determining the amount of first fuel supplied to the engine when the engine is operating in the second mode, and the second calculated signal determining the amount of second fuel supplied to the engine when the engine is operating in the second mode, wherein the second ECU is operatively connected to the first ECU in both the first mode and the second mode.