Control Method and Apparatus for Multi-Fuel Compression Ignition Engines

A method of operating a compression ignition engine on different fuels at different times comprising:

• selecting a target fuel whose engine operating characteristics are to be duplicated when using fuels other than the target fuel in the engine;
• determining the engine operating characteristics, including a measure of engine torque versus throttle setting and engine RPM when operating with the target fuel, and storing a desired indicated torque versus throttle setting and engine RPM;
• and
• when the engine is operating on a fuel;
• sensing a fuel control input and engine RPM;
• determining the desired indicated torque for that fuel control input and engine RPM;
• determining a measured indicated torque for the engine;
• and
• adjusting a fuel quantity command to cause the measured indicated torque to equal the desired indicated torque;
• whereby when the engine is operating on a fuel other than the target fuel, the engine torque for various fuel control inputs and engine RPM will equal the engine torque for that fuel control input and engine RPM as if operating on the target fuel.