The principle of fuel efficiency is analyzed systematically.The fuel consump- tion per kWh and fuel consumption per kilometer are proposed as the criterions of trac- tor fuel efficiency.By testing the JD3130 tractor PTO performance,the mathematical models for engine torque-rotating speed,fuel consumption per hour-rotating speed are established.The optimum economic operating conditions and the operating conditions of optimum exhaust smoke are derived.A fuel efficiency monitor for tractor engine based on sing...