using experimental data the oil cooler contributes to heat rejection by an amount q oc in dependence upon the rate of coolant flow and the rate of oil flow and upon the difference between the engine sump oil temperature sot and the engine inlet coolant temperature eit the heater cabin contributes to heat rejection by an amount q hc in dependence upon the air flow across the heater and the difference between the coolant control valve inlet coolant temperature vit and the ambient air temperature aat air_flow is heatercore air flow and is dependent upon the heater air con blower speed again constants a b and k different from those above are determined using experimental data at step 106 the required cylinder head temperature cht is determined as a function of engine speed and engine load at step 108 the limits of operation of the fan pump and valve are calculated the minimum speed of the fan is set in dependence upon the air conditioning requirement if air conditioning is required then the fan speed minimum is set to stationary air conditioning requirements if the vehicle speed exceeds the required fan speed then the fan is deactivated i e the maximum speed is set to 0 rpm the pump range is dependent upon a predefined maximum engine temperature cht and engine inlet temperature the pump speed minimum is set to allow a minimum u201c coolant_flow u201d in dependence upon q eng and the predefined maximum engine temperature the hvac setting is used to determine a minimum and maximum heater flow to avoid over pressurizing the heater core current data suggests that satisfactory heater performance can be obtained using 15 30 liters min heater flow the valve range degrees rotation is dependent upon heater flow oil flow and.