In this system, the temperature of the hot-wire (Rh) is continuously maintained at a constant temperature higher than the temperature of the intake air by using the thermistor (Ra). Consequently, since intake air mass can be measured accurately even if intake air temperature changes, it is not necessary for the engine ECU to correct the fuel injection duration for the intake air temperature.In addition, when air density decreases at high altitudes, the cooling capacity of the air decreases in comparison with the same intake air volume at sea level. As a result, the amount of cooling for the hot-wire is reduced. Since the intake air mass detected will also decrease, the high-altitude compensation correction is not necessary.
HINT:The voltage (V) required to raise the temperature of the hot-wire (Rh) by the amount of T from the intake air temperature remains constant at all
times even if the intake air temperature changes. In addition, the cooling capacity of the air is always proportional to the intake air mass. Consequently, if the intake air mass remains the same, the output of the air flow meter will not change even if there is a change in intake air temperature.