What is an IAT sensor or its full name, intake air temperature sensor?
The IAT sensor monitors the temperature of the air entering the engine and is usually mounted in the intake manifold with the tip or the open element exposed to the stream. The ECU requires this information to estimate the air density so it can adjust and optimise the air/fuel mixture. Colder air is more dense than hot air, so cold air requires more fuel to maintain the ideal AFR or air/fuel ratio. The ECU can change the AFR by changing the length (on time) of the injector pulse.
An IAT sensor is a thermistor, which means its electrical resistance changes in response to changes in the temperature of the air.
It works on the same principle as a coolant sensor. The ECU applies a reference voltage to the sensor (usually 5volts), then looks at the voltage signal it receives back to calculate air temperature. Each brand or model of sensor will have its own unique calibration data referencing either voltage or resistance to a given temperature which is held on the ECU for its look up reference. The return voltage signal will change in proportion to changes in air temperature. Most air temperature sensors are negative coefficient (NTC) thermistors with high electrical resistance when they are cold, but the resistance drops as they heat up. However some work in the opposite manner and they are positive temperature coefficient (PTC) thermistors with low resistance when cold and increases as the sensor heats up. The change in resistance of the IAT sensor causes a change in the return voltage going back to the ECU.
Symptoms of Failure
An IAT sensor can sometimes be damaged by backfire in the intake manifold or by carbon or oil commination or through age making it less responsive or not at all to changes in air temperature.
If the IAT sensor is no longer able to operate with accuracy the values being sent back to the ECU may be incorrect and fooling the ECU to the air is either cooler or warmer than it actually is the making the car run richer or leaner with an incorrect AFR for the given engine load or at throttle demand. All this will result in poor drivability, unstable idle, increase in fuel consumption and loss of power, surging when warm or erratic throttle response.
Advantages of a Fast Response IAT sensor for an RB?
All RB series engines come fitted as standard with an IAT sensor, but they are very slow responding and with out an open element to accurately measure air temperature. Further more the factory Nissan sensor is akin to a coolant sensor with an all brass body and is susceptible to heat soak thus giving inaccurate reading – modern sensors have come on a long way and a fast response IAT sensor can respond to air temperature change at 5-6 times the speed i.e. 3-5 seconds compared to 30-40 seconds of an older design sensor as such fitted to the RB engines.
The ideal solution for those who have an aftermarket ECU is to utilise a Supertec Racing fast response IAT sensor which will fit in the factory location, come complete with connector including pins and loom to connect to you existing factory wiring loom. We also supply calibration data so that a cal file can be created for your ECU.