Air Temp Sensor Resource
Measuring Air temp coming into the engine is important for the ECU to calculate the correct amount of fuel required. Getting accurate data into the ECU is very important, sensor location, wiring and calibration all work together to provide an accurate measurement of the temperature of the air entering the cylinders.
Sensor Location - Our preferred location is pre throttle body on an intake pipe. If you have aftermarket intake or charge piping then this is usually made out of aluminum or stainless steel. Both of those materials can have a bung welded on and the sensor installed in the bung, ensuring the sensor tip is in the airflow and there is no leaks.
The intake manifold is a common location for a sensor to be from the OEM, but these often heat soak or only measure the air getting into a few cylinders.
Important to note that in turbo or supercharged applications the Air temp sensor MUST be after the intercooler.
Wiring - NTC temperature sensors are 2 wire, a signal and sensor ground. Polarity is not really important, either pin can be signal or sensor ground. Best practice is to have them the same among all your 2 wire sensors.
The sensor changes its resistance value as the temperature changes. Most NTC sensors are negative coefficient, meaning the hotter they get the less resistance they are.
All our kits come with 3 different resistors, shown below. Most ECU's will have a built in pull up resistor on one or two inputs specifically for the IAT sensor but in the event you are adding a sensor to measure air temp for datalogging purposes and the input does not have on the resistors will be necessary.
One side of the resistor is connected to 5V, the other to the sensor signal wire.
1000 Ohm resistor
2000 Ohm Resistor
2200 Ohm Resistor
Calibration - Here is a table showing the temp sender's resistance vs the voltage value for each pull up resistor value. If there is not a file available for your brand of ECU the table can be populated manually from the information on this table. Note all pull up resistors are to the 5V supply.
Below are screenshots and links to table calibrations for various common aftermarket ECU's. We have noted the common pull up value that the table is built to work with. Using a different value resistor will result in a incorrect value in the ECU.
Note all temps are in Celsius unless otherwise stated.
ECUmaster - typical pull up 2200 OhmECUMaster Black Calibration
Haltech - typical pull up 1000 ohm
Link - typical pull up 1000 ohm (sensor cal is the same as "Bosch STD")
Holley - no pull up options, must use external. Table show is for 2k pull up
Holley Must entered manually, temperature in Fahrenheit.