It is impossible to predict how often the AFX needs to be calibrated without knowing the conditions under which the AFR sensor was used. However, here are some calibration guidelines:
・The first time before a new sensor is used: calibrate.
・For every 3000 ft. change in altitude: calibrate.
・For race engines: calibrate before every tune session.
・For wild, street performance engines: calibrate once every week of use on the street.
・For mild street engines: calibrate once every month of use on the street.
AFX Calibration
The procedure to calibrate the AFX is as follows:
1. Connect the harness to the control module and the AFR sensor. With power disconnected from the harness and the sensor removed from the exhaust, hold the sensor by its wires letting it hang free in air. You cannot reliably calibrate the AFX with the sensor mounted in the exhaust of an engine, even if the engine has been off for several days.
2. Attach power to the harness. In about 10 seconds, you will start to notice the AFR sensor getting hot. Use CAUTION, the sensor can burn you.
3. Wait 3 minutes. This is to allow the sensor to reach operating temperature.
NOTE: Although 3 minutes is normally sufficient time for pre-calibration warm-up, generally the longer you let the sensor hang in free air before calibration the better. If time permits, we recommend you let the sensor warm up for up to 30 or even 45 minutes for best results. A good method may be to power the system up and attend to other tasks, then come back after 30 or 45 minutes and perform the free air calibration. Keep in mind that this does not mean that performing the shorter warm-ups (3 to 5 minutes) will give bad results. It simply means that the longer warm-up time allows the sensor to acclimate to the atmosphere more thoroughly, and therefore can allow it to yield the most accurate results during on-vehicle use.
4. Turn the calibration knob on the back of the display head until the display reads “CAL-.” If the display reads “Air_” when the sensor is in air, turn the knob clockwise until the display reads “CAL-.” If the display reads “Air¯” when the sensor is in air, turn the knob counterclockwise unit the display reads “CAL-.”
5. Disconnect the power from the harness. When the AFR sensor cools down, install it in the exhaust and do not touch the calibration knob until the next time you calibrate the AFX.
NOTE: Caution should be taken not to accidentally knock the controller and inadvertently turn the calibration knob after calibration. However, the calibration circuit is designed to have a certain amount of leeway. Accidentally turning the knob a small amount will not affect the results. See the next section for guidelines on calibration intervals.