[dannichols1474]

So I was getting a displayed value of +/- 0.2 AFR on the lower calibration value and +/- 0.1 AFR on the upper calibration value - lower target = 13.328 & upper target = 16.66, and my MegaSquirt2 ECU is displaying AFR to the tenth of an AFR, so my closest displayed values would be 13.3 and 16.7 AFR.

I went back out to the garage with my notebook running the TunerStudio app and connected the notebook to the ECU and turned key ON, engine OFF. I unlocked the calibration tables and opened the AFR calibration table.

Now I started hacking. I took the average of the two Point 1 calibration values the Excel calibration worksheet had given me: (9.895030303 + 10.192) / 2 = 10.0435152 and entered that into Point 1 (0 Volts) of the AFR calibration table and wrote the values to the controller (pressed the "Write to Controller" button), turned the key OFF, waited 10 seconds, then turned the key ON, engine OFF and read the AFR gauge: 13.30 & 16.60.

Next, I increased the Point 2 (5 Volts) calibration value from 19.992 to 19.995, wrote the value to the controller, then cycled the key OFF to ON, engine OFF and read the AFR gauge: 13.30 & 16.60.

Again, I increased the Point 2 calibration value from 19.995 to 20.000, wrote the value to the controller, then cycled the key OFF to ON, engine OFF and read the AFR gauge: 13.30 & 16.60.

Finally, I increased the Point 2 calibration value from 20.000 to 20.100, wrote the value to the controller, then cycled the key OFF to ON, engine OFF and read the AFR gauge: 13.30 & 16.70.

I had now achieved the closed displayed AFR values to the ideal target AFR values thereby minimizing offset and linear errors and maximizing the accuracy of the AFR values the MegaSquirt2 ECU was reporting (and using for injector pulse width trimming) from the 14Point7 O2 sensor controller.

I locked the calibration tables, shutdown the TunerStudio app, disconnected the cable from the ECU and turned the key OFF.