Which SAE code / parameter to use for AFR during data logging?
 

I have OBDWiz software and I am trying to log RPM, MAF, STFT, and AFR to troubleshoot a misfire.


There are many different options for the AFR (o2 sensor wideband, o2 lambda current, o2 voltage, etc) and I don't know which to choose. Does anyone know the SAE code, or have familiarity with OBDWiz?


ANSWER: "SAE 0x34, O2 sensor lambda wide range (current probe) (Bank 1, Sensor 1).

PID list attached.


Commanded fuel/air equivalence ratio is what it's telling the engine to achieve. 0x44.


Commanded Equivalence Ratio -- Fuel systems that use conventional oxygen sensor displays the commanded open loop equivalence ratio while the system is in open loop. Should report 100% when in closed loop fuel.

To obtain the actual air/fuel ratio being commanded, multiply the stoichiometric A/F ratio by the equivalence ratio. For example, gasoline, stoichiometric is 14.64:1 ratio.

If the fuel control system was command an equivalence ratio of 0.95, the commanded A/F ratio to the engine would be 14.64 * 0.95 = 13.9 A/F.

I'm not sure what you are asking but at idle your AFR's should be trying to achieve stoich and sit at 14.6-14.7 at warm idle. At warm idle your STFT and LTFT should be within 3% of zero +/-.

I figured out to log "SAE 0x34, O2 sensor lambda wide range (current probe) (Bank 1, Sensor 1).


at 1.00, it is stoich. multiple the lambda by 14.65 to get the actual AFR.