Trying to tune my 02 civic ex with the aem fic and was wondering if anyone knew what voltage output of the primary O2 corresponds to what afr or if it is more complicated than that (which it seems to be). In idle my wideband settles close to 14.7 and the signal from my O2 seems to be a sine wave alternating between about .8 volts and .2 with a period of about 5 seconds. However when driving the signal changes but not in a similiar pattern. Anyone know how the O2 signal corresponds to the actual afr (or if a sine wave does). thanks

 

The 0.2-0.8 wave you see is during idle and cruise. The ECU is continuously adjusting fuel injection to get 14.7 AFR. During WOT operation, The ECU enters open loop and works only by tables, ignoring the O2 sensor.

The following is an approximate AFR to O2 volts conversion table. This has some validity only for heated 3 or 4 wire O2 sensors. Example: 0.18 volts is 14.84:1 AFR. While 0.86 volts correspond to 13.09 (good under full throttle for NA engines)

AFR ===== VOLTS

DW 1674 ; 3 0.06
DW 1615 ; 4 0.08
DW 1556 ; 5 0.10
DW 1532 ; 6 0.12
DW 1513 ; 7 0.14
DW 1496 ; 8 0.16
DW 1484 ; 9 0.18
DW 1472 ; 10 0.20
DW 1470 ; 11 0.22
DW 1470 ; 12 0.24
DW 1470 ; 13 0.25
DW 1470 ; 14 0.27
DW 1470 ; 15 0.29
DW 1470 ; 16 0.31
DW 1470 ; 17 0.33
DW 1470 ; 18 0.35
DW 1470 ; 19 0.37
DW 1470 ; 20 0.39
DW 1470 ; 21 0.41
DW 1470 ; 22 0.43
DW 1470 ; 23 0.45
DW 1470 ; 24 0.47
DW 1470 ; 25 0.49
DW 1470 ; 26 0.51
DW 1470 ; 27 0.53
DW 1470 ; 28 0.55
DW 1470 ; 29 0.57
DW 1470 ; 30 0.59
DW 1470 ; 31 0.61
DW 1470 ; 32 0.63
DW 1470 ; 33 0.65
DW 1470 ; 34 0.67
DW 1470 ; 35 0.69
DW 1470 ; 36 0.71
DW 1470 ; 37 0.73
DW 1470 ; 38 0.75
DW 1461 ; 39 0.76
DW 1449 ; 40 0.78
DW 1436 ; 41 0.80
DW 1424 ; 42 0.82
DW 1375 ; 43 0.84
DW 1309 ; 44 0.86
DW 1221 ; 45 0.88
DW 0951 ; 46 0.90