What would be the normal parameters for O2 sensor voltage readings at sustained WOT (as in a track pass) on a basically stock motor, indicating a healthy AFR?

 

Between .8 to .9 volts.

 

Is the lower number richer or leaner?

 

Lower voltage is lean, higher voltage is rich.

 

I have tried this and find that it is VERY unreliable. The O2's are good around stoich (14.7) and nowhere else.

At WOT you should have afr in the 12.5-13.0 range and that is WAY out of the range that narrow band (stock) O2 sensors can measure.

Doing with anything but a wideband will give inaccurate results.

 

LINK

 

Actually all it really means is that the fueling is richer then Stoich (14.63), nothing more nothing less. I have seen O2 mV readings range from low 800 to mid 950s, while the wideband reported around 12.8 AFR. Stock O2s are worthless for WOT tuning.