anybody have a chart with voltage from an o2 to a corresponding air/fuel ratio? possibly a formula though it doesn't seem to be linear. i've found this on the web but was wondering if anyone has one with more o2 to a/f ratio readings?

 

You're absolutely correct, its nowhere near linear. Depending on EGT, your voltage will also fluctuate at a different rate as you move away from stoich (14.7:1). Another variable is that all 02 sensors don't have the same curve. They're all pretty much the same at 14.7:1, but have different rates outside of this range. Unless you have a wideband 02 sensor, you can't accurately tell the difference between a 10.5:1 and a 11:1 ratio.