OXYGEN SENSOR (range of 0.0 to 1.0 volts)

The oxygen sensor is what the ECU to determine whether the engine is running rich, lean, or just right. 0 volts is lean, 1.0 volts is rich, and stoich is ~0.47v. Once again you want a good smooth pattern of peaks and valleys. At idle you will have a nice and slow switching rate. The higher the rpms and throttle position under a load (driving) the faster the switching rate until it stays constant at a higher reading. Once it stops switching that shows that you are not in closed loop anymore. Most importantly you want a smooth switching rate.

Once you go into open loop, it will show a constant reading. Under WOT you always want as low of O2 voltage reading as you can go WITHOUT any detonation or knock sum on the logger.

There is no absolute O2 voltage that is "safe." It will vary from car to car. Lack of detonation is a much more important than O2 voltage. With that in mind, on 92+ octane pump gas, most cars can run around 0.90v to 0.92v with a minimum of detonation. With race gas it's a whole different story. :-) You can run significantly lower O2 voltages, in the 0.8v range or even lower without knock. A nice smooth and steady O2 voltage reading is desired throughout the rpm range while at WOT.

NOTE: Oxygen sensors and WOT O2 readings seem to vary from car to car and even in the same car under different circumstances. Some cars won't read higher than say .94v no matter how much fuel you add, others may read .98v or even 1.0v. It also seems that your O2 voltage may change from pass to pass at the track without any adjustments made to the fuel curve, i.e. .85v one pass, .82v the next, .88v the next, etc.

If you get a sporadic "dip" in your O2 sensor reading, this can be a sign of a misfire. You didn't actually go lean during that "dip", but you had a excessive amount of unburnt fuel AND O2 go into your exhaust. The O2 sensor just reads how much O2 in the exhaust, therefore if you have a misfire, the excess O2 that is flowing by the O2 sensor shows up as a lean condition.