Datalogger and 02 sensor

[mini zilo]

I have obd-II datalogger program, and one of the parameters is o2 sensor bank 1, and 02 sensor bank 2...its reading in volts...My question is, how do I read this and translate these volts to something useful....in other words, whats the normal range for it so i know when somethings going wrong, and second, could i get away with using this readout rather than getting an A/F guage
or is it completely different? thanks...

 

[olmytsi]

The air fuel gauge reads exactly what you are reading with the logger. An air fuel gauge is useless, save your money.

Bank 1 = o2 sensor located in the turbo
Bank 2 = o2 sensor located after the cat

At idle, the voltage will go up and down. At wot (wide open throttle), the voltage will be anywhere from .94 to 1.00 (typical 2g 02 sensor range) depending on how rich or lean you are. Don't tune the car based on this, it's pretty much useless.

 

[spyderturbo007]

I have obd-II datalogger program, and one of the parameters is o2 sensor bank 1, and 02 sensor bank 2...its reading in volts...My question is, how do I read this and translate these volts to something useful....in other words, whats the normal range for it so i know when somethings going wrong, and second, could i get away with using this readout rather than getting an A/F guage
or is it completely different? thanks...

During idle and cruise, you should see the O2 voltage fluctuate between 0.20 and 0.80V. That's not a concrete range since it varies by car, but it's a good estimate. The rear O2 should read a steady voltage all the time and is of no interest unless it dies. If it does, it won't hurt anything other than throwing a CEL for "Catalysist Efficiency Threshold". I don't even bother checking the rear O2 voltage. I'll just wait for the CEL.

The AFR gauge is worthless and just intercepts the O2 voltage signal before it reaches the ECU and translates it into a blinking light show. Unless you really want a flashing LED in the car, there isn't any reason to have one. But I have heard they are a big hit with the ladies. In my case, it's just a flashing billboard to my wife that I've spent more money on my car.

As olmytsi said, at WOT you should see a consistent voltage in the 0.90 - 0.98V range. The actual voltage gives you a very rough estimate as to AFR. Not something that you can pin an actual AFR value on, but it will give you an idea if you are lean or rich.

As for something going wrong, that only applies if the O2 sensor is dead or dying. As the sensor ages, the voltage approaches zero. This is interpreted by the ECU (at idle/cruise) as a lean condition. The ECU then compensates by adding fuel by way of increasing your FT's. This doesn't hurt anything other than a drop in gas mileage. At some point, the ECU will max out the FT's and be unable to compensate for the false lean condition. Then comes a CEL for "Fuel Trim Malfunction, Bank 1".

A dead / dying O2 won't affect WOT operation.