narrowband o2 voltages

[knochgoon24]

Before I start, I don't have money for a wideband and I'm not tuning my car with the narrowband, just curious about the voltages I'm getting with my logger. I have little knowledge of O2 sensors and what the voltages mean. I know the narrowbands are inaccurate, but it's all I have to get a ballpark.

What is the ideal voltage to have?
Also, is a higher voltage lean or a lower one?

It read an average of .525v front and .493v on the back.
I also got reading ranging from 0v to .96v on both, so that may be affecting the average. It just seems like it jumps a lot.

I think my car is running pig rich by the way. It at least smells that way.

 

[JeffGST]

Front O2 are not inaccurate. Actually they are very accurate, but they are not precise. I always like to take a look at my Front O2 even though I always datalog my wideband. It is a very consistent sensor.

The problem with it is that 0.88 V is anywhere in between 12.0-13.2 AFR's and 0.90V is anywhere in between 11.8 - 12.2 AFR's. You just don't have an exact ratio to calculate by.

Just remember this at WOT...

1.00V is pig rich. Rich to the point that you may misfire. 1.02V and most cars sputter.
0.88V is lean. Even for E85 that is a pretty lean AFR.

It's not an ideal way of tuning at all because of all the guessing of where you actually are.

 

[kenamond]

Don't bother with the rear O2 sensor.

The front O2 sensor is only good at reliably detecting stoich AFR. This occurs at 0.5v.

The only time you can rely on what Jeff said is when the ECU is in open loop mode (full throttle, more or less). When you're at part throttle, the ECU goes into closed loop mode, and it tries to keep a stoich AFR. It does this by getting the O2v oscillating above and below 0.5v. If it stays above, the ECU knows it's running richer-than-stoich and adds to the fuel trim. Below, and it's running lean and subtracts from the fuel trim.

So you're probably seeing closed-loop O2v behavior when it's changing a lot.

You can look at your short and long-term fuel trims to see how you're doing in closed-loop mode, and you can follow Jeff's guidance when you're in open-loop (full throttle) mode. But as Jeff said, you don't know where your AFR really is without a wideband sensor. If you knew where your O2v were with stock fuel and boost, that'd give you a better idea of what is "okay". But if you change the sensor, all bets are off. I was getting 0.92v on one sensor and 0.96v on a new sensor for identical pulls.