[Diy_efi] Narrowband O2 to calibrate WB02?

[Geddes, Brian J]

In my research on the internet, I've seen several drawings of the =
response curve or a narrowband (standard) O2 sensor.  You've all seen =
the curve I'm sure - it shows very accurate around stoich (.2 to .8 =
volts), and not very accurate anywhere outside of stoich. =20

With all the discussion about the use/misuse of Rcal values in the DIY =
WB02 design, I've been thinking about how to have a little more =
confidence in my unit.  It occured to me that my car has a NB O2 sensor, =
so I decided to use it to try to calibrate my WB02. =20

I adjusted the fuel until the NB O2 readings were rapidly cycling around =
.3-.7 volts.  This should be stoich.  At this point by WB02 was reading =
2.7 volts, so I set up my WB02 voltage to AF ratio table with the stoich =
point centered at 2.7 volts.  I kept the shape of the response curve the =
same; I just shifted it over .2 volts.=20

So, a couple of questions:
- Does the response of NB O2 sensors "shift" over time?
- Is the NB response curve truly centered around stoich, or is it =
centered a little leaner for better economy/emissions?

I realize that this is far from a comprehensive calibration.  I also =
realize that the DIY WB still probably may have design flaws that may =
throw off readings.  Personally, I think that's okay.  I didn't pay for =
a laboratory-grade instrument, so I don't really expect one.  What I do =
expect is for it to give me resolution an order of magnitude greater =
than stock O2 sensors.  As long as the response curve is somewhat =
linear, and I know the point where stoich is, I think it's a very =
valuable tuning tool.   =20


- Brian


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