Lambda value/ AFR correlation

[Brad Sheridan]

>
>Hi Brad, I have a GM Service Technology Group document that lists AFR vs
>02 voltage.
>
>
>A/F                        02 Volts
>   Ratio                           Range
>========                   =============
>
>17.1                       0.090    0.110
>16.5                       0.190    0.205
>16.0                       0.290    0.310
>15.5                       0.390    0.410
>14.9                       0.490    0.510
>14.4                       0.585    0.605
>13.9                       0.680    0.700
>13.2                       0.780    0.800
>12.7                       0.870    0.890
>12.1                       0.965    0.985
>
>However I must say that this must be used with a caution. My experience
>is that even when I calculate my afr to be 10.14 - 1 @ 4000 rpm, based
>on the grams/sec air flow and ms pw of my injectors, my 02 sensor has
>never read higher than 813mv, with a 10.4 ms pw. With an 7.9 ms pw the
>02 sensor reads 793 mv, so the 02 sensor does not read in a linear
>manner the further you go from stoich. Also voltages vary between diff
>02 sensors.  Mark.

Interesting, That looks alot more linear than ANY manufacturers charts I've seen
on O2 out vs. AFR, could it be that newer O2 sensors have a more linear
response off stoich than the older design ones? The charts I've seen made
it appear that the O2 sensor was only accurate around stoich, the rest of
the time, it was pretty much worthless other than telling if it was lean or
rich, but not by how much.
  I have an NGK sensor(much more accurate than O2 sensor), and a chart of
output voltage vs. lambda that was supplied by NGK. What I'm missing is the
relationship between lambda and AFR, which I think is fairly simple, I just
can't recall what it is.

Thanks,
Brad