O2 sensor bias

[Greg Hermann]

>>Ok this isn't really true of an O2 sensor, but just pretend for a
>minute.
>>What you want, roughly, is an O2 sensor who's output crosses >through
>the 450mv range at say 16:1 rather than 14.7:1.
>
>A question that has remained unanswered in my head for many years now is
>if the O2 sensor outputs 0.45v at 14.7 mix,  what is the mix ratio when
>it outputs 0.8v? or 0.9v? or 0.2v?  Does anyone have a graph of a common
>O2 sensor characteristic of Voutput vs Fuel ratio? I have searched for
>Bosch data on this but have never seen it.


Yes I do. In the Accel EMIC Training Manual (don't ask!) on page 1-5 , Fig
1.3B presents a graph of the output vs. lambda of whatever Bosch 3 wire
sensor it is that Accel sells with their EFI kits. "Output voltage switches
rapidly from 200--800 mv" at lambda =1 (14.7:1). Looking at the graph, the
output is down to  100 mv by 15:1
and up to 900 mv by 14.4:1. It is nearly a vertical line between 200 and
800 mv, at 14.7:1, as they claim. (The far rich and far lean ends of the
curve are at 950 and 50 mv, respectively.) Basically, you are playing with
yourself to try to use a standard O2 sensor to try to control anywhere but
at 14.7:1 with this  shape output profile.

On the other hand, I also have voltage vs. lambda output curves for five
different models of the NGK/NTK 5 wire, wide band O2 sensor controllera.
With this puppy, you can control to any lambda ratio you want, and they
show data indicating that it is quick enough to pick up a random misfire
AFTER the CAT! Unfortunately, retail on one of these is $600 or so,
including the control box. God knows where to get them at any kind of a
discount, I don't---maybe one of you does???

Regards, Greg