Getting facts straight! (3/3) (EGO sensor function)

[Greg Hermann]

>So do the EGO sensors work at stoich because they were designed to work at
>this ratio, or is there something intrinsic about their operation and the
>conditions at stoich that causes this?

It is an intrinsic part of their operation. Basically--they detect the
presence or absence of oxygen in the exhaust gas stream, and they do so in
pretty much a switch fashion. This is the basic basic physics/physical
chemistry of a Zr O2 cell. BTW--this type of cell was in use on stack
gasses from large stationary boilers and the like for decades before they
came into use for automotive apps--at a _MUCH_higher price, of course!
>
. A better
>question would be are they cheaper than the wide band sensors because they are
>easy to make, or because they are used on so many cars?

Both. A UEGO (WBO2 sensor actually has a HEGO included as part of it, and
also has an ion "pumping" chamber as well). Naturally, higher production
rates would bring down the price.

Greg