effect of CAT on WBO2 readings?

Bernd Felsche bernie at innovative.iinet.net.au
Thu Mar 7 18:46:07 GMT 2002


rob files tapped away at the keyboard with:

> How much (if at all) will a WB measurement change if the sensor is
> placed post cat (tailpipe probe), as opposed to pre cat (header
> bung)?

Post-cat conditions are at lower pressure so the pp of O2 in the
exhaust gas will be lower when compared to the reference in the
Nernst cell of the sensor - that's the "switching" part of the
sensor the controller tries to keep at around 0.45V by changing the
pump current.

The amount of oxygen doesn't change - it's not thermo-nuclear. :-)
The O2 reading will change due to pressure effects and the sensor's
relative sensitivity to the various exhaust gas components.

The amount will depend on the exhaust gas conditions in situ.

-- 
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