Fw: Justa O2 Note

[Bruce Plecan]

May have been overheard at the grocery store this am.
Bruce

>->My understanding of the chemistry is that it has to go lean so there is
>->excess oxygen that the catalyst picks up, then rich so it can use that
>->oxygen to take care of the HC and CO.  It has to average stoichiometric
>->to keep things in balance.
>-
>-I'd always assumed that because they're using a cheap narrow-band o2
sensor
>-who's output right *at* stoch is a bit uncertain, they just compensated by
>-jumping across the boundary a lot, with the thinking that they'd get
>-"pretty close" to stoch on average.
>
>They may have started using this control strategy due to the limitations
>of the narrow-band oxygen sensor, but now they definitely cycle back and
>forth to keep the catalyst happy.  The excursions are very small, but they
>act in conjunction with the oxygen storage capability of the catalyst to
>allow a balance between oxidation of HC and CO, vs reduction of NOx.