Catera WBO

[Garfield Willis]

On Thu, 21 Sep 2000 21:06:19 -0400, "Bruce Plecan" <nacelp at bright.net>
wrote:

>I called the local dealer, and they had one.  The one they showed me was a
>normal 4 wire.  Local guys have been wrong before thou.
>Bruce
>
>> I have heard the Cadillac Catera uses a wide band, with  a Bosch Motronic
>maybe
>> low cost as or GM o2 sensors.
>> Alex

Alex, Bruce,

I thot sure I mentioned this some time back: the Catera uses a Denso
part that is the new kind of "4-wire WBO2 sensor". When I have some
time, I'll try to explain how they work, but essentially it's not as
suitable for high accuracy AFR measurement as the "O2-pump style
5-wire" like the Honda/NTKs, et al, BUT it can be operated in 3
"modes" of progressive accuracy/capability of O2 sensing, so it's
possible to get to C/L *very* soon after cold-start via very early
"stoich crossing" detection, and that's why you see even Honda
switching to these type of WBO2 sensors. It's a better compromise
between 'wider'-band AFR sensing and smog requirements. If you only
have a few target AFRs to hit, AND you want to get to C/L as fast as
possible to make your Fed smog budget, this type of sensor works
better in that tradeoff space.

The first warm-up phase is: to be able to detect just stoich crossing,
the second phase is to be able to detect crossings around a particular
target AFR, and the third and final warm-up phase is "measurement
mode", where any given AFR can be measured linearly. In this final
mode, it is still not as precise as the oxygen-pump type sensors, plus
it takes more complex sensing of the actual sensor temps to know when
you're IN that highest mode capable of AFR measurement.

There are some quite readable patents on this type of device, but I
don't yet have my main computer with those numbers available. End of
next week we're slated to setup all that stuff, so I'll post the
patent #s when I'm able. Quite a bit more complicated than even the Ox
pump types, but also pretty interesting. Not at all like the Bosch
LSM-11s either, BTW; a truly new type/approach to O2 sensing.

HTH,
Gar


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