Help on turbo app. + EGT & AFT

[Garfield Willis]

On Tue, 09 May 2000 16:39:49 -0400, Barry Tisdale
<btisdale at cybersol.com> wrote:

>At 12:45 PM 05/09/2000 -0700, Garfield Willis wrote:
>>When they (WB AFR) become affordable very shortly,..............
>
>Any official word on this?  Seems its been "shortly" for a longish
>time.....}:}E

Man, hasn't it ever! No one is more painfully aware of that than moi.

There won't be anything official until we announce; then both price and
availability will be made public. I *can* tell you that we're in pilot
production, tho!; that's a high-falutin technobabble term for trying to
make a lot of a certain number together, to make sure we can 'mfg' them
in batches. So they're in the oven, and the "soonium" is all the more
soonish than it's ever been.

I might slip a few sneak preview pictures up on a website, however, just
to whet the appetite. Keep your eyes peeled onlist. :)

>Is there a natural phenomena that centers the standard O2 sensor on stoich
>of 14.7:1 AFR?  Any reason one could not be done that centers on 12.5:1?

Yes, the 'nernst' phenomenon I gather is sensitive to this one unique
chemical state; so no, I would have to guess a simple 'cell' would not
likely be possible, that would have such a dramatic singularity at any
arbitrary/given AFR. I'm no physical chemist, so don't report me to the
Nobel committee if I err herein.

BUT, that's the clever work-around invention in the current-pump type
sensors; they artificially create an environment (by supplying needed or
depleting excess oxygen) so that the 'sensing cell' is made to see an
artificially created stoich point. For example, to tell when you're at
12.5AFR, there's a certain amount of additional oxygen needed (because
you're rich) to be added, to get the sample back in balance at 14.7. So
the oxygen-pumping cell in effect injects this required missing oxygen,
to create a small region of stoich in the sensing cell. As a result, the
amount of excess oxygen needed to "pump" the sample back up to stoich,
is a measure of how far it is rich from stoich. Voila.

In effect then, they have indeed created an arbitrary new "stoich" if
you want to think of it that way. The sensing cell is held in a state of
stoich by the pumping cell either adding or removing O2 to keep it
there. Thus, the amount of pumping needed in this process IS the measure
of AFR of the sample.

HTH,
Gar


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