Just try to sneak something in, and I've got questions on it <g>. That'll
teach me. . . lol
The statement I made about that value being set to the O2 sensor
stoich switch point, was from something, ah, I read, someplace, yea,
that's it, read it from a, uh, source.
This term has been a source of confusion. Other's have stated that
it's use is tied to different fuels, such as alcohol. This makes sense,
as the O2 stoich switch point would most likely be different.
However, I believe that there is more to it.
The AFR term is used as a divisor in the BPW calculation. To do
this, the AFR term is used as an index to do a table lookup. This
table is the inverse AFR, and the resultant lookup is multiplied into
the BPW. This has the same effect as using the AFR term as a
divisor in the BPW calc (which it is).
When open loop, the AFR term is determined by various
lookups depending upon engine operating conditions. IE: If in
PE, the AFR term is lower (~12.8), causing an increase in the
BPW. By setting 'stoich' to the O2 switch point, the BPW calc
is calibrated, it is based on a known. This way, it's all tied
together, it allows for calc'ing a BPW for another AFR, simply
by plugging that AFR into the BPW calculation.
BobR.
Scott Lundahl wrote:
> There is a God. Thank you - send more . .
>
> I had a question about the "stoich" byte. You say that it must match the
> O2 threshold settings which I assume means the very steep mV vs. AFR Lambda
> curve. I have always theorized that it was used as in calculations where
> things are expressed in therms of AFR (such WOT fueling, cold enrichment,
> etc). This byte tells the ECU what AFR the stored and/or derived values
> (and their associated bpw's) are supposed to represent (in a CL system this
> is almost always 14.7, but could be other values in an open loop
> system). In this way a meaningful, dynamic bpw's can be calculated for
> other parameters expressed as AFRs. Can you you explain more about it?
>
> _scott
>
> PS - I had to squeak the idle Prop gain up to 5, but other than that, the
> scaled Prop & Duration param's seem to be working much better. BLMs are
> rock stabile, INT is a happy 128. O2 cycle frequency much more
> respectable. No surging. It's Closed Loop Nirvana.
>
>
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