'747 and Proportional Stuff

[Scott Lundahl]

Sorry for the questions, but thank you for your answer.  I guess I spoke 
too soon - closed loop Nirvana is drifting away from Nirvana.  'May need to 
squeak the prop gains down a bit or change the slope of the O2 vs O2 error 
BIN lookup table a bit.  We'll see.  It's still a lot better though.

Scott

At 04:19 PM 7/11/00 -0400, you wrote:

>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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