more 747 questions

[Jason Weir]

steve ravet wrote:

> Gregory A. Parmer wrote:
> >
> > On Mon, 8 Jun 1998, steve ravet wrote:
> > > I'm still confused.  This table lists desired A/F ratios, right?
> But at
> > > WOT you're not measuring A/F because you're ignoring the O2
> sensor.
> > > Having a table of A/F values seems to imply closed loop operation
> in
> > > that you measure A/F, compare to what's in the table, and adjust
> if
> > > necessary.
> >
> > Steve, and others,
> >   If you haven't ran across it yet, the following URL offers
> > some super insight. It describes the GN system but I
> > expect it will apply to all delco systems. The ECM
> > learns differences required to achieve appropriate A/F
> > mixtures at part throttle conditions (and sets the Block
> > Learn Multipliers) and applies the same multiplier
> > even when you go WOT.  In other words "open loop" is
> > not entirely based on a pre-programmed map. The BLMs
> > provide a learned fudge-factor.
>
> Now I think I understand.  At WOT, the ECM looks up what A/F ratio it
> needs based on rpm or whatever.  It uses a block learn value plus the
> base pulse width that it thinks will give that A/F ratio.  It doesn't
> bother to check the O2 sensor to verify the A/F ratio, it wouldn't
> give
> a valid reading anyway.  I don't know why I had such a hard time with
> that.
>
>

Steve,    Dont feel bad the light bulb came on for me at the same time,
I had been following your posts, I just wanted to let you know that you
wernt alone... Jason Weir