Re: Editing proms (editorial)

["Kevin R" <KEReyn@gte.net>]

Thanks for the corrections. Being fairly new at this myself, I remember
thinking that whatever I put in the bin AFR wise the ECM would just
make-it-so. The statement I wanted to make is that there are variables and
that
the numbers shouldn't be take as absolutes. It's real easy to base bin
changes on perceptions rather than actual data and start doing things like
setting WOT to 11.5 because 12.5 "sounds" to lean because somebody said the
magic number was 11.x.

Now for my continued learning, are you (Ludis) saying that the ECM(in my
case a 747) will adjust the constant somehow thus making the numbers more
accurate?
Example:
Say I have a 350 with 70lb injectors and the constant is set for this
injector/CI combo. Then if I bump up the FP to increase the injector output,
thus throwing off the VE and AFR numbers in the ECM. Will it (the ECM)then
see that the command AFR is off and make an adjustment bringing everything
back to close to real numbers? I was under the assumption (never assume I
know) that it would just move the BLM and call it a day leaving the WOT, PE
etc AFR numbers off. Since in this case the constant (if not adjusted) would
be set for 70lb while the injectors would be actually putting out say
85-90lb making the AFR richer than the bin called for.

Kevin R


> Kevin R wrote:
> >
> > Keep in mind that the AFR settings and such aren't real numbers. It
would
> be
> > nice if they are close, but the ECM uses calculations based on what it's
> > told are the current injector size/ motor size etc. Since there is more
to
> > accurately gauging AFR than these variables, (and this assumes the prom
IS
> > set for YOUR injector and engine size) the WOT AFR setting much like the
> VE
> > table numbers shouldn't be thought of in terms of actual AFR or VE.
>
<Carl wrote replied>

> I have found, many times, if the VE table is correct and the injector
> constant and Cu In constant is correct....The PE AFR ends up really close
to
> whatever you command it to...
> -Carl

<Ludis replied>

> To an extent, the AFR numbers have to be real.  Part of the closed loop
> logic checks for a commanded AFR of 14.6:1, perhaps 14.7:1 in a few
> bins.  At that point it'll use the O2 sensor to learn the fuel
> adjustment so that it is actually running the engine at 14.6***:1.  If
> some input to the ECM then suddenly changes causing PE mode with an AFR
> of 12.5:1, the engine will be switched to running at 12.5:1.  Once the
> engine parameters go beyond the learned range, then the AFR value can be
> wrong.




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