Adjusting parameters that determine BLM cell - GM ECM

[Roger Heflin]

On Sun, 31 Jan 1999, Mike wrote:

> 
> I had a quick look at 0154 and it appears to be a convoluted representation
> of filtered MAP in actual kPa:
> 
>     MAP kPa = (0154*256 + 0155) / 256
> 
> or more simply (and somewhat less accurately) by eliminating the fractional
> part:
>     
>     MAP kPa = 0154
> 
> So, say, 0154 = 0x55 means 85kPa MAP pressure.
> 
> It's hard to see what they're doing with 015B which seems to be used as the
> next value to be added to the filtered 014E value. But 014E is initialized
> to the raw MAP counts so it's safe to assume, I think, that 015B is a MAP
> derived value.
> 

I am still digging through it.   It looks like the rpm part may be the
what is really causing the problem.  The lowest default setting is
700, which originally was above idle.  Now it is well below idle, so
probably I will try boosting the rpm values by 300 rpm.  The spread
with the $0154 parameter looks like it is spread out fairly well, ie I
hit all areas that are determined by it. 

 > >Have others changed the parameters to move BLM Cells
around? > >
> >Right now, I have rather bad BLM cell coverage.  With 4 or so hours
> >of data I dont get into BLM cells 0,1 4,5 8,9 12,13 at all.   Those
> >cells are the ones indexed by rpm (0-700,700-1200), my idle is raised 
> >to more like 900 (out of gear), 950 (in gear).
> >
> >Also right now my BLM are way out of tune (ie BLM values close to the
> bottom rail (110 or
> >so average), so everything is going to have to be tuned.
> >		Any help is appreciated from others with
> >		knowledge about this subject.
> 
> 
> If your BLM is at 110 or so, your running way fat. Any chance of turning
> down the fuel pressure a pound or two or three? Or is it okay up top and
> rich down low?
> 

The part throttle tables are rather rich.  At wot I am running 850-870
mv which should be pretty good.  It also varies quite a bit from cell
to cell on how excessivly rich things are.  There is at least 3 cells
that are within a reasonable amount.

			Roger