Adjusting parameters that determine BLM cell - GM ECM

[Mike]

>My car is quite modified (different cam, higher idle).
>
>I am looking at readjusting the parameters that determine what BLM cell is
used where.  I
>have determined the code that controls it and understand it.
>
>Right now:
>
>First:
>BLM = 0 		RPM 	< 700
>BLM = 1		 700 <	RPM 	< 1200
>BLM = 2		1200 <  RPM 	< 2000
>BLM = 3		2000 <  RPM
>
>Then:
>BLM = BLM		$0154	< 0x20
>BLM += 4	0x20 <	$0154	< 0x32
>BLM += 8	0x32 < 	$0154	< 0x50
>BLM += 12	0x50 <  $0154
>
>I don't at this time know what $0154, I am figuring it is map related, and
I going to
>determine what it is later today.
>

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.

>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?


--
 Mike