Adjusting parameters that determine BLM cell - GM ECM

[Roger Heflin]

On Sun, 31 Jan 1999, Mike wrote:

> >> 
> >> 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.
> >
> 
> Correct me if I'm wrong, but the block learn multiplier and integrator are
> ignored at WOT (or more correctly, open loop), at any RPM, so any tuning you
> do here won't affect WOT operation. If the system is running closed-loop,
> there aren't any tables per se (except maybe the block cells which are
> derived from the integrator anyway) that are used to adjust fuel. It's all
> done off the integrator and O2 sensor. I wonder if you can find if there's
> an injector "scaling" factor that could be used to apply a reduction in IPW
> rather than tweaking the logic.

I was hoping there were tables for each block learn cell.  I guess
there are not any tables for the BLM's.  I have found what I believe
may be the injector constant (0x867C), I don't have the stock
prom I started with, but I have some other copies of stock proms, and
it looks like that value was originally 0x09B9 (2489), my current
value is 0x0C4E (3150), the ratio of the two is 1.265, the stock
injectors were 22 lb and the current ones are 30 lb (ratio 1.364), so
if that is the injector adjustment it needs to be adjusted higher.  I
am figuring on trying to adjust things by about 2% or so at a time.
The injector adjustment will affect the BLM stuff and the WOT tables
right?  Is there something else this will affect?   I know I will have
to watch the WOT O2 levels and make sure they don't get too low, but
it is pretty fat throught the range, so things should be pretty safe
so long as I am careful.

> 
> To me, 850-870 on the O2 still sounds a tad fat but it's really a call that
> should be made after dyno pulls with other O2 voltages seen for comparison.
> I thought the Buick GN crowd shoot for somewhere around 700-800mV...
> 
Yeah, I have heard best hp is closer to 800-810 or so.    Someone on
the f-body list dyno tuned and got 810 as best hp.

				Roger