Found.. 8051 FAQ.

[Craig Pugsley]

> >This is what I plan to do to get it running: 
> > 
> >I'm going to just use a "3-D" look-up table, with RPM on one axis and
> >load on the other (load being just engine vacuum level for starters).
> >The location pointed to by RPM and load will be a number that is used
> >for a counter that turns on the injectors: 
> > 
> >I plan to use 4 bits (=16 points) for the RPM axis and 5 bits (=32 
> >points) for the load axis, giving a total of 512 settings - (Co 
> >incidentally the same way that other well known controllers are laid 
> >out). 
> > 
> >Craig. 
> > 
>  
>   It sounds like your line of reasoning is very similar to mine!  I'm
> working on some code to do 4 point linear interpolation for the fuel map.
> My fuel map will take an 8 bit number (0->255) for the engine RPM and an
> 8 bit number for the engine load.

One problem with using a 255 RPM x 255 LOAD = 64K settings - impractical
(impossible) to calibrate each and every one of those points.

I guess you could do your on dyno/road calibration with something like
what I suggested above (32 load settings x 16 rpm settngs) and then
linearly interpolate the intermediate settings (Either in real time in
the processor or via a PC and program the memory with the full 255x255
map)

> My map will be 17 x 17 x 8 bit numbers.

IE (17 load x 17 rpm settings?)
I'm un-decided if an 8 bit injection time will have enough 'dynamic
range' from idle to full throttle, though it's probably easier to deal
with an 8 bit number.

> Even though i will use the upper 4 bits (0->15)
> for the lookup of the map, to get a point on either side of the 0->15 
> number you need 17 points, hence the 17 x 17 map instead of 16 x 16.
> >From then I will use the lower 4 bits to do a 4 point linear interpolation.

Sorry, I don't understand. Can you explain it in a bit more detail?
(Maybe an ASCII diagram)

Thanks for re-posting the fuel amount theory article. (I have it
somewhere but finding it is another story)

Craig.