Rich,

here is a basic fuel calculation algorithm..... (sorry for those who dont understand)

OFFSET=MINIMUM_INJECTOR_PULSE_WIDTH
(this sets the basic minimum injector pulse width)

if LOAD < LIMIT then OFFSET=OFFSET+CO_ADJUSTMENT
(LIMIT is the pressure point at which CO adjusment is disabled)

BASIC_PULSE=OFFSET + MAP_VALUE[LOAD][RPM]
(This adds the offset to the map value taken from the 3D fuel map based on load and rpm.)

CORRECTIONS=START+COOLANT+CHARGE_AIR
(this creates a percentage value from coolant temperature and charge temperature)

FINAL_PULSE=(BASIC_PULSE/100) * CORRECTIONS)
(this multiplys the basic fuel pulse width with a percentage of corrections.)
(E.G fuel is enriched when the car is cold or charge air temp gets too high)


I have not included things like ACCELERATION,DEACCELERATION and STARTING fuelling
but it gives a pretty good desription of how nearly all ECU's calculate fuel.
There is much more going on in the background but it would take me all day to write out exactly everthing.

Looking at this, the mapper is able to set the point at which the CO adjustment is effective
so in theory the CO could be made to be global but I have NEVER seen
a chip that allows this to be the case above about 5 psi of boost !