EFI mapping ideas.

[Dale Ulan]

> Perhaps this means that RPM and LOAD are of similar importance. The odd
> number for load suggests that maybe only the load is interpolated in a
> MoTeC computer. (Hey, I'm speculating)  

Wierd. They should both be interpolated. It isn't that hard...
> 
> Am I correct in assuming that this load setting is just the engine
> vacuum? (IE using a MAP sensor). Is this relative to the ambient
> pressure or to absolute zero (IE a single ported sensor)?

Generally, absolute pressure is used, with a small correction factor
for the change in exhaust backpressure when the barometric pressure
changes.

> Really? I'm impressed/surprised that it is that straight forward.

There are a lot of other 'tweaks' that are added to make it work...

> > BASE_PW * AIR_DENS
> > result: 16 bits
> 
> Does BASE_PW come from the Load vs RPM table?

yes.
> Where does AIR_DENS come from? Would just an air temp sensor be OK?

yes. Dig out the ideal gas law... PV=nRT. It's a 1/x relationship, where
x is in degrees Kelvin.

> > * (POWER ENRICHMENT FACTOR + COLD START FACTOR)
> > result: 24 bits.
> 
> I presume the power enrichment is an 'accelerator pump', and the cold
> start is determined from the coolant temp sensor.

Cold Start is in part determined from coolant temperature, but also
the change in coolant temperature since starting, time since start,
and manifold vacuum:
   Coolant Temperature determines a 'COLD START' mixture, eg.
     3.5:1 at -10 C.
   delta coolant will indicate that the temperature has gone up
     by, say, 5 C since starting, so add (for example) 1.0:1
   engine vacuum is at 30 kPa, so add 1.5:1
     The engine has been running for 20 seconds, so add 0.4:1

   final ratio = 6.4:1

Typically, the 'timer' is an exponential lag filter.

The power enrichment is like the metering rods in real carburetors
(or the power valve in a Holley). In high load conditions, the
EFI computer will add enrichment, and typically run the mixture
at 13.0:1 or so.

> > * ADDITIONAL FACTOR
> > result: 24 bits.
> > round down to 16 bits.
> > 
> What's this part?

Anything that I've missed in ony describing a small fraction of the
tables. Things like correction factors based on fuel return line
backpressure, fuel pump voltage drop, canister purge vapor compensation,
EGR feed compensation, and a great deal of other things.

The accelerator pump is an additive pulse width, after the steady-state
fuelling has been calculated to open the injector 'X' us.

This is typically calculated by using a filtered delta-MAP contribution
table and temperature compensation table. This compensates for manifold
dropout effects of TBI systems, where fuel will condense on the manifold
walls when quick changes of MAP occur.
In addition, to compensate for manifold filling effects and fuel
evaporative rates, an additional AE is added, with its own dTPS
table, a temperature-dependant decay rate, and another temperature
dependant factor.

AE = DMAP_CONTRIB[dmap/dt] * TFDMAP[man_temp] + TPS_CONTRIB[dtps/dt] *
	  TFDTPS[man_temp] * TPS_ADJ[tps] * RPM_ADJ[rpm]

BFP= BASE_PULSE[rpm,map] * ADFACT[air_temp] * (POWFACT[rpm] + POWFACT[map])
     {* or +} (COLDENGFACT[ect] - TIMEOUT[engrunning])

PULSE_WIDTH = INJOPEN[battery] + AE + BFP

These are *very* simplified...

-Dale