[Diy_efi] MAP Sensor

[Eric Fahlgren]

Kent Martin wrote:
> 
> By this do you mean I should look up the injector on time
> from MAP and RPM and then scale the on time
> by a value in another lookup table for temperature.
> i.e.
> ontime = FuelTable[rpm][MAP]
> ontime = ontime *TempScaleLookup[temp]/0x80;
> where 0x40 =< TempScaleLookup[n] <= 0xFF;
> giving a possible adjust of 2 times larger or 1/2

No, you don't need a table for temperature or pressure,
since they are simple scalar factors in the density equation.

The table in a speed density system is a convenient means of
relating some of the inputs (speed==RPM and density~=MAP) into
an estimated volumetric efficiency, and then you just crank 
out pv=nrt to figure out how much air the engine is pumping.

So the amount of air ingested for a single cycle is:

   air = cylinder_volume * VE * temperature * MAP

where in SD

   VE = some function of RPM and MAP, usually a lookup table.

use this to compute the desired quantity of fuel:

   fuel = air / AFR + enrichments

then use injector flow rate to compute a pulse width.
All units conversions are left to the reader.

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