DIY_EFI Digest V2 #52

[adt1]

>From: mtaylorfi at juno.com (Michael R Taylor)
>Date: Fri, 14 Feb 1997 01:03:51 EST
>Subject: Fuel maps
>
>I'm looking for information regarding fuel maps.
>
>I'm attempting to program an HC11 in controlling the injection system,
>and I've roughly made a 2-D fuel map consisting of RPM on the abscissa
>and the MAP sensor on the ordinate.  I assume that as engine RPM
>increases, so does air flow (fair assumption) and as MAP increases so
>does air flow (a bigger assumption).
>
>I'm looks for "rule of thumb stuff" or actual fuel maps of other engine
>AS A GUIDE.  The best way to do it is on a dyno, but I ain't got a dyno.
>
>I'd appreciate any help.  Thanks in advance

Very basically, from the ideal gas law ...

    mRT = pV          then differentiate with respect to time,
                      make some assumptions, and drop some terms,
                      and get the following
    .      .
    mRT = pV          rearrange and account for volumetric 
                      efficiency, and get the following

    .     .
    m = epV/(RT)

             (where  m = mass, R = gas constant, T = absolute
              temperature, p = pressure (MAP), V = volume, 
              .                   .
              m = mass flow rate, V = volumetric flow rate,
              and e = volumetric efficiency)

    .
    V = Vd*N/2     for a 4 cycle engine

             (where Vd = engine volumetric displacement per cycle,
              and N = engine rotational speed)

That should help you get started in relating air flow to RPM and
MAP.