MAP calculations?

[Ludis Langens]

Reid Bishop wrote:
> 
> When reading the MAP voltage output on a 7747 ALDL datastream, how does one
> convert it to actual MAP pressure?  The only source I have says this:
> 
>         MAP kpa = MAP(AD)/2.706 + 10.3

Here's the formula (and table version of results) that I use:

>One bar MAP sensor to KPa conversion
>
>KPa = (n - 26) * 151/128 * 5/16 + 20
>
>      :     0      1      2      3      4      5      6      7      8      9
>  ....:.....................................................................
>    0 :  10.4KPa10.8   11.2   11.5   11.9   12.3   12.6   13.0   13.4   13.7
>   10 :  14.1   14.5   14.8   15.2   15.6   15.9   16.3   16.7   17.1   17.4
>   20 :  17.8   18.2   18.5   18.9   19.3   19.6   20.0   20.4   20.7   21.1
>   30 :  21.5   21.8   22.2   22.6   22.9   23.3   23.7   24.1   24.4   24.8
>   40 :  25.2   25.5   25.9   26.3   26.6   27.0   27.4   27.7   28.1   28.5
>   50 :  28.8   29.2   29.6   30.0   30.3   30.7   31.1   31.4   31.8   32.2
>   60 :  32.5   32.9   33.3   33.6   34.0   34.4   34.7   35.1   35.5   35.9
>   70 :  36.2   36.6   37.0   37.3   37.7   38.1   38.4   38.8   39.2   39.5
>   80 :  39.9   40.3   40.6   41.0   41.4   41.8   42.1   42.5   42.9   43.2
>   90 :  43.6   44.0   44.3   44.7   45.1   45.4   45.8   46.2   46.5   46.9
>  100 :  47.3   47.6   48.0   48.4   48.8   49.1   49.5   49.9   50.2   50.6
>  110 :  51.0   51.3   51.7   52.1   52.4   52.8   53.2   53.5   53.9   54.3
>  120 :  54.7   55.0   55.4   55.8   56.1   56.5   56.9   57.2   57.6   58.0
>  130 :  58.3   58.7   59.1   59.4   59.8   60.2   60.6   60.9   61.3   61.7
>  140 :  62.0   62.4   62.8   63.1   63.5   63.9   64.2   64.6   65.0   65.3
>  150 :  65.7   66.1   66.5   66.8   67.2   67.6   67.9   68.3   68.7   69.0
>  160 :  69.4   69.8   70.1   70.5   70.9   71.2   71.6   72.0   72.3   72.7
>  170 :  73.1   73.5   73.8   74.2   74.6   74.9   75.3   75.7   76.0   76.4
>  180 :  76.8   77.1   77.5   77.9   78.2   78.6   79.0   79.4   79.7   80.1
>  190 :  80.5   80.8   81.2   81.6   81.9   82.3   82.7   83.0   83.4   83.8
>  200 :  84.1   84.5   84.9   85.3   85.6   86.0   86.4   86.7   87.1   87.5
>  210 :  87.8   88.2   88.6   88.9   89.3   89.7   90.0   90.4   90.8   91.1
>  220 :  91.5   91.9   92.3   92.6   93.0   93.4   93.7   94.1   94.5   94.8
>  230 :  95.2   95.6   95.9   96.3   96.7   97.0   97.4   97.8   98.2   98.5
>  240 :  98.9   99.3   99.6  100.0  100.4  100.7  101.1  101.5  101.8  102.2
>  250 : 102.6  102.9  103.3  103.7  104.1  104.4  104.8

In the formula, n is ADC "counts".  All the other numbers in the formula
(5, 16, 20, 26, 128, 151) "appear" in the ECM software.  From what I
remember, a long time ago sometime ran an experiment and found that
Diacom uses exactly this same conversion.  If you work through my
formula, it is almost the same as yours.

-- 
Ludis Langens                               ludis (at) cruzers (dot) com
Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/


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