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Re: MAP calculations?
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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