MAP calculations?

[Louis Baiani]

On my old 1226519 ECM (CLCC ECM), I found some documents on the baro sensor
(supposed to output the same voltage as MAP for my vehicle).  I looked at the
formula someone typed up in the document, but found out it was wrong.  The
sensor itself tested okay using a meter and supplying negative pressure.  On
another ECM, the map formula was available, which was = (A/D cnts + 28.06) /
2.71.  My old formula was to add 38 or so and divide my 2.711.  Well, today is a
coudy day with a bit of rain.  Using the old formula, I got 101.4...using the
new one I found 97.4..which makes alot more sense.  Using your formula, I got
97.5.  It's not that far off actually :).  However, as the values change, that
little difference will probably split up, giving a higher error.  Therefore, i'm
not too sure about it either.  Is someone good with dealing with conversions,
and formulas we're not sure are right?

Louis

Reid Bishop wrote:

> I'll ask this question once again, having not heard an answer before.
>
> 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
>
> Is this correct?
>
> Here at 6300 feet, my 4.3 idles at about 37kpa, with the IAC running 38-42.
> I still am showing 110 BLM's at idle, and I am having trouble getting it
> leaned down some more.  I'm just wondering if I am adjusting the correct VE
> cell.
>
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