Re: MAP data...was Re: 48 +1 and sensor data

[Ludis Langens <ludis@cruzers.com>]

dhardin@ovec.com wrote:
> 
> It does appear that it is converted to PSI because it is multiplied by 0x97=151
> dec.  This gives a range of 0 to 151.  Is that PSI?

If this is from GM code from the 1980's, the 151 is actually part of the
fraction 151/128.  This multiply is done to expand the interesting MAP
range into the range 0 to 255.  The actual range chosen allows table row
and column headings to count in units of 5 KPa (or 10 or 20 KPa).

> Anyway why is there a
> correction added on: in your case you said it was 10.34.  Why is the calculation
> y=mx+b?  Would not y=mx be correct.  You are right though:  that is what is in
> my code: there is a b added on.    I would have thought 0 to 5 volts would give
> 0 to 100 KPA....doesn't appear to be the case.....anyone know why?

MAP sensors don't read down to zero KPa.  Hence the "b" term.

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

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