More silly ideas-MAP2

[Jeff M]

Bruce wrote:

>In theory.  when you have Air Densities of 96% to 101% and the
>scanner shows the engine is at 98 K/Pa under both sets of conditions then
>there is a fly in the ointment.

MAP gives you pressure and BARO readings (one in the sensed same), and
density is calculated by adding air temperature computations via a MAT
sensor (aside from the changes humidity does to the equation, but no RH
sensors in GM vehicles yet ;-).

To back up a bit, is not Barometric Pressure the measure of air pressure
relative to being at different altitudes and in varying climatic conditions?
Then when the engine is exposed to these varying outside pressures, it will
experience different cylinder filling (raw VE tables would not compensate
for this fully) while running.  And since warmer air is less dense (and the
reverse as well), MAT needs to be added to the equation so (near) true air
measuring can be performed.  So your fly has definitely landed but I
wonder if there is a need to compensate for this as it is already done on
better designed cars/computers.  MAP is used to measure barometric readings
at start up  on many GM vehicles and as an example, the Syclone/Typhoon use
the MAP to show on my scanner (Diacom Plus) Barometric Pressure, Manifold
Absolute Pressure and Boost Pressure, all supplied via the one MAP sensor.
Maybe your program (vehicle?) does not do this BARO check and associated
compensation and if so then I would suggest extracting the computation used
by the Sy/Tys (or others) to be incorporated into your vehicle's computer
program to get you what you want.  Another note on GM MAP sensors, they come
in many ranges depending on application (stay with me here) and not just 1
bar, 2 bar and 3 bar.  GM has found (as it gets it together) that the
reality of there being more than 1 bar of pressure at altitudes below see
level had a more dramatic effect on some vehicles than others so, GM has 1.1
and 1.2 and 1.25....... "1 bar" MAP sensors.

More FYI:                                            multiply by
Bars to Atmospheres                           0.9869233
Bars to Inches Mercury                      29.529983
Bars to Inches of Water                    401.48716
Bars to Kilograms per sq centimeter     1.0197162
Bars to Kilopascals                           100.00 (exact)
Bars to Psi                                         14.503774


>Weither do to filtering,  the design of the sensor, or pulsation
characteristics, that the >sensor is reading something is wrong.  Without
an emission lab to do the research >something needs done to compensate for
it.   "My" baro/map idea isn't perfect, but it's a >whole lot better than,
being in error all the time, IMHO.....
>Grumpy

You are right about being better, and that is the challenge we all do enjoy.

Jeff Middaugh
tystorm at email.msn.com