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Old 02-21-2011, 05:14 PM   #9 (permalink)
cfg83
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Location: Southern California
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1999 Saturn SW2 - '99 Saturn SW2 Wagon
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Backtobasics -

Quote:
Originally Posted by Backtobasics View Post
My truck is speed density, so no MAF. How does it use MAP and RPM to give FE numbers?

...
I think the SG is making a synthetic MAF :

Code:
IMAP = RPM * MAP / IAT
MAF = (IMAP/120)*(Volumetric_Efficiency/100)*(Engine_Displacement)*(MM)/(R)

Where :
- manifold absolute pressure (MAP) is in kPa
- intake air temp (IAT) is in degrees Kelvin
- R is 8.314 J/°K/mole (constant)
- The average molecular mass of air (MM) is 28.97 g/mole (constant)
Note that in the above formula, the Volumetric_Efficiency of the 
  (4-cycle!) engine is measured in percent 
Note that the Engine_Displacement is in liters.
In my opinion, there is an assumed Volumetric_Efficiency. When you do a fill-up and apply the correction factor, the correction factor modifies the Volumetric_Efficiency for your engine.

CarloSW2
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