Equations..

[atsakiri at ford.com]

>    I need help with equations for a MAP system. I have this 
> general equation.
> 
>         PV=nRTe
>            P = pressure [assuming intake from MAP sensor] in KPA
>            V = Displacement of Cylinder                   in Liters
>            N = moles of atmosphere                        in Moles
>            R = Universal gas constant : 8.31L/Kpa         W/ KPA & Liters
>            T = Absolute temp !K of intake air [temp sensors job]
>            
>            Could you help me nail down the real units on these 
> things? I'm a second year chemistry student, and I know this 
> simple Gas law but I don't know the units in this Application!!!

Here's one set of units that'll work:

P in pascals
V in meters^3
n in moles
R = 8.3143 joules/(mole*deg Kelvin)
T in deg Kelvin


> 
>            e = Volumetric Efficiency                      Unitless
>            
>            Could someone provide a formula to just get 
> a cheap estimate of this term. I can't solve for it since 
> I have no empirical data, also no staight substitutions work 
> either: as the e terms will cancel. 

Yes, e is unitless.  A very cheap formula is 
e(engine speed, manifold pressure) = 0.85.  This is a great
simplification of course, but is useful in getting started.

[snip]


Good luck,


Anthony Tsakiris

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