Calculating VE from MAF and MAP sensors

[Chris Bennight]

   We have been talking about this on the LT1 edit mailing list, but
thought I would ask you all to see what opinions you have, since
there is probably much more experience here.


   On LT1's we have MAF and MAP sensors, and have been trying
to use them to calculate a better VE for modified setups.

   Here is our logic - 


  VE = actual airflow / theoretical airflow.

   Theoretical airflow = Rpm / (2(rev/intake cycle) * 60 sec/min) * displacement 
                                 = RPM * 5.733 / (2 * 60)   in L/sec

      then using the ideal gas law to get mass from liters
 
     PV=nRT     
      n/V=P/(R*T)    use  R = 0.287 kJ/(K*g)    (kJ = kPa * L)
      density = P / (287 * T(K))

      Pressure would be equal to the MAP reading (so we get VE at part
      as well as WOT where MAP ~ BARO)

      Theoretical massflow =  RPM * 5.733 * MAP / (0.287 * T(K) * 2 * 60)
                                   units in g/sec

    Then actual massflow can be taken straight off the Mass Air meter in g/s
     so then it's just   actual / theoretical * 100 %.


    Assuming enough samples are taken, and all the VE's are averaged together, 
    should this be a reliable way to get close to the actual VE for a modified setup, 
    and any flaws/corrections in the reasoning?

    A spreadsheet implimenting this is at
    http://www.baylor.edu/~Christopher_Bennight/files/VECalc.zip


   Thanks,
   Chris Bennight

     

       

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