Calculating VE from MAF and MAP sensors

[Bruce Plecan]

Test drive a stock one, record as many grm/sec vs rpm/MAP locations as
possible.
Drive modified car record the same areas.
% change in MAF, gives % change needed for MAP.
Prolly too easy..

Be interesting to figure injector gm/sec, and amount of fuel used, as
compared to air consumed and see how the commanded AFR line up with actual,
and then use a WB to see how everything really lines up.

Jus sounds interesting to me
Bruce

>    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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