MAF and Calculated VE

[Scot Sealander <Sealand@clarityconnect.com>]

Good news!

After the chip cap change, the ECM is now reading the Buick 3800 MAF!  
DIACOM is now reading airflow of the installed MAF, and the ECM is
recording data.  If you wonder why someone would go to all this trouble, 
take a look at this piece of a post made by Andrew Rabbitt while he was 
still at Orbital:

========================================================================
Here's a formula that should work:

        VE = m_dot / ( N * Vol * Rho / 120 ) * 100

where:          VE - volumetric efficiency (%)
                m_dot - mass air flow (g/s)
                N - crank speed (rpm)
                Vol - Engine Displacement (litres)
                Rho - Manifold Air Density (g/litre)

where:          Rho = 1.202 * MAP / 101.325
                MAP = Manifold Absolute Pressure (kPa)

You should also compensate the air density for temperature too since
the 1.202 is air density at 20_C and inlet temperature is elevated due
to heat transfer from the manifold surfaces etc.

Also VE for family cars these days will probably be better than 80%.
========================================================================

Notice that if you know airflow (MAF), you can calculate VE.  But you
still have to have confidence in the ECM sensor numbers for air density.

Right now, the next move may be to install the 3300 MAF code, and see
if the MAF is reading correctly, that is, does it run right using
the MAF data.  If the MAF data is good then I will see if the calculated
VE numbers make any sense, as compared to those determined using O2
feedback.  

Thanks, Scot Sealander

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