I still see a lot of people using the old method of disabling the MAF to calibrate their VVE on 4th generation LS stuff, that generally being E38 controllers and up. This isn't necessary anymore because you can log those GMVE values in real time with HP Tuners. All you need to do is use the proper math parameter(s) and filters to transform the data into the classic '% error' you're used to, which I will describe here. One thing to remember, as you always should when calibrating anything airflow related...it must be at steady state. So you should be using a method of your choosing to filter out transients, which I won't get into here. This method also assumes using short term fuel trims (LTFT disabled), so any open loop guys or calibration into the power-enriched range will have to incorporate fueling error from a wideband.
The math:
GMVE STFT % error = ((MAF_af)*(1+(STFT_avg)/100)-(GMVE_af))/(GMVE_af)*100
Because steady state will always be looking at the MAF for airmass calculations, you must base your GMVE airflow error on the MAF airflow error. First, I normalize the STFT percentage so 0% becomes 1. A STFT of 5% would yield 1.05. Then multiply this by current MAF airflow to get an error corrected MAF airflow. From this value you subtract GMVE airflow to get a raw GMVE airflow error. Then, divide that error by the GMVE airflow to get your normalized VVE airflow error. Multiplying by 100 turns this back into % error to make pasting into the editor simpler.
To break the GMVE airflow calculation down a bit...
GMVE_af = (MAP*GMVE/IAT)*RPM/60*4
Take MAP in MEGApascals (important) and multiple by the raw GMVE value from CAN and divide by the IAT in KELVIN (also important). This gives a single cylinder airmass. To get flow rate, multiply by RPM, divide by 60 to get revolutions per second, and multiply by 4 for the number of induction cycles in one revolution. If you have a 4 or 6 cylinder, multiply by 2 or 3, respectively.
The full math parameter: GMVE STFT =
(([16.71]*(1+(.01*[6.156]+.01*[8.156])/2)-[12.56]/60*4*[11.92]*[2312]/[2127.240])/([12.56]/60*4*[11.92]*[2312]/[2127.240]))*100
Take this error data and plot it in your histograms and you would normally and save a bunch of time and disabling stuff in the calibration. As always, the more data points you get the better you filter out data noise.
Screen capture of the parameter working...
Capture.PNG
Notice at the cursor point, the average STFT in the third graph is showing -4.4%, so a MAF airflow overestimation. However the GMVE airflow, being slightly lower is showing only 0.3% error, so it's right on for that operating point.
GMVE STFT % error from MAF.MathParameter.xml