When logging MAF values with the Access Port, a unitless number is the resulting data. Alta says that dividing this number by 2 is close to the g/sec airflow, but did not really have a good answer. I've come up with a calibration value and was wondering of anyone else has done this so I can fine tune this number if needed. See below for the number and how I use it (MAF is plotted against pressure ratio on top of the compressor map using MS Excel)

MAF value/29 = pounds per minute air flow

The attached plot is for AP stage 1 tune (91 octane TPS map). Boost hits just below 21psi in this particular 3rd gear pull. The points are RPM from 2000 to 6000 in various increments.

-JL

edit:
The MAF data appears to be linear and matches to within 5-10% what my predictions show

 

Are your MAF numbers ranging anywhere between 400-600 at peak? If so, then the ecu is reporting Kg/hr. Divide this number by 0.27777 to get the g/sec figure.