Speed Density vs MAF

[Mike Klopfer]

After looking at some articles on engine modeling I'm wondering how
much is gained by either MAP or MAF. The primary input variables to the
system would seem to be throttle position, injection time and rpm (and 
time and ambient pressure, humidity?). Given a sufficiently good model 
of the
engine this should be enough to calculate the amount of air entering
the cylinders. Since airflow or manifold pressure are effect of these
inputs it would seem that these would provide quicker response to
transients. The main question I suppose is how difficult is it to
accurately calculate the number of moles entering the cylinder from 
these inputs. One paper as I recall got a good prediction using a lookup
table indexed by throttle angle and rpm.