did some crunching with some of the info from jeff's site this morning.
i think i've got some good results.
i used the info from from http://www.stealth316.com/2-air-fuel-flow.htm
to give me a good equation for air density:
D = D0 x (T0/T1) x (P1/P0)
p0 = 14.7psi (pressure at which d0 was defined)
p1 = MAP
d0 = 1.1649 g/L
t0 = 545.69r = 303.15k (temperature at which d0 was defined)
t1 = ºF + 459.69r = ºC + 273.15k (use either rankin or kelvin depending on iat data)
disregarding pressure, this gives us an equation of:density--simple form (no pressure correction)
adding pressure correction:density--with pressure correction
converting to mrp instead of map (this equation assumes you are at sea level!)density with mrp instead of map
all of the above equations result in units of g/L.
take logged mafg (g/s) divide by calculated density (g/L) to get true volumetric flow rate
now, calculate what the engine SHOULD be inhaling--ie, theoretical volumetric flow rate
rpm/2 * 1.994l = taf (l/min)
(rpm/2 * 1.994l) / 60 = taf (l/sec)
finally, divide true volumetric flow rate by theoretical volumetric flow rate to net VE.
after plugging and chugging and scatter-plotting on a 15 minute log file, i got this:
i didn't like the big scatter involved, and although in theory the throttle plate doesn't make a difference anymore (since we are taking air density at the manifold into consideration), i eliminated all tps <50%. this looks much cleaner:
i think with a lot of lines of log at 100% tps one could build up a quite accurate VE chart pretty quickly. the log file i used was a short commute into work and didn't have many lines >50%tps, and NO lines at WOT.
i think the big advantage of the above method is that the "artificial" inflation of VE is already corrected for by calculating density using boost pressure as a factor.
key assumption: iatc represents matc--how good your IC setup is and how prone to heatsoak may have big effects here. iatc may be in fact higher or lower than matc which cannot be accounted for.