o.k. back on lap top now found the calculation example
quote from luis
I "took" that information doing the proper calculations!
All it takes is the MAF vs RPM value, using the IAT and MAP values as well.
I'm trying to find a 4 year old log to re-make those calculations so I can have real numbers, but I don't seem to find it in this PC ...
Ok, here it is ... @4078rpms (260bhp), MAP=1.98, MAF=25.35, IAT=65ºC
@4078, with 100% of VE the engine would take 1912cm3/2*4078 = 3898568cm3 = 3.9m3 of air; PV=nRT; so, 101325 (atm pressure) * (1+1.98) * 3.9 = m * 288 * (65+273) ; m = 1177599.15/288/338 ; m = 12.1Kg/min ; m=26.88lb/min. In other words, @4078rpms, 1.98bar (relative pressure) of boost, 65ºC of intake pressure, a 1912cm3 engine would "suck up" 26.88lb/min. As we know the engine "sucks" 25.38lb/min of air, the calculated VE should be 25.35/26.88=94.3% ...
VE = 94.3% @ 4078rpms ... quite impressive figures aren't they?, either that, or one of the input variables is wrong ... not to sure if our MAF sensors can read reliably at these amount of flow rates, but if the 25.35lb/min are correct, so should the 94% be ...
dont know if its just me but i cant see whats going on in this equation some numbers just appear and some dont add up?
Last edited by sussexa; 18-03-12 at 16:47.