MAF vs MAP

[RABBITT_Andrew at mv8.orbeng.com.au]

>>I don't think the EGR actually represents a large volume compared to 
the volume of air inducted into the manifold.  Few percent maybe.  I 
don't think this is enough to alter manifold pressure significantly.<<

EGR rates are more that just a few percent, maybe as high as 30% at 
some speed-load points.  In any case, it's enough to give you a 3-4% 
fuel consumption advantage over an LA4 cycle.

>>Most MAP sensors are really differential pressure sensors with one 
port open to atmosphere.<<

This I can't quite believe, (since the A in MAP is 'Absolute').  If 
you know the absolute manifold pressure, why do you need altitude 
compensation?  Any ideas?

Andrew Rabbitt
Orbital Engine Company