Al Gietzen wrote:

I triggered some amount of discussion here a couple of weeks back when I
posted a plot of  the MAP pressure dropping somewhat at high rpm.  The
conclusion was that the throttle body dia I'm using is too small.

That could be; but looking at this again, I think there are other
factors.  The MAP port is just on the back side of the butterfly, about
4" in from the TB entrance.  Just doesn't seem I could be seeing 3-4" Hg
drop in that distance, even at 7000 rpm.

I think the inlet air box (actually kind of a manifold, see pic) is
causing some restriction.  It's size was limited by cowling clearance,
and I made it to have a flow cross-section that was a bit larger at each
point than the combined downstream ports.  And, kind of assumed that all
three ports weren't at high flow at the same time.  But looking again at
the port timing diagram for the three rotor, I note that there is
overlap of all three.  Long story short, I think a significant part of
the drop could be in the inlet air box.

Al

 
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