I can see using a tuner as a way of tuning once you are in cruise mode, but
even so, once in cruise do you really care how much HP you can draw out of
your engine unless you are in a race and willing to burn an extra 2.5gph for
10 MPH?  Will tuning the intake increase your BSFC to make it beneficial in
cruise?

Dan, There are obviously some compromises made in most intakes. Just getting things to fit is one
problem. There are some constants though. Max power and max rpm are going to be the same. (we have
no need to rev past the higest power in a plane) The method to make the variable system work is to
tune the shortest length to max power. Your bush tune is to pull the length short, go rich for
power, flat pitch and punch it!  All the tuning could be done in cruise when you are less
preoccupied. When at really high altitude you might not be able to get max rpm for takeoff but I
would then do a full power run-up anyway to set mixture. You could then try the intake to increase
rpm if possible. You would always test before moving down the runway. Bill Jepson

I forgot to answer the BSFC question. Yes there is a close correlation
with volumetric efficiency and BSFC. It so happens that there is
also a close correlation with vol. eff. and the torque peaks.
Tuned runners are all about volumetric efficiency.

Note the almost precise tracking of the torque and BSFC on this
Lemans 4 rotor engine with variable length intakes. Torque down BSFC up.

Paul Lamar
 
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