I'm missing something...

[Bob Wooten]

You were beating around the right bush talking about the air resistance
issue at altitude. At the flapper valve, the force of air against the
flapper decreases directly with the air  density, but it increases with the
square of the velocity.

The difference between the direct function and the square function means
that the higher velocity, but less dense air going into the engine to get
the same number of O2 molecules into the engine (to make the same power)
deflects the flapper further because the velocity has gone up while the
density has gone down. Lower density makes for less force, but the higher
velocity makes for significantly more force on the flapper.

In a carby, the main jet diameter required to give a particular mixture
varies with the fourth root of the air density ratio. Similar deal here.

Greg





I think that we are coming from the opposite directions, but coming to the
same point.  I was keeping TP constant but you were keeping air flow
constant (more throttle for the same air flow = same HP) I would have had
less air flow (& less HP) but you would have had more throttle position.

BW
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