Big Snip<<

There is a reduction in pressure after a slide throttle except at WOT. There
is also a reduction due to friction loss in the induction manifold. Both can
lead to ice formation. It's better to have the slide close to the PP.

The valve in a float bowl acts as an automatic vapor vent, a feature which
is missing in a direct feed low pressure fuel system. Maybe an AVV should be
incorporated.

Colin Smith

I agree about the reduction in pressure after a partially open
slide  throttle but it is not as bad as a venturi that is always
in the system regardless of the throttle opening. People
takeoff at WOT anyway. With ram air from the prop it could be
an inch or so of Hg above atmospheric.

Also the distance from the slide throttle to the
hot rotary engine is two inches. In a typical Continental
aircraft engine it is 10 or 12 inches from the venturi
to the engine. Lycomings run their intake runners
through the oil pan to heat them.

If you keep the feed pipe cool you won't have vapor
until you want it. The entire system will be under
five psi pressure or 14.7 feet of head from the  2 psi
regulator near the leaning valve all the way back
to the Facit pump near the fuel tanks.

We got vapor lock in the old days because the fuel
tank was in the back of the car and the fuel pump
was on the engine. Also the fuel line sometimes ran
right next to the exhaust pipe. Vapor lock disappeared
when they started putting fuel pumps at the back of
the car or better yet in the fuel tank.
Paul Lamar

------------
By far the biggest cooling effect that causes icing is the vaporization of
the gasoline, not the restriction and adiabatic expansion of the air itself.
The evaporating gas cools the air, bringing it below the frost point. The
venturi provides a convenient place for the ice to stick.

Bill schertz

KIS Cruiser # 4045

Right you are Bill. Forgot about that. As I recall it is called
the "heat of vaporization" or something like that.
In our case it happens within two inches of the hot engine
so it should not be a problem.