The tear drop can be replaced by any shape. The shape can be
    tailored to get any opening area as a function of throttle
    cable travel. However... due to entirely different turbulence
    patterns the two systems cannot be strictly compared on
    opening area alone.

    Paul Lamar

Make it round, meter it right and everything will be fine. We will be
using between 50% and WOT most of the time. If you set up for a
reasonable (read keeps running) idle you won't have any trouble. We
spend less time at partial throttle than a race car! The tear drop will
cost you power at top end PERIOD. We could cut a chamfer ramp on the
throttle face to improve the idle.

This is something done on carburetor
slides. Look at a old round motorcycle carb slide. Note the angled
cutaway on the upwind side? Wonder what that is for? This is a jetting
transition control device. The cutaway works between 1/8 and 1/3
throttle. IT is a VERY effective jetting tool. Less angle (flatter
bottom) is richer, and higher is leaner. A small taper in the face of
the slide throttle near the opening point at idle will improve airflow.
You wouldn't need more than half the slide width. since the ramp is
small the disruption of the airflow would be much less than the tear
drop opening at WOT. FWIW
Bill Jepson

Thanks for the info, Bill.
I am not sure what you mean, but it sure sounds good. :) Do you have a
picture? I am trying to finalize the design and get it to the NC shop
to produce a prototype.

Doc Custer
Retired software engineer and sometime Audiologist
Building RV9-A. Fuselage



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