I conducted a study of the induction areas of two different throttle
mechanism. One was a 2 inch throttle body with a lever arm arrangement
such that 3 inches of throttle cable movement was required to go from
fully closed to fully open. The second was a slide throttle with
12 various configurations. The configuration that most closely matched
the throttle body was the one with a 0.375 diameter metering hole with a
0.188 fillet to the 2 inch diameter main metering hole. Rhino was used
to generate the geometry and compute the areas.

Attached is a graph showing the induction areas of the two throttles for
the first 1 inch of throttle cable movement from the fully closed
position. As can be seen, the slide throttle has a slightly gentler
initial opening for the first 5.8 inches of cable movement. After about
0.6 inches of throttle cable movement, the slide throttle induction area
increases more rapidly than the throttle body induction area.

This slide throttle configuration should give gentle throttle response
when it is needed, e.g., taxi and approach and excellent induction at
full power.

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

I think you mean .58 and not 5.8 Doc.

I still don't think you can compare the two like this.
Regardless of how favorable looking the slide throttle comes
out :) The butterfly is more of a three dimensional
problem. Short of 3D CFD we will never know unless
we compare RPM's or HP as a function of throttle cable
position.

Paul Lamar

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