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Purpose of mixture screw on FS-70S II

Old 08-17-2006, 09:16 PM
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CDN-uavpilot
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Default Purpose of mixture screw on FS-70S II

Can you tell why a mixture screw is needed for idle adjustment. As far as I can tell, when the throttle valve is nearly closed for idle, the end of the screw approaches the jet tip for the purpose of limiting the fuel flow. When the valve is open above 1/4 or more, the screw loses its limiting effect because it has been retracted too far away from the jet tip. The fuel flow at that point is regulated by the venturi effect.

Is the mixture screw only used for setting the fuel mixture for the lowest idle speed possible or is it also used to ensure smooth transition from idle to 1/4 throttle?

Thanks for your help.
Frank
Old 08-18-2006, 10:11 AM
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Default RE: Purpose of mixture screw on FS-70S II

The 'mixture screw' is used to adjust the idle mixture, but it also influences the transition as you open the throttle from idle. After about 1/3-1/2 throttle, its effect is much-reduced, and the setting of the high-speed needle is the main influence over the fuel mixture.
Old 08-18-2006, 12:58 PM
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Default RE: Purpose of mixture screw on FS-70S II

Thanks for the clarification.

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