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HomeAircraftHelicopterEngines Plugs Mufflers Fuel › idle valve setup
01-24-2010 10:13 AM  8 years agoPost 1
Bogdan

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Netherlands

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In some manuals it is writen that the idle valve value has to be such that when disconnecting the glow plug the engine does not change the rpm. For instance for a YS 50st the factory setting is one turn.

My questions are: how much should you set idle value in throttle curve (normal mode) in order to set up the idle valve of the engine? Note that the idle value for the throttle curve can vary (in my case) from say 7% to 10% in my vibe 50. Is this interval narrow enough to set a proper value for the idle valve (screw)? This interval is different from model to model.

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01-24-2010 12:41 PM  8 years agoPost 2
airdodger

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Johnston USA

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The glow plug will have a large effect as well as nitro percentage on the engine slowing on heater disconnect. On a warm engine turn the idle needle lean and see if rpm increases, if it does keep going until it starts slowing, back off an eigth of a turn from the point where it starts to change. Go fly and hit auto, the engine should settle down quickly if it speeds up richen some until it settles right down. These settings will change with a different plug or nitro percentage, as well as an old plug so use a new one to adjust settings. Now go back and set the trim.

Chris

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01-24-2010 03:10 PM  8 years agoPost 3
Smok

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Antwerp, Belgium

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Bogdan, what is your engine and what fuel and glow plug are you using ?

By the way, in most airplane applications one can lean out the mixture for max power and smooth idle and it will give very good results, as plane engines are usually well cooled. On the other hand in most heli ( and also in RC cars ) the mixture setting is usually a compromise between power, engine temperature, avoiding detonation ( that can be seen as occasional tail kicking and metallic sound ), smooth running and so on.

Lots depends on the motor cooling solution in a particular helicopter - I guess cooling by fuel is more important on an average heli than for example on a Caliber 90 that has a special fan running at higher rpm than the motor - but otoh the Cali90 is often run in a closed fuselage ).

On YS motors I have tried different fuels and needle settings, only to go back to CP30% and to have the needle valve set by the book, with the high speed needle opened 45% more from factory settings ( that's due to the tuned muffler that I am using ). Also I have tried colder plugs, only to go back to Enya #3 again. Now the motor runs exceptionally smooth, idles well and in a hover the fuel in the tank looks like a glass of water on a table - no foaming, even very little ripples/fuel movements.

Too cold a plug will cause the engine to die too easily in idle,
also too lean mixture often results in high idle RPM after some flight time - if the motor takes several seconds to go down to idle then the motor temp could be too high or the idle needle too lean.

Btw. I do not set the idle RPM to be the lowest possible - but rather a bit higher from that, so the motor does not have tendency to die but still the clutch remains disengaged and the rotor does not move,

Pozdrowienia ;-)

Smok

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01-24-2010 08:48 PM  8 years agoPost 4
Bogdan

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Netherlands

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Many thanks for both reactions! I will use both advices for my ys50st and future rex57. So far I use 20%nitro 18%klotz-heli and os8.

Bogdan

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