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Al Gietzen wrote:
Chris;
If I "pump" the throttle a couple of times, it tends to settle back down to the 1700 range....if I mess with the mixture, I can get smooth idle around 1400 to 1500.
Sounds like maybe a problem with the throttle linkage. Can you check and see that when you pull it back the throttle plates are fully closed? Is there any adjustable idle-air bypass on your system? And you might want to check your idle stop – it should idle down to about 1000 so when you pull the power on final the prop will help you slow down.
Al G
Its possible that there is an intake air leak of some kind. What is your Manifold Pressure reading at idle? If the intake is not sealed well, and any possible other sources of air entry (including through the manifold pressure fittings themselves) are present, you will leak extra air into the engine and it will run faster/make more power. When discussing idle and wide open throttle and other power settings its VERY pertinent to include manifold pressure as a data point. RPM gives you engine speed. Manifold Pressure gives you power generation.
Something that may help you wrap your head around manifold pressure as a concept is to go to Avweb, and search the archived columns of John Deakin.. He does a masterful explanation of adjustable pitch props, manifold pressure, and a 6 part series on turbocharging.. most of this is circa 1999-2001.. but the content is timeless.
I am recommending this because I know that most if not all of your flight experience has been with fixed pitch, normally aspirated engines (and recommending this to anyone else out there who has a similar frame of reference)
Glad to hear that things are moving forward for you. For grins I went and looked up the youtube of you taxi testing last year and watched it again.. I WANT to know when you get ready to fly.. I will be there for that.
Dave
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