Hi,
Thanks for sharing this insightful article about proper leaning during idle and taxi operations which potentially can solve spark plug fouling problems, reduce valve guide wear and valve sticking problems, and prolong engine life. In the article it does state that an RPM rise of 25-50 indicates that the idle mixture is adjusted properly. An RPM rise of 25-50 indicates that your idle mixture is adjusted properly. If the RPM rise is greater than 50 RPM, your idle mixture is adjusted too rich. If you get no RPM rise at all, your idle mixture is too lean. In our experience, most engines are adjusted too rich.
I have a concern and was hoping you could share your expertise on this concern. My concern is whether the 25 to 50 RPM rage might be too lean for the tropical climate we operate in.
We operate DA40’s (Lycoming IO360M1A AVGAS engine) and the Lycoming handbook states that 50 RPM rise as the max. Is the limit of 25 to 50 RPM rise applicable to all environments? Or is it applicable based on a Standard Day Temperature (15 deg C)/60 Deg F)? We operate in a tropical climate where the Outside Air Temperature (OAT) is usually 30 to 34 Deg C (86 Def F /93 Deg F).
In such a climate, would the 25 to 50 RPM still be valid? Could it be higher? i.e. 25 to 100 RPM? Is there a graph one could use where we could interpolate the OAT, humidity and airfield elevation to determine the acceptable RPM rise range?
Appreciate any knowledge on this matter pls.
James Das
SYFC
vdassyfc@gmail.com