Hi,

Most engines don't need more than 10% to 15% nitro. I have been running 10% for many years in my motors which include an OS 40 FSR. If you run a motor inverted extra nitro 15% to 20% can help make the idle more reliable when on long finals.

Once you motor is tuned you shouldn't have to adjust your settings unless there is an enormous change in temp and R/H or you change your fuel brew. However glow plugs fail, (particularly with new motors being run in), fuel lines split, leaks may develop, etc, etc.

You have excellent advice already but there isn't any substitution for having experienced assistance in setting up your motor's high speed and idle needles for powerful and reliable running with smooth transition. A demonstration is worth many thousands of words particularly in ensuring you don't end up too lean[&o].

If you go to the engine and fuels forum and type "pinch test", (nothing to do with weight loss or BMIs), in the search facility you will see numerous ways of setting up from running in to pylon racing.

Cheers,

Colin