Nitro , Oil vs Neddle Setting
 

Is there some guide that one can use for:

If one uses a higher nitro content , must the neddle be leaned or must it be open more , the same if one uses castor or synthetic.

The higher the nitro , will the engine smoke more or less

Nitro , Oil vs Neddle Setting
 

When upping the nitro content you needle valve(s) will have to be opened. Nitro basically carries it's own O2 with it and allows more Methenol to be introduced and burned = more power! Run times per tank will also decrease. Along with more methenol will come more oil so your smoke will also increase! I got some 14% oil 30% nitro from Powermaster to try out last year and it ran very well...it was nice to have the power of 30% and still be able to see the heli!
With the difference between castor and synthetic oils; castor is a thick oil that needs a large orfice to get to the motor...a thinner oil (synthetic) will flow thru a smaller orfice = less needle valve.
Hope this helps you. Chris