Guys,
Got to the field today, it was a great day, light wind, slight clouds but the humidity was a bit higher. The engine run seemed to be a bit leaner than in the cooler weather.

Can anyone give some insight on how the humidity affects the engine run (4-2-4, 5% nitro, 27% 50/50, Fox 35 on 9x6 old Top Flite) and options to adjust?

Best,        DennisT

Guys,
Got to the field today, it was a great day, light wind, slight clouds but the humidity was a bit higher. The engine run seemed to be a bit leaner than in the cooler weather.

Can anyone give some insight on how the humidity affects the engine run (4-2-4, 5% nitro, 27% 50/50, Fox 35 on 9x6 old Top Flite) and options to adjust?

Best,        DennisT

   Less power. More nitro.

    Brett

It's all to do with Relative Air Density (RAD).

Basically in warmer weather air pressure is lower with less oxygen in the air. 2-Strokes generally prefer cold, drizzly conditions (ask any classic 2-stroke motorcycle racer!).

This is down to a higher RAD, with more oxygen present. In these conditions your engine may run a tad rich so just screw the needle valve in 2-3 clicks. Vice versa in warmer conditions; make it slightly richer at the needle.

You shouldn't need more than 15% nitro for a standard setup.

See how you go on with this, it might also be worth going for a colder plug (no5-8 range) in warmer weather also.



Tim