Tuning With the High
and Low Speed Needles

(RC Car Talk > Nitro RC Cars and Trucks)

Do you have a weak engine that runs at high temps? Don't search for the optimal high end setting. Instead, richen the high speed a lot and then lean the low end to compensate.

The high speed needle controls the engine temp and amount of fuel flow. The low speed needle controls the punch. Your engine's top speed will suffer but it will have great punch all the way through the mid range while keeping temps low so it will last longer and not flame out.