When it came to tuning my nitro engine, most guides referred to subjective measurements: “enough smoke”, “accelerates swiftly”, “sounds good”, … I, as a nitro-engine newbie, did not know what an engine should sound like and how much smoke it should produce.
I finally found some objective criteria to figure out whether the engine is too rich or lean: the temperature. This PDF by Tony Chaveiro reviews a CarbSmart needle controller, which uses the head-temperature as a feedback mechanism.
Apparently, 100°C is a nice head temperature to aim for. Leaning the mixture will increase the temperature, giving more fuel will cool it down.
I don’t know how I’ll use this knowledge to tune my engine, but at least I have an objective way judge the mixture.
