To answer your question 'how do you warm up a nitro vehicle':

Nitro engines generate their own heat. However, when an engine is new and tight, and still requires running-in, a hair-dryer can be used to get the engine up to a suitable starting temperature. This is especially helpful with competition engines which are VERY tight from new, or when trying to start an engine in cold conditions. Once an engine is run-in, generally you'll not need to use a hair-dryer.

Thereafter, how hot the engine runs is determined by the needle settings on the carb. The leaner the mixtures, the hotter the engine will run. The richer the mixtures, the cooler the engine will run. Gearing also determines how much work the engine has to do. The gearing needs to be appropriate for the conditions/amount of space you have to run in, to avoid over-revving the engine. From a track point of view, your gearing/mixtures will need to be slightly different for a tight, twisty track layout compared to a fast, open layout. Engine temps will reflect this fact.

Hope this helps.