They run on a gas. That's why they a choke. When the engine is cold the fuel doesn't vaporize, so you need a higher fuel/air mixture. Once the engine is warm enough the fuel droplets from the carburetor/injection are vaporized in the intake and so the air/fuel mixture can be turned down. Direct injection engines vaporize the fuel in the cylinder itself. Direct injection engines have to modify the injection pattern when the engine is cold.
Once the engine is warm enough the fuel droplets from the carburetor/injection are vaporized
Ahhh. Someone else said that the approach in the video is basically a high air-fuel ratio mode of running, which agrees with your model where more fuel is required when its surface area will be lower (when cold and it's not vaporizing the droplets).
a high air fuel ratio just ups the idle speed of the engine, and causes detonation and pinking.
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