What is the primary reason for power loss when applying carburetor heat?

The primary reason for power loss when applying carburetor heat is due to the introduction of hotter, less dense air into the carburetor. When carburetor heat is applied, it draws air from a source that is heated by the engine, which raises the temperature of the intake air entering the carburetor. This heated air, although it helps to prevent carburetor icing, is less dense than the cooler air that the engine typically ingests.

Less dense air results in a reduction in the mass flow rate of air entering the engine. Since the air-fuel mixture becomes less dense, the resultant mixture contains less oxygen, which can lead to a decrease in engine performance and power output. For combustion to occur efficiently, the engine relies on a proper air-to-fuel ratio, and the reduced density affects this ratio negatively. Therefore, while carburetor heat prevents icing, it simultaneously reduces the engine’s efficiency due to the decreased density of the air mixture, which is fundamentally responsible for the power loss experienced when applying this heat.