Carb heat reduces power due to which of the following reasons?

• A. Increased air density
• B. Loss of Ram air pressure
• C. Lower fuel vaporization
• D. Faster air flow

Answer: (B)

Carb heat warms the air going into the carburetor to prevent icing. Warmer air is less dense, so for each intake stroke less air mass enters the engine. Since engine power depends on the amount of air (and fuel) that can be burned each cycle, this reduction in air density lowers the maximum power output. The idea is similar to a drop in ram air effect—the air is pushed into the carburetor with less density, so there’s less air mass available to burn.

Other options don’t fit because increasing air density would improve, not reduce, power; faster air flow generally increases power by delivering more air; and while fuel vaporization matters, carb heat’s primary effect is on air density, not a direct reduction in vaporization.