Under a cold air induction system, a 40º drop yields what percent horsepower increase?

• A. 4%
• B. 2%
• C. 6%
• D. 8%

Answer: (A)

Cooler air is denser, so it contains more oxygen per unit volume. That means the engine can burn more fuel in each intake cycle, producing more power. When the intake air temperature drops by about forty degrees, the density gain is enough to give a noticeable but modest horsepower boost under typical, naturally aspirated conditions with a cold air intake. The exact amount varies with engine design and tuning, but the trend is clear: cooler air yields more power, and the forty-degree change corresponds to a small, practical increase.