What is the effect on horsepower for each 10° rise in temperature?

The decrease in horsepower for each 10° rise in temperature is primarily due to the effects of heat on engine efficiency and the combustion process. As the temperature increases, the air density decreases, which can lead to a less efficient air-fuel mixture entering the engine. This results in a reduction in the amount of oxygen available for combustion, ultimately diminishing the engine's capability to produce power.

Engines are typically designed to operate within a specific temperature range, where optimal performance can be achieved. When temperatures rise excessively beyond this range, the efficiency of combustion can decline, leading to a horsepower reduction.

Therefore, understanding that for every 10° rise in temperature there is an approximate 1% decrease in horsepower highlights the importance of managing operating temperatures to maintain engine performance.

Other choices, such as an increase or no change in horsepower, do not reflect the reality of how temperature impacts engine dynamics. The debate about higher performance at elevated temperatures overlooks the essential role of air density and combustion efficiency in determining horsepower.