What does engine performance depend heavily on, related to weight?

Engine performance is significantly influenced by the power-to-weight ratio, which is the measure of the engine's power output in relation to its weight. A higher power-to-weight ratio indicates that the engine can produce more power while maintaining a lower weight, which is crucial for performance aspects such as acceleration, climb rate, and overall efficiency. This ratio is particularly important in aviation applications, where every ounce of weight impacts performance dramatically.

For example, in aircraft engines, achieving a favorable power-to-weight ratio allows for better fuel efficiency, increased speed, and improved maneuverability. This concept is vital for ensuring that the engine can deliver the required performance without being unduly heavy, which could hinder the aircraft's operational capabilities.

Other factors listed, such as engine design complexity, fuel volatility, and cooling system efficiency, do impact engine performance but are not as directly tied to the relationship between weight and power output as the power-to-weight ratio is. Each of those aspects contributes to the overall functionality and reliability of the engine, yet they do not encompass the critical relationship that the power-to-weight ratio does in terms of maximizing performance.