At what temperature do diesel engines typically lose horsepower?

Diesel engines typically begin to lose horsepower as temperatures exceed 90 degrees Fahrenheit. This performance drop is primarily due to several factors affecting engine efficiency, including air density and fuel characteristics. As the temperature rises, the air becomes less dense, which reduces the amount of oxygen available for combustion. This decrease in oxygen can lead to incomplete combustion, resulting in a loss of power output.

Furthermore, higher temperatures can also affect the viscosity of the engine oil and fuel, leading to less effective lubrication and fuel flow. As the components operate less efficiently under these conditions, the engine's overall performance diminishes. Understanding this temperature threshold is crucial for pump operators and others in the fire service to ensure that equipment operates effectively, particularly in warmer climates or during heat events, where engine performance can be compromised.