How does the pressure in a diesel engine differ from a gasoline engine?

Diesel engines operate at higher pressures than gasoline engines primarily due to their differing ignition processes and fuel delivery methods. In a diesel engine, fuel is injected directly into highly compressed air within the cylinder, leading to a significant increase in temperature and pressure before ignition occurs. This process requires maintaining higher compression ratios, often ranging from 14:1 to 25:1, which results in higher cylinder pressures during the compression phase.

In contrast, gasoline engines typically operate at lower compression ratios, generally between 8:1 to 12:1, and rely on a spark plug for ignition. The ignition timing and fuel-air mixture in gasoline engines do not necessitate the extremely high pressures seen in diesel engines. As a result, the overall pressure during combustion in diesel engines is greater, which contributes to their efficiency and power output.

The higher pressure in diesel engines also allows for more effective combustion of fuel, maximizing energy extraction. This fundamental difference in operation is a key distinguishing feature between the two engine types.