What determines the efficiency of a compression ignition engine?

The efficiency of a compression ignition engine is primarily influenced by the compression ratio. The compression ratio is defined as the ratio of the maximum volume of the combustion chamber to the minimum volume. A higher compression ratio typically leads to improved thermal efficiency because it allows the engine to extract more energy from the fuel during combustion.

In a compression ignition engine, the fuel is ignited by the heat generated from compressing the air in the combustion chamber. When the compression ratio is increased, the air temperature rises significantly, leading to more efficient combustion of the fuel. This results in greater energy output from the same amount of fuel, enhancing the overall efficiency of the engine.

While fuel quality, engine size, and cooling systems can have impacts on performance and operation, they do not play as direct a role in determining the fundamental thermal efficiency as the compression ratio does. Consequently, optimizing the compression ratio is crucial for maximizing the efficiency of a compression ignition engine.