What is Engine Compression Ratio?
1 Answers
Engine compression ratio refers to the ratio of the volume of the air-fuel mixture before compression to its volume after compression in the combustion chamber. A higher engine compression ratio generally indicates stronger power output. Below is an explanation of engine compression ratio: 1. When the compression ratio is higher, the air-fuel mixture reaches a higher temperature after compression. When ignited by the spark plug, the mixture combusts almost instantaneously, releasing more energy and delivering greater power output. 2. With a lower compression ratio, the compressed air-fuel mixture remains at a relatively lower temperature. The spark plug takes longer to complete the combustion process, and additional energy is required to raise the mixture's temperature. As a result, power output decreases, and some energy is converted into heat, causing the engine temperature to rise instead of contributing to the vehicle's forward motion. 3. In summary, a higher compression ratio generally leads to better engine efficiency, improved performance, and superior fuel economy. However, an excessively high compression ratio is not necessarily better. If the compression exceeds the engine's capacity, abnormal combustion may occur on surfaces such as the combustion chamber walls, exhaust valve heads, spark plug electrodes, or carbon deposits. This surface ignition phenomenon generates extremely high pressure, significantly increasing the load on engine components and drastically reducing their service life. Therefore, the optimal engine compression ratio should be moderate rather than excessively high.
