What is Engine Compression Ratio?
2 Answers
The ratio of the maximum volume of the cylinder at bottom dead center to the minimum volume at top dead center is the compression ratio. Below is an introduction to compression ratio: 1. Compression ratio refers to the degree to which the engine's air-fuel mixture is compressed. It is expressed as the ratio of the total cylinder volume before compression to the cylinder volume after compression. 2. Compression ratio is closely related to engine performance. The higher the compression ratio, the greater the engine's power. (V swept volume by piston + V combustion chamber volume) / V combustion chamber volume. 3. An engine with a compression ratio of 10 compresses the combustible mixture to 1/10 of its original volume. An excessively high compression ratio can reduce stability and shorten engine lifespan.
Engine compression ratio simply refers to the volume ratio before and after cylinder compression. Taking my daily driving experience as an example, my old Honda engine has a 10:1 compression ratio, which means the initial space is 10 times larger than the compressed space when the piston compresses. Generally, the higher this ratio, the better the engine efficiency, because compressed gas can generate more energy, making the car more powerful. However, high compression ratios also have drawbacks, such as being prone to knocking—like internal ignition being too strong, producing a clicking sound—which can damage the engine if severe. That's why I always remind my friends to use high-octane fuel to match. If the ratio is too low, the engine lacks power and fuel consumption increases. Typically, a normal range is between 8:1 and 14:1. During maintenance, keeping the spark plugs and intake system clean ensures stable operation. Don’t underestimate this parameter—it directly affects how much you spend on fuel and how smoothly your car accelerates.
