The compression ratio is a key metric in internal combustion engines, representing the ratio between the maximum volume of the cylinder (when the piston is at the bottom dead center) and the minimum volume (when the piston is at the top dead center). This ratio plays a crucial role in determining how much the air-fuel mixture is compressed during the compression stroke. A higher compression ratio generally leads to better engine efficiency and performance, as it increases the pressure and temperature of the mixture, resulting in faster combustion and more power output. However, there are limitations. If the compression ratio is too high, it can lead to issues like knocking or pre-ignition, which can damage the engine and reduce its lifespan. Additionally, modern emission standards also restrict how high the compression ratio can be set, as higher ratios may increase harmful emissions. Therefore, engineers must carefully balance compression ratio with other factors to optimize engine performance while meeting environmental and mechanical constraints.