What do bore and stroke mean?

[DeAlejandro]

Bore refers to the diameter of the cylinder, while stroke is the distance between the top dead center and bottom dead center of the piston movement. Below is relevant information about the stroke-to-bore ratio: 1. Definition: The stroke-to-bore ratio is the most fundamental and critical structural parameter of an internal combustion engine. It not only significantly impacts scavenging efficiency and heat transfer but also affects engine power and fuel consumption rate. Additionally, it influences the structure and dimensions of all components, thereby affecting engine vibration, specific weight indicators, and service life. 2. Ratio: If S/D is relatively large, the volume occupied by residual exhaust gases in the cylinder increases, along with greater scavenging resistance. This results in a longer path for the fresh air-fuel mixture during the scavenging process, inevitably leading to mixing with exhaust gases and reducing scavenging quality. A larger S/D also increases the cylinder's surface area, leading to greater heat loss.