The major side thrust of a piston occurs during the __________ stroke.

The major side thrust of a piston occurs during the power stroke. During this phase of the engine cycle, the combustion of the air-fuel mixture generates high pressure in the combustion chamber, forcing the piston downwards. As the piston moves, it experiences a significant lateral force due to the angle of the connecting rod, which translates the linear motion of the piston into rotary motion for the crankshaft. This lateral force, or side thrust, is primarily a result of the combustion forces acting on the piston and the geometry of the piston and connecting rod assembly when the piston is not perfectly aligned with the cylinder bore.

The power stroke is crucial because it's when the maximum amount of force is exerted on the piston, leading to increased wear on the cylinder walls and piston rings due to this side thrust. Understanding the dynamics of the power stroke thus aids in designing engine components that can withstand these forces, ensuring longevity and performance.

In contrast, during the compression, intake, and exhaust strokes, the forces acting on the piston do not generate the same degree of side thrust as seen during the power stroke. In these other strokes, the piston is largely moving within the cylinder with less opposing force aimed toward the side, which does not produce significant lateral stress to the same extent