What influences engine displacement in a reciprocating engine?

In a reciprocating engine, engine displacement is primarily influenced by the stroke distance of the piston, which refers to how far the piston travels within the cylinder during its cycle. Displacement is calculated as the volume of the cylinders displaced by the pistons as they move from the bottom to the top of their stroke. This volume is determined by two key dimensions: the bore (diameter of the cylinder) and the stroke (the distance the piston travels).

The formula for calculating the displacement of a single cylinder is:

[ \text{Displacement} = \pi \left(\frac{\text{Bore}}{2}\right)^2 \times \text{Stroke} ]

When considering the entire engine, displacement is the total volume of all the cylinders combined, so both the stroke and bore play a crucial role. The stroke, therefore, directly affects how much air-fuel mixture can be drawn into the cylinder and subsequently compressed and ignited, impacting the overall power output of the engine.

Thus, the correct answer is rooted in understanding how the stroke distance contributes significantly to the volume of combustion that can occur within the engine, affecting its performance characteristics.