Engine cylinder sizing — conventional dimensions used to specify size In engine specifications, the size of a cylinder is generally stated in terms of which two dimensions?

Introduction / Context:
Bore and stroke are fundamental to engine geometry. They determine displacement, influence torque and power characteristics, and guide component design choices.

Given Data / Assumptions:

• Bore = cylinder diameter.
• Stroke = distance the piston travels between top dead centre and bottom dead centre.
• Question asks the standard pair used to describe cylinder size.

Concept / Approach:
Engine displacement per cylinder equals (pi/4) * bore^2 * stroke. Thus, bore and stroke are the canonical size descriptors. Terms like efficiency are performance metrics, not geometric size descriptors. Similarly, “diameter and bore” is redundant.

Step-by-Step Solution:
Identify geometric variables: bore and stroke.Relate to displacement formula and engine tuning implications.Select the option matching both: bore and stroke.

Verification / Alternative check:
Manufacturers list engines as, for example, 86 mm bore × 86 mm stroke (square), undersquare, or oversquare.

Why Other Options Are Wrong:

• Diameter and bore: duplicate descriptors.
• Displacement and efficiency: not raw cylinder size terms.
• Bore and length: cylinder block length is not a standard size descriptor.

Common Pitfalls:
Confusing engine displacement (derived) with the base dimensions used to compute it.

Final Answer:
bore and stroke