Bore vs Stroke ~ What Makes More Power?

What Makes An Engine Better? A Big Bore or Long Stroke?

All piston-cylinder internal combustion engines have a choice to make with regards to bore and stroke. Bore and stroke cause differences in both power and efficiency. What makes the most power may not always be the most efficient.

Should an engine have a large bore (the width of the cylinder)? Or would it be beneficial to instead have a small bore and a long stroke? Or should the bore and stroke dimensions of the engine be identical?

Engineering Explained discusses how bore & stroke affect engine RPM, engine airflow, heat losses with regards to surface area, and flame duration.

With regards to bore and stroke, an engine is called “oversquare” if the bore is longer than the stroke, “square” if the bore and stroke are identical, and “undersquare” if the stroke is longer than the bore.

SAE – A Study Isolating the Effect of Bore-to-Stroke Ratio on Gasoline Engine Combustion Chamber Development ~ www.sae.org/publications/tech…