Optimum B & S ratio

[icrman]

I would like to hear from others here, about findings, experiments of optimum Bore and Stroke Ratios for maximum power out put at various speeds.
Which will cause more losses, large bore or large stroke?

 

[SMOKEY44211]

I believe .8X bore= stroke is pretty close to the optimum ratio for a high speed SI engine. This is based on observations from own testing and data reviewed from others with an eye on final power output and BSFC.-----Phil

 

[Azmio]

when it comes to high speed naturally aspirated engine, the bigger bore to stroke ratio the better it would be. Of course there is a limit to it as well.

Bigger bore enables bigger intake valves for 2 or 3 intake valve configurations. Bigger intake valves mean lesser restriction and flow limitation. As a result, higher and higher rpm can be achieved thus contributing to higher engine rpm and horsepower

Bigger bore to stroke is also needed to maintain mean piston speed within reasonable limit.

 

[EngJW]

Also look back a few weeks- there was a long discussion on this same topic.