Honda/Acura Performance By Mike Kojima HPBooks
Bore-to-Stroke Ratio p65
The bore-to-stroke ratio of an engine can also affet the engine[s power characterisitics. Overquare engines, ones that have a bigger bore than stroke, have lower piston speeds and less internal stress at high rpm due to lower inertial loads. Thereis also more time to the cylinders because of the lower piston speed. Longer strokes with smaller bored engines, called oversquare, have more internal stress due to faster piston acceleration, higher piston speeds, which accelerates wear can induce seal-killing ring flutter. Undersquare engines have higher torque and low end power producing intake port velocities to ensure more complete cylinder filling at low rpm. Honda automotive engines are undersquare.