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Frequently asked questions about cars and motorcycles

From theory to practice: the bore/stroke ratio

Model: (Various brands) Various
Part: Engine

In this video we try to understand some things about the bore/stroke ratio: the square, undersquare or oversquare engine. To know what type of engine we have, we need to know the bore, which is the distance between the walls of the cylinder (in mm). The stroke, on the other hand, is the distance between the top dead center and the bottom dead center (also expressed in mm). Bore x stroke = we will know if it is a square, undersquare or oversquare engine. In a square engine, the stroke and bore are equal (let's say 50 and 50). The undersquare engine (also known as "long stroke") will have a longer stroke than bore (let's say 60 stroke and 40 bore), which will have high torque, low rotations and high thermal efficiency, like diesel engines. On the other hand, the oversquare engine is the opposite: it will have a shorter stroke and a larger bore (let's say 60 bore and 40 stroke), so the piston rotation speed will be very high and consequently all mechanical components will be highly stressed.

Posted on 22 May 2024 by ScegliAuto

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