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An engine is described as undersquare or long-stroke if its cylinders have a smaller bore (width, diameter) than its stroke (length of piston travel) - giving a ratio value of less than 1:1. At a given engine speed, a longer stroke increases engine friction and increases stress on the crankshaft due to the higher peak piston acceleration.
The stroke ratio, determined by dividing the bore by the stroke, traditionally indicated whether an engine was designed for power at high engine speeds or torque at lower engine speeds. [ 2 ] [ 3 ] The term "bore" can also be applied to the bore of a locomotive cylinder or steam engine pistons .
Below is an animation of the piston motion equations with the same values of rod length and crank radius as in the graphs above. Piston motion animation with the various half strokes from the graph above (using the same color code)
A fundamental specification for such engines, it can be measured in two different ways. The simpler way is the static compression ratio: in a reciprocating engine, this is the ratio of the volume of the cylinder when the piston is at the bottom of its stroke to that volume when the piston is at the top of its stroke. [1]
It is the ratio between the volume of the cylinder, when the piston is at the bottom of its stroke, and the volume when the piston is at the top of its stroke. The bore/stroke ratio is the ratio of the diameter of the piston, or "bore", to the length of travel within the cylinder, or "stroke". If this is around 1 the engine is said to be "square".
The rod-to-stroke ratio is the ratio of the length of the connecting rod to the length of the piston stroke. A longer rod reduces sidewise pressure of the piston on the cylinder wall and the stress forces, increasing engine life. It also increases the cost and engine height and weight.
Piston stroke: 90.7 mm (3.57 in) ... Below is a chart that consists all of the engines in the H Series. ... Power Compression Ratio Bore x Stroke Accord CD6 SiR H22A ...
The comparison of mean piston speed (black line) with real piston speed (color lines). Diagram shows one stroke from BDC to TDC. Revolution = 1.000 min-1, stroke = 88 mm. The connecting rod ratio l/r varies: 3 - red, 4 - green, 5,5 - blue. The mean piston speed is the average speed of the piston in a reciprocating engine.