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Piston Displacement or Swept Volume

Internal Combustion Engine
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Four-Stroke-Cycle Spark-ignition (Petrol) Engine
Valve Timing Diagrams
Two Stroke Spark Ignition Engine
Difference Between Two & Four Stroke Cycle Petrol Engines
Four Stroke Cycle Compression Ignition (Diesel) Engine
History of Diesel Engine
Two Stroke Cycle Diesel Engine
Comparison of Two and Four Stroke Cycle Diesel Engine
Comparison of S.I. and C.I. Engine
Piston Displacement or Swept Volume
Engine Torque & Engine Power
Compression Ratio

When the piston moves from one end of the cylinder to the other, it will sweep or displace air equal to the cylinder volume between TDC and BDC. Thus the full stroke movement of the piston is known as either the swept volume or the piston displacement.

The swept or displaced volume may be calculated as follows:

pd2L V 4000

where V piston displacement (cm3)

p 3:142

d cylinder diameter (mm) and L cylinder stroke (mm)

Mean Effective Pressure

Mean effective pressure is an important term for measuring engine performance.The cylinder pressure varies considerably while the gas expands during the power stroke. Peak pressure will occur just after TDC, but this will rapidly drop as the piston moves towards BDC. When quoting cylinder pressure, it is therefore more helpful to refer to the average or mean effective pressure throughout the whole power stroke. The units used for mean effective pressure may be either kilo Newton per square meter (kN/m2) or bars (note: 1 bar 100 kN/m2).