Compression ratio
A compression ratio is a value indicating the degree to which
drawn-in air is compressed.
That is, the ratio between the volume above the piston (cylinder
volume + combustion chamber volume) when it is at bottom dead
center and the remaining volume (combustion chamber volume) in
the cylinder head when the piston is at top dead center.
V = (π/4 × D × D) × L × N
V: Total displacement (cc) (rounded down to the nearest whole
number)
D: Cylinder inner diameter (cm)
L: Cylinder stroke (cm)
N: Number of cylinders π: 3.1416
Σ = (V ＋ VC)/VC
Σ: Compression ratio
VC: Combustion chamber volume when piston is at top dead
center
V + VC: Volume above piston when it is at bottom dead center
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