Automotive & Engines
Intermediate

Compression Ratio

Ratio of cylinder volume at bottom vs top of the stroke.

Formula

CR=Vd+VcVcCR = \frac{V_d + V_c}{V_c}

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Variables

CRCompression ratio
V_dDisplacement volume
V_cClearance volume

Example

V_d=450 cc, V_c=50 cc: CR = 500/50 = 10:1

Did You Know?

High-compression engines make more power but demand higher-octane fuel to avoid knock.

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