Compression Ratio Calculator
Calculate static engine compression ratio from swept volume and total clearance volume per cylinder.
Formula
CR = (Vs + Vc) / Vc
Swept volume Vs: 500 mL · Total clearance volume Vc: 50 mL · Static compression ratio (to 1) ≈ ((500 mL × 0.001 L/mL)+(50 mL × 0.001 L/mL))÷(50 mL × 0.001 L/mL)
How to use
- Enter the swept volume of one cylinder.
- Enter its total clearance volume at top dead center.
- Read the compression ratio as CR:1.
Examples
- 500 mL swept volume and 50 mL clearance give 11:1.
Frequently asked questions
What belongs in clearance volume?
Include the chamber, gasket and deck contributions, adjusted for piston dish or dome.
Is this dynamic compression ratio?
No. Valve timing and effective trapped volume are not modeled.
Does this give cylinder pressure?
No. Pressure also depends on the initial gas state, compression process and engine losses.
Sources
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