Engine Compression Ratio Calculator
Calculate your engine’s compression ratio with our comprehensive calculator. Determine static and dynamic compression ratios for optimal engine performance, fuel efficiency, and power output.
Step 1: Engine Characteristics
Understanding Compression Ratio
Compression ratio is the ratio between the volume of the cylinder and combustion chamber when the piston is at the bottom of its stroke, and the volume when the piston is at the top of its stroke.
Step 2: Dynamic Compression Ratio
About Dynamic Compression
Dynamic compression ratio takes into account the intake valve closing point and provides a more accurate measure of the actual compression that occurs in the cylinder during engine operation.
Compression Ratio Results
Your Engine’s Static Compression Ratio
Compression Ratio Comparison
| Engine Type | Typical CR | Your Engine | Performance |
|---|---|---|---|
| Economy Car | 9.5:1 – 10.5:1 | 10.5:1 | Good |
| Performance Car | 10.5:1 – 12.0:1 | 10.5:1 | Good |
| Race Engine | 12.0:1 – 14.0:1 | 10.5:1 | Low |
| Diesel Engine | 16.0:1 – 23.0:1 | 10.5:1 | Very Low |
Performance vs Fuel Economy
Compression Ratio Formulas
Static Compression Ratio
CR = (Swept Volume + Clearance Volume) / Clearance Volume
Swept Volume Calculation
Swept Volume = π × (Bore/2)² × Stroke
Clearance Volume Components
Clearance Volume = Combustion Chamber Volume + Gasket Volume + Deck Volume – Piston Dome Volume
Dynamic Compression Ratio
DCR = (Effective Swept Volume + Clearance Volume) / Clearance Volume
Effective Stroke Calculation
Effective Stroke = Rod Length + (Stroke/2) – √[Rod Length² – (Stroke/2 × sin(IVC))²] + (Stroke/2 × cos(IVC))
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