Compression Ratio to PSI – Ideal Gas Calculator
Estimate absolute pressure from volume compression ratio, initial absolute pressure and a stated ideal-gas exponent.
Formula
P₂ = P₁ × CRⁿ; pressure rise = P₂ − P₁. Use absolute pressures.
Initial absolute pressure P₁: 14.7 psi · Final absolute pressure ≈ (14.7 psi × 6,894.757293 Pa/psi)×(10)^(1)÷6894.757293168361 · Pressure rise P₂ − P₁ ≈ (14.7 psi × 6,894.757293 Pa/psi)×((10)^(1)-1)÷6894.757293168361
How to use
- Enter the volume ratio V₁/V₂.
- Enter initial absolute pressure and exponent n.
- Read final absolute PSI and the pressure rise.
Examples
- At n=1, 10:1 and 14.7 psi absolute give 147 psi absolute.
Frequently asked questions
What exponent should I use?
Use n=1 for constant temperature; use n=γ=Cp/Cv for reversible adiabatic compression with constant heat capacities.
Is this an engine compression-test prediction?
No. Valve timing, leakage, heat transfer and gas properties can change real engine readings.
Is the pressure rise gauge pressure?
Only if P₁ equals ambient pressure. The main result is always absolute pressure.
Sources
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