Otto Cycle Calculator
Otto efficiency depends only on compression ratio: r = 8 with γ = 1.4 gives η = 56.4725 %.
56.4724718351938 %
Full answer, then cut to fewer decimals (not rounded):
- 56.4724718351938 %
- 56.472471835193 %
- 56.47247183519 %
- 56.4724718351 %
- 56.472471835 %
- 56.47247183 %
- 56.4724718 %
- 56.472471 %
- 56.47247 %
- 56.4724 %
- 56.472 %
- 56.47 %
- 56.4 %
- T₂ after compression
- 689.219 K
- p₂
- 1837.92 kPa
- T₄ after expansion
- 870.551 K
- Peak pressure p₃
- 5333.33 kPa
- Heat added qin = cv(T₃ − T₂)
- 940.485 kJ/kg
- Net work w
- 531.115 kJ/kg
- Mean effective pressure
- 704.981 kPa
Step-by-step solution
- η = 1 − 1/r^(γ−1) = 1 − 1/8^0.4 = 0.564725
- T₂ = T₁ r^(γ−1) = 689.219 K, T₄ = T₃ / r^(γ−1) = 870.551 K
- w = cv[(T₃ − T₂) − (T₄ − T₁)] = 531.115 kJ/kg
Otto Cycle Formula
η = 1 − 1/r^(γ−1)
r compression ratio, γ = cp/cv
Worked Example
r = 8, γ = 1.4, intake 300 K and 100 kPa, peak 2000 K:
- η = 1 − 1/r^(γ−1) = 1 − 1/8^0.4 = 0.564725
- T₂ = T₁ r^(γ−1) = 689.219 K, T₄ = T₃ / r^(γ−1) = 870.551 K
- w = cv[(T₃ − T₂) − (T₄ − T₁)] = 531.115 kJ/kg
p₂: 1837.92 kPa · T₄ after expansion: 870.551 K · Peak pressure p₃: 5333.33 kPa · Heat added qin = cv(T₃ − T₂): 940.485 kJ/kg · Net work w: 531.115 kJ/kg · Mean effective pressure: 704.981 kPa
More Thermodynamics Calculators
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Carnot Efficiency Calculator
η = 1 − TL/TH
COPR = TL/(TH − TL), COPHP = TH/(TH − TL), absolute temperatures
Example: An engine between 600 K and 300 K: Carnot efficiency η = 50 %.
-
Diesel Cycle Calculator
η = 1 − [1/r^(γ−1)] × (ρ^γ − 1)/[γ(ρ − 1)]
r compression ratio, ρ = V₃/V₂ cut-off ratio
Example: r = 18, cut-off ratio 2, γ = 1.4, intake 300 K and 100 kPa: Air-standard efficiency η = 63.1578 %.
-
Brayton Cycle Calculator
η = 1 − 1/rp^((γ−1)/γ)
rp pressure ratio; optimum rp = (T₃/T₁)^(γ/2(γ−1)) for maximum work
Example: rp = 10, T₁ = 300 K, T₃ = 1200 K, ideal compressor and turbine: Thermal efficiency η = 48.2053 %.
-
Polytropic Process Calculator
W = (p₁V₁ − p₂V₂)/(n − 1), Q = W(γ − n)/(γ − 1)
pVⁿ = constant; n = 1 isothermal W = p₁V₁ ln(V₂/V₁)
Example: Air compressed from 100 kPa, 0.1 m³, 300 K to 800 kPa with n = 1.3: Work done by the gas W = -20.5289 kJ.
Frequently asked questions
Why can’t petrol engines use very high compression ratios?
The hot charge would knock (auto-ignite); diesel engines compress only air and can run r = 15–22.
What is mean effective pressure?
The constant pressure that would give the same net work over the swept volume: MEP = wnet/(v₁ − v₂).
Sources
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
Cite this page
APA
Scientific Converters. (2026, October 15). Otto Cycle Calculator. Retrieved October 25, 2026, from https://scientificconverters.com/calculators/otto-cycle-calculator/
IEEE
Scientific Converters, "Otto Cycle Calculator," scientificconverters.com. Accessed: Oct. 25, 2026. [Online]. Available: https://scientificconverters.com/calculators/otto-cycle-calculator/