Boost To HP Calculator converts boost pressure into estimated engine horsepower using pressure ratio and efficiency. Calculate turbo and supercharger power gain, total output, and boost performance instantly.
The fundamental calculation within the engine algorithm hinges on a fixed atmospheric baseline of 14.7 psi, scaling base horsepower linearly with the calculated pressure ratio before attenuating the theoretical gain via a static percentage-based efficiency modifier.
Field Observation The static 14.7 psi atmospheric baseline invalidates calculations at altitude. Furthermore, assuming linear volumetric efficiency scaling ignores thermal saturation and pumping losses at high RPMs. In reality, intercooler heat soak and progressive exhaust backpressure degrade the dynamic efficiency coefficient significantly faster than this idealized linear pressure ratio model suggests.
Core Algorithmic Logic Extraction The engine calculates the pressure ratio ($P_R$) and applies it to the naturally aspirated horsepower metric, subtracting the base power to find the ideal gain before factoring in the user-defined compressor efficiency ($\eta_{eff}$).$$P_R = \frac{14.7 + P_{boost}}{14.7}$$$$HP_{actual} = HP_{base} + \left[ \left( HP_{base} \times \left( \frac{14.7 + P_{boost}}{14.7} \right) – HP_{base} \right) \times \frac{\eta_{eff}}{100} \right]$$$$HP_{gain/kw} = \left( HP_{actual} – HP_{base} \right) \times 0.7457$$
Induction Efficiency Benchmarks & Constraints
| Induction Architecture | Baseline Efficiency ($\eta_{eff}$) | Parasitic Draw Factor | Max Effective PR Limit |
|---|---|---|---|
| Roots Blower (TVS) | 60% – 65% | High (Belt Driven) | ~2.2 |
| Twin-Screw Supercharger | 70% – 75% | Moderate (Belt Driven) | ~2.8 |
| Centrifugal Supercharger | 75% – 80% | Low (Belt/Gear) | ~3.0 |
| Standard Turbocharger | 72% – 78% | Negligible (Exhaust) | ~3.5 |
| Twin-Scroll Turbocharger | 75% – 82% | Negligible (Exhaust) | ~4.0 |
Environmental Barometric Derivations To account for the static $14.7$ psi atmospheric assumption failure in real-world environments, dynamic modeling requires calculating the barometric pressure attenuation based on altitude ($h$) and temperature ($T$), substituting the hardcoded $14.7$ with $P_{atm(h,T)}$:$$P_{atm(h,T)} = P_0 \cdot \left( 1 – \frac{L \cdot h}{T_0} \right)^{\frac{g \cdot M}{R \cdot L}}$$
Where $P_0$ is sea-level pressure ($101325$ Pa converted to psi), $L$ is the temperature lapse rate ($0.0065$ K/m), $T_0$ is standard temperature ($288.15$ K), $g$ is gravitational acceleration, $M$ is the molar mass of dry air, and $R$ is the universal gas constant.
Consequently, the actual intake air density $\rho_{air}$ modifying the ultimate volumetric flow equation becomes:$$\rho_{air} = \frac{P_{atm(h,T)}}{R_{specific} \cdot (T_{ambient} + \Delta T_{compressor} – \Delta T_{intercooler})}$$
Related Tools & Calculators: