How this calculator works
A turbocharger or supercharger packs more air into each cylinder. At a fixed air-fuel ratio and combustion efficiency, the mass of air trapped per cycle scales with absolute pressure, so the engine can burn proportionally more fuel and make proportionally more torque. The absolute pressure is atmospheric pressure plus gauge boost, which is why 7 psi gives a pressure ratio of about 1.48 rather than 7 divided by 14.7 alone. The model assumes unchanged volumetric efficiency, ignition timing and intercooling; in practice a hot intake charge, a boost threshold or a fuel limit will make the real gain smaller.
Formula
P_boosted = P_current x (P_atm + boost) / P_atm, with P_atm = 14.6959 psi or 101.325 kPa. For a target power, boost = P_atm x (P_target / P_current - 1). The gain is P_target / P_current - 1.
Worked example
A 200 hp engine at 10 psi of boost has a pressure ratio of (14.6959 + 10) / 14.6959 = 1.680, so the estimate is 336 hp, a gain of 136 hp or 68 percent.
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Frequently asked questions
What boost pressure is safe?
There is no universal number. Safe boost depends on the engine, compression ratio, fuel octane, intercooling and the tune. This page only estimates power; it does not give a safety limit.
Why does 1 bar of boost not double the power?
One bar of gauge boost is about 14.5 psi above atmospheric, so the absolute pressure roughly doubles and the theoretical power gain is near 100 percent. Real gains are lower because the intake charge heats up and the engine cannot always add the matching fuel and timing.
Does the engine need a different fuel pump?
Very likely. More air requires more fuel, and the original pump or injectors may run out of flow. Use the fuel pump or injector calculator to size the fuel system for the target power.
Is this valid for an electric vehicle?
No. An electric motor has no intake air and no boost pressure. Use the 0-60 or wheel horsepower calculators for electric drivetrains.