Boost Horsepower Calculator

Understanding Boost and Horsepower

Forced induction, through either a turbocharger or a supercharger, is a popular method for significantly increasing an engine's horsepower. Both systems work by forcing more air into the engine's cylinders than it could draw in naturally. More air allows for more fuel to be burned, resulting in a more powerful explosion in each cylinder and, consequently, more horsepower. The amount of extra air pressure created by the charger is measured as "boost," typically in pounds per square inch (PSI) or bar.

While not a precise science due to many variables, there is a general relationship between the amount of boost applied and the potential horsepower gain. A common rule of thumb is that for every 1 PSI of boost, an engine can gain approximately 7-10% of its original, naturally aspirated horsepower. This calculator uses this principle to provide a rough estimate of the potential horsepower an engine could produce at a given level of boost. It's important to remember that this is a simplification; real-world results depend heavily on factors like engine efficiency, fuel type, intercooling, and engine management tuning.

How to Use the Boost Horsepower Calculator

This calculator provides an estimate of the horsepower an engine might produce with the addition of a turbocharger or supercharger.

Enter the Base Horsepower: This is the engine's horsepower before any forced induction is added (naturally aspirated).
Enter the Desired Boost Pressure: Input the amount of boost you plan to run, measured in PSI.
View the Estimated Results: The calculator will instantly provide an estimated new horsepower figure and the total horsepower gain.

The Calculation Formula

The calculator uses a straightforward formula based on atmospheric pressure and boost pressure to estimate the new horsepower.

New HP = Base HP * ( (Boost PSI + 14.7) / 14.7 )

Where:

New HP is the estimated horsepower with boost.
Base HP is the original horsepower of the engine.
Boost PSI is the pressure added by the turbo or supercharger.
14.7 is the standard atmospheric pressure at sea level in PSI.

This formula calculates the new "absolute" pressure in the intake manifold and applies that pressure ratio to the base horsepower to find the theoretical new output.

Practical Example

Imagine a car enthusiast has a car with a naturally aspirated engine that produces 200 horsepower. They decide to install a turbocharger and plan to run it at 10 PSI of boost.

Base Horsepower: 200 HP
Boost Pressure: 10 PSI

Using the formula:

New HP = 200 * ( (10 + 14.7) / 14.7 )

New HP = 200 * ( 24.7 / 14.7 )

New HP = 200 * 1.68

New HP ≈ 336 HP

The calculator would estimate the new output to be around 336 horsepower, a gain of 136 HP. This gives the owner a target figure and helps them understand the potential of their setup. It also helps in planning supporting modifications, such as strengthening engine internals or upgrading the fuel system, to handle the significant increase in power. For more on engine performance, check out our Brake Specific Fuel Consumption (BSFC) Calculator.