What superchargers do to your engine's power output

A supercharger adds between 40 and 150 horsepower to most engines, depending on the engine size, the supercharger type, and how much boost pressure it creates. The real number for your specific car depends on what you start with — a supercharger on a 4-cylinder engine might add 50 horsepower, while the same supercharger on a V8 could add 100 or more.

The reason the range is so wide is that superchargers work by forcing more air into the engine than it would normally draw in. More air means more fuel can burn in each cylinder, which means more power. A small engine has smaller cylinders, so even with forced air, there's a limit to how much extra fuel it can burn. A large engine has room for much more extra fuel, so the same supercharger adds more power.

The actual horsepower gain also depends on whether you tune the engine after installing the supercharger. Many people install a supercharger and change the fuel map — the computer instructions that control how much fuel sprays into each cylinder — to take full advantage of the extra air. Without that tuning, you leave power on the table.

Key Takeaways

  • Superchargers typically add 40 to 150 horsepower, with larger engines gaining more than smaller ones from the same supercharger.
  • The amount of boost pressure the supercharger creates — measured in PSI — directly affects how much horsepower you gain, and different superchargers create different pressures.
  • Engine tuning after installation, especially adjusting the fuel map, can increase the horsepower gain by 20 to 40 percent compared to an untuned installation.
  • Centrifugal superchargers add less horsepower than positive displacement superchargers on the same engine because they create lower boost pressure at lower engine speeds.

How boost pressure determines the horsepower increase

Boost pressure is the amount of extra air pressure the supercharger forces into the engine, measured in pounds per square inch (PSI). Most street superchargers create between 6 and 10 PSI of boost. Each additional PSI of boost typically adds 5 to 15 horsepower, depending on the engine size and how the fuel system responds.

A supercharger that creates 8 PSI of boost on a 350-cubic-inch V8 might add 80 to 100 horsepower. The same supercharger on a 200-cubic-inch 4-cylinder might add only 40 to 60 horsepower, because the smaller engine has less total displacement for the air to fill. Think of it like filling two different containers with a pump: the pump adds the same pressure to both, but the larger container ends up with more total air.

Racing superchargers can create 15 to 20 PSI or higher, but at that pressure level, the engine needs a stronger block, forged pistons, and a completely different fuel system. Street cars rarely go above 10 PSI because the engine components start to fail under that much stress.

Centrifugal versus positive displacement superchargers

Centrifugal superchargers spin like a turbine and create boost pressure that increases as engine RPM increases. At idle and low speeds, they create very little boost — sometimes 2 to 3 PSI. At high RPM, they can reach 8 to 10 PSI. This means the horsepower gain is concentrated at higher engine speeds, and you feel less power increase during normal driving.

Positive displacement superchargers (also called Roots superchargers or screw superchargers) create the same boost pressure across the entire RPM range. A positive displacement supercharger set to 8 PSI creates 8 PSI at 2,000 RPM and 8 PSI at 6,000 RPM. This means the horsepower gain is spread across the entire power band, and you feel the extra power when ready when you press the accelerator, even at low speeds.

Because of this difference, a positive displacement supercharger typically adds 20 to 40 percent more total horsepower than a centrifugal supercharger on the same engine. A centrifugal might add 60 horsepower overall, while a positive displacement adds 80 to 90 horsepower. The centrifugal is cheaper and uses less engine power to run, but the positive displacement feels more powerful during everyday driving.

Engine size and displacement matter more than you might think

A supercharger adds horsepower by percentage of the engine's original power, not by a fixed amount. An engine that makes 200 horsepower from the factory will gain a smaller percentage boost from a supercharger than an engine that makes 400 horsepower, even if both use the same supercharger at the same boost pressure.

This happens because larger engines have more cylinders or larger cylinders, so the supercharger has more total volume to pressurize. A 5.0-liter V8 has five times the displacement of a 1.0-liter 3-cylinder, so the same supercharger creates five times as much extra air volume in the V8. That extra air volume translates to much more extra fuel burning, which means much more extra power.

A small turbocharged 4-cylinder engine might gain 30 to 50 percent more horsepower from a supercharger. A large naturally aspirated V8 might gain only 20 to 30 percent more horsepower from the same supercharger. In absolute numbers, the V8 gains more horsepower, but as a percentage of its original power, the 4-cylinder gains more.

What changes when you add a supercharger

Installing a supercharger is not just bolting on a part and driving away. The engine's fuel injectors need to spray more fuel to match the extra air. The spark plugs need to fire at a different timing to match the higher cylinder pressure. The cooling system needs to handle the extra heat from compressing the air. The exhaust system may need to be upgraded to flow the extra exhaust gases.

Most supercharger kits come with new fuel injectors and a tuning device that reprograms the engine computer to handle the extra air and fuel. Some kits also include an intercooler, which cools the compressed air before it enters the engine — cooler air is denser and allows more fuel to burn, which adds another 10 to 20 horsepower compared to an unintercoled supercharger.

If you install a supercharger without these supporting changes, the engine computer will sense the extra air and reduce fuel injection to keep the air-fuel ratio correct. This means you get much less horsepower gain than the supercharger is capable of producing. You might add only 30 to 50 horsepower instead of 80 to 100, because the engine is running lean — not enough fuel for the amount of air.

Real-world horsepower gains from popular superchargers

The horsepower numbers vary widely because different engines respond differently to the same supercharger. A Roots supercharger on a 5.0-liter Ford Coyote V8 typically adds 80 to 110 horsepower at 8 to 10 PSI of boost. The same supercharger on a 3.5-liter Dodge Pentastar V6 typically adds 60 to 80 horsepower at the same boost pressure.

A centrifugal supercharger on a 2.0-liter turbocharged 4-cylinder might add 40 to 60 horsepower because the engine is already forced-induction and the supercharger works alongside the turbo. A positive displacement supercharger on the same engine might add 70 to 90 horsepower because it creates boost across the entire RPM range, not just at high speeds.

These numbers assume the supercharger is properly tuned and the engine is in good condition. An older engine with worn rings or a weak fuel pump will not gain as much horsepower as a newer engine with fresh internals and a high-flow fuel system.

Frequently Asked Questions

Will a supercharger damage my engine?

A properly installed and tuned supercharger on a stock engine typically does not cause damage, but it does increase stress on engine components. The pistons, rods, and bearings experience higher pressure and temperature. If the supercharger is set to high boost pressure without engine modifications, or if the fuel system is not tuned correctly, engine failure becomes likely within months or years of driving.

How much does a supercharger cost?

Supercharger kits for common vehicles range from $3,000 to $8,000 for the parts alone. Installation labor typically adds $1,500 to $3,000. High-end kits for performance vehicles can cost $10,000 or more. The total cost depends on the vehicle, the supercharger type, and whether you need supporting modifications like fuel injectors or engine tuning.

Can I add a supercharger to any car?

Supercharger kits exist for many popular vehicles, but not all cars have kits available. Newer vehicles with complex engine management systems are harder to tune for supercharger use. Older vehicles may require custom fabrication. Check whether a kit exists for your specific year, make, and model before assuming you can install one.

Does a supercharger use a lot of engine power to run?

Yes — a supercharger is belt-driven by the engine, so it uses 10 to 20 percent of the extra horsepower it creates just to spin itself. A supercharger that adds 100 horsepower might use 15 horsepower to run, leaving you with a net gain of 85 horsepower. Centrifugal superchargers use less engine power than positive displacement superchargers because they spin faster and more efficiently.

Will a supercharger void my vehicle warranty?

Most manufacturers will void the powertrain warranty if you install a supercharger, because it increases stress on engine components beyond factory specifications. Some dealers may refuse to service the vehicle at all. Check your warranty documents and contact your dealer before installation if warranty coverage matters to you.