A supercharger is an air compressor that forces more air into an engine than it could draw in on its own. More air means more oxygen, so more fuel can be burned on each combustion cycle, and that produces more power. Most superchargers are driven by a belt from the engine’s crankshaft, so boost is tied directly to engine speed.
What does a supercharger do?
A naturally aspirated engine relies on atmospheric pressure to push air into the cylinders. A supercharger raises the pressure in the intake above atmospheric, which is called boost and is usually measured in psi. With denser air in the cylinders, the fuel system adds fuel to match, and the larger air and fuel charge makes more torque and horsepower. How much more depends on the boost level, the engine and the supporting parts; our guide on how much horsepower a supercharger adds covers that question.
How does a supercharger work?
- Drive. A belt from the crankshaft pulley spins the supercharger. The pulley sizes set how fast the supercharger turns relative to the engine, which affects how much boost it makes.
- Compression. Rotors, screws or an impeller inside the supercharger compress incoming air and push it toward the engine.
- Intercooling. Compressing air heats it, and hot air is less dense and more prone to detonation. Many systems pass the air through an intercooler, either air-to-air or air-to-water, to cool it before it enters the engine.
- Fuel and spark. The fuel system supplies enough fuel for the extra air, and the engine calibration controls fueling and ignition timing under boost.
- Pressure relief. Centrifugal systems typically use a bypass or blow-off valve to vent pressure when the throttle closes.
Because it is driven by the crankshaft, a supercharger uses some engine power to turn. That is part of the trade-off compared with a turbocharger, which is driven by exhaust gas.
Centrifugal vs positive-displacement superchargers
Positive-displacement superchargers, the roots and twin-screw types, usually sit on top of the engine in place of the intake manifold. They move a fixed volume of air per revolution, so they build boost from low rpm. Centrifugal superchargers use a high-speed impeller, similar to the compressor side of a turbocharger. They are usually mounted at the front of the engine and build boost progressively as rpm rises.
Among the kits we carry are ECS centrifugal systems for Corvette and Camaro platforms that use the Paxton Novi 1500 supercharger; you can browse them on our supercharger kits by platform page. Our supercharger vs turbo guide compares supercharging and turbocharging in more detail.
What else does a supercharger kit need?
- Fuel system capacity. More air needs more fuel, so many kits include or call for larger injectors or a higher-capacity fuel pump, depending on the vehicle and boost level.
- Calibration. The engine computer has to be recalibrated for the added air. Kit documentation states what calibration is required.
- Fuel octane. Boosted engines commonly require premium fuel; follow the kit documentation.
- A healthy engine. Boost adds cylinder pressure and heat, so the engine should have good compression, a sound cooling system and no existing oil or coolant problems before installation.
- Drivetrain strength. More torque also loads the transmission, torque converter, driveshaft and axles.
What about emissions rules?
Rules for aftermarket parts that affect emissions vary by state and by vehicle. Before buying or installing a supercharger kit, check your state’s rules and read the kit documentation for the applications it covers.
Related guides: what does an intercooler do? · what is E85? · Corvette generations · Camaro generations.
More guides: supercharger maintenance · twin-screw vs Roots · is a supercharger worth it? · how long a supercharger lasts · supercharger kit prices.
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