What is the main function of a supercharger?

The primary function of a supercharger is to enhance the volumetric efficiency of an engine. Volumetric efficiency refers to the effectiveness with which an engine draws in air and fuel for combustion. By forcing more air into the engine's intake manifold, a supercharger allows the combustion chambers to receive a greater amount of air than they would under natural atmospheric pressure alone. This increase in air density leads to more fuel being combusted, ultimately resulting in more power being generated by the engine.

When an engine operates with higher volumetric efficiency, it can produce more horsepower without necessarily increasing its size or weight. This is particularly beneficial in maintaining engine performance, especially in applications that require rapid response and high power output.

In contrast, the other options pertain to different aspects of engine performance. Increasing thermal efficiency relates to the engine's ability to convert heat from fuel into useful work, while increasing the compression ratio affects the performance and efficiency within the combustion cycle. Maintaining sea-level pressure at altitude involves compensating for reduced air density, which is more directly associated with turbochargers than superchargers.