What is the effect of altitude on the boost pressure of an engine with an internal supercharger?

The effect of altitude on the boost pressure of an engine with an internal supercharger is best understood in the context of how air density changes with altitude. As altitude increases, the atmospheric pressure decreases, which affects the amount of air that can be drawn into the engine. An internal supercharger compresses the incoming air to increase its density and pressure, thereby producing a boost effect.

Initially, as altitude increases, there can be a slight increase in boost pressure because the engine’s supercharger is designed to work effectively by compressing the thinner air. However, the supercharger's ability to maintain this boost diminishes with significant altitude changes. The decrease in atmospheric pressure eventually outweighs the supercharger's capacity, leading to a reduction in the overall boost pressure.

This understanding illustrates that while boost pressure may not immediately decrease with altitude, it does not remain constant and will eventually drop as altitude continues to increase. Therefore, although the choice may suggest that boost pressure increases at initial stages, it is important to recognize that the long-term effects of altitude will negatively impact boost pressure as the air continues to thin out.