Function of the Diffuser in a supercharged engine?

• A. Stationary case around the impeller that collects the fast-moving mixture and slows it down, converting velocity into pressure.
• B. A device that cools the intake air.
• C. A component that seals the crankcase.
• D. A part that bleeds excess boost.

Answer: (A)

In a supercharged engine, the diffuser is the stationary casing around the impeller that captures the air leaving the impeller and slows it down. By reducing the air’s velocity as it passes through the diffuser, its kinetic energy is converted into pressure, raising the air pressure before it enters the intake manifold. This pressure rise increases the density of the charge and helps improve boost and engine performance. It isn’t about cooling the intake air, sealing the crankcase, or venting excess boost—those are separate functions handled by other components.