Final answer:
The blanks inside an intake manifold that carry air or the air-fuel mixture to the cylinder head ports are called passages. They are distinct from valves, pistons, and tubes, serving the specific purpose of directing flow during the engine's cycles.
Step-by-step explanation:
The blanks inside an intake manifold that carry air or the air-fuel mixture to the cylinder head ports are known as passages. Unlike valves, which regulate the flow of the air-fuel mixture or air into the combustion chamber, or pistons, which compress the mixture within the cylinder, the passages are designed to efficiently direct the flow. These are not to be confused with tubes, which might have a broader range of applications in other engineering contexts.
In the context of the diesel cycle, during the intake stroke OA, only air is drawn into the chamber through these passages. The air-fuel mixture is not present until after the compression stroke, which heats the air to a high temperature, ready for the fuel to be added and ignited during the subsequent power stroke.