Who is correct about exhaust ports and passages: Technician A says they are large for free flow, while Technician B claims they are narrow for fast movement of gases?

In a diesel engine, exhaust ports and passages are designed to optimize the flow of exhaust gases out of the combustion chamber. Technician A's assertion that these passages are large for free flow is correct because larger exhaust ports facilitate the efficient escape of exhaust gases. This design helps reduce back pressure and improves engine performance by allowing gases to exit more quickly and efficiently, ultimately enhancing the overall power output.

In contrast, Technician B's statement about the passages being narrow for fast movement of gases does not accurately reflect how exhaust systems are structured in diesel engines. While it's true that gases need to maintain a certain velocity for optimal performance, excessively narrow passages can lead to increased back pressure, hindering the engine's efficiency and performance rather than enhancing it.

Thus, Technician A's understanding of exhaust port design aligns with the principles of maximizing exhaust flow and improving engine performance, making it the correct choice in this context.