Question 27 OSE02 - Assistant Engineer - OSV

The Correct Answer is B **Why Option B ("Unit injector type pump") is correct:** The Unit Injector (UI) system, particularly the Electronic Unit Injector (EUI) and the related Common Rail (CR) systems, are the primary technologies utilized on modern, high-performance marine diesel engines, especially those used on sophisticated multi-purpose supply vessels (PSVs). In EUI systems, each cylinder has its own integrated pump and injector unit. These systems inherently rely on sophisticated electronic controls (ECUs) to precisely manage two critical functions: 1. **Timing:** The ECU determines the exact moment the solenoid or piezoelectric actuator fires, initiating the high-pressure injection, allowing for variable and optimized timing based on engine load and speed. 2. **Metering (Fuel Quantity):** The ECU controls the duration of the electrical pulse to the unit injector, which directly dictates the amount of fuel injected (the metering). This level of electronic control is essential for meeting modern requirements for fuel efficiency, high power output, and stringent emission regulations. **Why the other options are incorrect:** * **A) Distributor type pump:** While this type of pump (often found in smaller, automotive applications or older, low-power marine engines) can incorporate some electronic timing control, the metering mechanism often relies heavily on mechanical methods (e.g., pressure-regulating valves or plungers) rather than purely sophisticated electronic controls over individual injection events like a unit injector or common rail system. * **C) Rotary plunger type pump:** This is a variant of the distributor pump. While modern versions (like the VP44 pump) integrated early electronic controls, they are generally superseded by Unit Injector or Common Rail technology in large marine applications where maximum precision and pressure are required, thus making them less likely to represent the *most sophisticated* electronic control system in use today. * **D) In-line multi-plunger pump:** This is historically the most robust and common pump type for large marine diesels. However, the traditional in-line pump is fundamentally a mechanical system (often governed by flyweights and racks). While modern versions can be assisted by mechanical or hydraulic actuators managed by an ECU, the actual high-pressure generation and initial timing control are predominantly mechanical, making it significantly less electronically sophisticated than a dedicated Unit Injector or Common Rail system.