Question 22 OSE02 - Assistant Engineer - OSV

The Correct Answer is B **Explanation of Correct Answer (B): Unit injector type system** The Unit Injector (UI) system, particularly the Electronic Unit Injector (EUI) or Hydraulic Unit Injector (HUI) system, integrates the high-pressure pump and the injector nozzle into a single physical unit located directly in the cylinder head. Fuel is supplied to this unit at low pressure (usually via a lift pump). The high pressure required for injection (up to 2,000 bar or more) is generated *within* the unit injector itself, directly above the combustion chamber. Because the high-pressure generation and injection occur in the same component, there is no need for external high-pressure fuel lines running between an external pump and the injector, thus fulfilling the characteristic of a complete absence of high-pressure fuel lines. **Explanation of Incorrect Options:** * **A) Common rail type system:** This system utilizes an external high-pressure pump (or pumps) that continuously pressurizes a single storage rail (the "common rail"). High-pressure fuel lines are absolutely essential to connect the pump to the rail, and then to connect the rail to each individual injector. * **C) Rotary plunger type system:** Also known as a Distributor Pump system, this design uses a single high-pressure pump to serve all cylinders. High-pressure fuel lines are required to carry the pressurized fuel from the outlet of the rotating distributor element on the pump to the nozzle holder installed in the cylinder head of each cylinder. * **D) In-line multi-plunger type system:** This older design features an individual plunger and barrel assembly for each cylinder housed within a single pump body. High pressure is generated by the pump and then transmitted to the nozzle holders via dedicated, rigid high-pressure fuel lines, one for each cylinder.