Question 1

What are the functions of a typical hydraulic injector nozzle?

Accepted Answer

Hydraulic injector nozzles are designed to define the nozzle opening pressure, atomize the fuel charge for efficient combustion, and target the fuel to the correct area of the engine cylinder for optimal performance.

Question 2

What is another way of saying popping pressure?

Accepted Answer

NOP stands for Nozzle Opening Pressure, which is another term for popping pressure, referring to the pressure at which a nozzle opens to release fluid.

Question 3

What type of injector nozzles are used with today's direct injected engines?

Accepted Answer

Modern direct injected engines typically use multi-orifice and electrohydraulic injector nozzles to achieve precise fuel metering and atomization, which are crucial for efficiency and emissions control.

Question 4

Technician A says that multi-orifice hydraulic injectors have hard value NOPs. Technician B says that NOPs in electrohydraulic injectors (EHIs) have variable NOPs that are controlled by the ECM. Who is correct?

Accepted Answer

Multi-orifice hydraulic injectors do indeed have hard value NOPs (Nozzle Opening Pressure), meaning the pressure at which the injector nozzle opens is fixed. Electrohydraulic injectors (EHIs), on the other hand, have variable NOPs that can be adjusted by the Engine Control Module (ECM) to optimize engine performance under different conditions. Therefore, both technicians are correct in their statements.

Question 5

Technician A says that electrohydraulic injectors (EHIs) may use a solenoid actuator. Technician B says that EHIs may use a piezo actuator. Who is correct?

Accepted Answer

Electrohydraulic injectors (EHIs) can use either a solenoid actuator or a piezo actuator to control the injection of fuel, making both Technician A and Technician B correct.

Question 6

What accounts for the response-delay of EHI nozzles using solenoid actuators compared with those using piezo actuators?

Accepted Answer

Solenoids require time to build and collapse magnetic fields before they can initiate mechanical movement, leading to a response delay compared to piezo actuators, which can act more directly and quickly.

Question 7

Which of the following correctly describes atomization?

Accepted Answer

Atomization refers to the process of breaking up a liquid into fine droplets. This is commonly seen in spray technologies, where a liquid is dispersed into a fine mist. It does not refer to phase changes between solid, liquid, and gas states, but rather to the physical process of dividing a liquid into smaller particles.

Question 8

When a pintle type nozzle is found on a current diesel engine system, which of the following would correctly describe its function?

Accepted Answer

The answer of When a pintle type nozzle is found...

Question 9

What is the function of an injector leak-off line?

Accepted Answer

The injector leak-off line returns excess fuel back to the fuel tank, ensuring that only the required amount of fuel is injected into the engine. This helps in maintaining the fuel pressure and prevents wastage of fuel.

Question 10

Identify the nozzle capable of soft opening pressures?

Accepted Answer

The answer of Identify the nozzle capable of soft opening...

Question 11

If a 4-stroke cycle diesel engine is run at 2000 rpm, how much real time is required for a single revolution of the engine?

Accepted Answer

The answer of If a 4-stroke cycle diesel engine is...

Question 12

If injector valve-to-nozzle body clearance in a multi-orifii injector is greater than specification, which of the following values would increase?

Accepted Answer

If the injector valve-to-nozzle body clearance is greater than specified, it would lead to increased back leakage. This is because the excessive clearance allows more fuel to escape back into the return line instead of being injected into the combustion chamber, thus reducing the efficiency of fuel injection and increasing back leakage.

Question 13

What is a typical NOP value of the multi-orifice nozzle used in an EUI (electronic unit injector)?

Accepted Answer

The typical NOP (Nozzle Opening Pressure) value of the multi-orifice nozzle used in an EUI (Electronic Unit Injector) system is around 5000 psi. This high pressure is necessary for achieving fine atomization of fuel, which is crucial for efficient combustion in modern diesel engines.

Question 14

When multi-orifice nozzles are used in hydromechanical diesel engines, what would be a typical NOP value?

Accepted Answer

Multi-orifice nozzles in hydromechanical diesel engines typically operate at high pressures, and 5000 psi is a common value for the Nozzle Opening Pressure (NOP) in such applications.

Question 15

In a typical multi-orifice, hydraulic injector, what force holds the nozzle valve on its seat?

Accepted Answer

The spring force is responsible for holding the nozzle valve on its seat in a typical multi-orifice, hydraulic injector. This ensures that the valve only opens when the fuel pressure overcomes the spring force, allowing for controlled fuel injection.

Question 16

The highest pressure that a diesel injection circuit is subject to is known as:

Accepted Answer

Peak pressure refers to the highest pressure reached in the diesel injection circuit during operation.

Question 17

As pressure increases in the injection circuit, what happens to the emitted droplet sizing?

Accepted Answer

As pressure increases in the injection circuit, the emitted droplet size decreases. This is because higher pressure breaks the fluid into smaller droplets.

Question 18

Technician A says that EHIs are ECM-controlled but are limited by hard value NOPs. Technician B says that EHIs are used with current common rail (CR) and electronic unit injector (EUI) diesel fuel injection systems. Who is correct?

Accepted Answer

Technician B is correct because EHIs (Electronic Hydraulic Injectors) are indeed used with current common rail (CR) and electronic unit injector (EUI) diesel fuel injection systems. Technician A is incorrect as EHIs are not limited by hard value NOPs (Nozzle Opening Pressures) since they are electronically controlled.

Question 19

Which of the following components in a multi-orifice hydraulic injector is constantly exposed to line pressure?

Accepted Answer

The nozzle pressure chamber in a multi-orifice hydraulic injector is constantly exposed to line pressure. This is because it is designed to hold the fuel at the system pressure before it is injected into the engine's combustion chamber.

Question 20

What is the geometric relationship between the sectional area of the nozzle seat, and that of the nozzle pressure chamber known as?

Accepted Answer

The geometric relationship between the sectional area of the nozzle seat and that of the nozzle pressure chamber is known as the nozzle differential ratio. This ratio is crucial in determining the flow characteristics and performance of the nozzle in various applications, such as in fuel injection systems.

Quiz 21: Injector Nozzles