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HET2 > 204B - Electronically Controlled Fuel Injection Systems > Flashcards

204B - Electronically Controlled Fuel Injection Systems Flashcards

1
Q

What are four common types of electronically controlled fuel systems?

A
  • Electronic Unit Injector (EUI)
  • Hydraulic Electronic Unit Injector (HEUI)
  • High pressure common rail (HOCR)
  • Electronic unit pump (EUP)

204B pg. 1

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2
Q

Who introduced the electronic unit injector (EUI) as one of the first fuel systems with full electronic control of the metering and timing processes?

A

Detroit Diesel in 1985

204B pg. 2

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3
Q

What is the purpose of the fuel transfer system in a EUI system?

A

Supply fuel to the injectors that is:
- Clean
- Cooled
- De-aerated
- Correct volume
- Correct pressure (approx. 65psi)

204B pg. 4

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4
Q

What components typically make up an EUI fuel transfer system?

A
  • Fuel tank
  • Fuel filters
  • Transfer pump
  • Pressure regulator
  • Connecting fuel lines
  • ECM cooling plate

204B pg. 4

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5
Q

How are EUI injectors mechanically actuated?

A

By the engine’s camshaft

204B pg. 6

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6
Q

The poppet valve in an EUI injector is opened by _________ and closed by ______.

A
  • Opened by spring tension
  • Closed by the magnetic field

Controls the flow of fuel for BOI & EOI

204B pg. 7

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7
Q

In an EUI injector, the rocker arm presses against the _______ which pushes on the ________ which is guided by the ______ with extremely small clearances.

A

Rocker arm presses against the tappet
Tappet pushes down on the plunger
Plunger is guided by the barrel

204B pg. 7

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8
Q

The EUI injector is ________ actuated and ________ controlled.

A
  • Mechanically actuated
  • Electronically controlled
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9
Q

What are the four stages of of an EUI injector process?

A
  • Pre-injection
  • Injection
  • End of injection
  • Fill

204B pg. 8

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10
Q

What is the path of fuel in an EUI pre-injection stage?

A

As the plunger begins its downward stroke, fuel is forced out of the injector by the plunger and back into the fuel supply passage.

Solenoid is de-energized
Poppet valve is open

204B pg. 8

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11
Q

What determines beginning of injection in an EUI system?

A

When the solenoid energizes and the poppet valve closes.

204B pg. 9

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12
Q

What determines end of injection in an EUI system?

A

When the solenoid de-energizes and the poppet valve opens by spring tension.

204B pg. 10

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13
Q

What controls the rate of injection in an EUI system?

A

Cam lobe design which affects the plunger speed.

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14
Q

What is the main advantage of the HEUI system over the EUI system?

A

HEUI:
- Hydraulically actuated plungers allows for pilot injection and rate shaping
- Rate of injection is electronically controlled

204B pg. 12

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15
Q

HEUI system injectors are _______ actuated and ________ controlled.

A

Hydraulically actuated
Electronically controlled

204B pg. 17

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16
Q

In an HEUI system, what is the role of the Injection Actuation Pressure Control Valve (IAPCV)?

A

Controlled by the ECM to maintain a specific actuation oil pressure from the high-pressure oil pump to the injectors.

Accomplished by varying the oil drain port opening.

204B pg. 15

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17
Q

What design element of the HEUI injector intensifier piston provides the increased injection pressures?

A

The top of the intensifier piston is 6-7 times larger than the plunger. Force multiplication.

204B pg. 18

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18
Q

Is there any movement in the plunger during the HEUI injector pre-injection stage?

A

Nope. At start of plunger movement, pilot injection occurs.

204B pg. 18

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19
Q

In an EUI injector, the plunger is pushed down by the _____.

A

Pushed down by the tappet.

204B pg. 7

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20
Q

What is the approximate cracking pressure of an EUI injector?

A

4500 psi

204B pg. 9

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21
Q

In an EUI system, the ECM determines the quantity of fuel to be injected based on: (4)

A
  • Throttle position
  • Boost pressure
  • Engine speed
  • Engine load

Normally expressed as a pulse width.
Minimal pulse width at idle
Increasing pulse width at increasing speeds

204B pg. 9

22
Q

During an EUI system pre-injection period:

Solenoid is ______
Poppet valve is ______
Fuel flow is ______

A
  • Solenoid is de-energized
  • Poppet valve is closed
  • Fuel flow is out of the injector and back into the fuel supply passage

204B pg. 8

23
Q

During an EUI injection stage:

Solenoid is ______
Poppet valve is ______
Injection nozzle is _______
Fuel flow is ______

A
  • Solenoid is energized
  • Poppet valve is closed
  • Injection nozzle is open
  • Fuel flow is into the cylinder

204B pg. 9

24
Q

During an EUI end of injection (spill) period:

Solenoid is _______
Poppet valve is ______
Injector nozzle is ______
Fuel flow is ______

A
  • Solenoid is de-energized
  • Poppet valve is open
  • Injector nozzle is closed
  • Fuel flow is out of the injector and back into the fuel supply passage

204B pg. 10

25
Q

During an EUI fill period:

Solenoid is _____
Poppet valve is ______
Fuel flow is _______

A
  • Solenoid is de-energized
  • Poppet valve is open
  • Fuel flow is into the injector beneath the plunger

204B pg. 10

26
Q

In an HEUI system, the poppet valve is closed by ________ and opened by __________.

A
  • Closed by spring tension
  • Opened by the solenoid energizing

204B pg. 18

27
Q

What are the five stages of a HEUI injection process?

A
  • Pre-injection
  • Pilot injection
  • Delay period
  • Main injection
  • End of injection

204B pg. 18

28
Q

During the pre-injection stage of a HEUI injector:

Solenoid is _______
Poppet valve is ______
Intensifier piston and plunger are ______
Injection nozzle is ____

A
  • Solenoid is de-energized
  • Poppet valve is closed (downward position)
  • Intensifier piston and plunger are stationary
  • Injection nozzle is closed

204B pg. 18

29
Q

During the pilot injection stage of a HEUI injector:

Solenoid is _______
Poppet valve is ________
Intensifier piston & plunger are ______
Injection nozzle is ______
Pilot injection duration is controlled by______

A
  • Solenoid is energized
  • Poppet valve is open (upward position)
  • Intensifier piston & plunger are moving down
  • Injection nozzle is open

Pilot injection duration is controlled by a groove in the plunger.

204B pg. 19

30
Q

Pilot injection in a HEUI injector is controlled by:

A

A groove in the plunger

204B pg. 19

31
Q

In a HEUI injector, the solenoid energizes to begin the pilot injection. When does the solenoid de-energize?

A

To end the main injection stage

204B pg. 22

32
Q

During the main injection stage of a HEUI injector:

Solenoid is _____
Poppet valve is _____
Intensifier piston & plunger are _____
Injection nozzle is ____

A
  • Solenoid is energized
  • Poppet valve is open (upward position)
  • Intensifier piston & plunger are moving down
  • Injection nozzle is open

204B pg. 20

33
Q

In a HEUI injector, injection ceases for a brief time between the pre-injection and main injection stages. What is this period called and what is taking place?

A

Delay period

A groove on the plunger is aligned with the fuel spill port in the barrel. Fuel pressure drops, nozzle closes, pilot injection ends.

Main injection then begins when the groove passes the spill port, traps and pressurizes the fuel, and nozzle opens.

204B pg. 20

34
Q

What are advantages of having a pilot injection in the combustion process?

A

Helps reduce overall engine noise and emissions.

204B pg. 20

35
Q

During the main injection stage of a HEUI injector, the quantity of fuel delivered is determined by:

A
  • Solenoid on-time
  • Actuation oil pressure

204B pg. 21

36
Q

What is injection rate shaping?

A

The varying injection actuation pressure and injector solenoid on-time controlled by the ECM. Allows manufacturers to reduce emissions and increase engine performance.

204B pg. 21

37
Q

At the end of the main injection stage in a HEUI injector:

Solenoid is ____
Poppet valve is ____
Intensifier piston & plunger _____
Injection nozzle ____

A
  • Solenoid is de-energized
  • Poppet valve is closed (downward position)
  • Intensifier piston & plunger stop moving down
  • Injection nozzle closes

204B pg. 22

38
Q

In a HEUI injector at the end of injection stage, the poppet valve closes the ______ and opens the ______ to allow actuation oil pressure to escape to the crankcase.

A

Poppet valve
- Closes the oil inlet port
- Opens the oil drain port

204B pg. 22

39
Q

What two companies are high pressure common rail (HPCR) systems typically made by?

A
  • Robert Bosch
  • Denso

204B pg. 23

40
Q

Within what range does the IAPCV regulate the injector actuation pressure to?

A

870 - 3500 psi

204B pg. 15

41
Q

What type of high pressure fuel pump is used in a HPCR system?

A

Multi-plunger radial piston

204B pg. 26

42
Q

Fuel pressure in the HPCR system could range from _____ to _____.

A

4000 to 26,000 psi

204B pg. 26

43
Q

Fuel injection pressure in a HPCR system is controlled by the ECM through what valve?

A

Rail pressure control valve.

Part of the high pressure pump. Receives a PWM signal.

204B pg. 27

44
Q

The ECU measures actual rail fuel pressure through what sensor?

A

Rail pressure sensor.

204B pg. 27

45
Q

What material is the high pressure fuel rail made of?

A

Heavy walled steel

204B pg. 27

46
Q

The high pressure fuel rail does not drop in pressure during injection, because the rail acts like an _____.

A

Rail acts like an accumulator, storing a sufficient quantity of fuel.

204B pg. 27

47
Q

What is the pressure limiting valve (safety valve) designed to do in a HPCR system?

A

To protect to system components from excess pressure. Mounted in the end of the high pressure rail opposite the inlet.

Opens if rail pressure exceeds the normal maximum pressure by approximately 2000-3000 psi

204B pg. 27

48
Q

What component is mounted in the end of the high pressure fuel rail to protect the system from excess pressure?

A

Pressure limiting valve.

Opens when rail pressure exceeds the normal max pressure by 2000-3000 psi

204B pg. 27

49
Q

What is the purpose of the flow limiting valve in a HPCR system?

A

Located at each injector outlet on the rail. Designed to prevent over-fuelling of a cylinder in the event of an injector failure.

Calibrated to shut off fuel flow when it exceeds about 1.5 times the normal flow rate.

204B pg. 28

50
Q

A HPCR injector consists of what four main components?

A
  • Injector body
  • Solenoid & controls valve assembly
  • Intermediate valve
  • Needle valve & nozzle assembly

204B pg. 28

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