FUEL-INJECTION COMPONENTS AND OPERATION 78
Objectives <ul><li>The student should be able to: </li></ul><ul><ul><li>Prepare for ASE Engine Performance (A8) certificat...
Objectives <ul><li>The student should be able to: </li></ul><ul><ul><li>Discuss central port injection (CPI) systems. </li...
ELECTRONIC  FUEL-INJECTION OPERATION
Electronic Fuel-Injection Operation <ul><li>Use powertrain control module (PCM) to control operation of fuel injectors, ot...
Electronic Fuel-Injection Operation <ul><li>Most electronic fuel-injection systems have: </li></ul><ul><ul><li>Electric fu...
Electronic Fuel-Injection Operation <ul><li>Most electronic fuel-injection systems have: </li></ul><ul><ul><li>Fuel-pressu...
Electronic Fuel-Injection Operation <ul><li>Most electronic fuel-injection systems use computer to control: </li></ul><ul>...
Electronic Fuel-Injection Operation <ul><li>Computer-controlled fuel-injection systems normally reliable systems </li></ul...
Electronic Fuel-Injection Operation <ul><li>Two types of electronic fuel-injection systems </li></ul><ul><ul><li>Throttle-...
Electronic Fuel-Injection Operation <ul><li>Two types of electronic fuel-injection systems </li></ul><ul><ul><li>Port fuel...
Electronic Fuel-Injection Operation <ul><li>Two types of electronic fuel-injection systems </li></ul><ul><ul><li>Port fuel...
Figure 78-1   Typical port fuel-injection system, indicating the location of various components. Notice that the fuel-pres...
Figure 78-2   A dual-nozzle TBI unit on a Chevrolet 4.3-L V-6 engine. The fuel is squirted above the throttle plate where ...
Figure 78-3   A typical port fuel-injection system squirts fuel into the low pressure (vacuum) of the intake manifold, abo...
SPEED-DENSITY  FUEL-INJECTION SYSTEMS
Speed-Density Fuel-Injection Systems <ul><li>One of two methods for measuring amount of air engine is breathing in to matc...
Speed-Density Fuel-Injection Systems <ul><li>Computer calculates amount of fuel required by engine from sensor information...
Speed-Density Fuel-Injection Systems <ul><li>Computer calculates amount of fuel required by engine from sensor information...
Speed-Density Fuel-Injection Systems <ul><li>Computer calculates amount of fuel required by engine from sensor information...
Speed-Density Fuel-Injection Systems <ul><li>Computer calculates amount of air in each cylinder from manifold pressure and...
Speed-Density Fuel-Injection Systems <ul><li>Formula to determine injector pulse width (PW) in milliseconds (ms): </li></u...
Speed-Density Fuel-Injection Systems <ul><li>Formula modified by values from other sensors: </li></ul><ul><ul><li>Throttle...
Speed-Density Fuel-Injection Systems <ul><li>Formula modified by values from other sensors: </li></ul><ul><ul><li>Intake a...
Speed-Density Fuel-Injection Systems <ul><li>Formula modified by values from other sensors: </li></ul><ul><ul><li>Adaptive...
MASS AIRFLOW  FUEL-INJECTION SYSTEMS
Mass Airflow Fuel-Injection Systems <ul><li>Formula used by mass airflow fuel-injection systems to calculate injection bas...
Mass Airflow Fuel-Injection Systems <ul><li>Formula modified by values from other sensors: </li></ul><ul><ul><li>Throttle ...
Mass Airflow Fuel-Injection Systems <ul><li>Formula modified by values from other sensors: </li></ul><ul><ul><li>Barometri...
THROTTLE-BODY INJECTION
Throttle-Body Injection <ul><li>Computer controls injector pulses in one of two ways: </li></ul><ul><ul><li>Synchronized <...
Throttle-Body Injection <ul><li>Computer controls injector pulses in one of two ways: </li></ul><ul><ul><li>Nonsynchronize...
Throttle-Body Injection <ul><li>Computer controls injector pulses in one of two ways: </li></ul><ul><ul><li>Injector alway...
Throttle-Body Injection <ul><li>Computer controls injector pulses in one of two ways: </li></ul><ul><ul><li>Amount of fuel...
Throttle-Body Injection <ul><li>Computer controls injector pulses in one of two ways: </li></ul><ul><ul><li>PCM commands v...
Throttle-Body Injection <ul><li>Computer controls injector pulses in one of two ways: </li></ul><ul><ul><li>PCM commands v...
Figure 78-4   The tension of the spring in the fuel-pressure regulator determines the operating pressure on a throttle-bod...
PORT-FUEL INJECTION
Port-Fuel Injection <ul><li>Advantages of port fuel-injection design also related to characteristics of intake manifolds <...
Port-Fuel Injection <ul><li>Advantages of port fuel-injection design also related to characteristics of intake manifolds <...
Port-Fuel Injection <ul><li>EFI injector simply a specialized solenoid </li></ul><ul><li>When solenoid energized, it unsea...
Port-Fuel Injection <ul><li>Systems have injector for each cylinder, but may fire injectors in different ways </li></ul><u...
Port-Fuel Injection <ul><li>Grouped Double-Fire  </li></ul><ul><ul><li>Groups fire alternately </li></ul></ul><ul><ul><ul>...
Port-Fuel Injection <ul><li>Grouped Double-Fire  </li></ul><ul><ul><li>Fuel injected remains near intake valve and enters ...
Port-Fuel Injection <ul><li>Simultaneous Double-Fire </li></ul><ul><ul><li>Fires all injectors at same time once every eng...
Port-Fuel Injection <ul><li>Simultaneous Double-Fire </li></ul><ul><ul><li>Easier for engineers to program system </li></u...
Port-Fuel Injection <ul><li>Sequential </li></ul><ul><ul><li>Sequential firing of injectors according to engine firing ord...
Port-Fuel Injection <ul><li>Sequential </li></ul><ul><ul><li>Also most complex and expensive to design and manufacture </l...
Port-Fuel Injection <ul><li>Sequential </li></ul><ul><ul><li>Mixture never static in intake manifold </li></ul></ul><ul><u...
Port-Fuel Injection <ul><li>Sequential </li></ul><ul><ul><li>Major advantage: intake manifolds only contain air, not air–f...
Figure 78-5   The injectors receive fuel and are supported by the fuel rail.
Figure 78-6   Cross-section of a typical port fuel-injection nozzle assembly. These injectors are serviced as an assembly ...
Figure 78-7   Port fuel injectors spray atomized fuel into the intake manifold about 3 inches (75 mm) from the intake valve.
Figure 78-8   A port fuel-injected engine that is equipped with long, tuned intake manifold runners.
FUEL-PRESSURE REGULATOR
Fuel-Pressure Regulator <ul><li>Typically consists of spring-loaded, diaphragm-operated valve in metal housing </li></ul><...
Fuel-Pressure Regulator <ul><li>For excess fuel (80%–90% of fuel delivered) to return to tank </li></ul><ul><ul><li>Fuel p...
Fuel-Pressure Regulator <ul><li>For excess fuel (80%–90% of fuel delivered) to return to tank </li></ul><ul><ul><li>Happen...
Fuel-Pressure Regulator <ul><li>Regulator shuts off return line when fuel pump not running </li></ul><ul><ul><li>Maintains...
Figure 78-9   A typical port fuel-injected system showing a vacuum-controlled fuel-pressure regulator.
Figure 78-10   A typical fuel-pressure regulator that has a spring that exerts 46 pounds of force against the fuel. If 20 ...
VACUUM-BIASED FUEL-PRESSURE REGULATOR
Vacuum-Biased Fuel-Pressure Regulator <ul><li>Many port fuel-injected systems use vacuum-controlled fuel-pressure regulato...
Vacuum-Biased Fuel-Pressure Regulator <ul><li>Many port fuel-injected systems use vacuum-controlled fuel-pressure regulato...
Vacuum-Biased Fuel-Pressure Regulator
ELECTRONIC RETURNLESS FUEL SYSTEM
Electronic Returnless Fuel System <ul><li>ERFS does not use mechanical valve to regulate rail pressure </li></ul><ul><li>F...
Electronic Returnless Fuel System <ul><li>Transducer sends low-level signal to controller </li></ul><ul><li>Controller cal...
Electronic Returnless Fuel System <ul><li>Power driver contains high-current transistor controlling pump speed using pulse...
Figure 78-12   The fuel-pressure sensor and fuel-temperature sensor are often constructed together in one assembly to help...
MECHANICAL RETURNLESS FUEL SYSTEM
Mechanical Returnless Fuel System <ul><li>First production returnless systems employed MRFS approach </li></ul><ul><li>Has...
Mechanical Returnless Fuel System <ul><li>Fuel sent by in-tank pump to chassis-mounted inline filter </li></ul><ul><li>Exc...
Figure 78-13   A mechanical returnless fuel system. The bypass regulator in the fuel filter controls fuel line pressure.
DEMAND DELIVERY SYSTEM (DDS)
Demand Delivery System (DDS) <ul><li>Combines control attributes of ERFS and cost and reliability attributes of MRFS </li>...
Demand Delivery System (DDS) <ul><li>Mounts at port entry and regulates pressure downstream at injectors </li></ul><ul><li...
Demand Delivery System (DDS) <ul><li>Fuel pump and low-cost, high-performance bypass regulator used within appropriate fue...
Figure 78-14   A demand delivery system uses a fuel pressure regulator attached to the fuel pump assembly.
FUEL INJECTORS
Fuel Injectors <ul><li>EFI systems use 12-volt solenoid-operated injectors </li></ul><ul><li>Injector opens same amount ea...
Fuel Injectors <ul><li>By angling director hole plates, injector sprays fuel more directly at intake valves </li></ul><ul>...
Fuel Injectors <ul><li>Typically top-feed design </li></ul><ul><ul><li>Passes through its entire length to keep it cool be...
Figure 78-16   A multiport fuel injector. Notice that the fuel flows straight through and does not come in contact with th...
Figure 78-17   Each of the eight injectors shown are producing a correct spray pattern for the applications. While all thr...
CENTRAL PORT INJECTION
Central Port Injection <ul><li>CPI cross between port fuel injection and throttle-body injection </li></ul><ul><li>Assembl...
Central Port Injection <ul><li>Central sequential fuel injection (CSFI) has six injectors in place of the one on CPI unit ...
Central Port Injection <ul><li>Eliminates individual fuel rail </li></ul><ul><li>Allows more efficient manifold tuning tha...
Figure 78-18   A central port fuel-injection system.
Figure 78-19   A factory replacement unit for a CSFI unit that has individual injectors at the ends that go into the intak...
FUEL-INJECTION MODES OF OPERATION
Fuel-Injection Modes of Operation <ul><li>All fuel-injection systems designed to supply correct amount of fuel under wide ...
Fuel-Injection Modes of Operation <ul><li>Starting Mode </li></ul><ul><ul><li>When ignition turned to start position, engi...
Fuel-Injection Modes of Operation <ul><li>Starting Mode </li></ul><ul><ul><li>PCM also pulses injectors on, basing pulse w...
Fuel-Injection Modes of Operation <ul><li>Clear Flood Mode </li></ul><ul><ul><li>If engine flooded, driver can depress acc...
Fuel-Injection Modes of Operation <ul><li>Clear Flood Mode </li></ul><ul><ul><li>PCM detects low engine speed and throttle...
Fuel-Injection Modes of Operation <ul><li>Open-Loop Mode </li></ul><ul><ul><li>Occurs during warm-up before oxygen sensor ...
Fuel-Injection Modes of Operation <ul><li>Closed-Loop Mode </li></ul><ul><ul><li>Used to modify base injector pulse width ...
Fuel-Injection Modes of Operation <ul><li>Acceleration Enrichment Mode </li></ul><ul><ul><li>During acceleration, throttle...
Fuel-Injection Modes of Operation <ul><li>Acceleration Enrichment Mode </li></ul><ul><ul><li>PCM supplies longer injector ...
Fuel-Injection Modes of Operation <ul><li>Deceleration Enleanment Mode </li></ul><ul><ul><li>During deceleration, leaner a...
Fuel-Injection Modes of Operation <ul><li>Deceleration Enleanment Mode </li></ul><ul><ul><li>If deceleration rapid, inject...
Fuel-Injection Modes of Operation <ul><li>Fuel Shutoff Mode </li></ul><ul><ul><li>PCM shuts off fuel entirely during rapid...
IDLE CONTROL
Idle Control <ul><li>Port fuel-injection generally uses auxiliary air bypass to control idle speed </li></ul><ul><li>Provi...
Idle Control <ul><li>Needs to overcome increased friction from cold lubricating oil </li></ul><ul><li>System maintains eng...
Idle Control <ul><li>PFI systems use idle air control (IAC) motor to regulate idle bypass air </li></ul><ul><ul><li>Also c...
Figure 78-20   The small arrows indicate the air bypassing the throttle plate in the closed throttle position. This air is...
STEPPER MOTOR OPERATION
Stepper Motor Operation <ul><li>Direct-current motors that move in fixed steps from de-energized (no voltage) to fully ene...
Stepper Motor Operation <ul><li>Controls engine idle speeds and prevents stalls due to changes in engine load </li></ul><u...
Stepper Motor Operation <ul><li>Computer pulses windings and changes their polarity </li></ul><ul><li>Causes armature of m...
Stepper Motor Operation <ul><li>Each 90-degree pulse recorded by computer as a “step” </li></ul><ul><li>Idle airflow in TB...
Figure 78-21   Most stepper motors use four wires, which are pulsed by the computer to rotate the armature in steps.
TECH TIP <ul><li>“ Two Must-Do’s” </li></ul><ul><ul><li>For long service life of the fuel system always do the following: ...
FREQUENTLY ASKED QUESTION <ul><li>How Do the Sensors Affect the Pulse Width? </li></ul><ul><ul><li>The base pulse width of...
FREQUENTLY ASKED QUESTION <ul><li>How Can It Be Determined If the Injection System Is Sequential? </li></ul><ul><ul><li>Lo...
TECH TIP <ul><li>Don’t Forget the Regulator </li></ul><ul><ul><li>Some fuel-pressure regulators contain a 10-micron filter...
FREQUENTLY ASKED QUESTION <ul><li>Why Are Some Fuel Rails Rectangular Shaped? </li></ul><ul><ul><li>A port fuel-injection ...
FREQUENTLY ASKED QUESTION <ul><li>How Can the Proper Injector Size Be Determined? </li></ul><ul><ul><li>Most people want t...
FREQUENTLY ASKED QUESTION <ul><li>What Is Battery Voltage Correction? </li></ul><ul><ul><li>Battery voltage correction is ...
FREQUENTLY ASKED QUESTION <ul><li>Why Does the Idle Air Control Valve Use Milliamperes? </li></ul><ul><ul><li>Some Chrysle...
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Halderman ch078 lecture

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  • Figure 78-1 Typical port fuel-injection system, indicating the location of various components. Notice that the fuel-pressure regulator is located on the fuel return side of the system. The computer does not control fuel pressure. But does control the operation of the electric fuel pump (on most systems) and the pulsing on and off of the injectors.
  • Figure 78-2 A dual-nozzle TBI unit on a Chevrolet 4.3-L V-6 engine. The fuel is squirted above the throttle plate where the fuel mixes with air before entering the intake manifold.
  • Figure 78-3 A typical port fuel-injection system squirts fuel into the low pressure (vacuum) of the intake manifold, about 2 to 3 in. (70 to 100 mm) from the intake valve.
  • Figure 78-4 The tension of the spring in the fuel-pressure regulator determines the operating pressure on a throttle-body fuel-injection unit.
  • Figure 78-5 The injectors receive fuel and are supported by the fuel rail.
  • Figure 78-6 Cross-section of a typical port fuel-injection nozzle assembly. These injectors are serviced as an assembly only; no part replacement or service is possible except for replacement of external O-ring seals.
  • Figure 78-7 Port fuel injectors spray atomized fuel into the intake manifold about 3 inches (75 mm) from the intake valve.
  • Figure 78-8 A port fuel-injected engine that is equipped with long, tuned intake manifold runners.
  • Figure 78-9 A typical port fuel-injected system showing a vacuum-controlled fuel-pressure regulator.
  • Figure 78-10 A typical fuel-pressure regulator that has a spring that exerts 46 pounds of force against the fuel. If 20 inches of vacuum are applied above the spring, the vacuum reduces the force exerted by the spring on the fuel, allowing the fuel to return to the tank at a lower pressure.
  • Figure 78-12 The fuel-pressure sensor and fuel-temperature sensor are often constructed together in one assembly to help give the PCM the needed data to control the fuel-pump speed.
  • Figure 78-13 A mechanical returnless fuel system. The bypass regulator in the fuel filter controls fuel line pressure.
  • Figure 78-14 A demand delivery system uses a fuel pressure regulator attached to the fuel pump assembly.
  • Figure 78-16 A multiport fuel injector. Notice that the fuel flows straight through and does not come in contact with the coil windings.
  • Figure 78-17 Each of the eight injectors shown are producing a correct spray pattern for the applications. While all throttle-body injectors spray a conical pattern, most port fuel injections do not.
  • Figure 78-18 A central port fuel-injection system.
  • Figure 78-19 A factory replacement unit for a CSFI unit that has individual injectors at the ends that go into the intake manifold instead of poppet valves.
  • Figure 78-20 The small arrows indicate the air bypassing the throttle plate in the closed throttle position. This air is called minimum air. The air flowing through the IAC (blue arrows) is the airflow that determines the idle speed.
  • Figure 78-21 Most stepper motors use four wires, which are pulsed by the computer to rotate the armature in steps.
  • Halderman ch078 lecture

    1. 1. FUEL-INJECTION COMPONENTS AND OPERATION 78
    2. 2. Objectives <ul><li>The student should be able to: </li></ul><ul><ul><li>Prepare for ASE Engine Performance (A8) certification test content area “C” (Fuel, Air Induction, and Exhaust Systems Diagnosis and Repair). </li></ul></ul><ul><ul><li>Describe how a port fuel-injection system works. </li></ul></ul><ul><ul><li>Describe the fuel injection modes of operation. </li></ul></ul>
    3. 3. Objectives <ul><li>The student should be able to: </li></ul><ul><ul><li>Discuss central port injection (CPI) systems. </li></ul></ul><ul><ul><li>Explain how a stepper motor works. </li></ul></ul><ul><ul><li>Discuss the purpose and function of the fuel-pressure regulator. </li></ul></ul><ul><ul><li>List the types of fuel-injection systems. </li></ul></ul>
    4. 4. ELECTRONIC FUEL-INJECTION OPERATION
    5. 5. Electronic Fuel-Injection Operation <ul><li>Use powertrain control module (PCM) to control operation of fuel injectors, other functions </li></ul><ul><ul><li>Based on information sent to PCM from various sensors </li></ul></ul>
    6. 6. Electronic Fuel-Injection Operation <ul><li>Most electronic fuel-injection systems have: </li></ul><ul><ul><li>Electric fuel pump (usually located inside fuel tank) </li></ul></ul><ul><ul><li>Fuel-pump relay (usually controlled by the computer) </li></ul></ul>
    7. 7. Electronic Fuel-Injection Operation <ul><li>Most electronic fuel-injection systems have: </li></ul><ul><ul><li>Fuel-pressure regulator (rubber diaphragm maintains proper fuel pressure) </li></ul></ul><ul><ul><li>Fuel-injector nozzle or nozzles </li></ul></ul>
    8. 8. Electronic Fuel-Injection Operation <ul><li>Most electronic fuel-injection systems use computer to control: </li></ul><ul><ul><li>Pulsing fuel injectors on and off </li></ul></ul><ul><ul><li>Operating fuel pump relay circuit </li></ul></ul>
    9. 9. Electronic Fuel-Injection Operation <ul><li>Computer-controlled fuel-injection systems normally reliable systems </li></ul><ul><li>Use gasoline flowing through injectors to lubricate and cool injector electrical windings and pintle valves </li></ul>
    10. 10. Electronic Fuel-Injection Operation <ul><li>Two types of electronic fuel-injection systems </li></ul><ul><ul><li>Throttle-body-injection (TBI) type </li></ul></ul><ul><ul><ul><li>Delivers fuel from nozzle(s) into air above throttle plate </li></ul></ul></ul>
    11. 11. Electronic Fuel-Injection Operation <ul><li>Two types of electronic fuel-injection systems </li></ul><ul><ul><li>Port fuel-injection-type </li></ul></ul><ul><ul><ul><li>Uses nozzle for each cylinder </li></ul></ul></ul>
    12. 12. Electronic Fuel-Injection Operation <ul><li>Two types of electronic fuel-injection systems </li></ul><ul><ul><li>Port fuel-injection-type </li></ul></ul><ul><ul><ul><li>Fuel squirted into intake manifold about 2–3 inches (70–100 mm) from intake valve </li></ul></ul></ul>
    13. 13. Figure 78-1 Typical port fuel-injection system, indicating the location of various components. Notice that the fuel-pressure regulator is located on the fuel return side of the system. The computer does not control fuel pressure. But does control the operation of the electric fuel pump (on most systems) and the pulsing on and off of the injectors.
    14. 14. Figure 78-2 A dual-nozzle TBI unit on a Chevrolet 4.3-L V-6 engine. The fuel is squirted above the throttle plate where the fuel mixes with air before entering the intake manifold.
    15. 15. Figure 78-3 A typical port fuel-injection system squirts fuel into the low pressure (vacuum) of the intake manifold, about 2 to 3 in. (70 to 100 mm) from the intake valve.
    16. 16. SPEED-DENSITY FUEL-INJECTION SYSTEMS
    17. 17. Speed-Density Fuel-Injection Systems <ul><li>One of two methods for measuring amount of air engine is breathing in to match correct fuel delivery </li></ul><ul><li>Does not require air quantity sensor </li></ul>
    18. 18. Speed-Density Fuel-Injection Systems <ul><li>Computer calculates amount of fuel required by engine from sensor information </li></ul><ul><ul><li>MAP sensor: value of intake (inlet) manifold pressure (vacuum) direct indication of engine load </li></ul></ul>
    19. 19. Speed-Density Fuel-Injection Systems <ul><li>Computer calculates amount of fuel required by engine from sensor information </li></ul><ul><ul><li>TP sensor: position of throttle plate and its rate of change part of equation to calculate proper amount of fuel to inject </li></ul></ul>
    20. 20. Speed-Density Fuel-Injection Systems <ul><li>Computer calculates amount of fuel required by engine from sensor information </li></ul><ul><ul><li>Temperature sensors: engine coolant temperature (ECT) and intake air temperature (IAT) used to calculate air density and engine’s need for fuel </li></ul></ul>
    21. 21. Speed-Density Fuel-Injection Systems <ul><li>Computer calculates amount of air in each cylinder from manifold pressure and engine RPM </li></ul><ul><li>Amount of air in each cylinder major factor in determining amount of fuel needed </li></ul>
    22. 22. Speed-Density Fuel-Injection Systems <ul><li>Formula to determine injector pulse width (PW) in milliseconds (ms): </li></ul><ul><ul><li>Injector pulse width = MAP/BARO × RPM/maximum RPM </li></ul></ul>
    23. 23. Speed-Density Fuel-Injection Systems <ul><li>Formula modified by values from other sensors: </li></ul><ul><ul><li>Throttle position (TP) </li></ul></ul><ul><ul><li>Engine coolant temperature (ECT) </li></ul></ul>
    24. 24. Speed-Density Fuel-Injection Systems <ul><li>Formula modified by values from other sensors: </li></ul><ul><ul><li>Intake air temperature (IAT) </li></ul></ul><ul><ul><li>Oxygen sensor voltage (O2S) </li></ul></ul>
    25. 25. Speed-Density Fuel-Injection Systems <ul><li>Formula modified by values from other sensors: </li></ul><ul><ul><li>Adaptive memory </li></ul></ul><ul><li>Fuel injector delivers atomized fuel into airstream where it is instantly vaporized </li></ul>
    26. 26. MASS AIRFLOW FUEL-INJECTION SYSTEMS
    27. 27. Mass Airflow Fuel-Injection Systems <ul><li>Formula used by mass airflow fuel-injection systems to calculate injection base pulse width: </li></ul><ul><ul><li>Injector pulse width = airflow/RPM </li></ul></ul>
    28. 28. Mass Airflow Fuel-Injection Systems <ul><li>Formula modified by values from other sensors: </li></ul><ul><ul><li>Throttle position </li></ul></ul><ul><ul><li>Engine coolant temperature </li></ul></ul>
    29. 29. Mass Airflow Fuel-Injection Systems <ul><li>Formula modified by values from other sensors: </li></ul><ul><ul><li>Barometric pressure </li></ul></ul><ul><ul><li>Adaptive memory </li></ul></ul>
    30. 30. THROTTLE-BODY INJECTION
    31. 31. Throttle-Body Injection <ul><li>Computer controls injector pulses in one of two ways: </li></ul><ul><ul><li>Synchronized </li></ul></ul><ul><ul><ul><li>Injector pulses once for each distributor reference pulse </li></ul></ul></ul><ul><ul><ul><li>Dual injector system: injectors pulse alternately </li></ul></ul></ul>
    32. 32. Throttle-Body Injection <ul><li>Computer controls injector pulses in one of two ways: </li></ul><ul><ul><li>Nonsynchronized </li></ul></ul><ul><ul><ul><li>Injectors pulsed once during given period </li></ul></ul></ul><ul><ul><ul><li>Completely independent of distributor reference pulses </li></ul></ul></ul>
    33. 33. Throttle-Body Injection <ul><li>Computer controls injector pulses in one of two ways: </li></ul><ul><ul><li>Injector always opens same distance </li></ul></ul><ul><ul><li>Fuel pressure maintained at controlled value by pressure regulator </li></ul></ul>
    34. 34. Throttle-Body Injection <ul><li>Computer controls injector pulses in one of two ways: </li></ul><ul><ul><li>Amount of fuel delivered by injector depends on amount of time (on-time) nozzle is open </li></ul></ul><ul><ul><ul><li>This is injector pulse width—on-time in milliseconds </li></ul></ul></ul>
    35. 35. Throttle-Body Injection <ul><li>Computer controls injector pulses in one of two ways: </li></ul><ul><ul><li>PCM commands variety of pulse widths to supply amount of fuel engine needs </li></ul></ul><ul><ul><ul><li>Long pulse width delivers more fuel </li></ul></ul></ul>
    36. 36. Throttle-Body Injection <ul><li>Computer controls injector pulses in one of two ways: </li></ul><ul><ul><li>PCM commands variety of pulse widths to supply amount of fuel engine needs </li></ul></ul><ul><ul><ul><li>Short pulse width delivers less fuel </li></ul></ul></ul>?
    37. 37. Figure 78-4 The tension of the spring in the fuel-pressure regulator determines the operating pressure on a throttle-body fuel-injection unit.
    38. 38. PORT-FUEL INJECTION
    39. 39. Port-Fuel Injection <ul><li>Advantages of port fuel-injection design also related to characteristics of intake manifolds </li></ul><ul><ul><li>Fuel distribution equal to all cylinders: each cylinder has own injector </li></ul></ul><ul><ul><li>Fuel injected almost directly into combustion chamber </li></ul></ul>
    40. 40. Port-Fuel Injection <ul><li>Advantages of port fuel-injection design also related to characteristics of intake manifolds </li></ul><ul><ul><li>Because manifold does not have to carry fuel to properly position TBI unit, can be shaped and sized to tune intake airflow to achieve specific engine performance characteristics </li></ul></ul>
    41. 41. Port-Fuel Injection <ul><li>EFI injector simply a specialized solenoid </li></ul><ul><li>When solenoid energized, it unseats valve to inject fuel </li></ul><ul><li>EFI systems use spray atomized fuel in timed pulses into manifold or near intake valve </li></ul>
    42. 42. Port-Fuel Injection <ul><li>Systems have injector for each cylinder, but may fire injectors in different ways </li></ul><ul><li>Grouped Double-Fire </li></ul><ul><ul><li>Divides injectors into two equalized groups </li></ul></ul>
    43. 43. Port-Fuel Injection <ul><li>Grouped Double-Fire </li></ul><ul><ul><li>Groups fire alternately </li></ul></ul><ul><ul><ul><li>Once each crankshaft revolution, or twice per four-stroke cycle </li></ul></ul></ul>
    44. 44. Port-Fuel Injection <ul><li>Grouped Double-Fire </li></ul><ul><ul><li>Fuel injected remains near intake valve and enters engine when valve opens </li></ul></ul><ul><ul><li>Sometimes called gang fired </li></ul></ul>
    45. 45. Port-Fuel Injection <ul><li>Simultaneous Double-Fire </li></ul><ul><ul><li>Fires all injectors at same time once every engine revolution </li></ul></ul><ul><ul><li>Many port fuel-injection systems on four-cylinder engines use pattern </li></ul></ul>
    46. 46. Port-Fuel Injection <ul><li>Simultaneous Double-Fire </li></ul><ul><ul><li>Easier for engineers to program system </li></ul></ul><ul><ul><li>Can make relatively quick adjustments in air–fuel ratio </li></ul></ul><ul><ul><li>Still requires intake charge to wait in manifold varying lengths of time </li></ul></ul>
    47. 47. Port-Fuel Injection <ul><li>Sequential </li></ul><ul><ul><li>Sequential firing of injectors according to engine firing order </li></ul></ul><ul><ul><li>Most accurate and desirable method of regulating port fuel injection </li></ul></ul>
    48. 48. Port-Fuel Injection <ul><li>Sequential </li></ul><ul><ul><li>Also most complex and expensive to design and manufacture </li></ul></ul><ul><ul><li>Each cylinder receives one charge every two crankshaft revolutions, just before intake valve opens </li></ul></ul>
    49. 49. Port-Fuel Injection <ul><li>Sequential </li></ul><ul><ul><li>Mixture never static in intake manifold </li></ul></ul><ul><ul><li>Mixture adjustments can be made almost instantaneously </li></ul></ul>
    50. 50. Port-Fuel Injection <ul><li>Sequential </li></ul><ul><ul><li>Major advantage: intake manifolds only contain air, not air–fuel mixture </li></ul></ul><ul><ul><li>Allows long, “tuned” intake-manifold runners </li></ul></ul><ul><ul><ul><li>Helps engine produce increased torque at low engine speeds </li></ul></ul></ul>
    51. 51. Figure 78-5 The injectors receive fuel and are supported by the fuel rail.
    52. 52. Figure 78-6 Cross-section of a typical port fuel-injection nozzle assembly. These injectors are serviced as an assembly only; no part replacement or service is possible except for replacement of external O-ring seals.
    53. 53. Figure 78-7 Port fuel injectors spray atomized fuel into the intake manifold about 3 inches (75 mm) from the intake valve.
    54. 54. Figure 78-8 A port fuel-injected engine that is equipped with long, tuned intake manifold runners.
    55. 55. FUEL-PRESSURE REGULATOR
    56. 56. Fuel-Pressure Regulator <ul><li>Typically consists of spring-loaded, diaphragm-operated valve in metal housing </li></ul><ul><li>Works with fuel pump to maintain required pressure drop at injector tips </li></ul>
    57. 57. Fuel-Pressure Regulator <ul><li>For excess fuel (80%–90% of fuel delivered) to return to tank </li></ul><ul><ul><li>Fuel pressure must overcome spring pressure in diaphragm to uncover return line to tank </li></ul></ul>
    58. 58. Fuel-Pressure Regulator <ul><li>For excess fuel (80%–90% of fuel delivered) to return to tank </li></ul><ul><ul><li>Happens when system pressure exceeds operating requirements </li></ul></ul>
    59. 59. Fuel-Pressure Regulator <ul><li>Regulator shuts off return line when fuel pump not running </li></ul><ul><ul><li>Maintains pressure at injectors for easy restarting and reduces vapor lock </li></ul></ul>?
    60. 60. Figure 78-9 A typical port fuel-injected system showing a vacuum-controlled fuel-pressure regulator.
    61. 61. Figure 78-10 A typical fuel-pressure regulator that has a spring that exerts 46 pounds of force against the fuel. If 20 inches of vacuum are applied above the spring, the vacuum reduces the force exerted by the spring on the fuel, allowing the fuel to return to the tank at a lower pressure.
    62. 62. VACUUM-BIASED FUEL-PRESSURE REGULATOR
    63. 63. Vacuum-Biased Fuel-Pressure Regulator <ul><li>Many port fuel-injected systems use vacuum-controlled fuel-pressure regulator to ensure constant pressure drop across the injectors </li></ul><ul><li>Pressure inside intake manifold changes as load on engine increases </li></ul>
    64. 64. Vacuum-Biased Fuel-Pressure Regulator <ul><li>Many port fuel-injected systems use vacuum-controlled fuel-pressure regulator to ensure constant pressure drop across the injectors </li></ul><ul><li>Pressure inside intake manifold changes as load on engine increases </li></ul>
    65. 65. Vacuum-Biased Fuel-Pressure Regulator
    66. 66. ELECTRONIC RETURNLESS FUEL SYSTEM
    67. 67. Electronic Returnless Fuel System <ul><li>ERFS does not use mechanical valve to regulate rail pressure </li></ul><ul><li>Fuel pressure at rail sensed by pressure transducer </li></ul>
    68. 68. Electronic Returnless Fuel System <ul><li>Transducer sends low-level signal to controller </li></ul><ul><li>Controller calculates a signal to pump power driver </li></ul>
    69. 69. Electronic Returnless Fuel System <ul><li>Power driver contains high-current transistor controlling pump speed using pulse width modulation (PWM) </li></ul><ul><li>System capable of continuously varying rail pressure </li></ul>
    70. 70. Figure 78-12 The fuel-pressure sensor and fuel-temperature sensor are often constructed together in one assembly to help give the PCM the needed data to control the fuel-pump speed.
    71. 71. MECHANICAL RETURNLESS FUEL SYSTEM
    72. 72. Mechanical Returnless Fuel System <ul><li>First production returnless systems employed MRFS approach </li></ul><ul><li>Has bypass regulator to control rail pressure </li></ul><ul><li>Located in close proximity to fuel tank </li></ul>
    73. 73. Mechanical Returnless Fuel System <ul><li>Fuel sent by in-tank pump to chassis-mounted inline filter </li></ul><ul><li>Excess fuel returns to tank through short return line </li></ul><ul><li>System limited to constant rail pressure (CRP) system calibrations </li></ul>
    74. 74. Figure 78-13 A mechanical returnless fuel system. The bypass regulator in the fuel filter controls fuel line pressure.
    75. 75. DEMAND DELIVERY SYSTEM (DDS)
    76. 76. Demand Delivery System (DDS) <ul><li>Combines control attributes of ERFS and cost and reliability attributes of MRFS </li></ul><ul><li>Also addresses pulsation dampening/hammering, fuel transient response </li></ul><ul><li>Different form of demand pressure regulator </li></ul>
    77. 77. Demand Delivery System (DDS) <ul><li>Mounts at port entry and regulates pressure downstream at injectors </li></ul><ul><li>Admits precise quantity of fuel into rail as consumed by engine </li></ul><ul><li>Improves pressure response to flow transients, provides rail pulsation dampening </li></ul>
    78. 78. Demand Delivery System (DDS) <ul><li>Fuel pump and low-cost, high-performance bypass regulator used within appropriate fuel sender </li></ul><ul><li>Pressure control valve (PCV) may also be used </li></ul><ul><ul><li>Can readily reconfigure existing design fuel sender into returnless sender </li></ul></ul>?
    79. 79. Figure 78-14 A demand delivery system uses a fuel pressure regulator attached to the fuel pump assembly.
    80. 80. FUEL INJECTORS
    81. 81. Fuel Injectors <ul><li>EFI systems use 12-volt solenoid-operated injectors </li></ul><ul><li>Injector opens same amount each time solenoid energized </li></ul><ul><ul><li>Amount of fuel injected depends on length of time injector remains open </li></ul></ul>
    82. 82. Fuel Injectors <ul><li>By angling director hole plates, injector sprays fuel more directly at intake valves </li></ul><ul><li>Further atomizes and vaporizes fuel before it enters combustion chamber </li></ul><ul><li>Typically top-feed design </li></ul><ul><ul><li>Fuel enters top of injector </li></ul></ul>
    83. 83. Fuel Injectors <ul><li>Typically top-feed design </li></ul><ul><ul><li>Passes through its entire length to keep it cool before being injected </li></ul></ul>
    84. 84. Figure 78-16 A multiport fuel injector. Notice that the fuel flows straight through and does not come in contact with the coil windings.
    85. 85. Figure 78-17 Each of the eight injectors shown are producing a correct spray pattern for the applications. While all throttle-body injectors spray a conical pattern, most port fuel injections do not.
    86. 86. CENTRAL PORT INJECTION
    87. 87. Central Port Injection <ul><li>CPI cross between port fuel injection and throttle-body injection </li></ul><ul><li>Assembly consists of single fuel injector, pressure regulator, six poppet nozzle assemblies with nozzle tubes </li></ul>
    88. 88. Central Port Injection <ul><li>Central sequential fuel injection (CSFI) has six injectors in place of the one on CPI unit </li></ul><ul><li>Hybrid injection system combines single injector of TBI with equalized fuel distribution of PFI </li></ul>
    89. 89. Central Port Injection <ul><li>Eliminates individual fuel rail </li></ul><ul><li>Allows more efficient manifold tuning than otherwise possible with TBI </li></ul><ul><li>Newer versions use six individual solenoids to fire one for each cylinder </li></ul>? ?
    90. 90. Figure 78-18 A central port fuel-injection system.
    91. 91. Figure 78-19 A factory replacement unit for a CSFI unit that has individual injectors at the ends that go into the intake manifold instead of poppet valves.
    92. 92. FUEL-INJECTION MODES OF OPERATION
    93. 93. Fuel-Injection Modes of Operation <ul><li>All fuel-injection systems designed to supply correct amount of fuel under wide range of engine operating conditions </li></ul>
    94. 94. Fuel-Injection Modes of Operation <ul><li>Starting Mode </li></ul><ul><ul><li>When ignition turned to start position, engine cranks and PCM energizes fuel pump relay </li></ul></ul>
    95. 95. Fuel-Injection Modes of Operation <ul><li>Starting Mode </li></ul><ul><ul><li>PCM also pulses injectors on, basing pulse width on engine speed, engine coolant temperature </li></ul></ul><ul><ul><li>The colder engine is, greater the pulse width </li></ul></ul>
    96. 96. Fuel-Injection Modes of Operation <ul><li>Clear Flood Mode </li></ul><ul><ul><li>If engine flooded, driver can depress accelerator pedal to greater than 80% to enter clear flood mode </li></ul></ul>
    97. 97. Fuel-Injection Modes of Operation <ul><li>Clear Flood Mode </li></ul><ul><ul><li>PCM detects low engine speed and throttle-position sensor voltage high </li></ul></ul><ul><ul><li>Injector pulse width greatly reduced or even shut off entirely </li></ul></ul>
    98. 98. Fuel-Injection Modes of Operation <ul><li>Open-Loop Mode </li></ul><ul><ul><li>Occurs during warm-up before oxygen sensor can supply accurate information to PCM </li></ul></ul><ul><ul><li>PCM determines injector pulse width based on values from MAF, MAP, TP, ECT, IAT sensors </li></ul></ul>
    99. 99. Fuel-Injection Modes of Operation <ul><li>Closed-Loop Mode </li></ul><ul><ul><li>Used to modify base injector pulse width as determined by feedback from oxygen sensor </li></ul></ul>
    100. 100. Fuel-Injection Modes of Operation <ul><li>Acceleration Enrichment Mode </li></ul><ul><ul><li>During acceleration, throttle-position voltage increases </li></ul></ul><ul><ul><li>Indicates richer air–fuel mixture required </li></ul></ul>
    101. 101. Fuel-Injection Modes of Operation <ul><li>Acceleration Enrichment Mode </li></ul><ul><ul><li>PCM supplies longer injector pulse width </li></ul></ul><ul><ul><li>May even supply extra pulses to supply needed fuel for acceleration </li></ul></ul>
    102. 102. Fuel-Injection Modes of Operation <ul><li>Deceleration Enleanment Mode </li></ul><ul><ul><li>During deceleration, leaner air–fuel mixture required </li></ul></ul><ul><ul><li>Helps reduce emissions and prevent deceleration backfire </li></ul></ul>
    103. 103. Fuel-Injection Modes of Operation <ul><li>Deceleration Enleanment Mode </li></ul><ul><ul><li>If deceleration rapid, injector may be shut off entirely and then pulsed on enough to keep engine running </li></ul></ul>
    104. 104. Fuel-Injection Modes of Operation <ul><li>Fuel Shutoff Mode </li></ul><ul><ul><li>PCM shuts off fuel entirely during rapid deceleration </li></ul></ul><ul><ul><li>Also shuts off injector when ignition turned off to prevent engine from continuing to run </li></ul></ul>
    105. 105. IDLE CONTROL
    106. 106. Idle Control <ul><li>Port fuel-injection generally uses auxiliary air bypass to control idle speed </li></ul><ul><li>Provides needed additional airflow and thus more fuel </li></ul><ul><li>Engine needs more power when cold to maintain normal idle speed </li></ul>
    107. 107. Idle Control <ul><li>Needs to overcome increased friction from cold lubricating oil </li></ul><ul><li>System maintains engine idle speed at specified value regardless of engine temperature </li></ul>
    108. 108. Idle Control <ul><li>PFI systems use idle air control (IAC) motor to regulate idle bypass air </li></ul><ul><ul><li>Also called electronic air control (EAC) valve </li></ul></ul>?
    109. 109. Figure 78-20 The small arrows indicate the air bypassing the throttle plate in the closed throttle position. This air is called minimum air. The air flowing through the IAC (blue arrows) is the airflow that determines the idle speed.
    110. 110. STEPPER MOTOR OPERATION
    111. 111. Stepper Motor Operation <ul><li>Direct-current motors that move in fixed steps from de-energized (no voltage) to fully energized (full voltage) </li></ul><ul><li>Often has as many as 120 steps of motion </li></ul><ul><li>Common use as idle air control (IAC) valve </li></ul>
    112. 112. Stepper Motor Operation <ul><li>Controls engine idle speeds and prevents stalls due to changes in engine load </li></ul><ul><li>Typical stepper motor uses permanent magnet and two electromagnets </li></ul><ul><li>Each electromagnetic winding controlled by computer </li></ul>
    113. 113. Stepper Motor Operation <ul><li>Computer pulses windings and changes their polarity </li></ul><ul><li>Causes armature of motor to rotate 90 degrees at a time </li></ul>
    114. 114. Stepper Motor Operation <ul><li>Each 90-degree pulse recorded by computer as a “step” </li></ul><ul><li>Idle airflow in TBI travels through passage around throttle and is controlled by stepper motor </li></ul>
    115. 115. Figure 78-21 Most stepper motors use four wires, which are pulsed by the computer to rotate the armature in steps.
    116. 116. TECH TIP <ul><li>“ Two Must-Do’s” </li></ul><ul><ul><li>For long service life of the fuel system always do the following: </li></ul></ul>BACK TO PRESENTATION <ul><li>Avoid operating the vehicle on a near-empty tank of fuel. The water or alcohol that may be in the tank becomes more concentrated when the fuel level is low. Dirt that settles near the bottom of the fuel tank can be drawn through the fuel system and cause damage to the pump and injector nozzles. </li></ul><ul><li>Replace the fuel filter at regular service intervals. </li></ul>
    117. 117. FREQUENTLY ASKED QUESTION <ul><li>How Do the Sensors Affect the Pulse Width? </li></ul><ul><ul><li>The base pulse width of a fuel-injection system is primarily determined by the value of the MAF or MAP sensor and engine speed (RPM). However, the PCM relies on the input from many other sensors to modify the base pulse width as needed. For example, </li></ul></ul>? BACK TO PRESENTATION <ul><li>TP Sensor . This sensor causes the PCM to command up to 500% (5 times) the base pulse width if the accelerator pedal is depressed rapidly to the floor. It can also reduce the pulse width by about 70% if the throttle is rapidly closed. </li></ul><ul><li>ECT . The value of this sensor determines the temperature of the engine coolant, helps determine the base pulse width, and can account for up to 60% of the determining factors. </li></ul><ul><li>BARO . The BARO sensor compensates for altitude and adds up to about 10% under high-pressure conditions and subtracts as much as 50% from the base pulse width at high altitudes. </li></ul><ul><li>IAT . The intake air temperature is used to modify the base pulse width based on the temperature of the air entering the engine. It is usually capable of adding as much as 20% if very cold air is entering the engine or reduce the pulse width by up to 20% if very hot air is entering the engine. </li></ul><ul><li>O2S . This is one of the main modifiers to the base pulse width and can add or subtract up to about 20% to 25% or more, depending on the oxygen sensor activity. </li></ul>
    118. 118. FREQUENTLY ASKED QUESTION <ul><li>How Can It Be Determined If the Injection System Is Sequential? </li></ul><ul><ul><li>Look at the color of the wires at the injectors. If a sequentially fired injector is used, then one wire color (the pulse wire) will be a different color for each injector. The other wire is usually the same color because all injectors receive voltage from some source. </li></ul></ul>? BACK TO PRESENTATION <ul><li>If a group- or batch-fired injection system is being used, then the wire colors will be the same for the injectors that are group fired. For example, a V-6 group-fired engine will have three injectors with a pink and blue wire (power and pulse) and the other three will have pink and green wires. </li></ul>
    119. 119. TECH TIP <ul><li>Don’t Forget the Regulator </li></ul><ul><ul><li>Some fuel-pressure regulators contain a 10-micron filter. If this filter becomes clogged, a lack of fuel flow would result. </li></ul></ul>BACK TO PRESENTATION <ul><ul><li>Figure 78-11 A lack of fuel flow could be due to a restricted fuel-pressure regulator. Notice the fine screen filter. If this filter were to become clogged, higher than normal fuel pressure would occur. </li></ul></ul>
    120. 120. FREQUENTLY ASKED QUESTION <ul><li>Why Are Some Fuel Rails Rectangular Shaped? </li></ul><ul><ul><li>A port fuel-injection system uses a pipe or tubes to deliver fuel from the fuel line to the intended fuel injectors. This pipe or tube is called the fuel rail. Some vehicle manufacturers construct the fuel rail in a rectangular cross-section. </li></ul></ul>? BACK TO PRESENTATION <ul><li>The sides of the fuel rail are able to move in and out slightly, thereby acting as a fuel pulsator evening out the pressure pulses created by the opening and closing of the injectors to reduce underhood noise. A round cross-section fuel rail is not able to deform and, as a result, some manufacturers have had to use a separate dampener. </li></ul><ul><ul><li>Figure 78-15 A rectangular-shaped fuel rail is used to help dampen fuel system pulsations and noise caused by the injectors opening and closing. </li></ul></ul>
    121. 121. FREQUENTLY ASKED QUESTION <ul><li>How Can the Proper Injector Size Be Determined? </li></ul><ul><ul><li>Most people want to increase the output of fuel to increase engine performance. Injector sizing can sometimes be a challenge, especially if the size of injector is not known. In most cases, manufacturers publish the rating of injectors, in pounds of fuel per hour (lb/hr). </li></ul></ul>? BACK TO PRESENTATION <ul><ul><li>The rate is figured with the injector held open at 3 bars (43.5 PSI). An important consideration is that larger flow injectors have a higher minimum flow rating. Here is a formula to calculate injector sizing when changing the mechanical characteristics of an engine. </li></ul></ul><ul><li>Flow rate = hp × BSFC/# of cylinders × maximum duty cycle (% of on-time of the injectors) </li></ul><ul><li>hp is the projected horsepower. Be realistic! </li></ul><ul><li>BSFC is brake-specific fuel consumption in pounds per horsepower-hour. Calculated values are used for this, 0.4 to 0.8 lb. In most cases, start on the low side for naturally aspirated engines and the high side for engines with forced induction. </li></ul><ul><li># of cylinders is actually the number of injectors being used. </li></ul><ul><li>Maximum duty cycle is considered at 0.8 (80%). Above this, the injector may overheat, lose consistency, or not work at all. </li></ul><ul><li>For example: </li></ul><ul><ul><ul><li>5.7 liter V-8 = 240 hp × 0.65/8 cylinders × 8 = 24.37 lb/hr injectors required </li></ul></ul></ul>
    122. 122. FREQUENTLY ASKED QUESTION <ul><li>What Is Battery Voltage Correction? </li></ul><ul><ul><li>Battery voltage correction is a program built into the PCM that causes the injector pulse width to increase if there is a drop in electrical system voltage. Lower battery voltage would cause the fuel injectors to open slower than normal and the fuel pump to run slower. </li></ul></ul>? <ul><li>Both of these conditions can cause the engine to run leaner than normal if the battery voltage is low. Because a lean air–fuel mixture can cause the engine to overheat, the PCM compensates for the lower voltage by adding a percentage to the injector pulse width. This richer condition will help prevent serious engine damage. The idle speed is also increased to turn the alternator faster if low battery voltage is detected. </li></ul>BACK TO PRESENTATION
    123. 123. FREQUENTLY ASKED QUESTION <ul><li>Why Does the Idle Air Control Valve Use Milliamperes? </li></ul><ul><ul><li>Some Chrysler vehicles, such as the Dodge minivan, use linear solenoid idle air control valves (LSIAC). The PCM uses regulated current flow through the solenoid to control idle speed and the scan tool display is in milliamperes (mA). </li></ul></ul>? BACK TO PRESENTATION <ul><li>Closed position = 180 to 200 mA </li></ul><ul><li>Idle = 300 to 450 mA </li></ul><ul><li>Light cruise = 500 to 700 mA </li></ul><ul><li>Fully open = 900 to 950 mA </li></ul>

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