1 FUEL-INJECTION COMPONENTS and also OPERATION78 FUEL-INJECTION COMPONENTS and OPERATION FUEL-INJECTION COMPONENTS and also OPERATION

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2 Figure usual port fuel-injection system, denote the place of miscellaneous components. An alert that the fuel-pressure regulator is situated on the fuel return side of the system. The computer does not control fuel pressure. Yet does regulate the operation of the electric fuel pump (on many systems) and also the pulsing on and also off of the injectors. Figure common port fuel-injection system, describe the ar of various components. Notice that the fuel-pressure regulator is located on the fuel return side of the system. The computer does not regulate fuel pressure. But does manage the procedure of the electric fuel pump (on most systems) and the pulsing on and also off of the injectors.

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3 Figure 78-2 A dual-nozzle TBI unit ~ above a Chevrolet 4. 3-L V-6 engineFigure A dual-nozzle TBI unit ~ above a Chevrolet 4.3-L V-6 engine. The fuel is squirted over the accelerator plate wherein the fuel mixes v air prior to entering the intake manifold. Number A dual-nozzle TBI unit ~ above a Chevrolet 4.3-L V-6 engine. The fuel is squirted over the throttle plate whereby the fuel mixes through air prior to entering the input manifold.

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4 number A usual port fuel-injection mechanism squirts fuel into the low pressure (vacuum) that the input manifold, around 2 come 3 in. (70 come 100 mm) indigenous the intake valve. Figure A typical port fuel-injection system squirts fuel into the low press (vacuum) that the intake manifold, about 2 to 3 in. (70 to 100 mm) native the intake valve.

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5 technology TIP: “Two Must-Do’s” for long organization life that the fuel system always do the following: 1. Avoid operating the auto on a near-empty tank of fuel. The water or alcohol that may be in the tank becomes much more concentrated when the fuel level is low. Dirt that settles close to the bottom that the fuel tank deserve to be drawn through the fuel system and cause damage to the pump and also injector nozzles. 2. Replace the fuel filter at regular organization intervals. Tech TIP: “Two Must-Do’s” for long company life the the fuel system constantly do the following: 1. Avoid operating the car on a near-empty tank of fuel. The water or alcohol that may be in the tank becomes much more concentrated once the fuel level is low. Dirt that settles near the bottom the the fuel tank have the right to be drawn through the fuel system and also cause damages to the pump and injector nozzles. 2. Change the fuel filter in ~ regular organization intervals.

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6 number The stress and anxiety of the feather in the fuel-pressure regulator determines the operating push on a throttle-body fuel-injection unit. Number The anxiety of the feather in the fuel-pressure regulator identify the operating press on a throttle-body fuel-injection unit.

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7 Figure 78-5 The injectors obtain fuel and also are supported by the fuel rail.

You are watching: Why are some fuel rails rectangular in shape

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8 FREQUENTLY inquiry QUESTION: just how Do the Sensors influence the Pulse WidthFREQUENTLY inquiry QUESTION: how Do the Sensors impact the Pulse Width? The base pulse broad of a fuel-injection mechanism is primarily established by the value of the MAF or MAP sensor and also engine speed (RPM). However, the PCM relies on the entry from numerous other sensors to modify the base pulse width as needed. Because that example, • TP Sensor. This sensor reasons the PCM come command up to 500% (5 times) the base pulse width if the accelerator pedal is depressed promptly to the floor. That can likewise reduce the pulse broad by around 70% if the throttle is quickly closed. • ECT. The value of this sensor determines the temperature of the engine coolant, helps identify the base pulse width, and also can account for up to 60% the the determining determinants ) • BARO. The BARO sensor compensates for altitude and also adds increase to about 10% under high-pressure conditions and subtracts as lot as 50% native the basic pulse width at high altitudes. • IAT. The intake wait temperature is offered to modify the base pulse width based upon the temperature that the wait entering the engine. It is usually qualified of adding as lot as 20% if very cold waiting is beginning the engine or minimize the pulse broad by up to 20% if really hot wait is start the engine. • O2S. This is just one of the key modifiers come the basic pulse width and can add or subtract up to around 20% come 25% or more, depending on the oxygen sensor activity. Generally ASKED QUESTION: how Do the Sensors impact the Pulse Width? The base pulse broad of a fuel-injection system is primarily determined by the worth of the MAF or MAP sensor and also engine rate (RPM). However, the PCM counts on the intake from many other sensors to change the base pulse width together needed. Because that example, • TP Sensor. This sensor reasons the PCM to command up to 500% (5 times) the base pulse broad if the accelerator pedal is depressed rapidly to the floor. It can likewise reduce the pulse width by about 70% if the throttle is rapidly closed. • ECT. The worth of this sensor identify the temperature that the engine coolant, helps identify the basic pulse width, and can account for up to 60% the the determining components ) • BARO. The BARO sensor compensates because that altitude and adds up to around 10% under high-pressure conditions and subtracts as lot as 50% from the base pulse broad at high altitudes. • IAT. The intake wait temperature is used to change the basic pulse width based on the temperature of the wait entering the engine. It is usually capable of including as much as 20% if an extremely cold air is beginning the engine or alleviate the pulse broad by approximately 20% if very hot wait is start the engine. • O2S. This is one of the key modifiers come the basic pulse width and also can add or subtract up to about 20% to 25% or more, relying on the oxygen sensor activity.

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9 generally ASKED QUESTION: How deserve to It Be identified If the Injection mechanism Is Sequential? Look at the shade of the wires in ~ the injectors. If a sequentially fired injector is used, climate one wire color (the pulse wire) will be a different color for every injector. The various other wire is usually the same color since all injectors receive voltage from some source. If a group- or batch-fired injection mechanism is gift used, climate the cable colors will be the very same for the injectors the are group fired. For example, a V-6 group-fired engine will have three injectors with a pink and also blue cable (power and also pulse) and also the various other three will have actually pink and also green wires. Typically ASKED QUESTION: How deserve to It Be identified If the Injection device Is Sequential? Look in ~ the color of the wires in ~ the injectors. If a sequentially fired injector is used, then one wire color (the pulse wire) will certainly be a different color for every injector. The various other wire is normally the exact same color due to the fact that all injectors obtain voltage from part source. If a group- or batch-fired injection mechanism is being used, then the wire colors will certainly be the same for the injectors that are group fired. For example, a V-6 group-fired engine will have actually three injectors through a pink and also blue cable (power and pulse) and also the various other three will have actually pink and green wires.

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10 figure Cross-section that a common port fuel-injection nozzle assembly. This injectors space serviced together an assembly only; no component replacement or company is possible except because that replacement of exterior O-ring seals. Number Cross-section the a common port fuel-injection nozzle assembly. This injectors room serviced as an assembly only; no part replacement or organization is feasible except for replacement of external O-ring seals.

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11 number Port fuel injectors spray atomized fuel right into the entry manifold about 3 customs (75 mm) from the intake valve. Figure Port fuel injectors spray atomized fuel right into the input manifold around 3 inches (75 mm) from the entry valve.

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12 Figure 78-8 A port fuel-injected engine the is equipped through long, tuned input manifold runners.

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13 Figure 78-9 A typical port fuel-injected system showing a vacuum-controlled fuel-pressure regulator.

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14 figure A usual fuel-pressure regulator that has a spring that exerts 46 pounds of force against the fuel. If 20 customs of vacuum space applied above the spring, the vacuum reduces the force exerted through the feather on the fuel, permitting the fuel to go back to the tank at a lower pressure. Figure A common fuel-pressure regulator that has a spring the exerts 46 pounds the force against the fuel. If 20 inches of vacuum are applied above the spring, the vacuum to reduce the force exerted by the feather on the fuel, allowing the fuel to go back to the tank at a reduced pressure.

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15 technology TIP: nothing Forget the Regulator part fuel-pressure regulators save on computer a 10-micron filter. If this filter becomes clogged, a absence of fuel circulation would result. - SEE figure 78–11 . Tech TIP: nothing Forget the Regulator some fuel-pressure regulators save on computer a 10-micron filter. If this filter becomes clogged, a absence of fuel flow would result. - SEE number 78–11 .

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16 number A absence of fuel flow can be due to a restricted fuel-pressure regulator. Notice the fine display screen filter. If this filter were to end up being clogged, greater than common fuel press would occur. Number A absence of fuel flow might be because of a restricted fuel-pressure regulator. Notification the fine screen filter. If this filter were to end up being clogged, greater than typical fuel push would occur.

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17 number The fuel-pressure sensor and fuel-temperature sensor room often built together in one assembly to assist give the PCM the needed data to control the fuel-pump speed. Figure The fuel-pressure sensor and fuel-temperature sensor room often constructed together in one assembly to aid give the PCM the essential data to manage the fuel-pump speed.

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18 Figure 78-13 A mechanically returnless fuel systemFigure A mechanically returnless fuel system. The bypass regulator in the fuel filter controls fuel heat pressure. Number A mechanical returnless fuel system. The bypass regulator in the fuel filter controls fuel line pressure.

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19 number A demand shipment system provides a fuel push regulator attached to the fuel pump assembly. Figure A demand distribution system supplies a fuel pressure regulator attached to the fuel pump assembly.

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20 FREQUENTLY inquiry QUESTION: Why space Some Fuel Rails rectangular ShapedFREQUENTLY request QUESTION: Why room Some Fuel Rails rectangular Shaped? A port fuel-injection system uses a pipe or tubes to supply fuel native the fuel heat to the intended fuel injectors. This pipeline or tube is called the fuel rail. Some automobile manufacturers build the fuel rail in a rectangular crosssection. - SEE number 78–15 . The sides of the fuel rail space able to relocate in and out slightly, thereby acting as a fuel pulsator evening out the press pulses produced by the opening and also closing of the injectors to minimize underhood noise. A ring cross-section fuel rail is not able come deform and, as a result, some manufacturers have had actually to use a different dampener. Frequently ASKED QUESTION: Why are Some Fuel Rails rectangular Shaped? A port fuel-injection system uses a pipeline or tube to provide fuel from the fuel line to the to plan fuel injectors. This pipeline or pipe is called the fuel rail. Some vehicle manufacturers build the fuel rail in a rectangle-shaped crosssection. - SEE number 78–15 . The sides of the fuel rail space able to relocate in and out slightly, thereby acting together a fuel pulsator evening out the press pulses created by the opening and also closing of the injectors to mitigate underhood noise. A round cross-section fuel rail is not able come deform and, as a result, some manufacturers have had actually to usage a separate dampener.

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21 number A rectangular-shaped fuel rail is used to aid dampen fuel system pulsations and also noise resulted in by the injectors opening and closing. Number A rectangular-shaped fuel rail is used to aid dampen fuel mechanism pulsations and also noise brought about by the injectors opening and also closing.

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22 Figure 78-16 A multiport fuel injectorFigure A multiport fuel injector. Notification that the fuel flows right through and also does no come in call with the coil windings. Figure A multiport fuel injector. Notice that the fuel flows right through and does not come in contact with the coil windings.

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23 number Each that the eight injectors displayed are creating a exactly spray pattern because that the applications. While every throttle-body injectors spray a conical pattern, many port fuel injections perform not. Figure Each that the eight injectors presented are creating a exactly spray pattern because that the applications. While all throttle-body injectors spray a conical pattern, most port fuel injections carry out not.

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24 Figure 78-18 A central port fuel-injection system.

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25 number A manufacturing facility replacement unit for a CSFI unit that has individual injectors at the ends that get in the intake manifold rather of poppet valves. Number A manufacturing facility replacement unit because that a CSFI unit that has individual injectors at the end that go into the input manifold rather of poppet valves.

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26 commonly ASKED QUESTION: How can the suitable injector dimension Be Determined? Most people want to increase the output of fuel to rise engine performance. Injector sizing have the right to sometimes be a challenge, especially if the size of injector is not known. In many cases, manufacturers publish the rating of injectors, in pounds of fuel every hour (lb/hr). The rate is figured v the injector organized open in ~ 3 bars (43.5 PSI). Vital consideration is that larger circulation injectors have actually a higher minimum flow rating. Below is a formula to calculation injector sizing when transforming the mechanical features of an engine. Circulation rate = hp X BSFC/# of cylinders X preferably duty bike (% the on-time the the injectors) • hp is the projected horsepower. Be realistic! • BSFC is brake-specific fuel usage in pounds every horsepower-hour. Calculated worths are provided for this, 0.4 come 0.8 lb. In many cases, start on the short side for normally aspirated engines and also the high side for engines with forced induction. • # of cylinders is in reality the number of injectors being used. • best duty bike is taken into consideration at 0.8 (80%). Above this, the injector may overheat, lose consistency, or not job-related at all. For example: 5.7 liter V-8 = 240 hp X 0.65/8 cylinders X 8 = lb/hr injectors require frequently ASKED QUESTION: How have the right to the proper injector size Be Determined? Most human being want to boost the calculation of fuel to boost engine performance. Injector sizing can sometimes it is in a challenge, specifically if the size of injector is not known. In most cases, manufacturers i announced the rating the injectors, in pounds of fuel every hour (lb/hr). The rate is figured v the injector organized open in ~ 3 bars (43.5 PSI). Vital consideration is that larger circulation injectors have a higher minimum circulation rating. Below is a formula to calculation injector sizing when an altering the mechanical attributes of an engine. Circulation rate = hp X BSFC/# the cylinders X maximum duty bike (% of on-time that the injectors) • hp is the projected horsepower. It is in realistic! • BSFC is brake-specific fuel usage in pounds every horsepower-hour. Calculated values are supplied for this, 0.4 come 0.8 lb. In many cases, start on the low side for naturally aspirated engines and the high side because that engines with forced induction. • # of cylinders is in reality the variety of injectors being used. • maximum duty cycle is considered at 0.8 (80%). Above this, the injector might overheat, lose consistency, or not job-related at all. Because that example: 5.7 liter V-8 = 240 hp X 0.65/8 cylinders X 8 = lb/hr injectors call for

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27 FREQUENTLY inquiry QUESTION: What Is Battery Voltage CorrectionFREQUENTLY inquiry QUESTION: What Is Battery Voltage Correction? Battery voltage mediate is a program built into the PCM that causes the injector pulse width to increase if over there is a fall in electrical system voltage. Reduced battery voltage would cause the fuel injectors to open up slower than normal and the fuel pump to run slower. Both the these conditions can cause the engine to operation leaner than regular if the battery voltage is low. Because a skinny air–fuel mixture can reason the engine to overheat, the PCM compensates because that the lower voltage by adding a percent to the injector pulse width. This richer problem will help prevent severe engine damage. The idle rate is likewise increased to turn the alternator faster if short battery voltage is detected. Typically ASKED QUESTION: What Is Battery Voltage Correction? Battery voltage mediate is a program constructed into the PCM that reasons the injector pulse width to rise if over there is a fall in electrical system voltage. Reduced battery voltage would reason the fuel injectors to open slower than normal and also the fuel pump to run slower. Both that these conditions can reason the engine to run leaner than typical if the battery voltage is low. Because a lean air–fuel mixture can reason the engine to overheat, the PCM compensates for the reduced voltage by adding a portion to the injector pulse width. This richer condition will assist prevent major engine damage. The idle speed is additionally increased to rotate the alternator faster if short battery voltage is detected.

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28 number The tiny arrows suggest the wait bypassing the throttle plate in the closed accelerator position. This air is referred to as minimum air. The wait flowing with the IAC (blue arrows) is the air flow that determines the idle speed. Figure The small arrows show the wait bypassing the accelerator plate in the closed throttle position. This air is referred to as minimum air. The air flowing with the IAC (blue arrows) is the airflow that identify the idle speed.

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29 generally ASKED QUESTION: Why walk the Idle Air regulate Valve use Milliamperes? some Chrysler vehicles, such together the evade minivan, use linear solenoid idle air manage valves (LSIAC). The PCM provides regulated current flow with the solenoid to manage idle speed and also the scan tool display screen is in milliamperes (mA). Closed position = 180 to 200 mA Idle = 300 to 450 mA light cruise = 500 to 700 mA completely open = 900 come 950 mA frequently ASKED QUESTION: Why does the Idle Air regulate Valve use Milliamperes? some Chrysler vehicles, such as the evade minivan, use linear solenoid idle air regulate valves (LSIAC). The PCM uses regulated existing flow v the solenoid to regulate idle speed and also the scan tool screen is in milliamperes (mA). Closed position = 180 to 200 mA Idle = 300 come 450 mA irradiate cruise = 500 to 700 mA totally open = 900 to 950 mA

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30 figure Most stepper electric motors use 4 wires, which room pulsed by the computer to turn the armature in steps. Number Most stepper motors use four wires, which space pulsed by the computer system to revolve the armature in steps.

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