Sistema de Admision y Escape C-15

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Producto: TRUCK ENGINE

Modelo: C15 TRUCK ENGINE SDP06265

Configuración: C15 On-highway Engine SDP00001-UP

Operación de SistemasC15 On-Highway EngineNúmero de medio-RENR9813-09 Fecha de publicación -01/09/2009 Fecha de actualización -30/09/2009

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Air Inlet and Exhaust System

SMCS - 1050

The engine components of the air inlet and exhaust system control the quality of air and the amount of air that is available for combustion. The components of the air inlet and exhaust system are the following components:

Air cleaner•

Turbochargers•

Precooler•

Aftercooler (If equipped)•

Cylinder head•

Valves and valve system components•

Piston and cylinder•

Exhaust manifold•

Clean Gas Induction (CGI) cooler•

Diesel Particulate Filter (DPF)•

Valve for the Combustion Air•

Aftertreatment Regeneration Device (ARD)•

The low pressure turbocharger compressor wheel pulls the inlet air through the air cleaner and into the air inlet. The air is compressed by the low pressure turbocharger. Pressurizing the inlet air causes the air to heat up. The pressurized air exits the low pressure turbocharger through the outlet and the air is forced into the inlet of the high pressure turbocharger.

The high pressure turbocharger is used in order to compress the air to a higher pressure. This increase in pressure continues to cause the inlet air's temperature to increase. As the air is

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compressed, the air is forced through the high pressure turbocharger's outlet and into the air lines to the precooler.

The pressurized inlet air is cooled by the precooler prior to being sent to the aftercooler. Theprecooler uses engine coolant to cool the air. Without the precooler, the inlet air would be too hot in order to be cooled sufficiently by the aftercooler. The inlet air then enters aftercooler core. The inlet air is cooled further by transferring heat to the ambient air. The combustion efficiency increases as the temperature of the inlet air decreases. Combustion efficiency helps to provideincreased fuel efficiency and increased horsepower output. The aftercooler core is a separate cooler core that is mounted in front of the engine radiator. The engine fan and the ram effect of the forward motion of the vehicle causes ambient air to move across the core.

Inlet air is forced from the aftercooler into the engine's intake manifold. The air flow from the intake manifold into the cylinders and out of the cylinders is controlled by engine's valvemechanisms.

Each cylinder has two inlet valves and two exhaust valves that are mounted in the cylinder head. The inlet valves open when the piston moves downward on the inlet stroke. When the inlet valves open, cooled, compressed air from the intake manifold is pulled into the cylinder. The inlet valves close when the piston begins to move upward on the compression stroke. The air in the cylinder is compressed by the piston. As the air is compressed by the piston, the temperature of the air in the cylinder is heated. Fuel is injected into the cylinder when the piston is near the top of the compression stroke. Combustion begins when the fuel mixes with the hot, pressurized air. The force of combustion pushes the piston downward on the power stroke. The exhaust valves are opened as the piston travels upward to the top of the cylinder. The exhaust gases are pushed through the exhaust port into the exhaust manifold. After the piston completes the exhaust stroke, the exhaust valves close and the cycle begins again.

Exhaust gases from the exhaust manifold flow into the high pressure turbocharger's exhaust inlet. The hot gases that are expelled from the engine are used to turn the turbine wheel of the turbocharger. The turbine wheel drives the compressor wheel that is used in order to compress the inlet air that enters the inlet side of the turbocharger. The exhaust gas exits from the high pressure turbocharger through the high pressure turbocharger's exhaust outlet.

The wastegate is used by the high pressure turbocharger to prevent an overspeed condition of the turbocharger's turbine wheel during engine acceleration. The wastegate also prevents excessive boost of the engine during engine acceleration. The wastegate is controlled by the boost pressure that is felt in the air hose assembly that connects the inlet side of the two turbochargers. The wastegate pressure line provides the air pressure to the wastegate's diaphragm. As the diaphragm reacts to high boost pressure, a valve is actuated. The valve allows exhaust gas to bypass the high pressure turbocharger's turbine. This effectively controls the speed of the turbine.

The exhaust gases then enter the exhaust inlet for the low pressure turbocharger. The exhaust gases drive the turbocharger's turbine. This energy is used in order to compress the inlet air in the same manner as the high pressure turbocharger. The exhaust gases then exit the low pressure turbocharger through the exhaust outlet for the low pressure turbocharger. The exhaust gases are then expelled into the vehicle's exhaust system.

Clean Gas Induction (CGI)

The CGI sends hot exhaust gas from the DPF to the CGI cooler. The hot exhaust gas is cooled in the CGI cooler. The now cooled exhaust gas passes through an electronic controlled flapper valve. The electronically controlled flapper valve is hydraulically actuated. The engine is using air from the truck's air filter system when the flapper valve is in the full OFF position. As the flapper valve starts to open the flow of cooled exhaust gas from the CGI cooler mixes with the air flow from the



air filter. As the demand for more cooled exhaust gas increases the flapper valve opens wider. This increases the flow of cooled exhaust gas from the CGI cooler. As the demand for more cooled exhaust gas increases, the demand for air flow from the engine's air filter decreases.

Diesel Particulate Filter (DPF)

The DPF and the Aftertreatment Regeneration Device (ARD) work together in order to reduce particulate emissions. The DPF collects the soot in the exhaust. The process of converting soot into gas is called regeneration. The ARD helps to accomplish this process when regeneration isrequired. Ash from the engine oil is also collected in the DPF.

The DPF filters soot from the exhaust gas. If the temperature that is in the DPF is hot enough, the DPF converts the soot into gas. If the temperature that is in the DPF is not hot enough, the DPF retains the soot. When the soot must be removed from the DPF, the electronic control module will activate the ARD so that the soot can be oxidized into gas. Regeneration will be required more frequently when the engine is operated at extended idle and when the engine is operated in cold conditions. The DPF will need periodic cleaning of the accumulation of ash that occurs from the engine oil.

Valve for Combustion Air

The valve for the combustion air controls the amount of boosted air that is used by the ARD for optimal operation.

Aftertreatment Regeneration Device (ARD)

The temperature of the DPF must be above a particular value in order for regeneration to occur. The exhaust gas provides heat for the regeneration process. There are two types of regeneration:

Passive Regeneration - The engine provides sufficient exhaust gas temperature for regeneration.

Active Regeneration - The engine's duty cycle does not provide sufficient exhaust temperature for passive regeneration. The ARD operates in order to raise the temperature of the exhaust gas. When the regeneration process is complete, the ARD turns off.

Fuel System



Illustration 1

The fuel system schematic with ARD turned off.

ARD fuel enable valve (13) is de-energized when the ARD is off. Manifold (2) and pressure sensor (3A) apply to C15 engines. Pressure sensor (3B) applies to C13 engines.

(1) Fuel filter base

(2) Manifold for the fuel pressure sensor on C15 engines

(3A) Fuel pressure sensor on C15 engines

(3B) Fuel pressure sensor on C13 engines

(4) Cylinder head

(5) 1034 kPa (150 psi) regulator

(6) Fuel temperature sensor

(7) Fluid sampling valve



(8) Bypass for hand priming pump (9)

(9) Optional hand priming pump

(10) Secondary fuel filter

(11) Air purge screw


(13) ARD fuel enable valve


(15) Return check valve

(16) Fuel transfer pump


(18) ARD fuel manifold

(19) Pilot fuel control solenoid

(20) Pilot fuel pressure sensor

(21) Manifold for the lines to the ARD

(22) Wire mesh filter

(23) ARD head

(24) Main fuel control solenoid

(25) Main fuel pressure sensor


(27) ARD purge air pump

(28) 40 micron filter

(29) Check valve

(30) Cleaning port

(31) Line for the purge air to the ARD head


(33) Primary fuel filter

(34) Fuel tank

The fuel system provides the engine and the Aftertreatment Regeneration Device (ARD) with pressurized fuel. The cylinder head requires a fuel pressure of approximately 552 kPa (80 psi). The ARD requires a maximum fuel pressure of approximately 1586 kPa (230 psi). This procedure verifies that the fuel system can provide adequate fuel pressure for the cylinder head and for the ARD.

The fuel system has two possible configurations. The following information describes each configuration.



Fuel Supply

Refer to Illustration 1. The vehicle's fuel tank (34) provides fuel for cylinder head (4) and ARD head (23). Primary fuel filter (33) is a ten micron filter. All of the fuel for the cylinder head and for the ARD passes through the primary fuel filter. Fuel transfer pump (16) pressurizes the fuel. The fuel transfer pump contains a pressure regulator (17) that limits the pump's output pressure toapproximately 2068 kPa (300 psi). Pressure regulator (17) is nonserviceable.

Fuel filter base (1) provides mounting locations for several components. Passages inside the fuel filter base route the fuel between the components.

Optional hand priming pump (9) provides a means for removing air from the system. Bypass (8) ensures that the hand priming pump pulls fuel from the dirty side of secondary fuel filter (10). Air purge screw (11) allows air to be removed from the system during priming.

Fluid sampling valve (7) provides a port for taking fuel samples. Secondary fuel filter (10) is a two micron filter. All of the fuel for the cylinder head passes through the secondary fuel filter.

Fuel pressure sensor (3A) or (3B) sends a signal to the ECM. The signal indicates the fuel pressure inside the cylinder head. Fuel temperature sensor (6) provides a signal to the ECM. The signal indicates the temperature of the fuel for the cylinder head.

The operation of the system with ARD turned Off

Refer to Illustration 1. ARD fuel enable valve (13) is controlled by the ECM. The valve is de-energized when the ARD is off. 1103 kPa (160 psi) regulator (5) is bypassed by the ARD fuel enable valve.

The fuel transfer pump develops a maximum pressure of approximately 552 kPa (80 psi). This pressure is regulated by 517 kPa (75 psi) regulator (12). Fuel at approximately 552 kPa (80 psi) is supplied to the cylinder head. 689 kPa (100 psi) regulator (14) provides a return path for the fuel to the fuel tank (34) if secondary fuel filter (10) becomes restricted.

Operation with the ARD turned On



Illustration 2

The schematic for the fuel system with the ARD turned on.

ARD fuel enable valve (13) is energized when the ARD is on. Manifold (2) and pressure sensor (3A) apply to C15 engines. Pressure sensor (3B) applies to C13 engines.



(3A) Fuel pressure sensor on C15 engines (If equipped)

(3B) Fuel pressure sensor on C13 engines (If equipped)

(4) Cylinder head





















(23) ARD head






(29) Check valve

(30) Cleaning port




(34) Fuel tank

Refer to Illustration 2. ARD fuel enable valve (13) is energized when the ARD is on. 1034 kPa (150 psi) regulator (5) is now part of the system. The fuel transfer pump develops a maximum pressure of approximately 1586 kPa (230 psi). This pressure is regulated by 1034 kPa (150 psi) regulator (5) and 517 kPa (75 psi) regulator (12) .

This configuration provides fuel at two different pressures. Fuel at approximately 1586 kPa (230 psi) is available for ARD head (23). Fuel at approximately 552 kPa (80 psi) continues to be supplied to cylinder head (4) .



Component Location

Illustration 3 g01376182

Fuel filter base on C13 engines

(3B) Fuel pressure sensor











(35) Fuel outlet line to the cylinder head

(36) Fuel outlet line to the ARD

(37) Fuel supply line from the fuel transfer pump



(38) Fuel return line from the cylinder head

(39) Fuel outlet port to the fuel tank


Fuel filter base on C15 engines

The optional hand priming pump is not shown.










(35) Fuel outlet line to the cylinder head

(36) Fuel outlet line to the ARD

(37) Fuel supply line from the fuel transfer pump



(38) Fuel return line from the cylinder head

(39) Fuel outlet port to the fuel tank


Left side of the C15 engine

(2) Manifold for the fuel pressure sensor

(3A) Fuel pressure sensor

Combustion Air

The system for the combustion air routes pressurized air (boost) from the outlet of theturbocharger to the ARD. The system for the combustion air consists of the following groups:

Sensor group•

Control Group•

Sensor Group

The sensor group consists of these components:

Venturi - The venturi is a restriction in the duct between the air pressure control valve and the head of the ARD. Two pressure taps on the venturi provide connection points for tubing.

Tubing - Tubing connects the venturi's pressure taps to a differential pressure sensor.

Differential Pressure Sensor - The differential pressure sensor produces an electrical signal that indicates the pressure drop across the venturi.



Electrical wiring sends the signals from the sensor to the Engine Control Module (ECM). The ECM uses the signal to determine the amount of combustion air that is flowing to the ARD.

The ECM creates a pulse width modulated signal that indicates the amount of combustion air that is desired. Wiring sends the PWM signal from the ECM to the control group.

Control Group

The control group maintains the ratio of air to fuel. The control group consists of the following components:

Coil - The coil receives the PWM signal from the ECM. The coil creates a magnetic field that is detected by the air pressure control valve.

Air Pressure Control Valve - The air pressure control valve uses pressurized engine oil to convert the coil's magnetic field to movement of a spool. Movement of the spool allows combustion air to flow to the ARD.

During a regeneration, the ECM commands the spool to a position that results in the desired flow of combustion air. The ECM can command the spool to any position between the closed position and the fully open position.

ARD Purge Air

The ARD purge air system produces pressurized air for the ARD. The pressurized air performs the following functions:

Carbon buildup on the nozzle is minimized.•

Residual fuel is removed from the fuel lines for the ARD.•

Cleaner is forced through the nozzle when cleaner is present in the fuel lines for the ARD.•



Illustration 6

Schematic diagram of the ARD purge air system and the fuel system





(4) Cylinder head





















(23) ARD head






(29) Check valve

(30) Cleaning port




(34) Fuel tank

Component Location

Refer to Illustration 7. The ARD purge air system consists of the following components:



Illustration 7

Typical view of the left side of the engine



(29) Check valve

(30) Cleaning port

(31) Line for the air purge to the ARD

(35) Electrical connector for the operating command from the ECM

(36) Electrical connector for the battery power




Typical manifold for the lines to the ARD head


(23) ARD head



ARD Purge Air Pump (27) - The ARD purge air pump receives filtered air from the vehicle's air cleaner. The pump compresses the air. Lines route the air to the ARD head via a filter and a check valve. The pump consists of two parts. One part of the pump contains the electrical components. The other part of the pump contains the moving components. The part that contains the moving components can be serviced separately.

Filter (28) - The 40 micron filter cleans the compressed air.

Check Valve (29) - The check valve allows the purge air to flow to the ARD head. The check valve prevents fuel or cleaner from entering the ARD purge air system.

Operation

The pump operates after the following conditions occur:

The keyswitch is turned On.•

The keyswitch is turned Off during an active regeneration.•



An active regeneration is completed.•

A "loss of combustion" event occurs.•

The ARD fails to ignite.•

The pump receives electrical power from the vehicle's battery. The circuit is protected by a fuse or by a circuit breaker.

The ECM sends a command to the pump. The command turns on the pump. The pump operates attwo speeds. The operating speed is determined by the electronics inside the pump. The sound of the pump will change as the pump operates at the different speeds. This is normal operation.

The pump operates for a period of time that is determined by the flash file in the ECM. The pump turns on and the pump turns off periodically. This is normal operation.

Refer to Illustration 8. The purge process has two parts. The following information describes each part of the purge process.

Purging the Nozzle

The ECM does not energize solenoids (19) and (24) during this part of the purge process. The solenoids are closed.

Pressurized air flows through filter (28) and check valve (29). The pressurized air flows through the nozzle in ARD head (23). The pressurized air cannot flow past de-energized solenoids (19) and (24). The system pressure is approximately 280 kPa (40 psi) during this part of the purgeprocess.

The ECM monitors the signal from pressure sensors (20) and (25) as the nozzle is purged.

Cleaner is introduced into cleaning port (29) in order to clean the nozzle. The cleaner must be introduced for the following reasons:

The ARD purge air system has become inoperative.•

According to the maintenance schedule in the engine's Operation and Maintenance Manual•

Purging Residual Fuel From the Fuel Lines for the ARD

The ECM sends a command to solenoids (19) and (24). The command completely opens the solenoids. This allows fuel and pressurized air to flow through the solenoids. The pressurized air forces residual fuel to return to fuel tank (34) via de-energized ARD fuel enable valve (13). The system pressure is approximately 75 kPa (11 psi) during this part of the purge process.

The ECM de-energizes solenoids (19) and (24) after the residual fuel has returned to the fuel tank. The ECM turns off the ARD purge air pump when the purge process is complete.

The ECM monitors the signal from pressure sensors (20) and (25) as the lines are purged. A code is activated if the following conditions are true:

The pilot pressure is significantly different from the main pressure while the nozzle is being purged.

•



The pilot pressure is approximately equal to the main pressure while the lines are beingpurged.

•

These conditions indicate that one of the check valves inside the ARD head is stuck in the closed position.

Pump Operation During Engine Operation

The pump runs continuously during normal engine operation. This minimizes the buildup of carbon on the nozzle. The pump is turned off during an active regeneration.

Heated Nozzle

There are two nozzles inside the ARD combustion head. The nozzles inject pilot fuel and mainfuel into the ARD for combustion. The nozzles can become plugged with carbon or with debris. The Engine Control Module (ECM) periodically tests the condition of the nozzles.

The ARD combustion head contains an electric heating element. The heating element operates periodically in order to clean the nozzles.



Illustration 9

Schematic diagram of the heated nozzle and the fuel system





(4) Cylinder head





















(23) ARD head





(34) Fuel tank

(37) Nozzle orifice

Component Location

Refer to Illustration 10 and Illustration 11. The system for the heated nozzle consists of the following components.




Left side of the engine

(38) Relay for the electric heating element


ARD combustion head

(39) Electrical connector for the heated nozzle

(40) ARD combustion head with a heated nozzle

(41) Fork bracket for the electrical connector



System Operation for the Electrical Heating Element

Illustration 12

Schematic diagram for the electric heating element

The dashed lines indicate the wiring that is provided by the Original Equipment Manufacturer (OEM).

Refer to Illustration 12. The relay is electronic. The relay contains no moving parts. The relay does not make a clicking noise when the relay is activated and deactivated. The relay is normally deactivated. The deactivated relay creates an open circuit for the electrical power to the heating element. The heating element is off. The ECM periodically activates the output for heater control.The output activates the relay. The activated relay creates a complete path for electrical power to the heating element. The ECM allows the heating element to operate for a programmed period of time. Then, the ECM deactivates the output.

Ignition

The ECM commands the spark plug to fire approximately 12 times each second whenever the keyswitch is ON and the engine speed is greater than 500 rpm.

The spark can be disabled via the "Disable" switch (if equipped) in the cab or by the "ARD Manual Disable Status" parameter on the Caterpillar Electronic Technician (ET). A 3530-31 codeis active when the spark is disabled.

Note: The spark is automatically enabled if the spark has been disabled via Cat ET and power is cycled to the ECM. This only applies if the "Disable" switch is off.



Component Location


Components for the ignition system near the ignition coil

The ignition coil is located near the oil filter.

(42) Harness connector for the ignition transformer

(43) Ground wire from terminal 2 to the engine block

(44) Insulation material for the ignition wire

(45) Engine block ground

(46) Ignition wire

(47) Ground wire between the engine block and the ARD head

(48) Ignition coil




Components for the ignition system near the ignition coil

The ignition coil is located above exhaust manifold (8) .

(44) Insulation material for the ignition wire

(45) Engine block ground

(46) Ignition wire


(48) Ignition coil

(49) Exhaust manifold




Components for the ignition system

(46) Ignition wire


(50) Ground point on the ARD head

(51) Spark plug


Typical ARD head

(51) Spark plug

(52) Spark plug's electrode

(53) Ground probe

Primary Ignition Circuit

The primary ignition circuit consists of the ECM, ignition coil (7), and the wiring between the ECM and the ignition coil. The ignition coil may be located near the oil filter, above the exhaust manifold, or on top of the valve cover.

The ECM creates an ignition pulse signal. The signal is sent to the primary ignition coil.

Secondary Ignition Circuit

The secondary ignition circuit consists of the following components:

Ignition coil (48) •



Ignition wire (46) •

Spark plug (51) •

Ground wire (47)•

Ignition coil (48) converts the ignition pulse signal into a high voltage signal. Ignition wire (46) connects the ignition coil's output to spark plug (51). The spark jumps between the spark plug's electrode (52) and ground probe (53). The spark ignites the air/fuel mixture.

Ground wire (47) ensures that the secondary ignition circuit is complete between the ARD head and the ignition coil. The ground wire runs inside the insulation (44) that is wrapped around ignition wire (46). The ground wire is connected to two ground points. One ground point (50) is on the ARD head. One ground point (45) is on the engine block near the ignition transformer.

Coolant

Two lines circulate coolant in the ARD head. The coolant is used to extend the life of the O-ringfor the ARD nozzle.

Turbochargers


Turbochargers



(54) Wastegate

(55) High pressure turbocharger

(56) Low pressure turbocharger

High pressure turbocharger (55) is mounted to the exhaust manifold of the engine. Low pressure turbocharger (56) is located below the high pressure turbocharger on the engine. The exhaust gas from the low pressure turbocharger is fed into the vehicle's exhaust system. Wastegate (54) is used in order to control the amount of exhaust gas that enters the turbocharger's turbine during engineacceleration.


Typical example of a turbocharger

(57) Air inlet

(58) Compressor housing

(59) Compressor wheel

(60) Bearing

(61) Oil inlet port

(62) Bearing



(63) Turbine housing

(64) Turbine wheel

(65) Exhaust outlet

(66) Oil outlet port

(67) Exhaust inlet

The exhaust gas from the engine enters the turbocharger's turbine housing (63) through exhaust inlet (67). The blades of the turbocharger's turbine wheel (64) are caused to rotate. As the turbine rotates, the exhaust gas flows around the turbine and exits through the turbocharger's exhaust outlet (65). Because the turbocharger's turbine wheel is connected by a shaft to the turbocharger'scompressor wheel (59), the turbine wheel and the compressor wheel are caused to rotate at very high speeds. The rotation of the compressor wheel pulls clean air through air inlet (57) of compressor housing (58). The action of the compressor wheel blades causes a compression of the inlet air. This compression allows a larger amount of air to enter the engine. With more air in the engine, the engine is able to operate more efficiently. The overall effect is an increase in power.

When the load on the engine increases or when a greater engine speed is desired, additional fuel is injected into the cylinders. The increased engine speed creates more exhaust gases. More exhaust gases cause the turbine wheel and the compressor wheel to turn faster. Additional air is forced into the engine as the compressor wheel turns faster. The increased flow of air allows the engine to produce more power. The engine produces more power because the engine is able to burn additional fuel with greater efficiency.


Turbocharger with wastegate

(68) Canister

(69) Actuating lever



The engine does not operate efficiently under conditions of low boost. Low boost is a condition that occurs when the turbocharger produces less than optimum boost pressure. There is a spring that is located inside canister (68). Under low boost, the spring pushes on the diaphragm within the canister. This moves actuating lever (69). The actuating lever closes the wastegate, which will allow the turbocharger to operate at maximum performance.

Under conditions of high boost, the wastegate opens. The open wastegate allows exhaust gases to bypass the turbine side of the turbocharger. When the boost pressure increases against the diaphragm that is in the canister, the wastegate is opened. The rpm of the turbocharger is limited by bypassing a portion of the exhaust gases around the turbine wheel of the turbocharger.

Note: The calibration of the wastegate is preset at the factory. No adjustment can be made to thewastegate.

Bearing (60) and bearing (62) in the turbocharger use engine oil that is under pressure for lubrication. The lubrication oil for the bearings flows through oil inlet port (61) and into the oil cavity in the center section of the turbocharger cartridge. The oil exits the turbocharger through oil outlet port (66). The oil then returns to the engine oil pan through the oil drain line for the turbocharger.

Valves And Valve Mechanism


Valve system components



(70) Rocker arm

(71) Valve adjustment screw

(72) Rocker arm shaft

(73) Camshaft follower

(74) Camshaft

(75) Valve bridge

(76) Valve rotator

(77) Valve spring

(78) Valve

(79) Valve seat

The valve train controls the flow of inlet air into the cylinders and the flow of exhaust gases out of the cylinders during engine operation. Specifically machined lobes on camshaft (74) are used in order to control the following aspects of valve function:

Height of valve lift•

Timing of valve lift•

Duration of valve lift•

The crankshaft gear drives the camshaft gear through the front gear train. The camshaft must betimed to the crankshaft in order to get the correct relation between the piston position and the valve position.

The camshaft has three camshaft lobes for each cylinder. Each cylinder has two inlet valves and two exhaust valves. One camshaft lobe operates both of the inlet valves for each cylinder. One camshaft lobe operates both of the exhaust valves for each cylinder. There is also one camshaft lobe that operates the unit injector for each cylinder. Camshaft follower (73) rolls against the surface of the camshaft lobe. The follower is used in order to transfer the lift that is machined into the camshaft lobe to rocker arm (65) .

The camshaft lobe lifts the camshaft follower of the rocker arm. This actuates valve (78). As the camshaft lobe lifts the follower, the rocker arm pivots at rocker shaft (72). This applies the lifting action to valve bridge (75). The valve bridge is used to transfer the lift from the rocker arm to the valves. Valve adjustment screw (71) is used in order to adjust the valve lash.

Valve springs (77) are used to hold the valves in the closed position when lift is not being transfered from the camshaft lobe. The springs provide the force on the valve in order to ensure that the valves will close at high rpm. The springs also ensure that the valves will remain closed under conditions of high boost pressures.

Valve rotators (76) cause the valves to rotate while the engine is running. The rotation of the valves in the valve seat prevents valve damage by constantly changing the contact area of the valve face and valve seat (79). This rotation gives the valves longer service life.




Front gear train

(80) Timing mark

(81) Camshaft gear

(82) Adjustable idler gear

(83) Idler gear

(84) Timing mark



(85) Cluster gear

(86) Crankshaft gear

The inlet valves and the exhaust valves are opened by the valve mechanism. The inlet valves and the exhaust valves are also closed by the valve mechanism. This occurs as the rotation of the crankshaft causes a relative rotation of the camshaft. Camshaft gear (81) is driven by a series of two idler gears. Adjustable idler gear (82) is driven by idler gear (83). This idler gear is driven by cluster gear (85). The cluster gear is driven by crankshaft gear (86). Timing mark (84) and timing mark (80) are aligned in order to provide the correct relationship between the piston and the valve movement.

The adjustable idler gear is designed to be adjusted so that backlash can be adjusted for the front gear train. The backlash adjustment is made between the idler gear and camshaft gear. If the cylinder head is removed, tolerances of the components will change. The components that change are the cylinder head and the head gasket. The adjustable idler gear must be relocated in order to maintain the correct backlash setting. For information on setting the timing gear backlash, refer to Testing and Adjusting, "Gear Group (Front) - Time".

The camshaft drive gear has integral pendulum rollers that act as a vibration damper for the front gear group. These thrust rollers are designed to counteract the torsional forces from the injector pulses. This eliminates vibration and noise. The engine also runs smoother at all operating speeds.

Variable Valve Actuator

The Intake Valve Actuation system (IVA) uses pressurized engine oil to delay the closing of the intake valves. The system is controlled by the Engine Control Module (ECM). The system contains the following components:

Check Valve (89) - Pressurized engine oil flows to a rail inside the valve cover base. A check valve prevents oil from flowing from the rail back to the main oil gallery.

Pressure Sensor (88) - A pressure sensor is threaded into the rail. The sensor converts the rail pressure into an electrical signal. The ECM monitors the signal in order to determine the pressure of the oil in the rail.

Control Valve (87) - A control valve is threaded into the rail. The control valve contains a coil and a cartridge assembly. The cartridge assembly contains a spool. The spool is normally closed. When the spool is closed, the oil is contained in the rail. The ECM sends a signal to the coil inorder to fully open the spool. The oil is released into the space underneath the valve cover and the rail pressure is reduced.

Actuator (90) - The actuators are located under the valve covers. Pressurized engine oil flows from the rail to each actuator. The actuators use the pressurized engine oil and electrical commands from the ECM in order to delay the closing of the intake valves.



Illustration 22

Component location on a typical C13 engine

(87) Control valve

(88) Pressure sensor

(89) Check valve

(90) Actuators

Illustration 23

Component location on a typical C15 engine

(87) Control valve



(88) Pressure sensor

(89) Check valve

(90) Actuators

System Operation During Engine Start

The ECM performs the following sequence of operations when the engine is started:

The ECM commands the control valve to open for 17 seconds.•

The ECM checks the temperature of the coolant.•

The ECM commands the control valve to close when the coolant temperature exceeds 20 °C (68 °F). This allows the temperature of the oil in the rail to warm up.

•

The ECM commands the control valve to open. The ECM samples the rail pressure. The ECM commands the control valve to close. The ECM takes a second sample of the rail pressure. The ECM compares the two pressure values. The ECM activates a code if the pressure difference is too low.

•

The control valve should remain closed during engine operation.•

System Operation During Engine Operation

The system does not operate until the engine has reached normal operating temperature.




Section view of the components

(90) Actuator

(91) Space

(92) Solenoid

(93) Piston

(94) Rocker arm

(95) Valve

(96) Rail

(97) Intake valves

Each actuator (90) contains two solenoids (92). Each solenoid is connected to a valve (95). The solenoid is normally de-energized. The valve is normally open. This allows oil to flow between rail (96) and the space (91) above piston (93) .

Rocker arm (94) is down when the intake valves are open. Pressurized oil flows from rail (96) to space (91) above piston (93). This causes the piston to move down. The piston contacts rocker arm (94) .



The ECM energizes solenoid (92) when the ECM requires intake valves (97) to remain open. The energized solenoid closes valve (95). This traps the oil in space (91). The trapped oil causes piston (93) and rocker arm (94) to remain down. This keeps intake valves (97) open.

The ECM de-energizes solenoid (91) when the ECM requires the intake valves to close. The de-energized solenoid lifts valve (95). Valve springs (95) raise intake valves (97), rocker arm (94), and piston (93). The piston that is rising forces the oil from space (91) into the rail (96) .

The flow of oil into the rail changes the pressure of the oil in the rail. The ECM monitors the rail pressure. The ECM determines if the changes in rail pressure are correct for the commands that were sent to a particular solenoid. The ECM activates a diagnostic code for the appropriate cylinder if the changes in rail pressure are incorrect for that solenoid.

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Mon May 30 20:02:48 EST 2011



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