Engine: Description and Operation

Engine

EXTERNAL VIEW





INTRODUCTION
The 5.0L NA (naturally aspirated) gasoline engine is a liquid cooled V8 unit featuring direct fuel injection, four overhead camshafts and four valves per cylinder. All four camshafts incorporate VCT (variable camshaft timing). The intake camshafts and valves also incorporate CPS (camshaft profile switching).
The main structural components of the engine are all manufactured from aluminum alloy. The engine is built around a very stiff, lightweight, enclosed V, deep skirt cylinder block. A structural windage tray is bolted to the bottom of the cylinder block to further improve the block stiffness, minimize NVH (noise, vibration and harshness) and help reduce oil foaming. To further enhance the stiffness of the lower engine structure, a heavily ribbed sump is installed. The sump also helps to reduce engine noise.

Engine Structure









CYLINDER BLOCK





The cylinder block is a 90 degree configuration with cast-in iron cylinder liners and an open deck die-cast coolant jacket. The low volume coolant jacket gives good warm-up times and low piston noise levels. The longitudinal flow design of the coolant jacket, with a single cylinder head coolant transfer port in each bank, provides good rigidity and head gasket sealing.

Cylinder Numbering
The cylinders are numbered as shown below, with cylinders 1 and 2 at the front of the engine.





Engine Data Location









Engine data is marked on the cylinder block at the rear of the RH (right-hand) cylinder bank.

CRANKSHAFT





The crankshaft is made from spheroidal graphite cast iron, which, compared with grey cast iron, has higher mechanical strength, ductility and increased shock resistance. The undercut and rolled fillets also improve strength. Eight counter-balance weights ensure low vibration levels and the large, cross-drilled main bearing journals are designed to contribute to stiffness.
An oil groove in the upper half of each main bearing transfers the oil into the crankshaft for lubrication of the connecting rod bearings. A thrust washer is installed each side of the top half of the center main bearing.

Crankshaft Data Location









The main bearings are numbered 1 to 5 starting from the front of the engine. There are five grades of main bearing available, each being color coded. Journal sizes are marked on the rear of the crankshaft. For additional information, refer to Crankshaft Main Bearing Journal Clearance Crankshaft Main Bearing Journal Clearance

Crankshaft Installation









The main bearing caps are made from cast iron and are cross bolted to increase rigidity. An identification mark on the bearing cap faces the front of the engine.
At the front of the crankshaft, a tuned torsional vibration damper is incorporated into the crankshaft front pulley. At the rear of the crankshaft a pressed steel drive plate, with a steel starter ring gear, is installed to transfer drive from the engine to the transmission. The reluctor ring for the CKP (crankshaft position) sensor is integrated into the perimeter of the drive plate.
The crankshaft seals are located in the front and rear covers.

PISTONS AND CONNECTING RODS





The diameter of each piston is graded and precisely matched to each cylinder bore to help reduce noise. In the vertical plane, the pistons have a slight barrel form, which helps to ensure a reliable oil film is maintained between the piston and the cylinder bore. A solid film lubricant coating is applied to both reaction faces of the piston to reduce wear and improve fuel economy.
A three-ring piston-sealing system is used. The steel top ring is treated with a PVD (physical vapor deposition) peripheral coating. PVD is a coating technique where material can be deposited with improved properties to ensure good cylinder bore compatibility and wear resistance. A Napier center ring helps cylinder pressure and oil management, while the three-piece oil control lower ring is produced from nitrided steel.
The connecting rods are forged from high strength steel. The cap is fracture-split from the rod to ensure precision re-assembly for bearing shell alignment. There are three grades of large end bearing available, each being color coded. For additional information, refer to Connecting Rod Large End Bore Connecting Rod Large End Bore

Cap Alignment with Connecting Rod









The correct alignment of the cap with the connecting rod is indicated by marks on adjacent faces of the two components.

Connecting Rod and Piston Orientation









The orientation of the connecting rods and pistons on the crankshaft are given below:
- Bank A - The arrow on the piston crown must face the front of the engine and the cap and connecting rod alignment marks must face the rear of the engine.
- Bank B - The arrow on the piston crown must face the front of the engine and the cap and connecting rod alignment marks must face the front of the engine.

CYLINDER HEADS

NOTE:
RH (right-hand) (A bank) cylinder head shown, LH (left-hand) (B bank) cylinder head similar.





The cylinder heads are manufactured in gravity die cast aluminum alloy and are unique for each cylinder bank. Deep-seated bolts reduce distortion and secure the cylinder heads to the cylinder block.
Each cylinder is served by four valves. To help achieve the required gas-flow characteristics, these are arranged asymmetrically around the cylinder bore. Each cylinder has a centrally mounted fuel injector and spark plug.
The cylinder head gasket is of a multi-layer steel construction.

EXHAUST MANIFOLD

NOTE:
LH (B bank) installation shown, RH (A bank) installation similar.









The high SiMo (silicon molybdenum) cast iron exhaust manifolds are unique for each cylinder bank. Each exhaust manifold installation includes two metal gaskets and two heat shields. Spacers on the securing bolts allow the manifolds to expand and contract with changes of temperature while maintaining the clamping loads.

VALVE TRAIN









Camshafts









The lightweight valve train provides good economy and noise levels and is chain driven from the crankshaft.
Double overhead camshafts on each cylinder head operate the valves. For each cylinder head, an inverted tooth timing chain transfers drive from the crankshaft to the VCT (variable camshaft timing) unit on the front of each camshaft. Graded tappets enable setting of exhaust valve clearances. Switchable tappets with hydraulic lash adjusters are installed on the intake valves.
Each timing chain has a hydraulic tensioner operated by engine oil pressure. The chain tensioners incorporate a ratchet mechanism, which maintains tension while the engine is stopped to eliminate start-up noise. The chains are lubricated with engine oil from jets located at the front of the engine block. Nylon chain guides control chain motion on the drive side.

Variable Camshaft Timing









The VCT (variable camshaft timing) system varies the timing of the intake and exhaust camshafts to deliver optimum engine power, efficiency and emissions. The timing of the intake camshafts has a range of 62 degrees of crankshaft angle. The timing of the exhaust camshafts has a range of 50 degrees of crankshaft angle.
In the base timing position:
- The intake camshafts are fully retarded.
- The exhaust camshafts are fully advanced.





The system consists of a VCT (variable camshaft timing) unit and a VCT (variable camshaft timing) solenoid for each camshaft. The ECM (engine control module) controls the system using PWM (pulse width modulation) signals to the VCT (variable camshaft timing) solenoids.
The torsional energy generated by the valve springs and the inertia of the valve train components are used to operate the system.

Variable Camshaft Timing Units
The VCT (variable camshaft timing) units change the position of the camshafts in relation to the timing chains.









Each VCT (variable camshaft timing) unit is attached to the camshaft by three bolts. A rotor assembly and a reed plate are installed inside a sprocket housing, which consists of a sprocket, an outer plate and an inner plate held together by six screws.
A reluctor ring, for the CMP (camshaft position) sensor, a center plate and a bias spring are installed at the front of the VCT (variable camshaft timing) unit. The ends of the bias spring locate on the center plate assembly and the sprocket housing, to give a turning moment to the camshaft in the advance direction. A snap ring locates the reluctor ring on to a sleeve installed in the center of the rotor assembly. The opposite end of the sleeve locates in a bore in the front face of the camshaft, which contains a filter.
A spring and spool valve are installed in the rotor assembly sleeve and retained by a snap ring. The spring keeps the spool valve in contact with the armature of the related VCT (variable camshaft timing) solenoid.
Each VCT (variable camshaft timing) unit is supplied with engine oil from an oil gallery in the cylinder head, through the camshaft front bearing cap and a bore in the center of the camshaft.

Variable Camshaft Timing Solenoids
The VCT (variable camshaft timing) solenoids control the position of the spool valves in the VCT (variable camshaft timing) units.





The VCT (variable camshaft timing) solenoids are installed in the front upper timing covers, immediately in front of their related VCT (variable camshaft timing) units. Each VCT (variable camshaft timing) solenoid is secured with two screws and sealed with an O-ring. A two pin electrical connector provides the interface with the engine harness.
Each VCT (variable camshaft timing) solenoid incorporates a spindle that acts on the spool valve in the related VCT (variable camshaft timing) unit to advance and retard the camshaft timing. The VCT (variable camshaft timing) solenoids operate independently and are controlled by a PWM (pulse width modulation) signal from the ECM (engine control module).

Variable Camshaft Timing Operation
When the engine is running, the compression and expansion of the valve springs causes momentary increases and decreases in the torque acting on the camshafts. These momentary changes of torque are sensed in the VCT (variable camshaft timing) units and used to change the camshaft timing.

Camshaft Torsional Energy (For a Single Valve Event)









Variable Camshaft Timing Unit Schematic - Base Timing

NOTE:
Intake camshaft VCT (variable camshaft timing) unit shown. For exhaust camshaft VCT (variable camshaft timing) unit, read advance for retard and retard for advance.









NOTE:
The following description is for intake camshaft VCT (variable camshaft timing) units. For exhaust camshaft VCT (variable camshaft timing) units, read advance for retard, and retard for advance.
At engine start-up, once the engine oil pressure in the camshaft is sufficient to open the inlet check valve, engine oil flows across the spool valve, through the advance and retard check valves and into the advance and retard chambers. During the start cycle, the ECM (engine control module) signals the VCT (variable camshaft timing) solenoid to move the spool valve into the sleeve and connect the lock pin to inlet oil pressure. The inlet oil pressure causes the lock pin to retract from the inner plate and unlock the rotor assembly and camshaft from the sprocket housing.
There is a constant supply of oil to the VCT (variable camshaft timing) to ensure the unit remains filled during operation.

Variable Camshaft Timing Unit Schematic - Advance





To advance the camshaft timing, the ECM (engine control module) adjusts the signal to the VCT (variable camshaft timing) solenoid to move the spool valve so that the advance chamber oil passage is closed and the retard chamber oil passage is connected to inlet oil.
Each momentary increase of the torque acting on the camshaft generates a pressure pulse in the retard chamber. Oil moves from the retard chamber, through the spool valve and the advance check valve to the advance chamber, to equalize the pressures in the two chambers. The displacement of oil from the retard chamber causes the rotor assembly to advance in relation to the sprocket housing. Each momentary decrease of torque acting on the camshaft also generates a pressure pulse in the advance chamber, but, with the advance chamber oil passage closed, no movement of oil between the advance and retard chambers occurs and the rotor assembly cannot move in the retard direction.

Variable Camshaft Timing Unit Schematic - Null





Once the camshaft has reached the required timing position the ECM (engine control module) adjusts the signal to the VCT (variable camshaft timing) solenoid to set the spool valve in the null position. In the null position, the advance and retard chamber oil passages are both closed by the spool valve and the rotor assembly is hydraulically locked to the sprocket housing.

Variable Camshaft Timing Unit Schematic - Retard





To retard the camshaft timing, the ECM (engine control module) adjusts the signal to the VCT (variable camshaft timing) solenoid to move the spool valve to close the retard chamber oil passage and connect the advance chamber oil passage to the inlet oil.
Each momentary decrease of the torque acting on the camshaft causes oil to transfer from the advance chamber, through the spool valve and the retard check valve to the retard chamber, and so retard the camshaft timing.

Camshaft Profile Switching





The CPS (camshaft profile switching) system switches the intake valves between two cam profiles which have different lift and period. The low lift profile improves driveability and emissions at lower engine speeds. The high lift profile improves power and torque output at higher engine speeds.
The intake camshafts have three lobes for each valve. The two outer lobes have identical profiles that produce the high lift of 10.53 mm (0.415 in.). The central lobe produces the low lift of 5.50 mm (0.217 in.). Switching between cam profiles is performed by a switchable tappet on each intake valve. The switchable tappets are operated by engine oil controlled by a CPS solenoid on each cylinder head. Operation of the CPS solenoids is controlled by the ECM (engine control module).

Camshaft Profile Switching Solenoids





The CPS solenoids control the supply of engine oil pressure to the locking pins in the switchable tappets, to switch the tappets between the two cam profiles.
A CPS solenoid is installed on the rear of each cylinder block. Each CPS solenoid has a pintle installed in a sleeve, which incorporates oil inlet and outlet holes. The sleeve is installed at the junction of oil galleries in the cylinder head, with the oil inlet and outlet holes aligned with the galleries. Movement of the pintle in the sleeve controls a connection between the oil galleries. When the CPS solenoid is energized, the pintle connects an oil supply gallery to the gallery along the outboard side of the switchable tappets. When the CPS solenoid is de-energized, the oil gallery along the outboard side of the switchable tappets is connected to drain.
The CPS solenoids receive a fused battery supply from the main relay. The ECM (engine control module) switches a ground connection to operate the solenoids.

Switchable Tappets









The switchable tappets are installed on the intake valves, in bores in the cylinder heads. The cylinder heads incorporate engine oil galleries along the inboard and outboard sides of the bores. The inboard oil galleries (between the tappets and the spark plug/fuel injector bores) supply an oil feed to the locking pins in the switchable tappets. The outboard oil galleries (over the inlet ports) supply an oil feed to the hydraulic lash adjusters in the switchable tappets.
Each switchable tappet consists of inner and outer tappets, which can operate independently or be locked together by locking pins. A hydraulic lash adjuster on the bottom of the inner tappet locates on the intake valve stem.
In low lift, the intake valve lift is controlled by the inner tappets, which run on the center lobes of the intake camshafts. The outer tappets run on the outer lobes of the intake camshafts, and move up and down the inner tappets without affecting the valve lift. The lost motion springs keep the outer tappets in contact with the outer lobes. Movement of the inner tappets is transferred to the intake valves through the hydraulic lash adjusters.
In high lift, engine oil is supplied to the locking pins, which lock the outer tappets to the inner tappets. Intake valve lift is controlled by the outer tappets, which run on the outer lobes of the intake camshafts. Movement of the outer tappets is transferred to the intake valves through the locking pins, the inner tappets and the hydraulic lash adjusters.









Camshaft Profile Switching Operation
The switching point is speed and load dependent. This strategy ensures that switching occurs at air flow neutral points in the engine's operation and is imperceptible to the driver.
At engine speeds from idle up to the range of 2825 - 4250 rev/min (depending on engine load), the CPS solenoids are de-energized and the switchable tappets are set to low lift. At engine speeds above the 2825 - 4250 rev/min range, the CPS solenoids are energized by the ECM (engine control module) and the switchable tappets are set to high lift. There is a 200 rev/min hysteresis when switching from high lift to low lift with decreasing engine speed. Switching between lift settings occurs within one revolution of the camshaft.
Switching is only enabled at engine oil temperatures of 20 °C (68 °F) and above. At oil temperatures below 20 °C (68 °F), CPS operation is disabled and the switchable tappets remain in the low lift setting. CPS operation is also disabled if a CPS solenoid fails. When CPS operation is disabled, engine speed is limited to 5000 rev/min.
The ECM (engine control module) can diagnose the operation of the CPS solenoids and store fault related DTC (diagnostic trouble code) if it detects a failure.

LUBRICATION SYSTEM









The oil pump is attached to the underside of the windage tray. The input shaft of the oil pump is driven from the front of the crankshaft, by the auxiliary chain, at 0.87 engine speed.
The oil pump draws oil from the sump through a centrally mounted pick-up pipe. The oil is pressurized and pumped through an output tube to the cylinder block. After passing through an anti-drain valve and a plate type oil cooler, the oil is filtered by a replaceable cartridge installed on the front of the RH (right-hand) cylinder head.
The output from the oil filter is distributed through oil galleries in the cylinder heads and cylinder block. All moving parts are lubricated by pressure or splash oil. Pressurized oil is also provided for the VCT (variable camshaft timing) system, the CPS system, the timing chain tensioners and the timing chain lubrication jets.
The oil returns to the oil pan under gravity. Large drain holes through the cylinder heads and cylinder block ensure the rapid return of the oil to the sump. System replenishment is through the oil filler cap on the LH (left-hand) cylinder head cover.
An oil evacuation tube is installed to allow oil to be drawn from the sump. The upper end of the oil evacuation tube is located under the oil filler cap.
An oil drain plug is installed in the RH (right-hand) side of the sump.





Oil Level Monitoring
Oil level monitoring is provided by an oil level and temperature sensor that measures the oil level in the sump. The oil level can be displayed in the message center of the instrument cluster.

Oil Level and Temperature Sensor





The oil level and temperature sensor supplies the ECM (engine control module) with a signal containing the level and temperature of the oil in the sump. The oil level and temperature sensor is secured to the bottom of the sump with three screws and sealed with a gasket.
The oil level and temperature sensor sends an ultrasonic pulse vertically upward and measures the time taken for the pulse to be reflected back from the top surface of the oil. This time is compared with the time taken for an ultrasonic pulse to travel a reference distance within the oil level and temperature sensor to determine the oil level. The oil level reading is combined with the oil temperature reading and transmitted in a PWM (pulse width modulation) signal to the ECM (engine control module).





Oil Level Check
For additional information, refer to Engine Oil Draining and Filling Engine Oil Draining and Filling
For accuracy, oil level checks should be performed with the vehicle on level ground when the oil is hot. The vehicle needs to stand for approximately 10 minutes, after the engine is switched off, to allow the oil to drain back into the sump and the oil level to stabilize. The oil level system will not give a reading until the oil level has stabilized.
To check the oil level, make sure that the ignition is on, the engine stopped and the transmission is in P (park). Access the vehicle information and settings menu, then select Oil Level Display from the Service Menu. An Engine Oil Level sight glass will be displayed in the message center. The current oil level will be displayed in the sight glass. One of the following messages will also be displayed:
- If the oil level is within acceptable limits, the message Level OK is displayed.
- If the oil level is less than acceptable, a message advising how much oil to add is displayed e.g. Add 1 Litre, or Add 1 Quart, depending on the market.
- If the message Overfilled is displayed, the oil level must be reduced to within acceptable limits before starting the engine again.
- If the message Not available is displayed, the oil level is still stabilizing. Wait 10 minutes and then recheck level.