Engine: Description and Operation
Engine
EXTERNAL VIEW
OVERVIEW
The V8 supercharged petrol engine is a 4.2 liter, 8-cylinder, 90 degrees 'Enclosed' V unit, with 4 valves per cylinder, operated by 2 overhead camshafts per cylinder head. The engine emissions comply with ECD4 (European Commission Directive) legislative requirements and employs catalytic converters, electronic engine management control and positive crankcase ventilation to limit the emission of pollutants. The cooling system is a low volume, high velocity system. The Engine Control Module (ECM) controls the fuel injection system, the ignition system and the electric throttle.
The cylinder block is of aluminum alloy construction with cast iron liners. A cast aluminum bedplate is bolted to the bottom of the block to improve lower structure rigidity. The cylinder heads are cast aluminum with thermo-plastic camshaft covers. The single-piece oil sump is also cast aluminum. The fabricated stainless steel twin skin exhaust manifolds are unique for each cylinder bank. A moulded plastic acoustic cover is fitted over the upper engine to reduce engine-generated noise.
Engine Structure
TECHNICAL FEATURES
The technical features include:
- An 8-cylinder 90-degree 'Enclosed V' configuration liquid cooled aluminum cylinder block with cast iron liners
- Pistons are of open-ended skirt design, with 2 compression rings and a 3-piece oil control ring
- Two aluminum cylinder heads, each incorporating 2 camshafts manufactured in chilled cast iron
- Four valves per cylinder
- Graded valve lifters (shimless)
- Belt driven supercharger
- Top fed, 12-hole fuel injectors
- Engine front cover manufactured from aluminum, accommodating the crankshaft front oil seal
- Primary and secondary chain drive for the camshafts
- An aluminum bedplate
- A cast iron crankshaft
- Fracture-split connecting rods in sintered-forged steel
- A twin multi-V belt, driving the front-end accessories
- Fabricated stainless steel twin skin exhaust manifolds
- An advanced engine management system incorporating electronic throttle control
- Meets with the fault handling requirements, as detailed in the European On-Board Diagnostic (EOBD) III, US Federal OBD and California OBDII legislation.
ENGINE DATA
CYLINDER BLOCK COMPONENTS
Cylinder Block
The cylinder block is an 'Enclosed V' design, which provides an inherently rigid structure with good vibration levels. A low volume coolant jacket improves warm-up times and piston noise levels; the longitudinal flow design of the jacket, with a single cylinder head coolant transfer port in each bank, improves rigidity and head gasket sealing. The right hand cylinder bank is designated as 'A' bank, and the left hand as 'B' bank. The cylinder bores are numbered from 1 to 4, for bank 'A' and 5 to 8 for bank 'B', starting from the front of the engine (for more information refer to the Vehicle Specification Book (VSB)).
Engine Data Locations
Engine data is marked at 3 locations, 2 on the cylinder block (shown) and 1 on the engine front cover, which consists of a label displaying the engine number. Component diameters are represented by alphabetical and numerical codes; keys to the codes are in the Service Repair Procedures (SRP) section of this product.
Piston Cooling Jets
Jets located in the cylinder block provide piston and piston pin lubrication and cooling. These jets spray oil on the underside of the piston.
Lubrication oil is distributed through the cylinder block, via the main oil gallery and channels bored in the block, to all critical moving parts. These channels divert oil to the main and big-end bearings via holes machined into the crankshaft.
Connecting Rods and Pistons
The connecting rods are manufactured from sinter-forged steel and have fracture-split bearing caps. The bearing caps are produced by fracturing the opposing sides of the connecting rod at the bearing horizontal centre line. As well as being easier to manufacture, when reassembled the fractured surfaces interlock to form a strong seamless joint. The cylinder position is marked on adjoining sides of the joint to identify matching connecting rods and bearing caps. The connecting rod bearings are aluminum/tin split plain bearings.
The pistons are of the open-ended skirt design with a dished crown. They are also manufactured from a higher strength aluminum alloy and incorporate a thicker top land to resist the increased thermal and mechanical loads produced by supercharging. Three piston rings, 2 compression and 1 solid oil control ring, are installed on each piston. Each piston is installed on a piston pin located in an bronze bushing in the connecting rod.
Connecting Rod and Piston Installation
The piston grade number is stamped on the crown of the piston and must coincide with that for each cylinder bore. The piston must be assembled in the correct orientation for the designated cylinder bore:
- Bank 'A' - piston grade number and the thick flange of the connecting rod must face the front of the engine
- Bank 'B' - piston grade number and the thin flange of the connecting rod must face the front of the engine
Crankshaft Position Sensor
The CKP sensor is installed at the rear of the sump. It is a variable reluctance sensor that provides an input of engine crankshaft speed and position. For additional information, refer to Electronic Engine Controls Electronic Engine Controls
Knock Sensors
The knock sensors are installed in the cylinder block on the inboard side of each cylinder bank. They are piezo-electric sensors that provide inputs to detect and locate detonation during combustion. For additional information, refer to Electronic Engine Controls Electronic Engine Controls
Starter
The engine starter motor is installed at the rear right side of the engine, at the cylinder block to bedplate split line. For additional information, refer to Starting System Description and Operation
Coolant Drain Plug/Heater
A coolant drain plug is installed on the rear left side of the cylinder block. On vehicles with the cold climate package, the cylinder block heater replaces the drain plug.
On vehicles destined for Canada, the coolant heater is installed during engine manufacture, but for Scandinavian vehicles the heater is supplied in kit form to be installed at the dealership.
Coolant Pump
The coolant pump is installed between the 2 cylinder banks, on the front face of the cylinder block.
Coolant Inlet and Outlet Assembly
To accommodate the installation of the supercharger, the thermostat housing and coolant outlet duct are combined into an aluminum alloy coolant outlet assembly, which is installed between the 2 cylinder banks, immediately above the coolant pump. A hose connects the coolant outlet assembly to a coolant inlet housing attached to the coolant pump intake on the cylinder block. The thermostat controls the flow of coolant through the radiator.
CRANKSHAFT AND SUMP COMPONENTS
Crankshaft and Main Bearings
Six counter-balance weights ensure low vibration levels from the 4 throw, 5 bearing crankshaft. Manufactured in cast iron, the crankshaft also has undercut and rolled fillets for improved strength.
The crankshaft rear oil seal is a press fit in the bedplate to cylinder block interface.
The main bearings are aluminum/tin split plain bearings. An oil groove in the upper half of each bearing transfers the oil into the crankshaft for lubrication of the connecting rod bearings. An aluminum/tin thrust washer is installed each side of the top half of the centre main bearing.
Bedplate
The bedplate is a structural casting bolted to the bottom of the cylinder block to retain the crankshaft. The use of a bedplate further improves rigidity. Iron inserts, cast into the main bearing supports of the bedplate, minimize main bearing clearance changes due to heat expansion.
Two hollow dowels align the bedplate with the cylinder block.
Beads of sealant seal the joint between the bedplate and the cylinder block.
Sump
The aluminum alloy structural sump is bolted to the bedplate. A windage tray attached to the underside of the bedplate isolates the oil pan from the disturbed air produced by the rotation of the crankshaft, to prevent oil aeration and improve oil drainage. A rubber plug at the rear of the structural sump seals the port that provides access to the torque converter securing bolts. The engine oil drain plug is located in the pressed steel oil pan, which attaches to the underside of the aluminum alloy structural sump.
A bead of sealant seals the joint between the structural sump and the bedplate.
Oil Pump
The oil pump is installed on the crankshaft at the front of the engine. The pump outlet port aligns with oil passages in the bedplate (See lubrication section for more information).
Starter Drive Plate
The starter drive plate is attached to the rear of the crankshaft. A timing disc, for the CKP sensor, is spot welded to the front face of the drive plate.
CAMSHAFT TIMING COMPONENTS
Timing Gear
Multiple link primary and single row secondary chains drive the camshafts of each cylinder bank. The primary chains transmit the drive from 2 sprockets on the crankshaft to variable valve timing units on the intake camshafts. The secondary chains transmit the drive from the variable valve-timing units to sprockets on the exhaust camshafts.
A key locates the 2 drive sprockets on the crankshaft. The crankshaft's torsional vibration damper retains the sprockets in position. The variable valve timing units and the exhaust camshaft sprockets are non-interference, non-keyed fits on their respective camshafts; the drive being transmitted by the face to face friction load produced by the valve timing unit/sprocket securing bolt.
Each chain has a hydraulic tensioner operated by engine oil. The primary chains are lubricated via oil squirt tubes located at the front of the engine block near the crankshaft drive sprockets. A jet of oil from the end of each secondary chain tensioner lubricates the secondary chains. The primary chain tensioners act on pivoting flexible tensioner blades. The secondary chain tensioners act directly on the chains. Guide rails are installed on the drive side of the primary chains.
Timing Cover
The aluminum alloy timing cover accommodates the crankshaft front oil seal (a PTFE lip seal). Silicon rubber in-groove gaskets seal the joint between the timing cover and the front face of the engine.
CYLINDER HEAD COMPONENTS
Cylinder Heads
The cylinder heads are unique to each cylinder bank. Deep-seated bolts, to reduce distortion, secure the cylinder heads to the cylinder block. Two hollow dowels align each cylinder head with the cylinder block.
The 14 mm (0.55 in) spark plugs, 1 per cylinder, locate in recesses down the centre line of each cylinder head.
The engine-lifting eyes are bolted to the cylinder heads, 2 on the rear (1 per head) and 1 at the front.
Camshaft Covers
The camshaft covers are manufactured from thermo-plastic. The A bank camshaft cover incorporates an outlet for the part load engine breather and the Pressure Control Valve (PCV). The B bank camshaft cover incorporates an outlet for the full load engine breather and the engine oil filler cap. Identical oil separators are incorporated below the breather outlet in each cover.
Silicon rubber in-groove gaskets seal the joints between the camshaft covers and the cylinder heads. Together with spacers and seals on the camshaft cover fasteners, they also isolate the covers from direct contact with the cylinder heads, to reduce noise.
Cylinder Head Gasket
The multi-layered steel cylinder head gasket has cylinder specific water flow cross-sections for uniform coolant flow.
Camshafts
The camshafts are manufactured in chilled cast iron. Five aluminum alloy caps retain each camshaft. Location numbers, 0 to 4 for the intake camshaft and 5 to 9 for the exhaust camshaft, are marked on the outer faces of the caps.
Sensor Ring
Timing rings for each camshaft position sensor are located at the rear of both intake camshafts. A flat, machined near the front of each camshaft, enables the camshafts to be locked during the valve timing procedure.
Camshaft Position Sensor
The camshaft position sensors are installed in each cylinder head at the rear of the intake camshaft. It is a variable reluctance sensor that provides an input to the ECM regarding the position of the camshaft. For additional information, refer to Electronic Engine Controls Electronic Engine Controls
Inlet and Exhaust Valves
Each cylinder head incorporates dual overhead camshafts operating 4 valves per cylinder via solid shimless valve lifters.
The lightweight valve gear provides good fuel economy and noise levels. Valve head diameters are 31 mm (1.220 in) for the exhaust and 35 mm (1.378 in) for the intake. All valves have 5 mm (0.197 in) diameter stems supported in sintered metal seats and guide inserts. Collets, valve collars and spring seats locate single valve springs on both intake and exhaust valves. Valve stem seals are integrated into the spring seats.
CAUTION: Due to slight variations in length, the valves are not interchangeable between marques (Land Rover, Jaguar and Aston Martin).
Fuel Injectors
Eight, top fed, 12-hole, fuel injectors are installed in the fuel rails and are held in position by spring clips. Two O-rings are installed between the injector mounts of the fuel rails and the related recesses in the intercooler adapters. The injectors are electromagnetic solenoid valves controlled by the ECM. The fuel jets from the injectors are directed onto the back of the intake valves. For additional information, refer to Electronic Engine Controls Electronic Engine Controls
Fuel Rails
The fuel rails are installed on the intercooler adapters. A fuel crossover pipe connects the fuel rails together at the front of the engine.
VARIABLE VALVE TIMING (VVT)
The continuously VVT unit turns the intake camshaft in relation to the primary chain to advance and retard the timing.
The system improves low and high-speed engine performance, engine idle quality and exhaust emission.
The VVT system changes the phasing of the intake valves, relative to the fixed timing of the exhaust valves, to alter:
- the mass of air flow into the engine's cylinders,
- and the engine's torque response and emissions
The VVT unit uses a vane device to control the camshaft angle (refer to VVT operation). The system operates over a range of 48 degrees and is advanced or retarded to the optimum angle within this range.
The ECM controls the VVT, using engine speed and load, and engine oil temperature signals to calculate the appropriate camshaft position. For additional information, refer to Electronic Engine Controls Electronic Engine Controls
The continuous VVT system provides the following advantages:
- Reduces engine emissions and fuel consumption by further optimizing the camshaft timing, this improves the engine's internal exhaust gas re-circulation (EGR) effect over a wider operating range
- Improves full-load torque characteristics as the camshaft timing is optimized at all engine speeds for superior volumetric efficiency
- Improves fuel economy by optimizing torque over the engine's speed range
This system also has the added benefits of operating at a lower oil-pressure and faster response time when compared to a non-VVT system.
Variable Valve Timing (VVT) Operation
The VVT unit is a hydraulic actuator mounted on the end of the intake camshaft, which advances or retards the intake camshaft timing and thereby alters the camshaft to crankshaft phasing. The oil control solenoid, controlled by the ECM, routes oil pressure to either the advance or retard chambers located either side of the 3 vanes interspersed within the machined housing of the unit.
The VVT unit is driven by the primary chain and rotates relative to the exhaust camshaft sprocket. When the ECM requests the camshaft timing to advance, the oil control solenoid is energized moving the shuttle valve to the relevant position to allow engine oil pressure, via a filter, into the VVT unit's advance chambers. When the camshaft timing is requested to retard, the shuttle valve moves position to allow oil pressure to exit the advance chambers, while simultaneously routing the oil pressure into the retard chambers.
When directed by the ECM, the VVT unit will be set to the optimum position between full advance and retard for a particular engine speed and load. This is achieved when the ECM sends the energizing signal to the oil control solenoid until the target position is met. At this point, the energizing signal is reduced to hold the solenoid position, and as a result the position of the shuttle valve. This function is under closed-loop control, where the ECM will assess any decrease in shuttle-valve oil-pressure, via signals from the camshaft position sensor. The ECM will increase the energizing signal, when required, to maintain the shuttle-valve hold position.
Engine oil properties and temperature can affect the ability of the VVT mechanism to follow demand changes to the cam phase angle. At very low oil-temperatures, movement of the VVT mechanism is sluggish due to increased viscosity, and at high oil-temperatures the reduced viscosity may impair operation if the oil pressure is too low. To maintain satisfactory VVT performance, an increased capacity oil pump is installed, plus an engine oil temperature sensor to enable monitoring by the ECM. The VVT system is normally under closed-loop control except in extreme temperature conditions, such as cold starts below 0°C. At extremely high oil temperatures, the ECM may limit the amount of VVT advance to prevent the engine from stalling when returning to idle speed.
The VVT does not operate when engine oil-pressure is below 1 bar (14.5 psi), as there is insufficient pressure to control the phasing. This usually occurs when the engine is shutting-down and the VVT has returned to the retarded position. The stopper pin locks the camshaft to the VVT unit to ensure camshaft stability during the next engine start-up.
SUPERCHARGER
The supercharger is a compressor used to pump air into the cylinders. This increases the concentration of oxygen and fuel in the charge to create a more powerful combustion inside the cylinder. This increases cylinder pressure upon ignition and creates more power.
As the supercharger compresses the air its temperature increases. This raise in air temperature reduces the potential for power gains. By installing intercoolers the air is cooled to overcome this.
The supercharger is an Eaton M112 unit attached to the 3 mounting bosses between the 'V' of the cylinder block. Positive alignment with the drive belt is provided by a dowled mounting bracket. An 8-ribbed belt drives the supercharger, via the crankshaft, at 2.1 engine speed. The maximum pressure increase is approximately 0.8 bar.
On the 4.2L V8 supercharged engine the intake manifold is replaced by:
- A supercharger
- Two intercoolers
- Outlet assembly
- A bypass valve
- A bypass valve actuator
- Two intercooler adapters
The supercharger has a sealed-for-life internal lubrication system.
Intercooler
Each of the 2 intercoolers is a fin and tube air-to-liquid heat exchanger. Two rubber ducts, secured by clamp plates, provide the interfaces between the outlet duct and the intercoolers. After passing through the heat exchanger core, the air flows into individual outlets to the cylinders. At the rear of the B bank intercooler there is a mounting boss for an air intake temperature sensor.
Outlet Assembly
The outlet assembly directs air from the supercharger into the 2 intercoolers. A filler point for the intercooler coolant system is integrated into the front and right side of the outlet duct. A vacuum take-off for the fuel pressure regulator/cruise control system is located on the right side of the outlet assembly. Isolating bolts, to reduce noise, secure the outlet assembly to the supercharger and a rubber gasket seals the supercharger to the outlet assembly throttle body and by-pass valve adapter.
Bypass Valve
The bypass valve attaches to an opening in the induction elbow and controls a bypass flow from the intercoolers back to the inlet side of the supercharger. At closed or partially open throttle settings (i.e. idle and most cruise conditions), the bypass valve is fully open to provide maximum bypass and optimum fuel economy. As the throttle opens, the bypass valve progressively closes to reduce the bypass flow and increase the pressure of air supplied to the engine for optimum power output.
Bypass Valve Actuator
The bypass valve actuator is a diaphragm-operated actuator attached to the valve spindle of the bypass valve. A vacuum pipe connects the actuator to the induction elbow.
Intercooler Adapter
The intercooler adapters provide an interface between the intercoolers and the cylinder heads, and also locate the fuel rails and injectors. One-piece gaskets seal the joints between the intercoolers and the intercooler adapters, and between the intercooler adapters and the cylinder heads.
LUBRICATION SYSTEM
Oil is drawn from the reservoir in the oil pan and pressurized by the oil pump. The output from the oil pump is then filtered, cooled and distributed through internal oil passages.
All moving parts are lubricated by pressure or splash oil. Pressurized oil is also provided for the timing gear chain tensioners and the piston cooling jets.
The oil returns to the oil pan under gravity. Large drain holes through the cylinder heads and cylinder block ensure the quick return of the oil, reducing the volume of oil required and enabling an accurate check of the contents soon after the engine stops.
System replenishment is through the oil filler cap on the 'B' bank camshaft cover.
Oil Pick-up
The fabricated steel oil pick-up is immersed in the oil reservoir to provide a supply to the oil pump during all normal vehicle attitudes. A mesh screen in the inlet prevents debris from entering the oil system.
Oil Pump
The oil pump is installed on the crankshaft at the front of the engine. The pump outlet port aligns with oil passages in the bedplate.
The pumping element is an eccentric rotor, which is directly driven by flats on the crankshaft. An integral pressure relief valve regulates pump outlet pressure at 4.5 bar (65.25 psi).
Oil Filter Assembly
The oil filter is a replaceable cartridge installed on an adapter. An internal bypass facility permits full flow bypass if the filter is blocked.
The oil pressure switch connects a ground input to the instrument cluster when oil pressure is present. The switch operates at a pressure of 0.15 to 0.41 bar (2.2 to 5.9 psi).
Oil temperature is monitored through a Negative Temperature Coefficient (NTC) sensor. The sensor is mounted near to the oil pressure sensor at the front of the engine and locates into the oil filter head assembly.
Oil Level Gage
The oil level gage locates along the left side of the oil pan, supported in a tube installed in the sump. Two holes in the end of the gage indicate the minimum and maximum oil levels. There is a difference of approximately 1.5 liters (1.58 US quart) between the 2 levels.
EXHAUST MANIFOLD
The fabricated stainless steel twin skin exhaust manifolds are unique for each cylinder bank.
Each exhaust manifold assembly includes 2 metal gaskets, located either side of the inner heat shield, 2 heat shields and a connection for the Secondary Air Injection (SAI) system. For additional information, refer to Engine Emission Control Description and Operation
Spacers on the securing bolts allow the manifolds to expand and retract with changes of temperature while maintaining the clamping loads.