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Diesel engined cars discussion forum - ALL variants

 
  #21  
Old 10-23-2010, 02:46 PM
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Originally Posted by ronbros View Post
HI , Delta66, tell us about that two turbos diesel ,2.7L?

does it have an intercooler, and what type?

is it common rail FI system?

sounds like a great car,, are any computor remaps available?

what transmissions were available? overall vehicle specs.

gives us something to talk about also!

RON
Ron
Delta66 and I have cars with the same engine, as you can see from my sig its had a remap.Its due to go back to the tuners to get a full out power remap expecting to take the power from a std 207 bhp to 267 bhp and from 321 ibs ft to over 420 lbs ft torque.
Of course having (twin variable vain) turbos they have an intercooler..... much more below on the engine sorry havent time to edit or add the excellent diagrams that go with it
 
  #22  
Old 10-23-2010, 04:39 PM
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Diesel Engine
Having made its debut in the S-TYPE and now introduced in the XJ, the 2.7 liter diesel engine is a V6 configuration with two banks of three cylinders arranged at 60 degrees. Fuel charging is supplied by a next generation common-rail direct injection system, characterized by the use of piezo injectors.
This combined with the air charge system, which utilizes 2 electronically actuated variable vane turbochargers provides an engine of outstanding power, economy and emission
performance.
Delivering premium level refinement was central to the design philosophy of the engine architecture. The engine features were selected and optimized for radiated noise level and noise quality using advanced analytical and measurement techniques. Management of the engine’s noise characteristics has focused particularly on the areas of mechanical noise and the combustion process. The latter has been subject to especially detailed optimization and has benefited from the work carried out on the design of the engine structure.
Further control is achieved with the use of next generation common-rail technology, including pilot injection and closed loop injection control to ensure the quality of combustion is maintained under all operating conditions.
The cylinder block is one of the most significant technical aspects of the engine. Cast in compacted graphite iron (CGI), it will be the first use of this material in volume engine production. As a result, of the outstanding strength and durability of CGI, less material is used in comparison to a conventional cast iron block. This provides reduced weight and length with superior structural capabilities. The engine is the lightest unit of its type, a factor that contributes significantly to the excellent power-to-weight ratio and fuel
economy.
Overall, the result is class leading refinement, with the V6 engine demonstrating impressively low levels of radiated noise in terms of both mechanical and combustion noise.
Environmentally Efficient
The diesel engine was designed from the outset to meet future emissions levels and is further proof of the way in which common-rail direct injection diesels provide an effective
solution for controlling pollutant emissions. The high technology incorporated in this power unit reduces emissions at source through a highly optimized and efficient combustion process, managed by advanced control strategies. Further benefits in reduced emissions have been made through the use of the electronically actuated turbochargers, an exhaust gas recirculation system, port deactivation and the recently

developed diesel particulate filter;
Engine Emission Control
A low, by diesel standards, compression ratio of 17.3:1 contributes to improved emissions quality, quieter combustion and compatibility with the engine’s unique forced induction system. In a diesel engine reduced compression means less heat build up in the piston bowl and more efficient fuel burn resulting in the production of lower levels of pollutants.
The advanced design of the V6 diesel engine complies with European Stage 4 Diesel Emission Legislation.

Engine Specifications
Arrangement and number of cylinders V6
Engine capacity 2720 cm3
Compression ratio 17.3 : 1
Cylinder bore 81 mm
Piston stroke 88 mm
Firing order 1 - 4 - 2 - 5 - 3 - 6
Engine Components
Integrated Valve Cover and Intake Manifold
The integrated valve covers and intake manifolds, which house the port deactivation mechanism.The integrated covers are designed to ensure their surfaces radiate the minimum amount of noise, they are also isolated from the engine structure by use of elastomeric material to reduce the transfer of vibration.
Camshafts
The camshafts are hollow steel tube construction with pressed-on sintered lobes and drive sprockets. The camshaft sprockets and drive chain are marked for timing purposes;
Camshaft Timing
Primary Drive
A single toothed belt provides the primary drive by transferring drive from the crankshaft to the exhaust camshafts. The belt is manufactured from the latest in material technology: k-glass cord and aramid fabric (high-grade rubber and fabric), which
is peroxide cured.
This material provides long-life capability and contributes to the excellent refinement delivered by the drive system.
An hydraulic tensioner automatically adjusts the timing belt

Secondary Drive
Two short crossover chains, which transfer drive from the exhaust camshafts to the intake camshafts, provide the secondary drive. The crossover chains are located at the rear of the right-hand cylinder bank and the front of the left-hand cylinder bank. This allows for a much shorter and simpler route for the primary drive belt. Hydraulic camshaft-drive tensioners provide the adjustment of the crossover chains.
Camshaft Drive Tensioner
The camshaft drive tensioners are one-way hydraulic dampers with tensioning function. The oil from the engine lubrication system provides the tensioner’s damping fluid.
When the tensioner’s internal piston is subjected to load, oil is forced out of the high-pressure chamber through a leakage gap. This generates piston movement and consequently movement of the pads. This movement is dependant upon the size of the gap and viscosity of the oil.
When the tensioner’s piston is relieved of load, an internal return spring acting against the piston presses the piston against the tensioning pad.
The advantage of this type of tensioner is that it compensates for changes in length of the chain due to operating wear and thermal expansion.
An oil release hole integrated into the tensioner cools and lubricates the chain, while also reducing chain noise.
Hydraulic Lash Adjusters
Two overhead camshafts operate four valves per cylinder via finger followers and hydraulic lash adjusters. The hydraulic lash adjusters, supplied with oil from the engine lubrication system, automatically take up the slackness caused by expansion and contraction of the valve gear mechanism.
The main advantage of the valve lash remaining constant is the improved exhaust emissions due to the small variation in overlap stroke curves over all operating cycles during the life of the engine.
Contact between the finger followers, formed from sheet metal, and the camshaft is by means of a cam bearing (needle roller bearing). This type of contact arrangement provides very low valve-train friction. The cam bearing is lubricated with the oil released from the lash adjuster.
Cylinder Head
The aluminum gravity die-cast cylinder heads are unique to each cylinder bank. Two hollow dowels align each cylinder head, and eight deep-seated bolts to minimize distortion secure each cylinder head to the cylinder block. 4 bolts are located beneath each camshaft.
Equipped with 4 valves per-cylinder and double overhead camshafts, this combination provides optimum induction and exhaust actuation with attendant benefits in performance and emissions. The four valve ports are machined into the cylinder head at each cylinder location: two exhaust and two intake ports. One of the intake ports is helical and functions as swirl port, while the other is arranged laterally and functions as a
charge port.
The fuel injectors are centrally mounted one above each cylinder. The glow plugs are arranged centrally on the intake side of the cylinder head between the two intake ports.
The cylinder head design also includes a port deactivation system
 
  #23  
Old 10-23-2010, 04:44 PM
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Cylinder Head Gasket
The cylinder head gasket is of a three-layer laminated steel construction with excellent service life and sealing properties.
The gasket is available in five thicknesses depending on the maximum piston protrusion height. The number of tabs on front edge of the gasket indicates the thickness of the gasket thickness indicator tab

Cylinder Block

The cylinder block is one of the most significant technical aspects of the engine. Cast in compacted graphite iron (CGI), it will be the first use of this material in volume engine production. As a result of the outstanding strength and durability of CGI, less material is needed than for a conventional cast iron block, while providing reduced weight and length with superior structural capabilities.

The engine is the lightest unit of its type, a factor that contributes significantly to the excellent power-to-weight ratio and fuel economy. As the benefits of CGI derive from its

strength, this enables lightweight and thin-wall designs to be created for high-compression diesel applications.

CGI sits in the middle between gray iron and ductile iron. It is significantly tougher and more durable than the former, while having better thermal conductivity than the latter. CGI offers the following benefits over conventional gray cast iron:

• 80% improvement in tensile strength,

• 90% improvement in fatigue life,

• 20% improvement in bore distortion,

• 40% improved modulus leading to enhanced NVH characteristics.

CGI strength lies in the rounded worm-shaped graphite particles that make up its structure. The particles are elongated and randomly orientated similar to gray iron

particles, however CGI particles are shorter and thicker and have rounded edges. While the compacted graphite particles appear worm-shaped when viewed in two dimensions,

deep-etched scanning electron micrographs show that the individual worms are connected to their nearest neighbors.

This complex coral-like graphite morphology, together with the rounded edges and irregular bumpy surfaces of the graphite particles, results in strong adhesion between

the graphite and iron matrix. The compacted graphite morphology inhibits crack initiation and growth and is the source of the improved mechanical properties relative to gray iron.

Stiffening Frame

The cylinder block is coupled with a separate die-cast aluminum stiffening-frame to provide a lightweight, compact and very stiff bottom end of the engine. The stiffening frame also incorporates an oil baffle plate to reduce oil foaming.

Crankshaft

Manufactured from forged steel with fillet rolled induction hardened journals, the crankshaft rotates in aluminum/tin plate main bearings. The upper and lower, rear main bearings are flanged to limit end-float of the crankshaft.

4 counterbalance weights ensureminimum vibration levels from the 3-throw, 4 -bearing arrangement.

The main bearing caps are double-bolted at each side for strength and rigidity. Cross-bolts ‘tie’ the main bearing caps into the cylinder block to control their high frequency

behavior.

Connecting Rods and Bearing Caps

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 centerline. When reassembled the fractured surfaces interlock to form a strong seamless joint. The cylinder position is etched on the adjoining sides of the joint to identify matching connecting rods and bearing caps. The selectable big end bearings are ‘sputter coated’,a manufacturing process that layers the bearing material to produce a higher-load capacity for improved durability and a reduced bearing width.

The connecting rod small-ends have a trumpeted bore for superior force distribution onto the weight-optimized piston pin.

Pistons

The pistons, manufactured of cast aluminum, incorporate ‘double wave-gallery’ to ensure optimum piston cooling. Oil is sprayed precisely on to the inside of the pistons by spray jets located in the block. The oil then flows through 2 wave-shaped channels to help cool the piston crown. This arrangement also has the benefit of reducing piston ‘slap’ noise.

The piston crown incorporates a pronounced bowl which forms the combustion chamber. The combustion chamber promotes swirl and turbulence of the fuel charge to provide

optimum combustion and reduced emissions. 3 piston rings, two compression and one oil control are employed.

The area of piston skirt that comes into contact with the cylinder bore has a molybdenum-coated surface. This surface counteracts scoring of the piston and cylinder bore to prolong engine life.

Engine and Transmission Mounts

The function of the engine mounts is to support the engine and transmission, while also isolating vibrations transmitted from the engine to the vehicle’s frame. In recent years

vibration and noise problems have been intensified with the combination of diesel and more powerful engines with lighter vehicle frames. This has resulted in vibration problems that passive elastomeric and hydraulic mounts cannot adequately isolate.

The vibrations engine mounts have to isolate originate from two different sources:

• Low frequency vibrations resulting from the movement of the engine when the vehicle is inmotion. These vibrations are typically in the region of 1 to 30 hertz (Hz) with

amplitudes greater than 0.3 mm.

– To isolate low frequency vibrations the engine mounts should be stiff and possess a large amount of damping to hold the engine to the chassis at a small relative

displacement. The use of hard rubber would provide high stiffness and be good for providing firm support for the engine to give good driving stability. However, the use of hard rubber enables engine rotation vibrations to be easily transmitted to the vehicle’s frame.

• High frequency vibrations are caused by engine rotation.

These engine vibrations are typically in the region of 30-200 Hz, with amplitudes generally less than 0.1 mm.

– High frequency vibrations are evident when the vehicle is at a standstill and the engine is idling. To isolate vibration due to engine rotation, the mounts should be soft to isolate the vehicle’s frame from engine vibration.High frequency vibrations can excite components in contact with the driver and passengers, eg the steering column and seat rails. High frequency vibrations can also generate significant acoustic noise in the passenger cabin.One solution to overcome the problem of these competing vibration sources is the use of active engine mounts, which incorporate both active and passive elements, to reduce the vibrations transmitted from the engine to the vehicle frame.

Active Engine Mounts

The active element of the engine mount is functional only when the engine is at idle, as this is when the engine high frequency vibrations are the dominant vibrations noticeable

to the vehicle’s occupants.

The mechanical construction of the active engine mount is similar to the passive hydraulic engine mount but with the added element of an internal shaker mechanism. The shaker mechanism works on the same principle as audio speaker technology where a coil actuator is highly efficient in converting electrical energy into mechanical motion and is capable of moving an inertial load at an extremely quick operating speed, for example the audio speaker’s diaphragm.

The shaker mechanism of the active engine mount works on the same concept as the speaker diaphragm to move the top section of the engine mount to oppose the vibrations generated by the engine. The active engine mount mechanism estimates the vibration caused by fluctuations in the engine crank rotation and isolates these vibrations by generating additional vibrations through the internal shaker mechanism.

The result gives vibration isolation and a reduction of chassis vibration.

To ensure accurate vibration suppression the active engine mount has an electronic control module attached to its body and an accelerometer attached to its base. The control module contains a processor which monitors vibration levels measured by the accelerometer to determine the correct counter action signals to transmit to the shaker mechanism.

To assist this process the control module also uses the engine crankshaft position signal provided by the engine management system.

Crankshaft rotational vibrations are 3rd and 6th harmonics of the engine crank speed, which the active mount is pre-programmed to target. Under normal operation the active mount will reduce 3rd order vibrations by a factor of ten at the chassis.

This reduction in vibrations at the engine mount produces a reduction in vehicle occupant vibration and perceived noise.

NOTE:

The passive element of the mount provides a fail-safe feature in the event of an actuator failure.
NOTE:

The active engine mount’s control module supports a diagnostic function; refer to GTR


Engine Lubrication System


The engine is lubricated by distribution of oil at pressure, created by the oil pump, through channels bored into the cylinder block and cylinder head. Oil is diverted through the channels to the moving engine components, which include:


• Camshafts.


• Main and big end bearings through holesmachined into the crankshaft.


• Vacuum pump.


• Turbocharger bearings through a tapping at the rear of the cylinder block and connecting pipes. Oil drainpipes return the oil to the oil pan.


Oil splash created by the crankshaft also lubricates the engine.


Piston cooling jets provide lubrication and cooling of the pistons and piston pins. Oil pressure is also used for the hydraulic operation of the valve lash adjusters and camshaft drive tensioners. A channel provides the oil pressure to the oil pressure switch.


A cyclone type oil-separator provides crankcase ventilation


Oil Pump

The oil pump is a gear type pump bolted to the front of the engine block and directly driven by the crankshaft. A rubber gasket recessed into the oil pump casing seals the pump to the block; a pressure relief valve is incorporated into the pump.

Piston Cooling Jets

Piston cooling jets provide lubrication and cooling of the pistons and piston pins.

Oil Cooler and Filter

The oil cooler, oil filter and high-pressure system fuel cooler are a combined unit, mounted centrally on top of the engine.The oil is cooled before entering the filter by the engine’s cooling system, eliminating the requirement for a remotely mounted cooler.

The high-pressure system fuel cooler is also cooled by engine coolant
 
  #24  
Old 10-23-2010, 04:47 PM
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Accessory Drive

Accessory Drive (front)

The drive belt is a single six-ribbed belt driven from the crankshaft pulley.

The belt is adjusted by an automatic tensioner


Accessory Drive (rear)

A single-toothed belt provides the drive from the exhaust camshaft sprocket to the common-rail fuel pump. The fuel pump is not timed to the engine.The belt is manufactured from the latest in material technology; k-glass cord and aramid fabric (high-grade rubber and fabric), which is peroxide cured. This material provides long-life capability and contributes to the excellent refinement delivered by the drive system.

The timing belt is adjusted by an automatic tensioner


Engine Cooling

The cooling system is of the pressure relief type. A centrifugal pump mounted on front of the engine, driven by the accessory drive belt, circulates the coolant.

Pressure Relief Thermostat

The pressure relief thermostat (PRT) controls the flow of coolant depending on system pressure and temperature. The PRT is a dual function unit comprising a wax-controlled

thermostat and a spring controlled pressure-bypass valve.

The PRT has three basic functions:

1. Engine cold at idle (low engine revs):

– Thermostat is closed therefore no flow through radiator.

– Pressure bypass valve is closed as pressure generated by the coolant pump is less than 32 kPa. This directs coolant flow through the heater matrix,and transmission fluid cooler (automatic derivative vehicles).

2. Engine is cold with the vehicle being driven (higher engine revs):

– Thermostat is closed therefore no coolant flow through radiator.

– Pressure in system greater than 32 kPa, bypass valve opens a variable amount depending upon system pressure. This allows heated coolant from the top hose into the engine.

3. Engine warm:

– As the coolant reaches thermostat-opening temperature, the thermostat will partially open allowing coolant flow through both the radiator and bypass valve. As the coolant temperature increases the thermostat opens fully which in turn closes the bypass valve. From this moment the thermostat controls the coolant temperature, unless it reverts to

one of the transient conditions above.

Cooling Pack Sealing

To accommodate the new diesel engine and modified cooling pack a new sealing arrangement between the cooling pack,the body and the front bumper, has been employed. This redesigned sealing maximizes airflow through the cooling pack.

Cooling Fan

The temperature of the cooling system is monitored by the PCM via input signals from various sensors

The PCM uses these signals to control the cooling fan operation.

To control the cooling fan the PCM sends a pulse width modulated (PWM) signal to the cooling fan module (integral to the fan motor). The frequency of the PWM signal is used

by the cooling fan module to determine the output voltage supplied to the fan motor.

The PCM varies the duty cycle of the PWM signal within a predetermined range, to vary the fan speed. If the PWM signal is outside of this range the cooling fan module interprets this as an open or short circuit and runs the fans at maximum speed to ensure the engine and transmission do not overheat.

The speed of the cooling fan is also influenced by vehicle road speed. The PCM adjusts the speed of the cooling fans to compensate for the ram effect of vehicle speed using the controller area network (CAN), road speed signal received from the ABS module.

Fuel Charging and Controls


Fuel charging of the 2.7 liter, V6 diesel engine is provided by the next generation common-rail fuel injection system, characterized by the use of piezo injectors. This combined with the air charge system, which utilizes two electronically actuated variable vane turbochargers provides a class-beating power unit.


Both fuel charging and air charging systems are discussed separately within this section.

Basics of Diesel Engine Fuel Charging

The diesel engine, commonly referred to as a compression ignition (CI) engine, burns fuel injected into the engine’s combustion chamber when the air charge is fully compressed.


Ignition of the finely atomized fuel is initiated by the generation of heat when the compression temperature of the air is high enough to ignite the fuel.


NOTE:

The following is a basic description of the ‘cycle of piston operation’ in a diesel engine, a more detailed operation is discussed in this section.
Cycle of Piston Operation


Induction:


The descending piston increases the cylinder volume and decreases the pressure. The turbochargers forces air through the open intake ports into the cylinder.


Compression:


With the intake and exhaust valves closed, the ascending piston compresses and raises the temperature of the air. During the compression stroke intake air is compressed to 30 - 55 bar while its temperature increases to 700 - 900 C.


Power:


With the intake and exhaust valves closed and the piston almost at the end of the compression stroke. The diesel fuel, which has a self-igniting temperature of 400 C, is injected at high pressure into the cylinder as finely atomized particles.


After a short delay, the fuel begins to burn and liberate heat, raising the pressure to provide the thrust for the power stroke.The amount of power output is controlled by the period of fuel injection (quantity of fuel injected).


Exhaust:


As the piston nears the end of the power stroke, the exhaust ports are opened. The ascending piston pumps out the burnt gas in readiness for the new cycle.


Fuel Charging

The common rail fuel injection system is of the next generation and is characterized by the use of the piezo-controlled injectors. It is a decoupled system where there is no direct dependence between the crankshaft angle and the generation and distribution of the high-pressure fuel. The system comprises:

A low-pressure fuel circuit
A high-pressure fuel circuit, as discussed in this section, comprising the following main components, controlled by the powertrain control module (PCM):

• Fuel pump, with the following integrated components:


– Volumetric control valve,


– Transferpump,


– High pressure pump,


– Pressure control valve.


• Fuel rails, distribution rail and pressure pipes.


• Fuel pressure sensor.


• Piezo controlled injectors.


Air bleed return



Fuel pressure generated by the fuel pump is transferred and stored in the fuel-rails, ready for injection into the engine’s cylinders. This storage of high-pressure fuel makes it possible to provide a constant injection pressure regardless of the quantity of fuel required and engine speed.


The selection of injection parameters such as:


• injection pressure,


• number of injections,


• timing of injections,


• injection quantity,can be freely selected for each injection phase within the piston cycle.


This system uses a pre-injection (pilot injection) and a main-injection. Pre-injection reduces:


• combustion noise,


• mechanical load,


• exhaust emissions.


Overview of Fuel Charging System


The transfer pump and high-pressure pump, which are internal elements of the fuel pump, are directly driven by the engine at 5/6 of engine speed. The fuel pump is not timed to the engine.


The fuel tank’s internal lift-pump,

provides a low-pressure supply, approximately 0.5 bar, to the transfer pump. The transfer pump delivers the fuel to the high-pressure pump via the volumetric control valve, which governs the amount of fuel supplied to the high-pressure pump.

The high-pressure pump delivers the fuel to the fuel rails at a pressure of up to 1650 bar. The fuel rails act as an accumulator storing the fuel at a constant pressure over the duration of the injection process.


The fuel-rails and piezo injectors are connected via the high-pressure pipes. The piezo injectors allow extremely short response times and make it possible to freely select the injection discharge and fuel quantity according to the demands of the PCM.


The appropriate fuel rail pressure will be set for every engine operating condition. The PCM monitors continually the momentary fuel rail pressure through the fuel pressure


sensor. The PCM then adjusts this to the nominal value stored in its characteristics and regulates the pressure control valve and the volumetric control valve. A closed rail-pressure control-loop is thereby developed.


The volumetric control valve serves the purpose of customizing the delivered amount of fuel from the high-pressure pump according to the needs of the engine. The power requirement of the fuel pump will thereby be reduced when demand is low.


When the engine is stopped, the system’s fuel pressure is depleted within a few seconds, making the system pressureless.


Fuel Charging Components in Order of Function:


Powertrain Control Module


Management of the fuel injection system is performed by the PCM, which monitors and processes the input signals from various sensors, relating to engine operating conditions and driver demand.


The PCM, using calibrated data-tables and maps, compares and evaluates these input signals with pre-stored memory data. The PCM uses the results to command an appropriate response from the actuating devices to provide the correct quantity and pressure of fuel delivery plus optimum injection timing for the prevailing engine conditions.


Fuel Pump

The fuel pump is located at the rear of the engine and is driven by the rear end accessory drive-belt fromthe left-hand exhaust camshaft. The pump is the interface between the low-pressure and high-pressure fuel systems and rotates at 5/6 of the engine crankshaft speed. The fuel pump comprises the following components:


Transfer Pump


The transfer pump is a vane type pump, which draws fuel from the fuel tank’s lift-pump to supply the high-pressure pump with fuel. In addition, the transfer pump supplies the


high-pressure pump with fuel for lubrication purposes.


Volumetric Control Valve


The volumetric control valve is directly screwed into the fuel pump and is an electronically operated 2/2-way proportional valve, which is spring returned, and closes when no electrical current is present. The volumetric control valve regulates the delivery of fuel flow from the transfer pump to the high-pressure pump in response to engine operating conditions.


Function of the volumetric control valve


• Volumetric control valve - non controlled:


– The piston closes the link between the two connections by means of the force generated by the spring (without utilizing electrical current). The fuel delivery to the


high-pressure pump is interrupted.


• Volumetric control valve - controlled:


– The force exerted by the anchor is proportional to the electrical current and works against the force of the spring. Therefore, the opening between the two connections is proportional to the electrical current.


High-pressure Pump


The high-pressure pump is a central cam-plate, driven-plunger pump, with three-cylinder plungers each staggered at 120 degrees.


Capable of delivering a maximum pressure of 1650 bar, the pump supplies the volume fuel-flow for the generation of high-pressure in the fuel rail. Thereby, providing the


necessary fuel quantity to the fuel injectors for all engine operating conditions.


When engine demand is low the energy absorption of the high-pressure pump is reduced, providing improved engine efficiency.


Pressure Control Valve


The pressure control valve is directly flanged to the fuel pump and is an electromagnetically operated 2/2-way seat valve with spring support.


The pressure control valve governs the fuel pressure at the high-pressure outlet of the fuel pump, and consequently the fuel pressure stored in the fuel rails. In addition, the pressure control valve dampens the pressure fluctuations which occur in the fuel pump and injectors during the fuel delivery process.


Function of the pressure control valve


• Pressure control valve - non controlled:


– The valve ball is operated through the force exerted upon it by the spring. Therefore, a small amount of fuel pressure will be withheld.


• Pressure control valve - controlled:


– The current flowing through the solenoid (1) draws down the anchor, this in turn transfers the magnetic force via the pin to the valve ball. The pull of the anchor


(2) and the pressure on the valve ball is proportional to the valve flow (proportional pressure limitation valve).


Fuel Process in the Fuel Pump


The diesel fuel is drawn from the fuel tank by the negative pressure created by the transfer pump (1), and the fuel delivery of the fuel tank’s lift-pump. Fuel pressure in the transfer pump rises with engine speed to a maximum of 6 bar. When the pressure exceeds 6 bar, and the volumetric control valve (2) is closed, the regulating valve (5) returns excess fuel, via the scavenging valve (6), to the fuel return (C). The returning fuel lubricates and cools the fuel pump.


Function of high-pressure elements


• Fuel suction:


During the downward motion of the piston (1) a vacuum in the pump cylinder is generated, which opens the inlet valve (2), against the force exerted by the valve spring. The fuel (A) flowing from the volumetric control valve is drawn in. At the same time, the outlet valve (3) will be closed due to the pressure difference between the pump cylinder and the fuel pressure in the ring line.


• Fuel delivery:


The volumetric control valve, governed by the PCM determines the amount of fuel, which will be delivered to the high-pressure pump’s three elements (3).


The high-pressure fuel from the outlets of the high-pressure pump’s elements is united in the ring line and routed to the high-pressure outlet (B). The high-pressure control valve (4), which governs the fuel quantity to the high-pressure outlet and the fuel pressure in the fuel rail, is located between the high-pressure channel and the return line.


The cam (4) pushes the piston (1) upwards, the inlet valve (2) closes by the force exerted by the valve spring and the pressure being built up in the pump cylinder. The outlet valve (3) opens if the pressure in the pump cylinder is greater than the pressure in the ring line (B).


Fuel Rail and High Pressure Pipes


The system consists of two fuel rails: one fuel rail for each cylinder bank. A distribution rail is used to divide the fuel supply from the outlet of the fuel pump to the fuel rails. The distribution rail also provides the mounting socket for the fuel pressure sensor.


The pressure produced by the fuel pump is transferred to the fuel-rail. The fuel-rail acts as an accumulator, which stores the fuel at a vital volume and constant pressure of 1600 bar. This enables fuel injection pressure to remain mainly constant for the duration of each injection process, regardless of engine speed. The fuel-rail’s volumetric storage capacity has a critical importance to the function of the fuel system’s performance


and is designed around three factors:


• The storage volume of the fuel rails has to be large enough to counter the pressure fluctuations created by the working movement in the fuel pump and the operation of the piezo injectors.


• While taking the above factor into consideration, the volume has to be small enough to allow rapid replenishment of the fuel rails when starting the engine.


• Additionally, a volume too large would necessitate more fuel returning to the fuel tank resulting in a rise in fuel temperature.
 
  #25  
Old 10-23-2010, 04:51 PM
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Fuel Cooler


Two fuel coolers are used: one on the high-pressure side of the system and one on the low-pressure side:


• The high-pressure fuel-cooler is located on the engine


• The low-pressure fuel cooler is air cooled and located underneath the vehicle;




Fuel Pressure Sensor


The fuel pressure sensor is directly screwed into the distribution rail.



The fuel pressure sensor measures the instantaneous pressure of the fuel in the fuel rails. The fuel pressure is converted into an electrical potential signal, which is evaluated by the PCM.




In accordance with the recorded performance characteristics in the PCM, the fuel pressure sensor signal is used for the calculation of the control period of the injectors, and the




high-pressure regulation through the pressure control valve.




Function of the fuel pressure sensor




The membrane (8) is deformed to reflect the fuel pressure in the fuel rail. The deformation of the membrane alters the resistance value of the shield (7). The electronic module assembly (6) evaluates the change of the resistance value and converts this into an electrical potential signal, which is transmitted to the PCM.




System Priming




To avoid the vehicle running out of fuel a fuel run-dry strategy is programmed into the PCM.





Piezo Injectors




The injectors are controlled by the PCM via an internal injector driver, which boosts the supply voltage to the injectors. The injectors are characterized by the use of a piezo stack instead of a solenoid to govern injection. The piezo stack provides a more rapid response time to enable a shorter and more variable distance between the pre-injection





and main-injection. Exact injection dosage, irrespective of how small the fuel discharge, is also obtained by the use of the piezo stack. Furthermore, excellent repetition is ensured.




Through the possible energy recovery with piezo injectors a substantially smaller triggering energy is used in comparison to previous systems. In addition, the simplified electrical control enables a greater electromagnetic toleration and thereby an essential reduction in the susceptibility for failure is achieved. The injectors have six orifices, with each having a diameter of 145 microns, which is equivalent to the thickness of a single




hair. They provide an extremely fine spray of diesel fuel, which ensures the most uniform fuel-air mixture possible. As a result, the combustion process is more complete.




Injection Phasing





The common-rail fuel injection system provides a variable pilot-injection, where a small amount of fuel is injected at a calculated period before the main injection.




Injecting a small amount of fuel into the combustion chamber during the pilot injection phase initiates precombustion. This produces a slight increase in compression pressure,




which shortens the delay in ignition of the main fuel charge. In addition, rises in combustion pressure peaks are reduced. This improves combustion efficiency at all engine-operating conditions. These effects reduce combustion noise, mechanical loads, fuel consumption and emissions.




The allocation of fuel to individual cylinders is adjusted to deliver the correct quantity and pressure depending on engine speed and load. This aids cylinder-balancing factors, so that a smoother running engine can be achieved.




Function of the Injectors




The fuel, which comes from the fuel rail at high-pressure, via the high-pressure fuel delivery (1) reaches the control chamber (2) and the high-pressure chamber (3). The bore-hole to the fuel return (4) is closed via the mushroom valve (5), which is shut by spring force and pressure force.




The hydraulic force, which will be exerted (6) through the high-pressure of the fuel on the nozzle needle (7) in the control chamber (2), is greater than hydraulic force, which is effected on the tip of the nozzle (8). This is due to the surface of the control piston in the control chamber being greater than the surface at the tip of the nozzle.




The nozzle of the injector is closed.

Piezo injector open

The piezo actuator (9) presses on the valve piston (10) and the mushroom valve (5), thereby opening the boring which joins the control chamber (2) with the fuel return line. In this manner, a reduction in the pressure occurs in the control chamber and the hydraulic force, which is effected at the tip of the nozzle (8), is greater than the force on the control piston (6) in the control chamber. The nozzle needle (7) moves upwards

and the fuel is injected into the combustion chamber via the 6 spray orifices.

When the engine is no longer running, the valve, which connects the control chamber with the fuel return line, and the nozzles of the injectors are closed via the force of the

springs.A small amount of fuel will be directed for lubrication purposes between the nozzle needle and the guide from the high-pressure side directly into the return line.

Fundamentals of the Piezo Stack

Piezo stacks belong to the family of multi-layer ceramic components, which take advantage of the inverse piezoelectric effect discovered by Curie and Lippmann in 1881. If a voltage is applied to a piezoelectric crystal its dimensions change.

This effect cannot be exploited and no significant change in length obtained until several piezoelectric elements are superimposed. Therefore, made up of multiple thin ceramic

layers, the length of the piezo stack increases when an electric voltage is applied to the stack. These components will expand within one ten thousandth of a second (0.1ms)

with enormous, yet controlled force. The injector exploits this effect to open and close a valve.

The piezo diesel injector is four times faster than traditional solenoid injectors, and is based on highly precise injection technology developed for ink jet printers. This enables

minimal quantities of fuel to be metered with extreme accuracy, and the start of injection to be determined with even greater precision and at multiple times during each

engine stroke. That means substantially greater precision for timing and

dosing fuel injection. In practice, 5 or 6 fuel injection operations can take place per cycle, but injection is limited to 2 operations per cycle in the XJ diesel engine.

Air Charging

Air Cleaner and Associated Components

The intake air temperature sensor is not monitored on bank-2.
 
  #26  
Old 10-23-2010, 04:57 PM
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Variable Vane Turbochargers

Air charging of the 2.7 liter diesel engine is provided by 2 electronically actuated variable vane turbochargers.

While normally aspirated diesel engines operate with a cylinder charging level of approximately 60%. Turbocharged diesel engines can achieve a cylinder charging level of as much as 90%. The increased air-density entering the engine cylinders, and therefore oxygen, enables a correspondingly greater quantity of fuel to be injected. This increases the engine’s power output and also improves specific fuel consumption.

Each turbocharger consists of two turbo elements:

• a turbinewheel,

• and compressor wheel, enclosed separately in cast housings and mounted on a

common shaft, which rotates in two semi-floating bearings.

The turbine wheel uses the energy of the engine’s exhaust-gases to drive the compressor wheel. The compressor wheel in-turn draws-in fresh-air, which is supplied to the engine’s cylinders in compressed form.

Normally, a bypass/wastegated turbocharger is sized appropriately for a particular engine. This turbocharger matching involves either:

• A quick response at low engine speeds, achieved by selecting a smaller turbine-housing diameter.

• Or full utilization of the exhaust gas energy at high engine speeds, achieved by selecting a larger turbine housing.

With variable vane turbochargers being used, as on this engine, the inlet geometry (inlet area and flow angle) can be optimized over a wider range of engine operating conditions.

This leads to a more rapid speed of response and higher boost pressures at low engine speeds without sacrificing performance at higher engine speeds. The variable vane angle

determines both the inlet area as well as the flow angle, as controlled by the PCM.

The variable vane turbocharger, provides the following benefits over an engine fitted with a traditional bypass/wastegated turbocharger:

• higher engine power and torque,

• reduced fuel consumption,

• reduced emissions,

• quicker turbocharger response.

The quick response rate of the variable vane turbocharger contributes to a more uniform acceleration providing improved vehicle behavior.

Turbocharger Operation

In response to signals from various sensors the PCM, via a rotary electronic actuator, controls the rotation of the turbocharger’s adjustment ring, which in turn rotates the

vanes. The rotary electronic actuator has been developed as a replacement for the pneumatic actuator as used on earlier variable vane and turbine bypass/wastegated turbochargers. The rotary output shaft has a high-accuracy contact-less

position sensor, which can supply the PCM with its actual position.

The rotary electronic actuator provides the following advantages over conventional actuators:

• quicker response

• fewer parts.


The variable vanes are attached to a rotating adjustment ring, located at the inlet of the turbine housing. The adjustment ring, operated by the rotary electronic actuator, rotates to alter the angle of the variable vanes. The vanes in-turn vary the flow of the exhaust gases directed onto the turbine wheel, which enables the shaft to spin faster or slower. This varies compressor speed and boost pressure.

Due to the location of the turbochargers and actuators, the operation of components is different for left and right bank. In order to close the turbine vanes, one actuator is rotating clockwise while the other is rotating counter clockwise.

At low engine speeds and low exhaust gas flow, the PCM maintains the vanes at a narrow angle to maximize gas velocity onto the turbine wheel. This consequently increases turbine speed and boost pressure at low exhaust-gas flow to provide optimum low-speed engine performance.

As engine speed increases and decreases at intermediate engine speeds. The PCM adjusts the vanes to optimize the exhaust gas flow and velocity on to the turbine wheel to maintain the required boost pressure over the intermediate engine speed range.

At high engine speed and high exhaust gas flow, the PCM increases the vane opening to avoid turbocharger over-speed and provide smooth high-end operation, as well as reducing engine back pressure.

Barometric Pressure Sensor

A barometric pressure sensor integrated into the PCM protects the turbochargers against altitude changes by adapting the turbocharger’s boost pressure.

Turbocharger Lubrication

The rapid acceleration and deceleration response demands of the turbocharger rely greatly on the steady flow of clean oil.

The oil supplied from the engine’s lubrication system provides lubrication to the turbocharger’s spindle and bearings, while also acting as a coolant for the turbocharger center housing.

To maintain the life expectancy of the turbocharger, it is essential that the oil has a free-flow through the turbocharger and unrestricted return to the engine’s oil pan. It is therefore imperative that the engine oil is replenished at regular service

intervals with the recommended quality of oil.

Charge Air Cooler

is used to increase the density of air as it flows from the turbocharger’s compressor to the intake manifold.

Compression of the charge air by the turbochargers raises the temperature of the charge air. This generation of heat expands the air density and consequently less oxygen is able to enter the cylinders, reducing the engine’s power. To overcome this, the air is routed through the charge air-cooler before it enters the engine; the air temperature is reduced by transferring the heat to atmosphere.

Cooling of the intake air also helps to reduce engine emissions by limiting nitrogen oxides (NOx) production.


Engine Cranking System

Starter Motor

The starter motor is fitted to the rear right-hand side of the engine, and is secured to the flywheel housing by two bolts. A bracket supports the other end of the starter motor. 2 bolts secure the bracket to the end cap of the starter and 1 bolt secures the bracket to the cylinder block.Approximate cranking current is 250 amps at 20 C.

Engine Emission Control

Crankcase Ventilation System

Crankcase ventilation is a two-stage system; the first stage comprises a horizontal choke cavity in the cylinder block, which is fed through eight orifices. This partially removes the oil from the crankcase gases.

When the primary oil separation is complete the gases are sucked through a centrifugal separator,

The separator captures the gases and separates the remaining oil from the gases before returning them to the crankcase and air intake system respectively.

The centrifugal separator is an air circulation systemthat swirls the crankcase gases. As oil is heavier than gas, the oil is drawn to the outside of the separator into the drain pipe then into the reservoir before returning to the engine oil pan.

Prior to the oil-free gases entering the engine at the turbocharger’s compressor, a diaphragm pressure-balance valve, within the separator, operates to minimize the

crankcase pressure variations caused by engine air demand and engine operating conditions.

Exhaust Gas Recirculation System

Nitrogen oxides (NOx) are formed by the reaction between oxygen and nitrogen at high temperatures. A reduction in the amount of NOx produced is achieved by recirculation of

a proportion of exhaust gases. The exhaust gas recirculation (EGR) process replaces some of the normal intake air received from the charge air cooler to reduce the oxygen content within the cylinders and lower the peak combustion temperature by several hundred degrees. To reduce the temperature as well as increase the density

of the inducted fuel charge, the recirculated exhaust gases are passed through the EGR cooler. The EGR cooler utilizes coolant from the engine cooling system

Exhaust gases entering the EGR cooler reach temperatures of approximately 500 C. The EGR cooler lowers the temperature of the exhaust gases, to between 250-300 C before they exit the cooler.

The 2.7 liter diesel engine uses a twin EGR system, a separate system for each cylinder bank. An electrically actuated valve, mounted on the outlet side of the EGR cooler and

controlled by the PCM, regulates the amount of exhaust gases recirculated into the air intake system

The powertrain control module (PCM) uses signals from various engine sensors and calculates a response based on the embedded software algorithm to control exhaust gas

recirculation

Both valve actuators receive the same signal and are closed-loop controlled with the mass air flow (MAF) sensor providing the feedback to the PCM.

Port Deactivation

Port deactivation, also known as variable swirl-control, provides a reduction in exhaust emissions at certain engine conditions.

The integrated valve cover and intake manifold incorporates a twin-plenum intake system, where two tracts within the intake manifold directs the airflow to each piston cylinder. The port deactivation device incorporated into the intake manifold acts on the high-flow intake ports by adjusting the airflow to these ports as instructed by the PCM.

This in-turn directs the remaining airflow to the tangential intake port to create a greater swirl effect in the piston cylinder, which improves fuel mixing at certain engine conditions

The variation of airflow into the high-flow intake ports is effected by control flaps positioned in the runners of the ports. The flaps are operated by vacuum, as controlled by the PCM, via a solenoid and two actuators: one for each cylinder bank.

The solenoid has three ports, connected to:

• The vacuum pump, which is driven by the exhaust-camshaft (supply vacuum).

• The two actuators for controlling the operating flaps (control vacuum).

• The air-filter box (ventilation).

The solenoid is energized in response to the pulse width modulated (PWM) signals received from the PCM. Each rapid on-off pulse allows corresponding pulses of vacuum to flow to the actuators.

Dependant upon engine speed and load, the width of the on-pulse determines the amount of vacuum allowed to pass to the actuators. Which in turn determines the angle of the control flaps.

Oxidizing Catalytic Converter

The oxidizing catalytic converter has a 100% platinum coating with 400 cells per square inch. The converter has integrated turbocharger de-couplers for turbocharger whine suppression.

The oxidizing catalytic converter utilizes catalytic action to oxidize hydrocarbon and carbon monoxide emissions to carbon dioxide and water.

The close proximity of converter to the turbochargers and exhaust manifolds advances the light-off point. This ensures that the catalysts reach their required operating temperature faster, significantly reducing emissions during the warm-up phase.

NOTE:

Catalyst light-off is the point at which conversion efficiency exceeds 50%.
 
  #27  
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Diesel Particulate Filter

Diesel emissions are 90% lower than they were in the 1980s; however exhaust regulations based on statistical studies dealing with the health impact of exhaust emissions continue to demand even lower gaseous and particulate diesel emissions. Particulate emissions are responsible for the characteristic black exhaust fumes emitted from the diesel engine. They are a complex mixture of solid and liquid components with the majority of particulates being carbon microspheres on which hydrocarbons from the engine’s fuel and lubricant condense.

In order to comply with the strict European Stage IV emission standard, which now stipulates a further 50% reduction in particulate emissions, an exhaust emission control system is used on the XJ 2.7 liter and S-TYPE 2.7 liter diesel vehicles.

The primary component of the system is the diesel particulate filter (DPF), which has been proven to be effective in reducing particulate emissions to negligible levels. The main ability of the particulate filter is its capacity for regeneration; that is burning the particulates trapped in the filter at calculated intervals in such a way that the process is unnoticed by the driver of the vehicle.

Operation of the Diesel Particulate Filter

To enable the exhaust emission control system to store and when conditions determine, burn the particulates, the diesel particulate filter uses new filter technology based on a filter with a catalytic coating. Made of silicon carbide the filter is packaged into a steel container installed in the exhaust system of the vehicle. The filter has good thermal shock resistance and thermal conductivity properties, plus a closely controlled porosity. The filter is tailored to the engine’s requirements to maintain the most favorable exhaust backpressure.

The porous substrate in the filter’s interior consists of thousands of small parallel channels running in the exhaust’s longitudinal direction, adjacent channels in the filter are alternately plugged at each end. This arrangement forces the exhaust gases to flow through the porous walls, which acts as the filters medium. Particulates that are too big to pass through the porous walls are left behind and stored in the channels. To prevent the particulates creating an obstruction to the exhaust gas flow, the filter system provides a regeneration mechanism, which involves raising the temperature of the filter to such an extent that the particulates are incinerated and as a result removed from the

filter.

The most important parameters influencing filter regeneration is the temperature of the exhaust gases and filter. With this in mind the composition of the filter also includes a wash coating to the surface of the filter comprising platinum and other active components; materials used in the manufacture of oxidation catalytic converters. At certain exhaust gas and filter temperatures the catalytic coating promotes combustion

and therefore burning of the particulates, while also oxidizing carbon monoxide and hydrocarbon emissions.

Exhaust gas and filter temperatures are controlled by the DPF module, which is incorporated in the powertrain control module (PCM). The DPF module monitors

the load status of the particulate filter based on driving style, distance driven, and signals from the differential pressure sensor. When the particulate loading in the filter reaches a threshold, the filter is actively regenerated by adjusting, in accordance with requirements various engine-control functions; such as:

• fuel injection,

• intake-air throttle,

• glow-plug activation,

• exhaust-gas recirculation, and

• boost-pressure control.

This control function is made possible by the flexibility of the common-rail fuel injection engine in providing the precise control of:

• fuel-flow

• fuel pressure, and

• injection timing,

all essential requirements for an efficient regeneration process.

2 processes are used to regenerate the particulate filter,‘passive regeneration’ and ‘active regeneration’ both of which are discussed below:

Passive Regeneration

Passive regeneration involves the slow environment-protecting conversion of the particulates deposited in the filter into carbon dioxide. This regeneration process comes into effect when the filter’s temperature reaches 250 C and occurs continuously when the vehicle is being driven at higher engine loads and speeds. No special engine management intervention is initiated during passive regeneration, allowing the engine to operate as normal. Only a portion of the particulates are converted to carbon

dioxide during passive regeneration and due to chemical reaction this process is only effective within the temperature range of 250 C to 500 C. Above this temperature range the conversion efficiency of the particulates into carbon dioxide subsides as the temperature of the filter increases.

Active regeneration

Active regeneration commences when the particulate loading in the filter reaches a threshold as monitored and determined by the DPF module. This calculation is based on driving style, distance driven and exhaust backpressure signals supplied by the differential pressure sensor. Active regeneration generally occurs approximately every 400 kilometers (250 miles) although this will depend on how the vehicle is driven.

EG, if the vehicle has operated for a length of time at low-loads for instance in urban traffic, active regeneration will be initiated more often. This is due to a more rapid

build up of particulates in the filter than if the vehicle has been driven periodically at greater speeds, where passive regeneration would have occurred.

A mileage trigger incorporated within the DPF module is used as a backup for initiating active regeneration. If after a threshold distance has been driven and regeneration has

not been activated by backpressure signals; regeneration will then be requested on the basis of distance driven.Active regeneration of the particulate filter is started by raising the temperature in the particulate filter up to the combustion temperature of the particulates. A principal method of increasing the exhaust gas temperature is by

introducing post-injection of the fuel, that is after the pilot and main fuel injections have taken place. This is achieved by the DPF module processing signals from the temperature sensor to determine the temperature of the particulate filter and depending on the filter’s temperature, the DPF module commands either one or two post-injections:

• 1st post-injection retards combustion inside the cylinder to increase the heat of the exhaust gas.

• 2nd post-injection injects fuel late in the power stroke cycle; fuel partly combusts in the cylinder but also sweeps down the exhaust where unburned fuel triggers an exothermal event in the catalyst, raising the filter’s temperature further.

Active regeneration takes approximately 20 minutes to complete. The first phase is to raise the temperature of the filter to particulate combustion temperature of 500 C.

In the second phase the temperature is raised to 600 C, the optimum particulate combustion temperature. This temperature is maintained for 15 to 20 minutes to ensure

complete incineration of the particulates captured in the filter. The incinerated particulates produce carbon dioxide and water. Active regeneration is controlled to achieve a target temperature of 600 C at the inlet of the particulate filter without exceeding the temperature limits of the turbochargers and close-coupled catalysts

During the active regeneration period:

• The turbochargers are maintained in the fully open position to minimize heat transmission from the exhaust gas to the turbochargers and to reduce the rate of gas flow through the particulate filter. This enables optimum heating of the particulate filter. If the driver demands a higher torque the turbochargers will respond by closing the vanes as required.

• The throttle is closed as this assists in increasing the exhaust gas temperature and reducing the rate of exhaust gas flow, both of which increase the speed at which particulate filter is heated.

• The exhaust gas recirculation (EGR) valve is closed as the use of EGR lowers exhaust gas temperatures and therefore makes it difficult to achieve the regeneration temperature in the particulate filter.

• The glow plugs are sometimes activated to provide additional heat in raising the temperature of the particulate filter. To maintain glow plug serviceability the activation

period of the glow plugs is restricted to 40 seconds.

The regeneration process also compensates for ambient temperature changes.

Engine Oil Dilution


A disadvantage of active regeneration is engine oil dilution caused by small amounts of fuel entering the engine crankcase during the post-injection phases. This has made it necessary, in some circumstances to reduce the oil service intervals; the


driver of the vehicle is alerted to this by the instrument-cluster message centre.


An algorithm programmed in the DPF module monitors driving style, active regeneration frequency and duration. Using this information the module predicts the level of oil


dilution. When the oil dilution level reaches a threshold value (the fuel being 7% of engine oil volume), a red warning lamp and ‘Service Required’ message is displayed.


Depending on driving style, a small percentage of vehicles will require an oil change before the standard 15,000 miles service interval. If an engine oil dilution event does occur the vehicle will undergo its full service and the service mileage counter will be reset to zero by the service technician.


Fuel Consumption


There will be a small increase in fuel consumption due to active regeneration of the particulate filter. During regeneration the fuel consumption approximately doubles. However, because regeneration happens relatively infrequently the overall increase in fuel consumption is small.This is accounted for in both the instantaneous and average


fuel economy displayed in the instrument cluster.


Driver and Dealer Intervention


For drivers who make frequent short journeys at low speeds, it may not be possible to effectively regenerate the particulate filter. In this case, the DPF module will detect a particulate overload condition and a warning message will displayed to the driver via the message centre.This message will read ‘DPF Full - See Handbook’ accompanied by an amber warning light. The driver will be given the opportunity to regenerate the particulate filter by driving the vehicle until the engine’s normal operating


temperature is attained, and then for an additional 20 minutes at a speed of 48 km/h (30 mile/h) or above. Successful regeneration of the filter is indicated to the driver by both the message and amber warning light being extinguished. If the message is ignored and no action is taken there is the possibility that the DPF will become blocked. If this occurs the vehicle must be taken to an authorized dealer for the filter


to be force regenerated.
 
  #28  
Old 10-23-2010, 05:02 PM
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Diesel Particulate Filter Module

The diesel particulate filter (DPF) module is incorporated in the powertrain control module (PCM). The DPF module monitors and supervises the operation of


the DPF system while also monitoring diagnostic data. The DPF module is divided into three sub-modules controlled by a coordinator module. The DPF coordinator module manages the operation of different features when a forced regeneration is requested or cancelled.


• The DPF supervisor module is a subsystem of the coordinator module.


• The DPF fuel-management module calculates the timing and quantity of four fuel injections as well as the injection pressure during regeneration.


• The DPF air-management module contains the control for EGR, boost pressure, air temperature and pressure in the intake manifold.


In the following, the functionality of each sub-module is explained:


DPF Coordinator Module


The DPF coordinator responds to a regeneration request from the supervisor module by initiating and coordinating the following DPF regeneration specific requests:


• EGRcut off


• Boost pressure control


• Engine loadincrease


• Control of gas pressure and temperature in the intake manifold


• Fuel injectioncontrol.


Once a regeneration request is set by the supervisor module the coordinator requests EGR cut off, and regeneration specific boost pressure control. It awaits a feedback signal from the EGR system indicating that the valve is shut. Once this occurs, the coordinator initiates requests to increase engine load by activating electric consumers and controlling the intake air temperature and pressure. Once it receives a confirmation that intake conditions are adequately controlled or expiration of a calibratable time, it switches to a state waiting for an accelerator pedal release manoeuvre from the driver. If this occurs or a calibratable time elapses, the coordinator initiates a request to control fuel injections to increase exhaust gas temperature.


DPF Fuel Management Module


The fuel management module controls:


• Timing and quantity of four split injections per stroke (pilot,main,and 2post injections).


• Injection pressure and transition between three different levels of injection.


All of which are dependent on the state of the close-coupled catalysts and the state of the particulate filter.


The control injection determines the required injection level as well as an indication of the activity of the close-coupled catalyst and particulate filter. The injection management


calculates the quantity and timing for the four split injections, each for the three calibration levels for injection pressure, and manages the transition between levels.


The two-post injections are required to de-couple the functionality of elevating in-cylinder gas temperature and production of hydrocarbons (to be burnt in the particulate filter). The first post injection is used to generate higher in-cylinder gas temperature and at the same time retain the same torque produced under normal operation mode (non


regeneration mode). The second post is used to generate hydrocarbons which are burnt partly in-cylinder and partly over the close-coupled catalyst, but without producing


increased engine torque.


DPF Air Management Module


The DPF air management module consists of:


• EGRcontrol


• Boost pressure control


• Intake air temperature and pressure control.


During regeneration, the EGR feature is shut off, and the closed-loop activation of the boost controller is calculated. The module controls the state of the air in the intake manifold to a predetermined level of pressure and temperature. This is required to achieve correct in-cylinder conditions for a stable and robust combustion of the post-injected fuel.


The module controls the intake air pressure during regeneration by actuating the EGR throttle and adjustment of boost pressure control.


Active Regeneration Protection Limits


For engine and other component protection and durability the DPF module implements some limits during the active regeneration phase, in particular:


• Temperature before the turbocharger inlet must remain below 830 C for turbocharger protection.


• Close-coupled catalyst in-brick temperatures must not exceed 800 C and exit temperature must remain below 750 C.


Electronic Engine Controls


The XJ, 2.7 liter diesel engine is equipped with a microprocessor controlled common-rail fuel injection system. This system includes hot-film measurement of the intake


air mass flow and provides closed-loop control of the fully modulated exhaust gas recirculation (EGR) and variable geometry turbochargers.


The control strategy is fuel supply based and the majority of controls are dictated by a combination of engine speed and injected fuel quantity.


The fuelling demanded by the driver is modified and limited by the powertrain control module (PCM) according to the inputs of various sensors fitted to the engine and chassis of the vehicle.


The following are also dictated by the PCM and are mapped according to fuelling and modified for diverse vehicle operating conditions:


• injection pressure,


• injection timing,


• exhaust gas recirculation rate,


• boost pressure,


• pilot injection quantity,


• and pilot separation.


The electronic engine control system has many chassis based sensor and actuator similarities to the gasoline derivative vehicle. The main differences are the engine based sensors and actuators, which are discussed in this section.


Fuelling Control


The engine management system uses a torque based fuelling strategy. Torque set points are continuously calculated and are dependant on the operating conditions of the vehicle at any one time. Required torque values are then converted into relevant fuelling demands.


European On-board Diagnostics


The advanced design of the V6 diesel engine complies with European Stage 4 Diesel Emission Legislation. The diesel European on-board diagnostics (EOBD) system


consists of a series of monitors designed to observe the operation of strategic aspects of the emission control system and detect sensor and actuator failure. The EOBD system incorporates a malfunction indicator lamp (MIL), which will only illuminate to report emission related failures. It will not be used for any other purpose.


To illuminate the MIL, the failure condition must be observed on at least two drive cycles. The first occurrences will set a fault code and the second occurrence will illuminate theMIL. Therefore, if an OBD reset is performed, a minimum of two


drive cycles is required to illuminate the MIL. De-activation of the MIL will be effected if no further separate failure conditions are detected and three subsequent and


sequential drive cycles have been completed where the original failure condition that illuminated the MIL initially is no longer detected.


The fault code will be completely erased if the same failure condition is not detected after forty warm up cycles. A warm up cycle is defined as:


• Ignition on, engine start and driving pattern from cold whereby the engine temperature increases by at least 22 C and reaches 70 C.


A drive cycle is defined as:


• Ignition on and engine start; drive and key off, where the drive cycle is sufficient to test the monitor.


At very low fuel tank levels the engine runs in a reduced torque mode. This is to protect the system against any potential fuel injection damage.


Engine Sensors


Barometric Pressure Sensor


The barometric pressure sensor integral to the PCM protects the turbocharger against altitude changes by adapting the turbocharger’s boost pressure.


This is achieved by adjusting the fuel and EGR to limit the turbocharger boost pressure set point therefore, preventing turbocharger damage and excessive smoke at high-altitude conditions.


If the sensor fails a substitute value will be used for the barometric pressure. A DTC will be recorded; the MIL does not illuminate.


Camshaft Position Sensor


The camshaft position (CMP) sensor is designed to operate with a ferromagnetic camshaft target wheel. The sensor, a magneto-electronic module, generates a magnetic field induction and reads the magnetic signal (Hall integrated circuit), which is an image of the camshaft target wheel and transforms it into a digital signal.


The sensor has been especially designed for applications that require a high signal accuracy and repeatability, eg: injection variable valve timing.


It includes an adaptive algorithm, which enables the sensor to reach high angular position accuracy over various functional conditions, for example, air-gap, temperature,


and component spread. It has built-in protection against electromagnetic interferences.


The sensor’s function is to provide the PCM with a digital signal, which is the image of the camshaft position. This enables the identification of the cam position of the No. 1


cylinder, at top dead center (TDC) compression stroke.


The CMP sensor signal is used in conjunction with the crankshaft position sensor and is used by the PCM to:


• Synchronize the PCM to the engine cycle during engine starting.


• Actuate the individual fuel injectors in the correct sequence.


If the CMP sensor fails the engine will continue to operate, but once shutdown will not restart. The MIL does not illuminate.


Charge Air Temperature Sensor


Located in the air box, the charge air temperature sensor measures the intake air charge temperature and supplies the PCM with an analogue signal. The sensor signal is used to determine minimum air/fuel ratio and boost pressure set-point limitation for turbocharger over-speed protection.If the charge air temperature sensor fails a substitute value will be used for the air charge temperature. A DTC will be


recorded; the MIL does not illuminate.


Crankshaft Position Sensor


The crankshaft position (CKP) sensor monitors the magnet-ring attached crankshaft to provide the crankshaft position and engine speed.


The CKP sensor is an active Hall effect type which monitors 60 magnetic poles, including two gaps, located on the circumference of the magnetic ring. The two gaps are used by


the PCM as a reference to the position of the crankshaft.


The CKP signal is used in conjunction with the camshaft position sensor by the PCM to determine:


• quantity of fuel tobeinjected,


• startof fueldelivery,


• quantity of exhaust gases to be recirculated.


If the CKP sensor fails the engine will shutdown. The MIL does not illuminate.
 
  #29  
Old 10-23-2010, 05:04 PM
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Engine Coolant Temperature Sensor


The PCM and engine coolant temperature (ECT) sensor circuit consists of an internal voltage divider circuit which incorporates a negative temperature coefficient (NTC)


thermistor. As the coolant temperature rises the resistance through the sensor decreases, the opposite occurs when the coolant temperature decreases. The output from the sensor is the change in voltage as the thermistor allows more current to pass to earth relative to the temperature of the coolant.The ECT sensor provides the PCM with engine coolant temperature status. The PCM uses the temperature information for the following functions:


• fuelling calculations


• limits engine operation if coolant temperature becomes too high


• cooling fan operation


• glow plug activation


• exhaust gas recirculation.


The PCM transmits the ECT temperature over the CAN network for use by other systems.


The instrument cluster uses the temperature information from the CAN network for temperature gauge operation.


If the ECT sensor fails a DTC will be recorded and the MIL will illuminate. The fuel temperature sensor will provide a substitute engine temperature.


ECT sensor failure symptoms are:


• Thermo management limp home is invoked


• Limited engine torque


• Disablement of the EGR controller


• Disablement of the fuel fired heater


Fuel Pressure Sensor


The fuel pressure sensor is located on the fuel distribution rail and measures the instantaneous pressure of the fuel in the fuel rails. The sensor incorporates a steel diaphragm, which deforms according to the fuel pressure in the fuel rails and injectors. The sensor’s signal changes in response to the deformation of the diaphragm. The fuel pressure signal is converted into an electrical potential signal, which


is evaluated by the PCM.


In accordance with the recorded performance characteristics in the PCM, the fuel pressure sensor signal is used for the calculation of:


• determining the start of injection,


• quantity of fuel injection,


• high-pressure fuel regulation through the pressure control valve incorporated within the fuel injection pump.


If the fuel pressure sensor fails, the vehicle will lack power, and a DTC will be recorded. The MIL does not illuminate.


Fuel Temperature Sensor


The fuel temperature sensor, located in the fuel return pipe, is a negative temperature coefficient (NTC) thermistor type, which measures the temperature of the fuel in the


low-pressure system. The sensor works on the same principle as the engine coolant temperature sensor. The PCM monitors the fuel temperature constantly and the


signal from the sensor is used as a constituent by the PCM to calculate the quantity of fuel to be injected. If the fuel temperature exceeds a set threshold the PCM


invokes an engine ‘de-rate’ strategy. This reduces the amount of fuel delivered to the injectors in order to allow the fuel to cool. When this occurs the driver of the vehicle may


experience a loss of performance. In the event of fuel temperature sensor failure a substitution value is used. A DTC will be recorded; the MIL does notilluminate.


Integrated Mass Air Flow and Intake Air Temperature Sensor


Mass Air Flow Sensor


Two mass air flow (MAF) sensors are used, one for each bank, mounted on the clean-air side of the air filter. The MAF sensor is housed in a plastic molding, and works on the hot-film principle, where two sensing elements are contained within a film. One element is maintained at ambient (air intake) temperature. The other element is heated to 100 C above the ambient temperature.


Intake air entering the engine passes through the MAF sensor and has a cooling effect on the film. The PCM monitors the current required to maintain the 100 C differential between the two elements and uses the differential to provide a precise signal which equates to the volume of air being drawn into the engine.


The MAF sensor output is a frequency-based signal, proportional to the mass of the incoming air. The PCM uses this data in conjunction with signals from other sensors and information from stored fuelling maps to determine the precise fuel quantity to be injected into the cylinders. The signal is also used as a feedback signal for the EGR system. If one MAF sensor fails a substitute value equivalent to the


MAF reading on the other bank is used. A DTC will be recorded; the MIL does not illuminate.


Intake Air Temperature Sensor


NOTE:

The bank-2, intake air temperature sensor is not monitored by the PCM.
The intake air temperature (IAT) sensor is mounted on the clean-air side of the air filter and housed in a plastic molding.


The IAT sensor incorporates a NTC thermistor in a voltage divider circuit. The NTC thermistor works on the principle of decreasing resistance in the sensor as the temperature of the intake air increases. As the thermistor allows more current to pass to ground, the voltage sensed by the PCM decreases.The change in voltage is proportional to the temperature change of the intake air. Using the voltage output from the IAT sensor, the PCM can correct the fuelling map for intake air temperature. The correction is an important requirement as hot air contains less oxygen than cold air for any given


volume.


The IAT sensor is used for compressor outlet temperature calculations, boost set-point limitation for turbocharger over-speed protection and as correction for the basic


set-point. If the IAT sensor fails a substitute value will be used for the intake air temperature. Thermo management limp home will be invoked, and a DTC will be recorded; the MIL does not illuminate.


Knock Sensor


Two knock sensors are used one for each cylinder bank.


The knock sensor, an accelerometer type sensor, produces a voltage signal, which reflects the vibrations caused by combustion knock levels.


The PCMuses this signal as an adaptation factor for calculating the timing and quantity of fuel injection during the pilot injection phase to minimize audible combustion knock.


In the event of a sensor failure the injector timing adaptation will be inhibited on both cylinder banks. A DTC will be recorded; the MIL does not illuminate.


Manifold Absolute Pressure Sensor


The manifold absolute pressure (MAP) sensor, located in the throttle body, provides a signal to the PCM, which is proportional to the vehicle intake manifold pressure. The


output of the sensor is an analogue voltage signal, which the PCM uses as a reference value of engine load, boost control and a calculation of the turbocharger outlet temperature. The signal influences:


• quantity of fuel injected


• exhaust gas recirculation


• turbocharger control.


If the MAP sensor fails a substitute value will be used for manifold pressure. A DTC will be recorded; the MIL does not illuminate.


Oil Temperature Sensor


The oil temperature sensor, located in the engine’s oil pan is an NTC thermistor type.


Oil Pressure Switch


The oil pressure switch is connected to the instrument cluster and is not directly used as part of the electronic engine control system.


Engine Actuators


Exhaust Gas Recirculation Actuator


The 2.7 liter diesel engine uses a twin exhaust gas recirculation (EGR) system, a separate system for each cylinder bank. The EGR valve actuators are controlled by the PCM to control the amount of exhaust gases being recirculated in order to


reduce exhaust emissions and combustion noise


The PCM uses signals from various engine sensors to position the actuator’s valve and calculates a response based on the embedded software algorithm to control exhaust gas

recirculation. Both valve actuators receive the same signal and are closed-loop controlled with the MAF sensor providing the feedback to the PCM.


The EGR valve actuators receive a voltage signal from the main relay. The ground for the actuator is via the PCM and is controlled by a PWM signal.


In the event of a failure a DTC will be recorded, and depending on the nature of the failure the MIL will be illuminated to report an emission related failure only.


If possible the EGR system will use a substitute value and position the valves in the closed position.
 
  #30  
Old 10-23-2010, 05:05 PM
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Fuel Injection Timing Control


The injectors are controlled by the PCM via an integrated injector driver which boosts the supply voltage to the injectors. The injectors are characterized by the use of a piezo stack instead of a solenoid to govern injection. The engine management system uses a torque based fuelling strategy. Torque set points are continuously calculated and are dependant on the operating conditions of the vehicle at any one time. Required torque values are then converted into relevant fuelling demands.


A pilot injection and main injection discharge the fuel. Each injection event is controlled by a charge and discharge cycle allowing energy to be dissipated in, and recovered from the injector.


A range of electrical checks are conducted which determine wiring/connection errors and faults with the electrical stages of the injectors.


General electrical faults result in:


• engine speed limitation,


• inhibition of torque loss adaptation,


• disablement of closed-loop energy control,


• disablement of traction control and transmission control.


If an injector fault occurs, a DTC will be recorded; and the MIL will be illuminated.


Fuel Pump

The fuel pump output is controlled by a volume control valve and pressure control valve, see below, which are closed-loop controlled through the fuel pressure sensor. Fuel pump


diagnostics work in conjunction with the fuel pressure sensor.


Volumetric Control Valve


The volumetric control valve is directly screwed into the fuel pump, and is an electronically operated 2/2-way proportional valve, which is spring returned, and closes when no electrical current is present.


The volumetric control valve regulates the delivery of fuel flow from the transfer pump to the high-pressure pump, both integral to the fuel pump, in response to engine operating conditions.


Pressure Control Valve


The pressure control valve is directly flanged to the fuel pump and is an electromagnetically operated 2/2-way seat valve with spring support.


The pressure control valve governs the fuel pressure at the high-pressure outlet of the fuel pump, and consequently the fuel pressure stored in the fuel rails. In addition, the pressure control valve dampens the pressure fluctuations which occur in the fuel pump and injectors during the fuel delivery process.


Glow Plugs

Glow plug control module


The glow plug control module is responsible for controlling the engine glow plug operation during cold and hot engine starts. The module also generates fault code signals in the event of a glow plug system failure and transmits the signals to the PCM.


The MIL does not illuminate.


Typical functions performed by the module are:


• Glow plug activation before cranking, during cranking, and after the engine has started.


• Thermal protection of the glow plugs.


• Execution of the glow times as governed by the PCM.


• On-board diagnostic functions.


The PCM is connected to the glow plug control module via a line in the main wiring loom, which consists of a control line and diagnostic line. The fundamental purpose of the module is to provide electrical power to the glow plugs to improve engine cold starting capability and cold start emissions. Driver qualitative perceptions are also enhanced with short engine cranking times due to minimum glow times, with the added benefit of lowcombustion noise at lowambient temperatures.


The main sensor utilized by the module, indirectly via the PCM, is the engine coolant temperature sensor. Using this sensor’s signal the PCM makes a decision, whether to activate the module based on a function algorithm.


Glow Plug Switching Function


The glow plug control module acts as a current switch to the glow plugs, controlled by the PCM:


• Above a given coolant temperature the glow plugs will not be switched on before, during or after engine cranking.


• Within a certain range of coolant temperatures, the activation of the glow plugs is selective.


• Below a certain temperature the glow plugs will be active before cranking to assist engine firing, and after the engine has started to reduce emissions.


Glow Plug Bridge Connector


Each bank of glow plugs is connected to the glow plug control module via a bridge connector. The function of the bridge connector is to distribute electrical power to the glow plugs as controlled by the module.


Each bridge connector comprises the following components:


• rail,


• fly-lead with support,


• interconnection,


• three terminals.


The bridge connector has a current capacity of 20A per glow plug over a continuous period of three minutes. This is achieved with no adverse increase in the bridge connector’s temperature, therefore, eliminating an increase in electrical resistance.


Port Deactivation Actuator


Port deactivation, also known as variable swirl control, provides a reduction in exhaust emissions at certain engine conditions.


The port deactivation flaps are operated by vacuum, as controlled by the PCM, via a solenoid and two actuators: one for each cylinder bank.


If an actuator fault occurs, a DTC will be recorded; the MIL does not illuminate.


Rotary Electronic Actuators - Turbocharger

In response to signals from various sensors the PCM, via the rotary electronic actuator, controls the rotation of the turbocharger’s adjustment ring, which in turn rotates the


vanes. The rotary electronic actuator has been developed as a replacement for the pneumatic actuator as used on earlier variable vane and turbine bypass/wastegated turbochargers. The rotary output shaft has a high-accuracy contact-less


position sensor, which can supply the PCM with its actual position.


The MAF sensor monitors turbocharger boost pressure, this signal is transmitted to the PCM where it is matched against the engine speed signal. An imbalance between these two signals will record a fault code in the PCM.


The rotary electronic actuator generates fault code signals in the event of a turbocharger system failure and transmits the signals to the PCM.


Various fault codes will be recorded, for example a sticking or non-functioning component. The MIL will be illuminated if a fault code is emission related.


Throttle Body Actuator

The throttle body actuator, controlled by the PCM, is used to improve vehicle refinement while shutting off the engine by limiting undesired accelerations, by closing the engine intake. The intake throttle is not used to increase EGR rate. The intake throttle is controlled to a desired position via a closed-loop position controller. If the throttle valve signal is not detected the throttle valve will go to the fully open position.


Chassis Based Fuelling Components Interfacing with the PCM


ABS Module - Vehicle Speed Signal


The ABS module receives its signal from four individual wheel speed sensors. The vehicle speed signal is sourced from the ABS module and transmitted to the PCM via the CAN. Fault codes stored in the ABS module are transmitted via the CAN to the PCM. A DTC will be recorded and the MIL will illuminate.


Accelerator Pedal Position Sensor


The fuelling demanded by the driver is calculated from the position of the accelerator-pedal according to a series of three-maps used for vehicle speed. At a given vehicle speed, one of the three-dimensional maps defines fuelling for a given


pedal position and engine speed. The accelerator pedal position sensor uses two rotary sensors to convert the rotational action of the accelerator pedal into


two separate voltage signals (twin resistive track), based on a voltage supply from the PCM. In the event that one rotary sensor should fail, the engine will operate at a reduced speed. If a sensor fault occurs, a DTC will be recorded.


Automatic Transmission


Introduction


The 6–speed electronically controlled, automatic transmission is carryover from the gasoline derivative XJ. Besides the modified control strategies to accommodate the diesel application, a major modification in comparison to the gasoline derivative is the

Transmission Fluid Cooler.

Data


• Six forward gears;


• One reverse gear;


• Coaxial planetary transmission;


• Hydrodynamic torque converter with an integral-converter lock-up clutch;


• Hydraulic valve body with integral transmission control module;


• Electronic-hydraulic shift point position and gear shift control;


• Manual shifting;


• Self-diagnosis;


• Fill for life transmission fluid.
 
  #31  
Old 10-23-2010, 05:07 PM
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Transmission Operation


• The transmission unit uses planetary gears with hydraulic-electronic control.


• The valve body and transmission control module (TCM) form a combined element, installed in the transmission’s fluid pan.



• The TCM uses a newly developed shift strategy known as adaptive shift strategy.


Engine power reaches the transmission via a torque converter.


The six-forward gears and one-reverse gear are obtained from a single-web planetary gear set, followed by a double planetary gear set, known as the Lepelletier-type gear sets. These gears make it possible to obtain six-forward speeds.


Gear selection is achieved by controlling the flow of automatic transmission fluid to operate various internal clutches. The TCM controls the electrical components for gear-selection shift pressure and torque converter slip-control. In the event


of a system malfunction the TCM provides failure-mode effect management, to maintain maximum functional operation of the transmission, with minimum reduction in vehicle and occupant safety. In the event of loss of transmission control through electrical


power failure, the basic transmission functions: Park, Reverse, Neutral and Drive are retained by the hydraulic system. The transmission will operate in limp-home mode: third or fifth gear fixed, dependent upon gear selection at the time of the


malfunction.


Parking Lock


The parking lock acts by inserting a pawl into the teeth of the parking lock gearwheel on the transmission output shaft.


Fluid Pump


The half-moon type fluid-pump is located between the torque converter and transmission housing. The pump is driven directly by the engine via the torque converter shell, and supplies fluid to the transmission and valve body. The pump draws in fluid through a filter and delivers it at high-pressure to the main pressure valve in the valve body. The valve adjusts the pressure and returns excess fluid to the fluid pan.


Shift Elements


In addition to the torque converter lock-up clutch the other shift elements are:


• Three rotating multi-plate clutches ‘A’, ‘B’ and ‘E’.



• Two fixed multi-disc brakes ‘C’ and ‘D’.


All gear shifts ‘1st to 6th’ or from ‘6th to 1st’, are power-on overlapping shifts. When during a shift, one of the clutches must continue to transmit the drive at lower main pressure until the other clutch is able to accept the input torque. The shift elements, clutches or brakes are engaged hydraulically. The fluid pressure is built up between the


cylinder and the piston, therefore pressing the plates together.


When fluid-pressure drops, the cup-spring that is pressing against the piston moves it back to its original position. The purpose of these shift elements is to perform in-load shifts with no interruption to traction. Multi-plate clutches ‘A’, ‘B’ and ‘E’ supply power from the engine to the planetary gear train. Multi-disc brakes ‘C ’ and ‘D’ press against the transmission housing in order to achieve a torque reaction effect.


Shift Overlap Control


Another feature of the transmission is that freewheels (one-way clutches) are replaced by actuation of the relevant clutches when overlap gearshift takes place. This arrangement provides a reduction in transmission weight and size.


The electronic-hydraulic shift action is obtained by means of various valves in the valve body being actuated by pressure regulators. They engage or disengage the relevant clutches or brakes at the correct moments.



Transmission Control Module / Valve Body


The transmission control module (TCM) and valve body are a combined unit, installed in the transmission’s fluid pan. This combination of components provides the following


advantages:



• Minimum tolerances as the TCM is directly connected to the solenoids;


• Better coordination of gearshifts;


• Increased refinement;


• Optimized shift quality;


• Good reliability, since the number of plug connections and interfaces are reduced.


The TCM controls the operation of the transmission, by


processing signals, for example:



• transmission input and output speeds; via the CAN:


• throttle pedal position;


• gear selector position;


• engine torque and speed;


• transmission fluid temperature;


• brake pedal status;


• engine oil temperature;


• engine coolant temperature;


• wheel speed.


Using these signals and stored information, the TCM calculates the correct gear and torque converter lock-up clutch setting, plus the optimum pressure settings for gear shift and lock-up clutch control.


Five pressure regulators and one solenoid valve are used to direct transmission-fluid flow, select internal clutches, and control the fluid pressure at the clutch for gear control. A separate pressure regulator is used exclusively for torque-converter clutch control. The TCM monitors input and output signals to confirm correct system operation. If a


malfunction does occur, the TCM reverts to a default state and informs the driver of a problem via the instrument-cluster message center.


System diagnosis is performed using ‘WDS’.


Sensors


Speed sensors


The TCM monitors the two transmission speed-sensors located on the valve body: one for measuring input shaft speed (turbine speed), and one for measuring output shaft


speed.



Temperature sensor


The TCM uses the input signals from the temperature sensor located on the valve body, to activate various shift strategies.


Gearshift position sensor


The gearshift position sensor is located on the valve body. The TCM uses inputs from this sensor to determine the selected gear-range on the automatic side of the J-gate. Signals from the position sensor also ensures that the engine will only start


when the gear selector is in the park or neutral position. The PCM uses the signals to prohibit operation of the starter relay if the incorrect gear is selected.





• Each time the vehicle is started a ‘fail-safe’ check is performed on the TCM and associated electronics;


• A ‘limp-home’ mode is functioned, if a power failure occurs;



• Prevents reverse gear selection at forward speeds;


• Prevents manual gear down-shifting at excessive engine speeds.


Shift Selection


The TCM uses various driver selected modes and adaptive modes as below. Each mode introduces a different gear selection strategy, depending on driver requirements and


driving conditions (vehicle status).



Driver selected modes:


• Normal mode:


– Activated by the sports ‘S’ switch on the J-gate surround, the switch does not illuminate when normal mode is selected.


– Normal mode will remain active until the driver selects ‘sports mode’ or ‘cruise control’. On the deactivation of ‘cruise control’, the system returns to the mode previously activated.


– Normal mode can be overridden by various adaptive modes.


• Sportmode:


– Activated by the sports ‘S’ switch on the J-gate surround, the switch will illuminate when sport mode is selected.


– The sport mode strategy enables gearshift points to be extended to higher engine speeds, and downshifts at lower accelerator-pedal angles.


– Sport mode will remain active until the driver selects ‘normal mode’ or ‘cruise control’. On the deactivation of ‘cruise control’, the system returns to the mode previously activated.


– Sport mode can be overridden by various adaptive modes.


• Cruise control mode:


– When activated the TCM receives signals from the PCM via the CAN.


– The TCM implements a shift-map strategy to reduce gearshift activity and subsequently increase fuel economy.


Adaptive modes, these modes are selected automatically depending on driving conditions and vehicle status:


• Hot mode:


– A gear selection and torque converter lock-up strategy is implemented to reduce heat generated in the transmission when any of the following become hot enough to reach a critical threshold value:


transmission fluid,


transmission casing,


engine oil,


engine coolant temperature.


– The hot mode strategy reduces generated heat by selecting higher gears and engaging the lock-up clutch at lower vehicle speeds.


NOTE:




With hot mode implemented the driver may experience unexpected up-shifts when running at high vehicle speeds and loads.
• Traction controlmode:



– Under normal driving conditions an increase or decrease in wheel speed would be recognized by the TCM as the vehicle accelerating or decelerating and a gear would be selected in proportion to the speed of wheel rotation.



– In a situation where the vehicle is not accelerating in proportion to the wheel rotation speed, for example a slipping wheel. The TCM, in response to signals from the ABS module, will still command the transmission to select a higher-gear to help reduce wheel slip. The high gear will remain engaged until traction at the slipping wheel is regained.


• Gradient and towing mode:


– The gradient and towing mode is activated when the TCM detects reduced vehicle acceleration at given throttle positions. This reduction in acceleration is recognized by the TCM as the vehicle either towing or ascending a gradient. Therefore, to provide the vehicle with maximum traction effort, a shift-map is used that extends the amount of time lower-gears are engaged, and subsequently delays the selection of higher gears.


Adaptive Shift Strategy


By increasing the linking of the transmission control system with other vehicle systems such as engine, brakes (ABS) and steering, a number of signals are made available to the TCM, which describe how the vehicle is being driven and on what road conditions. Using this information the TCM is able to exploit the vehicle’s performance capability, and conversely maximize driving refinement and economy.


By monitoring signals associated to:



• longitudinal and lateral acceleration,


• engine speed and engine torque,


• engine oil temperature,


• position and movement of the accelerator, and


• individual wheel speed, additional functions in the TCM can be realized. On the basis,


of this information the TCM recognizes whether:


• the vehicle is maneuvering round a corner,


• all thewheels aregripping,


• the driver is braking,


• or if the driver wishes to accelerate.


From these signals, conclusions are made regarding the vehicle’s actual load status and the topography of the stretch of road (uphill or downhill gradient), and what shift strategy should be applied to the transmission function.


For example, when ‘sport’ mode is selected and an enthusiastic driving style is detected on a demanding road. The TCM will adjust the transmission shift strategy to complement the conditions by inhibiting sixth-gear and selecting lower gears earlier to prevent ‘hunting’ between gears.


Under heavy braking, the TCM will select a lower gear to enable an immediate acceleration response on application of the accelerator pedal. Similarly, if the accelerator pedal is released rapidly following hard acceleration, selection of a higher gear is inhibited to increase engine braking and improve subsequent acceleration response.


To complement these features, when the TCM detects the vehicle rounding a corner, selection of a higher gear is inhibited until the vehicle exits the corner.


Once a more sedate driving style is detected, sixth gear will be reinstated and the shift strategy will return to normal.


Transmission Fluid Cooler


The transmission fluid cooler is a separate liquid cooled-type and has replaced the unit integrated into the coolant radiator as fitted to the gasoline derivative.




The cooling system has the ability to quickly warm-up the transmission fluid and maintain it at between 50 C and 100 C.


With the target temperature being 90 C the most efficient temperature for shift quality and fuel economy at all ambient temperatures.



A transmission coolant valve

controls the coolant flow to the transmission fluid cooler by switching between the heating function and cooling function.





The transmission coolant valve is effectively a thermostat in a ‘T’ housing, with a hot feed from the main radiator’s top hose and a cool feed from a sub-cooled section of the main radiator. From engine start-up the coolant is taken from the top hose, providing hot coolant to the transmission fluid cooler to heat the transmission fluid. When the coolant reaches 95 C, the thermostat shuttles across the ‘T’ to change the feed from a




hot flow to a cool flow to keep the transmission fluid below 100 C.




If the vehicle is driven aggressively in demanding conditions the transmission fluid could reach 125 C or above, in these circumstances the transmission will switch to ‘hot mode’




function.




The purpose of the transmission hot mode is to protect the powertrain by monitoring the transmission fluid, engine oil and coolant temperatures.




There are two stages of hot mode:




1. Adjusts the torque converter schedule to lock-up earlier.




2. Employs a more conservative shift-map, which up-shifts earlier and disables manual J-gate operation over certain vehicle speeds.




Torque Converter




A new generation lightweight hydrodynamic torque converter with integral lock-up clutch and torsional vibration dampers is employed.




Automatic Transmission External Controls




Transmission Selector Mechanism




J-gate




The J-gate is designed to accommodate either automatic or manual driving techniques:




• Automatic, right-hand side of the J-gate:




– Enables selection of park ‘P’ through to drive ‘D’.




– The link between the selector lever and the transmission is via a cable.




– A position switch within the transmission informs the transmission control module (TCM) of gear selection.




– The TCM transmits gear selection information to other vehicle modules via the CAN.




– With drive ‘D’ selected, gear selection is controlled by the TCM in response to signals received relating to vehicle status, for example throttle position, vehicle




speed, etc. These signals are received via the CAN.




– In addition, when ‘D’ is selected and sixth gear is engaged, the selector lever can be shifted sideways across the gate to fifth gear. Sixth gear will be inhibited until the selector lever is moved back to ‘D’.




• Manual, left-hand side of the J-gate:




– Enables individual selection of second, third, fourth and fifth gears.




– The TCM detects the driver’s gear selection through signals transmitted from the selector mechanism, via the CAN.




The sports mode switch, marked ‘S’ on the J-gate surround enables the driver to select either normal ‘N’ or sport ‘S’ modes.




Selector Interlock





The selector interlock is solenoid-operated
Its function, is to prevent the selector lever being moved from park ‘P’ until the ignition is ‘ON’ and the brake pedal is depressed. The solenoid remains in a de-energized state until the brake pedal is depressed.





NOTE:





If the brake pedal is depressed while the ignition is switched ‘ON’ the position ‘P’ on the J-gate will flash. This indicates to the driver that the brake pedal must be released
and then depressed to enable the selector lever to be moved out of park ‘P’.




NOTE:





If the selector lever is moved into park ‘P’ when the driver is simultaneously operating the brake pedal, the position ‘P’ on the J-gate will flash. This indicates to the driver
that the brake pedal must be released and then depressed to enable the selector lever to be moved out of park ‘P’.




Selector Interlock Override




In the event of a discharged or disconnected battery a provision is made to manually override the selector interlock solenoid enabling the selector lever to be moved from the




park ‘P’ position. The interlock override is accessed by removing the top cover of the J-gate




Key Interlock

The key interlock system prevents the removal of the ignition key when the gearshift lever is not in the park ‘P’ position.

Limp Home Mode

In the event of an electrical or mechanical malfunction, the selector ranges on the right-hand side of the J-gate will still function. The selector mechanism performs its own internal fault monitoring and relays any fault codes to the TCM for diagnosis using ‘WDS’.

Exhaust System

The stainless steel exhaust system is similar to that used for the XJ gasoline derivative with:

• New muffler internals tuned for diesel application.

• Similar exhaust routing along the vehicle.

• Same mounting locations on the body.

A major addition to the exhaust system is the diesel particulate filter

Fuel Tank and Lines

The diesel fuel tank shares a common casingwith the gasoline derivative fuel tank, with a fuel capacity of 85 liters (80 liters usable).

A stainless-steel filler neck is introduced with a wide-bore filler neck specially designed to reduce diesel frothing while the fuel tank is being replenished.

An internal fuel lift-pump with low-level fuel pick-up features, as used in the gasoline derivative, is employed to maintain an equal fuel level in both compartments of the saddle tank. The lift-pump also provides a low-pressure supply, approximately

0.5 bar, to the common-rail high-pressure fuel system.


The fuel tank’s lift-pump is operated by signals from the PCM, via the fuel pump relay located in the rear power distribution box. When the ignition is switched on the fuel pump will operate for 25 seconds to build-up fuel pressure. As engine cranking commences the fuel pump will stop running until the engine starts; this relieves load on the battery.
 
  #32  
Old 10-23-2010, 05:09 PM
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Fuel Run-Dry Strategy





Fuel level is transmitted to the instrument cluster by a resistor tile and float rod. A low-fuel warning lamp is provided in the fuel level gauge.




A fuel run-dry strategy has been programmed into the PCM software to prevent the fuel tank emptying completely. This strategy prevents damage to the fuel tank pump and the necessity of priming the fuel system. In the event that the fuel is allowed to run too low, signals transmitted from a low-level switch, located in the swirl-pot of the fuel tank, and both fuel level sensors initiate the fuel run-dry strategy.




Due to the location of the low-level switch there will only be a small amount of fuel left in the tank when the fuel run-dry strategy initiates. The driver will have been notified much




earlier that the vehicle was low on fuel. Although this is a simulated run-dry procedure, it provides the symptoms of the vehicle running out of fuel and the driver will perceive it as such. The engine will stop when there is approximately 4 liters of fuel remaining in the fuel tank.




Fuel Filter




The fuel filter is a disposable canister type.




To prevent diesel waxing in cold conditions and aid warm-up, a temperature-sensitive regulating valve incorporated in the fuel filter housing, diverts a portion of the warm-fuel returning from the engine into the fuel filter.




The regulating valve commences closing at 0 C and fully closes at 35 C. When the valve is closed the returning fuel is diverted to the fuel filter via the under-vehicle fuel cooler to maintain an optimum fuel temperature.


The filter canister incorporates a chamber for collecting moisture. The moisture contained in the diesel fuel collects on the internal filter element and forms droplets, which fall into the moisture chamber. A drain plug located on the bottom of the filter canister is used to discharge the water.




Fuel Cooler


Two fuel coolers are used: one on the low-pressure side of the system and one on the high-pressure side:



• The low-pressure-side fuel cooler is air cooled and situated under the vehicle, below the front passenger seat.
 
  #33  
Old 10-24-2010, 03:37 AM
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Following the even handed approach, the Jaguar diesel engine DID start life as a Peugeot-Citroen engine, and that one is in use in the Citroen C6 and some C5s. The Jaguar version is of course much modified, chiefly as stated above, the piezoelectric injectors and the block material.
The contribution by BuckMR2 will serve as a reference on this Jaguar version. This diesel engine is of course now in 3litre form, and I for one would love to check it out.
Leedsman.
 
  #34  
Old 10-24-2010, 12:08 PM
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wow ,wow and more wow,
i asked for some info about the 2.7 jag diesel, and did BUCK ever deliver.

i asked for something to talk about ,but we may be here forever!!LOL.

thanks,

im lately impressed with the CGI cyl. blocks, lot of diesel and race engines are startingto use it, most NASCAR engines now use it,but cant find where thet are manufactured??

not many factory production blocks are CGI, any info to that?

i understand they are die-cast not gravity cast,,true?

thanks again ,,Ron
 
  #35  
Old 10-24-2010, 01:39 PM
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Hi ronbros. Looks like Buck beat me too it! I could have told you all that, of course
 
  #36  
Old 10-26-2010, 12:30 PM
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thanks anyway delta66,

you gents seem to get available information, my studies for where CGI blocks and heads are actually cast, foundry locations, seem to be in only two countries,INDIA and BRAZIL SA.

i wonder if its about foundry emission or labor unions.

or are they simply ahead of things??
 
  #37  
Old 10-26-2010, 02:39 PM
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I've read the full text of the contribution now (I didn't have time earlier) and find some disturbing detail about the design assumptions re. heating the ATF fluid and it's target operating temperature for synthetic fluid life of 100,000mile. There seems to be a mismatch here. Most authorities say that for this mileage target for synthetic fluid life, an operating temperature of 175deg.F. OR LESS is required. But the Jaguar design quoted here is for considerably higher than this at 95deg.C to keep the temperature below 100degC., or 212deg.F. Something not right here. Again, most authorities state for every rise of 20deg.F over 175deg.F, cuts the ATF fluid life in half, in this case around 50,000mile. I say all this because I understand from many directions that the design life of this partic. fluid and box combo is 100,000mile. (Sealed for life). The situation would be far worse for non-synthetic fluid of course.
BTW., I shortly will be applying a remote probe type thermometer to my autobox to read the temperature as I drive. I will report my findings, as I don't necessarily believe the printed word just because it's printed. I regard this issue as important because of potential very expensive damage to the autobox.
Leedsman.
 
  #38  
Old 10-26-2010, 05:40 PM
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interesting info leeds!
i have read of the useful life of synthetic lubes life is double that of standard oils!

and 200F is a normal temp. for syn. fluids lubes.

a lot of newer cars have sealed transmissions, and final drives.

around USA, most aftermarket repair shops, have recommended against even changin fluids, sayin to many troubles show up after fluid changes, just leave it alone and drive it! ( go figure).

i have personaly run auto boxes for 150K without fluid change, add a small friction and seal conditioner, and on my way.
all the while it is against normal procedure, but seems as tho it works.

it is common practice(in USA) to get rid of the vehicle if serious engine of trans.
probs show up, they go to recycle yards.

let us know what you find with temp probe, could be interesting.
 
  #39  
Old 11-18-2010, 03:22 PM
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some interesting performance stuff.

last month at the TEXAS MILE a top speed event, GM Duramax diesel engine fitted in a Street driven Ford Mustang,2002, went 205 MPH, drove 1000miles to and from track averaging 36 MPG,US gal.

OH, YEAH !! go diesels

Ron
 
  #40  
Old 12-13-2010, 02:10 PM
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Anyone had problems starting in the cold weather?

Diesel apparently goes cloudy at -9.5 degrees and can cause problems starting. I have had no issues at all so far with the coldest start being -13.
 

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