Engine - System Operation and Component Description
System Operation
Variable Camshaft Timing
TiVCT (twin independent variable camshaft timing) is used on this engine.
Continuous adjustment of the valve timings allows the following to be achieved:
- Smoother idling
- Increase in power and torque
- Sufficient internal exhaust gas recirculation
- Performance optimization at wide open throttle
There is a VCT unit on each camshaft for making the adjustment. The valve timings can be controlled by making engine speed and load dependent adjustments of the intake and exhaust camshafts.
Component Description
Cylinder Head
| Item | Description |
|---|---|
| 1 | Camshaft bearing cap - intake camshaft with jacking point - high-pressure pump |
| 2 | Cover - vacuum pump |
| 3 | Drive - vacuum pump |
| 4 | Camshaft bearing cap - exhaust camshaft Comments: The camshaft bearing caps are identified by the numbers 1 - 4 |
| 5 | Exhaust camshaft |
| 6 | VCT unit - exhaust camshaft |
| 7 | Exhaust camshaft VCT control valve |
| 8 | Intake camshaft VCT control valve |
| 9 | VCT unit - intake camshaft |
| 10 | Intake camshaft |
| 11 | Camshaft bearing cap - intake camshaft Comments: The camshaft bearing caps are identified by the letters A - D |
| 12 | Triple cam |
The cylinder head is made of a light metal alloy.
The exhaust manifold is part of the cylinder head and therefore cannot be replaced separately in service.
The intake camshaft is made longer by the additional triple cam for driving the high-pressure pump. It is therefore impossible to confuse it with the exhaust camshaft. It is mounted on five bearings. In addition, the intake camshaft bearing cap nearest the transmission forms the jacking point for the high-pressure pump used to create fuel at high pressure. The seal to the cylinder head is achieved using sealing compound.
The exhaust camshaft is mounted on four bearings and has an additional groove by which the vacuum pump is driven. The vacuum pump cover carries the seal for the valve cover and the vacuum pump.
The VCT units are bolted on the corresponding camshaft with the respective VCT control valve. The control valves are operated by a solenoid valve.
Valves
| Item | Description |
|---|---|
| 1 | Valve collets |
| 2 | Valve spring retainer |
| 3 | Valve springs |
| 4 | Oil shield ring |
| 5 | Inlet valve |
| 6 | Outlet valve |
| 7 | Bucket tappet - exhaust valve |
| 8 | Bucket tappet - intake valve |
There are four valves per cylinder in the cylinder head. Two intake valves (larger head) and two exhaust valves (smaller head).
The intake valves are made of one material and are solid .
The exhaust valves are designed as hollow valves . The cavity is filled with sodium . The sodium melts at about 97 °C and has good thermal conductivity. The temperature at the valve spring retainer can thus be reduced by about 100 °C.
The valves are operated by mechanical bucket tappets.
Cylinder head gasket
A multi-layer steel laminate cylinder head gasket is used.
Two guide sleeves are pressed into the cylinder block to locate the cylinder head and its gasket.
Timing gear
| Item | Description |
|---|---|
| 1 | Intake camshaft pulley with integrated VCT |
| 2 | Exhaust camshaft pulley with integrated VCT |
| 3 | Crankshaft timing gear |
| 4 | Automatic timing belt tensioner |
| 5 | Timing Belt |
A newly developed oil bath timing belt drive is used to drive the camshafts.
Advantages of oil bath timing belt drive over an oil lubricated chain drive:
- Reduced frictional losses (about 20 per cent), thereby lower fuel consumption and thus reduced CO2 emission
- Reduction in noise
- The guide rails usual with chain drive are eliminated
Advantages of oil bath timing belt drive over a comparable dry timing belt drive:
- The timing belt is maintenance-free
The timing belt is tensioned using an automatic timing belt tensioner.
Engine front cover
| Item | Description |
|---|---|
| 1 | Jacking point - coolant pump |
| 2 | Guide - oil dipstick |
| 3 | Gasket - coolant inlet |
| 4 | Crankshaft front oil seal |
The aluminum timing cover seals the camshaft drive to the outside. The lower area accepts the crankshaft oil seal which is installed from the outside. The special tools intended for the purpose must be used to remove and install the O-ring seal (see current service literature).
The seal to the engine is made using a sealing compound (arrows).
The oil dipstick guide is secured to the inside of the timing cover with three bolts.
In addition, the timing cover contains the jacking point for the coolant pump. To be able to remove it, the coolant pump must first be detached.
Variable Camshaft Timing
| Item | Description |
|---|---|
| 1 | Variable camshaft timing solenoid, intake camshaft |
| 2 | Intake camshaft VCT solenoid seal |
| 3 | Intake camshaft VCT control valve |
| 4 | VCT unit - intake camshaft |
| 5 | CMP Sensor - intake camshaft |
| 6 | CMP Sensor - exhaust camshaft |
| 7 | VCT unit - exhaust camshaft |
| 8 | Exhaust camshaft VCT control valve |
| 9 | Exhaust camshaft VCT solenoid seal |
| 10 | Variable camshaft timing solenoid, exhaust camshaft |
This is an electro-hydraulically controlled camshaft adjustment system that allows variable timing for the intake and exhaust camshafts independently of each other.
To do this, each camshaft is equipped with a VCT unit. The front closing plates of the units are marked with I (intake) and e (exhaust).
| Item | Description |
|---|---|
| 1 | VCT unit (intake camshaft) |
| 2 | Front closing plate |
| 3 | Rotor |
| 4 | Return spring |
The units have the same basic design. They are equipped with three oil brackets. A return spring is used to reach the closing position.
The difference between the VCT unit intake and exhaust camshafts is in the closing position. The unit of the intake camshaft closes in "retarded" position and the unit of the exhaust camshaft closes in the "advanced" position.
The VCT units are bolted with the associated VCT control valve on the respective camshaft. This means that:
- Securing bolt and control valve form one component.
Both VCT units have a maximum mechanical adjustment angle of 49 degrees crank angle. The maximum programmed adjustment angle is 45 degrees crank angle.
The particular control valve is operated by a VCT solenoid. Both solenoids are secured to the front of the timing case with three securing bolts each.
| Item | Description |
|---|---|
| 1 | Magnetic alignment of the magnetic disk |
| 2 | Signal from CMP sensor |
| 3 | Setting of the camshaft Comments: Figures given in degrees camshaft |
The exact angular position of the intake and exhaust camshaft is each detected by a CMP sensor. The sensor scans a magnetic disk which is shrunk onto the particular camshaft. This signal is changed into a square-wave signal by the built-in converter electronics and sent to the PCM.
Both sensors are mounted from above on the valve cover with one securing bolt.
Cylinder block and crankshaft assembly
| Item | Description |
|---|---|
| 1 | Crankshaft upper bearing shell (1 required) Comments: Bearing shell with integral thrust washers (bearing no. 3) |
| 2 | Crankshaft upper bearing shell (1 required - bearing no. 1) |
| 3 | Crankshaft upper bearing shell (2 required - bearings no. 2 and 4) |
| 4 | Crankshaft bearing cap (quantity: 4) |
| 5 | Crankshaft lower bearing shell (1 required - bearing no. 1) |
| 6 | Crankshaft |
| 7 | Crankshaft lower bearing shell (3 required - bearings no. 2, 3 and 4) |
| 8 | Pistons (3 required) |
| 9 | Connecting rod (3 required) |
| 10 | Connecting rod upper bearing shell (3 required) |
| 11 | Connecting rod lower bearing shell (3 required) |
| 12 | Connecting rod bearing cap (3 required) |
The cylinder block is an 'open-deck' construction made of cast iron.
The engine code is stamped on the transmission flange on the exhaust side (arrow).
The side walls which are drawn down contribute to the rigidity of the cylinder block. These measures achieve a low weight as well as high rigidity.
The pistons are made of an aluminum-silicon alloy and are equipped with:
- an upper compression ring,
- a lower compression ring and
- a 3-part oil scraper ring (oil scraper ring as well as upper and lower tensioning spring elements).
The crankshaft runs in four bearings. The three crankshaft journals are at 120 degrees to one another.
Crankshaft rear seal
| Item | Description |
|---|---|
| 1 | Rear seal with steel carrier |
| 2 | Crankshaft |
The crankshaft rear seal is vulcanized into a pressed steel carrier. The complete carrier must be replaced in the event of service work.
Oil Spray Nozzles
There are three oil spray nozzles for piston cooling, located at the bearing positions for the crankshaft in the cylinder block.
They are aligned so that engine oil is sprayed onto the underside of the piston.
The oil spray nozzles are equipped with a ball valve. The valve opens from an engine oil pressure of about 1.2 bar.
Oil pan baffle/oil pan
| Item | Description |
|---|---|
| 1 | Oil baffle plate |
| 2 | Oil sump |
The oil pan baffle is bolted to the cylinder block from underneath with three securing bolts.
The oil pan is made of an aluminum alloy. It is equipped with a solid rib and at the same time forms the lower transmission flange. This achieves a rigid engine/transmission combination.
There are two guide pins (arrows) on the sealing surface of the cylinder block for exact alignment of the oil pan.
The seal of the oil pan to the cylinder block is made using sealing compound.
For installation and removal of the oil pan or the oil pan baffle, the detailed instructions in the current service literature must be followed.
Crankshaft pulley
| Item | Description |
|---|---|
| 1 | Crankshaft pulley |
| 2 | CKP sensor |
| 3 | Crankshaft position magnetic disk |
| 4 | Balance weight |
| Item | Description |
|---|---|
| 1 | Crankshaft front seal |
| 2 | Friction washer (service part to be installed whenever the crankshaft pulley is removed) |
The crankshaft pulley forms a single unit together with the magnetic disk for the crankshaft position.
There is an exactly positioned balance weight built into the crankshaft pulley and this reduces the vibrations of the crankshaft.
The crankshaft pulley is secured on the crankshaft only by the contact force of the securing bolt, which must be changed for a new one after removal.
The exact position of the crankshaft is detected by the CKP sensor. The sensor scans the crankshaft position magnetic disk. This signal is changed into a square-wave signal by the built-in converter electronics and sent to the PCM. When the sensor is renewed, no adjustment is necessary because this is predetermined by the way in which the sensor is secured.
| Item | Description |
|---|---|
| 1 | Magnetic alignment of the magnetic disk |
| 2 | Signal from CKP sensor |
| 3 | Reference mark 90° before TDC Comments: Figures given in degrees crankshaft |
Engine Lubrication
Oil pump
With manual transmission
| Item | Description |
|---|---|
| 1 | Oil pump drive pulley |
| 2 | Oil pump drive belt |
| 3 | Oil pump gear |
| 4 | Oil pump |
With automatic transmission
| Item | Description |
|---|---|
| 1 | Oil pump drive belt pulley |
| 2 | Oil pump drive belt tensioner |
| 3 | Balance shaft gear |
| 4 | Oil pump cover |
| 5 | Oil pump drive gear |
| 6 | Oil pump |
| 7 | Oil pump drive belt |
Conventional oil pumps account for up to 10% of the mechanical power losses at the nominal speed of an engine, leading to increased fuel consumption. This is caused by the high output of the oil pump, especially at high engine speeds.
When a variable oil pump is used, the output can be matched to the required oil flow in a flexible manner, depending on the temperature and the engine speed.
Layout
| Item | Description |
|---|---|
| 1 | Vane-type pump |
| 2 | Adjusting ring, vane pump |
| 3 | Pressure spring |
| 4 | Control pressure space |
The principle component of the variable oil pump is formed by a vane-cell pump with an adjusting ring.
The illustration shows the adjusting ring in the starting position . The pressure spring pushes the adjusting ring to the left against the stop. In this position the vane-cell pump creates the maximum possible oil flow.
The oil pressure in the control pressure space can be changed depending on the oil pressure demand. If the oil pressure in the control chamber exceeds the force of the pressure spring, then the vane-cell pump adjusting ring is moved to the right. This reduces the supply capacity of the pump.
Operation
| Item | Description |
|---|---|
| 1 | Oil pressure from the main oil gallery |
| 2 | Oil pump control solenoid |
| 3 | Leakage line |
| 4 | Oil sump |
| 5 | Pressure relief valve |
| 6 | Spring |
| 7 | Oil pressure to oil filter |
| 8 | Pressure port of the vane pump |
| 9 | Hydraulic control piston |
| 10 | Control chamber |
| 11 | Adjusting ring, vane pump |
The oil pressure is controlled via a hydraulically operated control piston integrated into the oil pump. The pressure on the control piston is determined by a solenoid valve which is activated by the PCM according to the requirements.
In the rest position, the solenoid valve is closed (see previous illustration). The engine oil supplied by the oil pump flows to the control chamber. Because the solenoid valve is closed, the oil flows through the control chamber and drains to the oil pan via a bypass in the solenoid valve. No pressure can therefore be built up in the control chamber.
The control piston is pushed to the left by the spring force. Because of this, the control piston closes the oil gallery to the vane-cell pump adjusting ring.
In this position, the pressure gallery of the transfer pump has the largest aperture cross-section . The maximum possible oil flow is thus available for engine lubrication.
| Item | Description |
|---|---|
| 1 | Oil pressure from the main channel |
| 2 | Oil pressure control solenoid valve |
| 3 | Leakage line |
| 4 | Oil sump |
| 5 | Pressure relief valve |
| 6 | Spring |
| 7 | Oil pressure to oil filter |
| 8 | Pressure channel of the transfer pump |
| 9 | Hydraulic control piston |
| 10 | Control chamber |
| 11 | Adjusting ring, vane pump |
When operating conditions permit the vehicle to be driven with a lower oil pressure, the PCM opens the solenoid valve .
The oil pressure supplied by the oil pump now acts directly and via the solenoid valve on the control chamber and with it pushes the control piston to the right against the spring force.
Because of this, the control piston opens the oil channel to the vane-cell pump adjusting ring. The pump pressure now acts on the adjusting ring and presses it towards the center of the pump.
In this position, the pressure channel of the transfer pump has only a small aperture cross-section . A lower oil pressure is thus available for engine lubrication.