Land Rover Discovery: Pistons and Connecting Rods

1. Oil control ring
2. Upper piston ring
3. Lower compression piston ring
4. Circlip
5. Piston
6. Connecting rod
7. Connecting rod bearing cap
8. Bolt (2 off)
9. Lower large end bearing
10. Upper large end bearing
11. Small end bearing
12. Circlip
13. Gudgeon pin

The connecting rods are manufactured from forged steel and have fracture split connecting rod bearing caps to ensure precision re-assembly for bearing shell alignment. The connecting rod bearing caps are not selectable. Adjustment for large end bearing journal size is made by selecting the correct large end bearings after measuring the crankshaft journals.

There are a number of grades of large end bearing available, each being colour coded and inkjet marked with a letter on the running face of the bearing. The crankshaft is laser etched with a string of four alpha characters in the order of crankshaft journals 1-4 and a data matrix code containing the same data. The correct large end bearing shells are selected with reference to a selection chart in order to achieve optimum running clearances.

For additional information, refer to: Specifications (303-01B Engine - INGENIUM I4 2.0L Diesel, Specifications).

There is only one grade of piston diameter. The pistons are marked to ensure correct assembly, with the marks facing the front of the engine. The top face of piston has an arrow which must also point towards the front of the engine. The piston crown has a recess for optimisation of the fuel / air mixture and combustion.

A three-ring piston-sealing system is used. An oil control ring is located in the lower groove. Two compression piston rings are located above the oil control ring. The piston ring gaps must be positioned at 120 degrees to each other.

The pistons are cooled with engine oil from four piston cooling oil jets installed in the cylinder block.

The pistons are attached to the connecting rods with a gudgeon pin, which is secured with 2 circlips. The gudgeon pin is located through the small end bearing in the connecting rod which allows the piston to articulate with the linear movement of the connecting rod. The circlips locate in grooves in the piston.

PISTON COOLING OIL JETS

1. Piston cooling oil jets solenoid
2. Piston cooling oil jet - cylinder 1
3. Piston cooling oil jet - cylinder 2
4. Piston cooling oil jet - cylinder 3
5. Piston cooling oil jet - cylinder 4
6. Bolt
7. Support bracket
8. Oil jet outlet nozzle

Four piston cooling oil jets are located in the cylinder block. Each jet is located adjacent to a cylinder and secured in the cylinder block with a bolt.

The oil jet outlet nozzle and the support bracket are an assembly.

The piston cooling oil jets provide piston and gudgeon pin cooling and lubrication. Each piston cooling jet has a single outlet nozzle which sprays oil into the cooling chamber in the piston. The jets are supplied pressurized engine oil from the variable flow oil pump with integral vacuum pump via a drilling in the cylinder block. The oil supply to the drilling is controlled by a piston cooling oil jets solenoid which is controlled by the Engine Control Module (ECM). The solenoid can open and close the oil supply depending on engine speed and load.

In addition to supplying oil to the piston cooling gallery the oil lubricates the small end bearing and gudgeon pin.

DYNAMIC BALANCE SHAFTS

1. Needle roller bearing (4 off)
2. Dynamic balancer
3. Dynamic balancer gear
4. Flange bolt (2 off)
5. Bearing housing
6. Bearing housing
7. Idler gear
8. Dynamic balancer gear
9. Dynamic balancer

The engine balance system consists of two eccentric weighted dynamic balancer shafts which oppose vibrations created by the engine's reciprocating components. The dynamic balancers are mounted into machined bores inside the cylinder block. The two dynamic balancers rotate in opposite directions, driven at twice the speed of the crankshaft by a dynamic balancer gear pressed onto the crankshaft. The equally sized eccentric weights are phased so that the inertia reaction to their counterrotation cancels out vibration caused by the engine.

One of the dynamic balancers is driven off an 86-teeth dynamic balancer ring gear located on the crankshaft which rotates a 43-teeth driven gear on the driven dynamic balancer. The second dynamic balancer is driven off the same ring gear through a 45-teeth idler gear which rotates the 43-teeth driven gear on the driven dynamic balancer.

The idler gear is mounted on to the cylinder block using a steel idler bush which is pressed into the cylinder block. Driven gears on one of the dynamic balancers and the idler gear are anti-backlash "scissor" gears in order to minimize noise. All the gears are helical to ensure smooth operation. The dynamic balancers are located on needle roller bearings which run on outer races installed in the cylinder block machined bores. The bearings are lubricated by oil mist during engine operation.

It is important to make sure that each dynamic balancer is timed correctly in respect to the crankshaft using specialized alignment tool(s). Refer to xxxxxxxx for further details.

CrankshaftOil Pan

READ NEXT: