Design and Function

Design and function

Engine block










Cylinder head, camshaft bearing housing









The cylinder head is of the cross-flow type, (Cross-flow = in from one side and out from the other side).
The two camshafts are supported by seven bearing caps each, directly in the cylinder head and camshaft cover. The camshaft cover works like a combined valve cover and camshaft bearing cap. The camshaft cover has cast oil ducts on the underneath which ensure good oil supply to the camshafts and the valve lifters.
The maintenance-free valve lifters, valve springs and valves are in the cylinder head.

Cylinder head gasket




The seal between the cylinder head and cylinder block is a conventional cylinder head gasket. The seal between the other gasket faces is a liquid gasket.
The cylinder head gasket is made of steel and has multiple layers.

Cylinder block




The cylinder block consists of 3 sections.
- Cylinder block
- Intermediate section
- Gear housing
All three sections are made of die cast aluminum, molded under high pressure.
The mating flange between the cylinder block and intermediate section is in the center line of the crankshaft. The gear housing for the camshaft drive is secured on top of the cylinder block.
The cylinder block houses six cast iron cylinder sleeves. These cylinder sleeves cannot be replaced. The stroke length of the cylinders is greater than the cylinder diameter. This produces good torque and competitive power.
The intermediate section's seven main bearing caps have cast iron reinforcements.
On the top of the intermediate section there are cast oil channels which distribute the oil to the main bearings and on via the crankshaft to the big ends.

Oil sump and oil volume




The oil sump is made of die-cast aluminium with baffles (splash walls). This is so that the oil stays in the sump during active driving (heavy braking/acceleration, sharp turns, etc). Liquid gasket ensures the seal between the cylinder block and the oil sump.
The oil pan is designed to reduce mechanical noise from the engine, at the same time as providing a reliable supply of oil at different angles. A composite oil scraper keeps the larger section of the oil volume away from the rotating crankshaft. It minimizes power loss, improves fuel economy and prevents the oil from foaming.
The oil suction line, which runs from the oil pan, is made of plastic. The oil pan is equipped with an oil level sensor.
The oil pan contributes to the rigid design and operates as an extra reinforcement of the cylinder block.
The oil volume for engines B6324S4/S5 and B6304T4 have been reduced by 0.6 liters. Reasons for reducing the oil volume are, among others, lower service costs (cost of ownership), lower friction, and increased power. Lower friction and higher power are attained by facilitating the engine's internal 'breathing' with a lower oil surface, that is, easier evacuation of gases under the pistons.
The change of the oil volume is partly connected to a changed oil scraper plate, which means that the oil system also works with a reduced oil volume, as well as cooling for IVD ( Internal Viscous Damper), which is removed since 09w11. Since the volume reduction is partly connected to IVD-cooling it is not possible to reduce the oil volume on an older engine with IVD-cooling, even if the new oil scraper plate is retrofitted. Due to the volume reduction, a new oil dipstick is introduced with adapted markings.

Oil scraper plate




Under the crankshaft there is an oil scraper plate that is to prevent the oil from following along with the crankshaft in the crank movement. The plate is updated and is now located closer to the crankshaft and has integrated drain pipes. With these changes it has been possible to reduce the oil volume.

Piston




1. Piston cooling nozzle
The pistons are die cast in aluminum and the connecting rods are forged in steel.
The heat received by the pistons from combustion, is cooled, partly via the coolant jacket in the block but also by the oil from the six piston cooling nozzles.

Sparkplugs




To further improve the engine's features, a new type of spark plug is used, from Denso. The designation is " SIP" which means Super Ignition spark Plug.
An SIP-spark plug has a special design which improves a number of features with a more stable spark. By using a special alloy for both the center and side electrode, these can have a smaller diameter than normally. The smaller diameter of the electrodes minimizes heat losses during the flame build process, concentrates the electric field, and gives a stronger spark. The stronger spark gives higher engine power, improved fuel economy, better cold-cranking performance, and longer service life. It is the same spark plug for all versions of engine B63x4x, and can also be used for older versions. Electrode gap is 1.0 mm.

Crank system









The crankshaft is made from forged steel with induction hardened bearing surfaces.
The sprocket is crimped on the crankshaft's rearmost shank.
The crankshaft is supported by seven main bearings. The main bearings are replaceable main bearing shells. The sixth main bearing is a thrust bearing that holds the crankshaft in a determined position along the length of the axle.
An internal vibration damper is on the front end of the crankshaft. Inside the enclosed vibration damper, a circular flywheel works on a silicone fluid, which dampens the crankshaft torsion oscillations. The vibration damper gives longer service life for the crankshaft and smoother engine operation.
Engine versions without turbo were changed 10w20 with a modified crankshaft. The goal is to reduce the crankshaft's torsion vibrations at high engine speeds (4,500 rpm and up) and to save weight. The reduced torsion vibration means reduced noise level at high rpms at the same time as it reduces the load (torque) on the geartrain that drives the camshafts and auxiliary unit drive. It is the crankshaft's forged blank that is changed, reworking is unchanged.
To reduce vibrations material has been added between crank pin and main pin for the rear cylinders, which gives increased stiffness. At the crankshaft's front end, material has been removed instead, to reduce the crankshaft's oscillating mass. A new strategy has been used to design the crankshaft's balance weights to reduce weight. This can be seen by some balance weights having become small while others have become bigger. The changes have reduced the crankshaft's weight by a total of 1 kg. The change does not apply to turbo engines, but can be used on earlier versions of aspiration engines.

Main bearing




To improve the cold-cranking capacity, all main bearings have a changed appearance. In the middle of the bearing the thickness is unchanged but toward the end of the bearing the thickness is approx. 10microm thinner. The new type of bearing is possible to use on all versions of engine B63x4x, also those built earlier than 10w20.

Intermediate shaft









The intermediate shaft is located in the gear housing on the cylinder block. The intermediate shaft drives the camshafts and the auxiliary unit.
There is a sprocket on the rear section of the crankshaft, which drives the intermediate shaft via an intermediate wheel. The intermediate wheel drives the intermediate shaft via the intermediate shaft's centrally mounted gear. The intermediate shaft has a further two gear wheels of different sizes.
The intermediate shaft's front gear wheel has a freewheel clutch that drives the alternator at 2.7 times the engine speed. A free wheel clutch drives in one direction and slips/freewheels in the other direction.
The rear gear wheel drives the overhead camshafts.

Camshaft transmission









Both camshafts are driven by a camshaft chain, which in turn is driven by the crankshaft via the intermediate shaft. The camshaft chain has inverted teeth, so called, "silent chain".
The chain drive is maintenance free.
The exhaust side's camshaft has a vibration damper, which guarantees optimum balance in the gear and chain sprockets.

Timing cover









The timing cover is cast in aluminum.
The coolant pump shell is integrated in the timing cover. This saves weight. The coolant pump is still driven by the auxiliary unit's transmission.
The chain us tensioned by a hydraulic chain tensioner, which is located in the timing cover. Oil injection pipes supply the chain with oil.

Variable camshaft profile (CPS), only applies to B6324S5









The ideal engine should have low valve lift for low engine rpms and loads, and high valve lift at high rpms and loads.
To achieve this, an engine with two completely different camshaft profiles is required.
This engine has a patented system for camshaft profile switching. The system uses two completely different cam profiles designed on the same camshaft.
The inlet camshaft is provided with three cams for each valve, one centrally located with small lift height, 3.6 mm, and two equally sized outer cams with big lift height, 10.0 mm. With a small lift height at low load and at engine speeds up to approx. 3000 rpm, the primary benefit is lower fuel consumption.
In principle, during the time that the lift height is small, the air damper is completely open. Control of the incoming air volume to the cylinders takes place through control of the camshaft's opening times. Hereby the pump losses are reduced, which in turn gives lower fuel consumption. For more information, see Design and function, Engine control module (ECM).

Low lift
At small lift height (4), only the centrally placed cam acts on the valve, which takes place trough the inner valve depressor. The outer cams act on the outer valve depressors, which follow the cams' movement. Since the centrally located valve depressor and the outer depressor are not connected, the outer depressor moves without affecting the valve. Thus, lift height becomes small.

High lift
At high lift height (3), the inner valve depressor is connected with the outer valve depressor with lock pins. The outer camshaft cams' movement is transmitted through the outer valve depressor, on through the lock pins and the inner valve depressor to the valve. Thus, lift height becomes big.
The position of the lock pins is controlled hydraulically with two electro-hydraulic valves. One electro-hydraulic valve controls the valves for cylinders 1, 2 and 4, while the other controls the valve for cylinders 3, 5 and 6. Thus, the electro-hydraulic valves control 6 valves each (as the engine has 2 inlet valves and 2 exhaust valves per cylinder).
The position, on/off, of the electro-hydraulic valves is controlled by the Engine control module (ECM). For more information, see Design and function, Engine control module (ECM).
The inner valve depressor works like a hydraulic valve depressor, which compensates any wear. Thus, the valve clearance is "0".
The exhaust camshaft is conventional and has a lift height of 10.0 mm. The valve depressors are mechanical, that is, they "have" valve clearance.

Valve depressor




Valve depressors without CPS -functionality ( Camshaft Profile Shifting) have a coating of DLC ( Diamond Like Carbon).
It is the tops of the valve depressors that are coated with DLC. The layer with diamond-like carbon structure has a depth of 2microm, is very hard and has self-lubricating properties. The surface reduces the friction against the camshaft lobes and thus gives lower fuel consumption and longer service life.
Thanks to very good adhesion and toughness the DLC-coating can handle very high loads. The change applies to valve depressors without CPS-functionality.
This means that it concerns depressors in position:
- Engine B6304T4 (Ulev2) Exhaust, inlet
- Engine B6324S4 (Pzev) Exhaust, inlet
- Engine B6324S5 (Ulev) Exhaust
If needed the DLC-coated depressors can also be used on older engines.

Lubrication system









The task of the lubrication system is to build-up a protective film of oil between the moving parts of the engine. The lubrication system must also transport dirt particles away from the moving parts and cool hot engine parts.
This is carried out by the oil pump supplying oil to the oil filter through an oil pressure line of treated steel.
Clean oil is supplied to the oil cooler from the oil filter to the oil cooler. From there the oil is further distributed, through a duct system, out to the various engine functions.
A pressure sensitive valve controls the oil flow to the vibration damper's oil cooler pipe if necessary.

Oil pump




The oil pump is in the oil pan, mounted underneath the intermediate section. The oil pump has an integrated relief valve. The pump is directly driven by the sprocket on the rear end of the crankshaft.
The oil pump draws oil from a centrally located nozzle in the sump.
The pump increases the pressure of the oil for lubrication, cooling and hydraulic functions.

Oil filter module




The oil filter module consists of an oil filter reservoir and an oil cooler. It is mounted on the intermediate section. The oil filter module is element based and can be taken apart.
The oil cooler is connected to the coolant system. Coolant is led through the oil cooler.

Cooling system




The coolant pump shell is integrated in the timing cover. The pump wheel is still driven by the auxiliary unit's transmission.
The coolant pump pumps coolant through the cylinder block, and also cools the cylinder head, cylinder sleeves, spark plug wells, intake ducts and fuel injection nozzles.
The coolant flows in at the coolant pump and passes through a number of channels before it collects and then flows out to the thermostat housing. If the thermostat housing is closed, the coolant passes via the by-pass channel directly to the coolant pump to then circulate through the cylinder block again.
For the turbocharged engine, the task of the cooling system is to supply the turbocharger with coolant.

Coolant pump and drive gear




Engines B6324S4/B6324S5/B6304T (does not apply to XC90) are equipped with EHPAS ( Electro Hydraulic PPower Assisted Steering) instead of a conventional belt-driven servo pump. This means that drive of the coolant pump changes. With a belt-driven servo pump drive of the coolant pump takes place via a clutch on the servo pump. To drive the coolant pump, a belt pulley of reinforced plastic has been added and the attachment for the belt pulley on the coolant pump has been changed, which means that the pump is driven directly by the auxiliaries belt. To further reduce weight the coolant pump's housing is made of aluminum instead of steel, as before.
The fastening bolts for the coolant pump are longer since the coolant pump's flange is slightly thicker due to the change of material. Same gasket as before is used.

Alternator/clutch




The belt pulleys on alternator and intermediate shaft have improved surface treatment.
On the alternator shaft between alternator and intermediate shaft there is a clutch with a freewheel (one-way clutch) at each end. The function is to filter the engine's different irregular shape and thus avoid gear rattle/noise in the geartrain.
In connection with introduction of EHPAS (electric servo pump), the belt-driven servo pump with its heavy steel belt pulley is discontinued as well as the clutch for the coolant pump. The reduced rotating moment of inertia means more freewheeling, primarily when idling.
To reduce/avoid wear, the drive gears' outer ring (against the one-way clutch's friction band), are treated with nitride.

AC bracket




The AC compressor's fastening bracket is simplified. Earlier solution with a main bracket and three separate stays, is replaced by a modified bracket which has the front reinforcement stay integrated and a new fastening point in the transmission. The change means, except that the fastener assembly has 9 fewer bolts, that the installation method becomes easier and there is no longer a need for any special tools when assembling.

Crankcase ventilation




The crankcase ventilation is maintained internally in the engine.
An oil separator is on top of the engine's camshaft cover. It separates the oil drops from the air in the crankcase. The drops are collected in a separator and flow back inside the engine to the oil pan. This prevents extra weight and space for external pipes.

Auxiliary unit transmission









The auxiliary units are located at the upper edge of the cylinder block, above the transmission. They are driven by two systems, a Poly-V-belt driven system and a clutch system. These two systems are driven by the intermediate shaft transmission.
The belt system consists of a 6-ribbed Poly-V belt, an automatic belt tensioner and a guide pulley. This system drives the servo pump and AC compressor. The coolant pump is driven by the servo pump via the clutch system.

Turbocharger (TC)

Note! Only applies to turbocharged engines.




The exhaust gases enter via the manifold (1) down to the turbine housing (8) and out to the exhaust system via a downpipe and catalytic converter.
The turbine expels the exhaust gases and rotates the compressor wheel (3). The compressor wheel creates a certain amount of suction using the intake air. This intake air enters the compressor via the air filter and uses a rotational movement to speed up the air, creating the boost pressure. The air then continues into the intake system via the charge air pipe and charge air cooler.
The electronically controlled By-pass valve (4) then controls the boost pressure in the turbocharger by determining the amount of exhaust gases which must pass the turbine. The turbine transfers drive to the compressor. The wastegate valve (2) is a membrane which equalizes the pressure of the intake and exhaust air to eliminate noise.
The turbocharger is lubricated by the engine's oil system (7). The oil system also acts as a supplement to the coolant system (5 and 6).

Exhaust manifold / Catalytic converter




Exhaust manifold/ CCC ( Close Coupled Catalyst) and front exhaust pipe/catalytic converter for engine are improved with regards to weight and efficiency. Heat shield plates are modified.

Manifold with catalytic converter
The catalytic converter's cross-section is changed from oval to round, which means better contact pattern of the exhaust flow against the catalytic converter's substrate. This means that the amount of precious metals in the coating on the catalytic converter can be reduced at the same time as the emission standards are fulfilled. In addition to a great cost-saving, reducing the need for precious metals also results in less environmental impact.
The outlet flange is changed from a thickness of 8 mm with threaded holes (x4) to a 4 mm thick plate with press bolts (x4). This gives weight and cost-savings. Gaskets are changed to 1.2 mm flat gaskets.

Downpipe/Catalytic converter
The catalytic converter's inlet flange is also changed from 8 mm to 4 mm thick, which gives a weight and cost-saving. The bellows is more flexible which gives less noise from resonance and vibrations as well as longer service life. Also, the rear catalytic converters have a reduced amount of precious metals in the substrate's coating at the same time as the emission standards still are fulfilled, which gives another big cost-saving.