Design
Design
Engine block
The cylinder heads and valve covers are made of aluminum.
The seal between the cylinder head and cylinder block occurs using two cylinder head gaskets, one for each cylinder head. The cylinder head gasket is made up of three layers of stainless steel. Two outer and a center which act as a seal around the cylinders. The outer surfaces of the gasket are covered by a rubber layer which functions as a seal. The seal between the other planes is made using liquid gasket.
The engine has two cylinder banks. The left cylinder bank is slightly offset compared to the right. This allows the use of the vehicle's existing member system and crumple zones.
The engine has double pairs of overhead camshafts - one intake camshaft and one exhaust camshaft in each cylinder head. The camshafts are chain-driven.
The cylinders are numbered in the order in which they are installed on the crankshaft when seen from the front (from the camshaft's timing gear).
The engine has four valves per cylinder. The valves are angled at 19 degrees. The valve diameter of the intake valves is 35 mm and the exhaust valve's is 30 mm. The valves are stellite coated. The valve stem diameter for both inlet and exhaust is 5.5 mm.
The combustion chamber is the "Pent roof" type. Together with the V arranged valves this gives optimal and fast filling and direct flushing via the intake channel followed by the combustion chamber (cross-flow) and exhaust channel.
The squish surfaces together with the centrally positioned spark plug provide optimal combustion of the air/fuel mixture, low knock sensitivity and low, stable exhaust emissions.
Cylinder head
The engine's two cylinder heads are in principle mirror images of each other. The cast oil galleries in the cylinder head ensures good oil supply to the camshafts and the mechanical valve lifters.
Cylinder block
The cylinder block is made of cast aluminum. It has a stiff rib structure for better rigidity and thereby better sound and vibration properties.
The cylinder block has eight cast-iron cylinder liners molded into the cylinder block. They cannot be replaced.
The coolant jacket goes halfway down the cylinders to ensure quicker heating and thereby reduce hydrocarbon emissions. Certain sections of the coolant jacket are deeper to reduce the risk of the cylinder deformation.
Intermediate section
The intermediate section is made of aluminum. The crankshaft bearing caps are integrated in the intermediate section. The bearing caps are made of cast iron. The caps are fixed with four screws per cap.
Oil sump
The oil pan is made of pressed aluminum. It has baffles to prevent the oil moving too much. Because of the exterior dimensions of the engine, the oil pan has a unique shape in order to hold the necessary oil volume. The oil pan is made in two parts for manufacturing reasons.
An electric oil level sensor is located in the pan. There is also a normal oil dipstick for manual checks of the oil volume.
Pistons and connecting rods
The pistons are cast and are made of a light metal alloy. The piston mantle is coated with graphite. The first groove is hard anodized to minimize wear.
The piston is equipped with two compression rings and a three piece oil ring.
The connecting rods are forged. The contact surface between the bearing cap and the connecting rod is treated. Guide pins contribute to good alignment. The connecting rod bearings are aluminum bearings. The bearings are lead free.
The piston transfers the compressive force of the ignited fuel/air mixture to the crankshaft via the connecting rod. The piston rings form a seal so that the fuel/air mixture does not force its way down past the piston. The top ring ensures a seal between the piston and the cylinder. The second ring also seals and scrapes away any oil during the downward movement of the piston. The third ring makes sure the oil drains via the drain hole.
The pistons are oil-cooled. This is necessitated by the short distance between the piston head and the top piston ring.
Crankshaft and balancer shaft
1. Balancer shaft
2. Crankshaft
The crankshaft is made of carbon steel with a nitride hardened surface. The crankshaft bearings have separate caps, the intermediate section of the cylinder block makes up the lower half of the bearing. The crankshaft has five main bearings where the third also acts as an axial bearing. The main bearings are aluminum bearings.
The crankshaft has offset pins. Two connecting rods are mounted on each crankshaft pin with an internal offset of 30°.
Big-end bearings and axial bearings are lead-free.
Two splined joints are located at the front end of the crankshaft, the inner one drives the oil pump. The timing chain gear is located on the outer joint.
S80
The crankshaft has a two part vibration damper consisting of a hub and an active mass. The crankshaft vibration damper drives the auxiliary belt.
XC90
The crankshaft has a three part vibration damper consisting of a hub and two active masses. The hub is located between the inner and outer masses. The crankshaft vibration damper drives the auxiliary belt.
The 60 degree angle between the two cylinder banks means that the engine is equipped with a balancer shaft. This is to give the vibration characteristic which corresponds to a 90 degree V8. The balancer shaft is located in the center of the engine, above the crankshaft. The balancer shaft rotates in the opposite direction to the crankshaft. It is driven by the crankshaft using the same chain that drives the intake camshafts. The balancer shaft rotates at the same speed as the crankshaft.
The balancer shaft is made of spherolitic cast iron (nodular iron).
Camshafts and valve system
The engine has double pairs of overhead camshafts, one intake camshaft and one exhaust camshaft in each cylinder bank. The intake camshafts are located in the middle of the engine while the exhaust camshafts are placed on the outside.
The camshafts are made of cast iron. They are hollow to keep the weight down. Each camshaft pair is mounted in its respective cylinder head with five loose bearing caps per camshaft.
The camshafts work directly on the valve stem via the valve lifters. There is a certain amount of play (valve play) between the valve depressors and the cam lobes. Valve play is adjusted to make up for the longitudinal differences between the valve and cylinder head that occur upon warm-up. The valve depressors are solid and made of steel.
Each camshaft has a CVVT unit. The reset angle is 40.5 crankshaft degrees for the intake camshafts and 42.5 crankshaft degrees for exhaust camshafts.
- Intake camshafts open -8° to 32,5° before top dead center (BTDC) and close 60° to 19.5° after the bottom dead center.
- Exhaust camshafts open 62° to 19.5° before bottom dead center and close -10° to 32.5° after the top dead center (TDC).
Camshaft chain drive
The crankshaft drives the intake camshafts and the balancer shaft using a camshaft chain (1). The camshaft is tensioned by a hydraulic chain tensioner. The tensioner is supplied with oil from the normal lubrication system. The camshaft chain is lubricated with oil via a separate nozzle (2).
The intake camshafts in turn drive the respective exhaust camshafts via their chain (3). This intermediate drive means that the outer exhaust camshafts can have smaller pulley wheels which reduces the size of the engine. The intermediate drive chains each have their own hydraulic tensioner. The tensioner is supplied with oil from the normal lubrication system.
A cover seals the area for the camshaft chain drive.
The system requires no maintenance during the entire life of the engine. Both the chain guide and the chain tensioner have plastic inserts on the treads for quiet operation.
Lubrication system
The lubrication system has a large supply line with a strainer which prevents large contaminants from reaching the oil pump.
The oil pump (1) is driven by the crankshaft. The oil pump is a rotor pump with integrated pressure control valve. The valve opens at approximately 5.0 bar and prevents excessively high pressure which could damage the oil cooler.
The oil cooler is a flat oil cooler. The space for oil and coolant is divided alternately between the plates.
The oil filter (2) is a loose filter element placed in a housing. The overflow valve for a blocked filter is in the cover.
Fuel system
A specially designed fuel system is used to reduce the height of the engine.
The fuel system is made of stainless steel to ensure reliability. The fuel hose is made of nylon to reduce the weight of the engine.
Intake system
An induction system with two modes is used to increase torque at low engine speed. Both the intake manifold and the equalizer tank are made of aluminum.
A moveable damper is located in the common area of the intake pipe. The damper separates the area lengthways into two chambers. The damper is controlled from completely closed to completely open, with no intermediate position. Up to an engine speed of 3200 rpm the damper is closed and the damper is open at higher engine speeds.
By dividing the area into two separate chambers, the area functions as two secondary intake pipes. The primary pipes are the cast pipes which lead to the inlet valves of the respective cylinder's intake valves from the collection volume. A closed damper provides secondary pipes while an open damper gives short secondary pipes.
Engine speeds up to 3200 rpm
The combined length and volume of the pipes is tuned to the piston movement and the valve opening times. The result is that the air pulses in time with the valve opening times. this means that the air is pumped into the cylinders when the inlet valves are open. The system gives a high a volumetric efficiency, that is, fills the cylinders and therefore produces a high torque.
In order not to disturb the pulse frequency the left chamber supplies 1, 4, 6 and 7 while the right chamber supplies cylinders 8, 3, 5 and 2, this is to interact with the firing order 1-8-4-3-6-5-7-2.
Engine speed (RPM) greater than 3200 rpm
At engine speeds greater than 3200 rpm the throttle opens. At these speeds the character of the pulses change character at the same time as a greater volume is required to supply the cylinders with air. The whole area/volume now supplies all cylinders. The common volume and the shape of the pipes is designed to exploit the pulses which occur in this engine speed (rpm) range.
If the damper does not open at 3200 rpm there is marked deterioration in performance from 3200 rpm up to 5000 rpm.
Throttle body
The throttle body is made of cast aluminum. The position sensor, which is located under the plastic cover, reads the position of the throttle disc and two engine connections that turn the throttle disc. The throttle disc position is determined by how much the driver depresses the accelerator pedal. The throttle body is warmed via engine coolant.
Cooling system
1. Cylinder block
2. Right cylinder head
3. Electric coolant pump
4. Heat exchanger (passenger compartment)
5. Preheating crankcase ventilation
6. Throttle body
7. Upper cooling hose
8. Bypass pipe
9. To cylinder head
10. Radiator
11. Oil cooler
12. Lower cooling hose
13. Thermostat housing
14. Coolant pump
15. Left cylinder head
16. Expansion tank with level sensor
17. Air bleed circuit
The engine is cooled used reversed cooling, that is, the cylinder head is cooled first. The system gives fast heating and contributes to reducing emissions.
The radiator is made of aluminum to withstand thermal fatigue as the radiator is alternately cooled with cold air and heated with hot coolant. The cooling system is regulated by a mechanical thermostat, which is located in the thermostat housing. The thermostat housing, in turn, is located on the inlet side of the coolant pump, between the radiator and the coolant pump.
The heart of the thermostat is a wax body which expands when energy, in the form of heat, is applied. A jiggle pin is located in the thermostat. Any air in the cooling system can be evacuated from the system using the jiggle pin.
Cold air is sucked through the cooler using an electric engine cooling fan installed on the fan shroud behind the radiator. The engine cooling fan is brushless and has six fixed stages. It is controlled by the engine control module (ECM).
Oil cooler
The oil cooler is round and has an inlet and outlet for oil as well as for coolant. The oil cooler is structured in layers, with alternating layers of coolant and oil flow. Because the oil cooler has very small slits, there is a large pressure drop here.
Auxiliaries belt
1. Generator (GEN)
2. Belt tensioner
3. Servo pump
4. Water pump
5. air conditioning (A/C) compressor.
All auxiliary units, the alternator, servo pump and A/C compressor are directly mounted in the engine block. They are driven by the vibration damper via an auxiliaries belt. This solution gives a compact design.
The coolant pump is also driven by the auxiliaries belt.
The auxiliaries belt has a mechanical belt tensioner.
Exhaust system
Hint: The illustration displays the exhaust system for the XC90.
The exhaust system is made of double-layer sheeting to keep the temperature down. The inner sheet is 1.0 mm thick while the outer is 1.5 mm thick. There is 4-8 mm of space between the sheets.
An exhaust system extends from each cylinder bank. Each side consists of a manifold with close-coupled catalytic converter, pipes, bellows and a rear catalytic converter. Both sides join to form a common pipe after the rear catalytic converter.
The pipes are designed in such a way that the gas flow from the cylinders is not disruptive and there is good flow distribution to the catalytic converters. Bellows in front of the two rear catalytic converters absorb engine movements and compensate for manufacturing and assembly tolerances.
A catalytic converter consists of perforated stones of ceramic or metal (known as substrate). These are coated with a surface enlarger (washcoat) on which the precious metals platinum, palladium and rhodium, the catalysts, are applied.
The catalytic converter has an extra heat shield toward the radiator fan to reduce the temperature.
Four oxygen sensors are used to regulate the engine and monitor the catalytic converter. There is an oxygen sensor upstream and downstream of each close-coupled catalytic converter.
The two banks are almost exactly the same length to ensure good sound. The exhaust system provides the engine's characteristic V8 sound.