Volvo B12R, DH12E460-Engine.pdf

IMPACT 3.0

Thursday, 20 September 2012

Chassis ID

Path 2/Description, Design and function/B12R, DH12E460/Engine

Model B12R

Identity 118510762

Publishing Date Thursday, 15 May 2008

Operation No.

Engine Contents General Engine Lubrication system Fuel system Inlet and exhaust system, turbo Cooling system

General Engine outputs Identification

Engine outputs

© Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

1 / 41

IMPACT 3.0

Thursday, 20 September 2012

Identification

The engine specification, in the form of cast and punched characters, can be found on the underside of the block. © Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

2 / 41

IMPACT 3.0

1

Thursday, 20 September 2012

Casting marks:

2

06

year (2006)

W14

week (14)

3

day (Monday)

100963

billet number from forge in Skövde. Only used for internal engine production. The clock face is for 16 hours and shows when the block was cast.

The engine manufacturing number is stamped into the cylinder block: DH12

engine type

600468

serial number

D1

generation

A

manufacturing factory, Skövde

(E

manufacturing factory, Curitiba)

(F

manufacturing factory, Flen)

The engine identification and other engine data can be found on two plates on the top of the engine. 3

Chassis identification

4

Serial number

5

Certificate number for UN directive 49 (emissions)

6

Country: E = Europe 5 = Sweden 11 = Great Britain

7

Certificate number for EU directive 88/77 (emissions)

8

Certificate number for UN directive 24 (full load performance and smoke values)

9

Smoke value in the certificate

10

Engine variant Explanation of designation DH12E340 EC06: D

Diesel

H

Horizontal engine

12

Displacement in litres

E

Generation

340

Power in horsepower

EC06

Euro4

© Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

3 / 41

IMPACT 3.0

Thursday, 20 September 2012

11

Data set, SW calibration

12

Maximum torque

13

Rated max power

14

Engine speed at rated max power

15

Cylinder volume

16

Slow idling

17

Unit injector: 1

18

Delphi

Engine brake: EPG

Exhaust Pressure Governor (exhaust brake)

VEB

Volvo Engine Brake (compression brake and exhaust brake)

The upper plate, apart from a number of bar-codes, contains the following: 3

Chassis identification

4

Serial number

5

Certificate number for UN directive 49 (emissions)

6

Country: E = Europe 5 = Sweden 11 = Great Britain

7

Certificate number for EU directive 88/77 (emissions)

8

Certificate number for UN directive 24 (full load performance and smoke values)

9

Smoke value in the certificate

10

Engine variant Explanation of designation DH12E340 EC06: D

Diesel

H

Horizontal engine

12

Displacement in litres

E

Generation

340

Power in horsepower

EC06

Euro4

11

Data set, SW calibration

12

Maximum torque

13

Rated max power

© Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

4 / 41

IMPACT 3.0

Thursday, 20 September 2012

14

Engine speed at rated max power

15

Cylinder volume

16

Slow idling

17

Unit injector: 1

18

Delphi

Engine brake: EPG

Exhaust Pressure Governor (exhaust brake)

VEB

Volvo Engine Brake (compression brake and exhaust brake)

The upper plate, apart from a number of bar-codes, contains the following: 15

Engine factory code

16

Engine type

17

Assembly factory code

Engine Cylinder head Cylinder block Pistons, cylinder liners and sealing joints Valve mechanism Engine timing gear Crankshaft Camshaft and exhaust rocker arms The outlet valve’s function Engine compression brake cycle of operation

Cylinder head

© Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

5 / 41

IMPACT 3.0

1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

Thursday, 20 September 2012

Cylinder head. Bearing housing Inlet air channel. Outlet exhaust channel. Valve guide. Valve seat. Injector. Copper sleeve. Fuel channel. Coolant jacket.

The cylinder head is made from cast iron alloy and cast in one piece for all six cylinders. This is a requirement for obtaining stable support of the overhead camshaft. The camshaft is supported in seven bearing housings and is driven by the crankshaft via two intermediate gears. The engine has a four valve system and centrally located injectors which means that the combustion chamber is completely symmetrical. The cylinder head is bolted to the cylinder block with 38 M16 screws, equally positioned around each cylinder. The cylinders have separate intake and exhaust passages on opposite sides, i.e. cross flow. The valves and valve seats are new and are specific for bus applications. The valve guides are manufactured of cast iron alloy and the valve seats of steel. The valve guides and valve seats are replaceable. All valve guides have oil seals. The lower part of each injector is located in a copper sleeve. The copper sleeve is enlarged with a drift in the lower part and sealed with a rubber ring at the upper end. The copper sleeve now has a new shape. The new design provides better injector cooling. The fuel passages for the injectors are machined directly into the cylinder head. The frost plugs have a new design and are now pressed into the cylinder head instead of the previous version which was screwed.

Cylinder block © Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

6 / 41

IMPACT 3.0

1. 2. 3. 4. 5. 6.

Thursday, 20 September 2012

Cylinder block. Cylinder liner. Dry sump. Oil tank. Oil filter. Oil dipstick.

The cylinder block is made from cast iron and cast in one piece. It is equipped with wet cylinder liners that are replaceable. Wet cylinder liners are in direct contact with the coolant, which gives good cooling. To achieve high stiffness and good sound absorption in the cylinder block, the block sides are curved around each cylinder. The external stiffening ribs have been changed to increase stiffness in the block which also has a sound absorbing effect. The oil sump is screwed to the cylinder block base. The horizontally mounted engine has a dry sump. It is manufactured of aluminium and consists of three parts screwed together. The oil tank and the dry sump are integrated into the engine. The oil filter is mounted on the side of the engine. The dipstick is on the top of the oil tank.

Pistons, cylinder liners and sealing joints

© Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

7 / 41

IMPACT 3.0

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

Thursday, 20 September 2012

Piston. Cylinder liner. Coolant jacket. Sealing rings. Liner shelf. Gasket. Crown. Skirt. Gudgeon pin. Compression ring. Oil ring. Connecting rod.

The wet cylinder liner is sealed towards the coolant mantle with rubber rings. The seal at the cylinder liner collar made of EPDM rubber and is fitted in a groove in the liner. The seals at the cylinder bottom consist of three rings mounted in grooves in the block. The two closest to the coolant are made from EPDM rubber and the lower, on the oil side, is made from fluoro rubber. The gasket is one-piece solid steel for the whole engine. There are rubber sealing rings for coolant and oil connections between the cylinder head and the cylinder block. The liner’s contact surface towards the steel gasket is convex and its height above the cylinder block surface is 0.15-0.21 mm. The pistons in the D12E engine are pendulum pistons. The pendulum piston consists of two parts: The piston crown is manufactured of steel and the skirt of aluminium. Both parts are separately mounted in bearings on the piston pin. The piston has two compression rings and one oil scraper ring. The upper compression ring is a Keystone type. The connecting rod is forged of steel and has a trapezoidal shaped upper part. The compression ration of the piston is 19.1:1 on 340 and 380 hp variants and 18.3:1 on 420 and 460 hp variants. The ratio is determined by the depth of the piston bowl. © Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

8 / 41

IMPACT 3.0

Thursday, 20 September 2012

Valve mechanism

1. 2. 3. 4. 5. 6. 7. 8.

Camshaft. Bearing housing. Oscillation damper. Gear wheel for position sensor. Flange for camshaft marks. Rocker arm. Roller. Valve yoke.

The valve mechanism is a four valve system with overhead camshaft. The camshaft is induction hardened. It is mounted in seven bearing housings equipped with replaceable bearing bushings. The front bearing is in addition a thrust bearing. The camshaft has three cams per cylinder; intake cam, exhaust cam and one cam for the unit injector. On the camshaft’s front flange, outside the camshaft gear, there is a hydraulic oscillation damper and a toothed wheel for the position sensor which is attached with screws. On a flange beside the front bearing housing are the camshaft markings. The markings differ dependent on whether the engine is equipped with an exhaust brake EPG (Exhaust Pressure Governor) or VEB (Volvo Engine Brake). For EPG variants there is a TDC (Top Dead Centre) mark and the digits 1-6. The TDC mark is used for camshaft basic settings and should be in the middle between the bearing housing’s two lines when the engine’s flywheel is on the O mark. The EPG variant uses number markings for adjusting valves and injectors. For example inlet and outlet valves and the injector for cylinder no. 5 is adjusted in this way at the number 5 between the bearing housing’s marks. The VEB variant uses the same markings as near as on the outlet valves. These use the V markings. For example, the outlet valves are adjusted for cylinder 5 at the 5 mark.

© Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

9 / 41

IMPACT 3.0

Thursday, 20 September 2012

The rocker arms have impacted surface treated steel bushings and are mounted in bearings on a shaft attached with the same screws as the camshaft bearing housing. The rocker arms make contact with the camshaft via rollers and with the valve yokes via ball seats. The outlet valves have double springs and the inlet valves single. All valve guides are equipped with oil seals.

Engine timing gear

1. Crankshaft gear. 2. Idler gear. 3. Hydraulic pump gear. 4. Coolant pump gear. 5. Idler gear (adjustable). 6. Camshaft gear. 7. Power steering pump and fuel pump gear. 8. Idler gear. 9. Idler gear. 10. Lubrication oil pump gear (suction side). 11. Air compressor gear. 12. Lubrication oil pump gear (pressure side). 13. Spray nozzle. 14. Seal moulding. 15. Timing gear cover, cast iron 16. Sound insulation. 17. Timing gear cover, aluminium © Copyright Volvo Group North America 18. The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled. 10 / 41

IMPACT 3.0

Thursday, 20 September 2012

18. Seal moulding. 19. Oscillation damper, camshaft. 20. Toothed wheel for position sensor. The engine timing gears are at the front of the engine on a 10 mm thick steel plate. The steel plate is screwed to the cylinder block. It is level with the cylinder head front edge and is sealed towards the cylinder head by a sealing moulding of reinforced rubber. It is sealed towards the cylinder block with silicone rubber. The timing gear cover is in two parts, one part being die cast in aluminium and partly covered with sound insulation manufactured of laminated sheet. The other part is manufactured of cast iron. Both covers are sealed towards the plate with silicone rubber and towards each other with an H shaped rubber moulding. All gear wheels are beveled to reduce wear and give quieter running. Intermediary gears are mounted in bearings with bushings and are pressure lubricated. Other lubrication is via a spray nozzle. The intermediary gears which drive the camshaft gear are bolted to the cylinder block and adjustable.

Crankshaft

1. 2. 3. 4. 5. 6. 7. 8.

Crankshaft. Main bearing. Support bearing. Crankshaft gear. Hub. Oscillation damper. Steel ring. Flywheel.

The crankshaft is drop forged and has induction hardened bearing surfaces and recesses. It is mounted in seven main bearings of which the middle bearing is a support bearing. The crankshaft gear is pressed onto the shaft and also has a splined key. The hub has a polygon profile and is also pressed onto the shaft. © Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

11 / 41

IMPACT 3.0

Thursday, 20 September 2012

The oscillation damper is hydraulic. In the damper’s housing there is a counterweight in the form of a steel ring which can rotate freely. The space between the steel ring and the housing is filled with silicone oil of high viscosity. When the crankshaft rotates, oscillations occur in the crankshaft due to the power pulses from the pistons. The viscous silicone oil equalises the crankshaft’s pulsating rotation and the steel ring’s even rotation, so damping the oscillations. The flywheel is screwed onto the crankshaft, and its position is determined by a guide pin. On the flywheel’s periphery surface there are, in addition to the flywheel ring gear, a number of grooves machined for the injection system’s rotational speed sensor. The crankshaft is sealed towards the flywheel housing by a so-called lip seal.

Camshaft and exhaust rocker arms

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14.

Outlet cam. Outlet lobe. Charging lobe. Decompression lobe. Outlet rocker. Spring tab. Check valve. Rocker arm piston. Shims. Pressure limiting valve. Piston. Spring. Ball. Valve yoke.

The camshaft on an engine with VEB has, in addition to the ordinary exhaust cams, a charging lobe and a decompression lobe on each exhaust camshaft. The charging and decompression lobes height of lift above the base circle is 0.8 mm, which is equivalent to a valve opening of around 1.1 mm. The charging lobe is © Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

12 / 41

IMPACT 3.0

Thursday, 20 September 2012

positioned so that it opens the outlet valves at the end of the inlet stroke and holds them open at the beginning of the compression stroke, when the engine compression brake is active. The valve clearance must be zero if the charging and decompression cams are to open the outlet valves. The exhaust rocker arms on an engine with VEB are stronger than on a standard engine. In each rocker arm, there is a non-return valve and a piston. A spring tab holds the rocker arm in its position of rest against the valve caliper. The clearance between the rocker arm and the valve caliper is greater for an engine with VEB as the charging and decompression cams do not open the outlet valves during engine operation. Valve clearance is adjusted with maximum two shims which are placed on the valve yoke. The difference between the shims thickness is 0.05 mm. There is a pressure limiting valve in the piston, which opens and releases oil through a channel in the piston’s lower part when the pressure on the piston becomes too high. The non-return valve consists of a piston, a spring and a ball. The piston’s position is determined by the spring force and the pressure of the oil which is forced into the valve from the rocker shaft. A

When the engine is running, the control valve lowers the oil pressure. This pressure is not capable of overcoming the spring force, and the piston therefore does not move out of its position of rest. The piston pin holds the ball away from the seat and oil can flow in both directions through the non-return valve. No oil pressure is built up above the rocker arm piston.

B

When braking using the engine compression brake, the control valve raises the oil pressure to the oil system pressure. This pressure overcomes the spring force and the piston moves so that it no longer affects the ball. The ball will then act as a non-return valve and the chamber above the rocker arm piston is filled with oil. When the valve yoke presses against the rocker arm piston, the non-return valve’s ball is forced against the seat. The oil above the rocker arm piston can no longer flow past the ball, and a high oil pressure is built up above the rocker arm piston, whereupon the rocker arm piston zeroes the valve clearance.

The outlet valve’s function

© Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

13 / 41

IMPACT 3.0

Thursday, 20 September 2012

A

When the engine is running, no pressure acts on the rocker arm piston. The valve clearance of 1.6 mm between the rocker arm and the valve yoke is sufficient to give a clearance of around 0.3 mm between the rocker arm roller and the engine compression brake’s lobes on the camshaft. The flat spring holds the rocker arm against the valve yoke so that the rocker arm roller does not come into contact with low lobes.

B

When the engine compression brake is applied, the rocker arm piston zeroes the valve clearance. The rocker arm roller will then follow the cam profile (1). This makes it possible for the charging cam to lift the rocker arm roller so that the valve is opened (2). The same applies to decompression lobes. The cams’ height of lift is 0.8 mm, which gives a valve opening of around 1.1 mm.

Engine compression brake cycle of operation

© Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

14 / 41

IMPACT 3.0

Thursday, 20 September 2012

The engine compression brake cycle of operation can be divided into two phases. A

The charging phase starts at the end of the inlet stroke and continues a little into the compression stroke. When the piston is on the way down towards lower dead centre, the charging lobe opens the outlet valves momentarily. The cylinder is filled by the high pressure that the exhaust brake has built up in the exhaust manifold. This high pressure increases the compression pressure significantly during the compression stroke, which gives a large braking force during the piston’s upward movement.

B

The decompression phase starts at the end of the compression stroke and continues a little into the power stroke. When the piston is close to TDC, the decompression lobe opens the outlet valves momentarily. The high pressure is released from the cylinder. In this way, the force effect that the compressed air should have on the piston during the power stroke is avoided.

Lubrication system Lubrication system The function of the lubricating system Oil cooler and oil pump

Lubrication system

© Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

15 / 41

IMPACT 3.0

1. 2. 3. 4. 5. 6. 7.

Thursday, 20 September 2012

Safety valve (yellow). Overflow valve 1, filter. Overflow valve 2, filter. By-pass valve, oil cooler. Reduction valve (blue). Piston cooling valve 1. Piston cooling valve.

The oil sump is the dry type and consists of a separate dry sump and oil tank. The engine is pressure lubricated and has three gear pumps (two sump pumps and a pressure pump) which are driven by the crankshaft via two intermediary gears. The lubricating system has three full flow filters and one bypass filter. The oil flow is regulated by seven valves. Two of the valves are so called unit valves. They are colour marked to eliminate the risk of incorrect fitting.

The function of the lubricating system

© Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

16 / 41

IMPACT 3.0

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23.

Thursday, 20 September 2012

Safety valve (yellow). Overflow valve, lubrication oil filter. Overflow valve, lubrication oil filter. By-pass valve, oil cooler. Reduction valve (blue). Piston cooling valve 1. Piston cooling valve 2. Oil sump. Sump pump for crankcase. Sump pump for valve cover. Oil tank. Pressure pump. Full flow filter. Bypass filter. Oil cooler. Oil distribution housing. Air compressor. Turbocharger. Oil gallery line. Camshaft and rocker arms mechanism. Piston cooling nozzle. Solenoid valve. Level sensor.

The sump pump for the crankcase draws oil from the oil sump to the oil tank, and the sump pump for the valve cover draws oil from the valve cover to the oil tank. The suction lines for the crankcase have a strainer where the oil passes through a strainer screen of metal. The pressure pump forces the lubricating oil from the oil tank to three full flow filters and a by-pass filter which sit on the side of the oil tank. After the full flow filter, the oil is drawn to the oil jacket built in to the oil cooler and further to the oil distribution housing. The air compressor and the turbo are lubricated from here via external pipes. From the oil distribution housing the oil is also led to the cylinder block gallery line to be distributed via channels to all the engine’s lubrication points. The camshaft and rocker arm mechanism is lubricated via a channel through the cylinder block and the cylinder head. For engines with VEB, the oil passes through the control valve. © Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

17 / 41

IMPACT 3.0

Thursday, 20 September 2012

The oil for piston cooling is taken both from the oil distribution housing and the by-pass filter. The oil is fed via the longitudinal channel in the block and is sprayed via jets, one for each piston, onto the insides of the pistons. The valves have the following function: 1

Safety valves open if the pressure in the lubrication system becomes too high, for example during cold starts in the winter. The opening pressure is 6.9 bars.

2, 3

The by-pass valves for the full flow filter open if the filter becomes blocked to ensure engine lubrication. The opening pressure is 1.1 bars.

4

The by-pass vale for the oil cooler has the task of, during cold starts, of leading the oil past the cooler. In this way, the engine receives lubrication faster at low temperatures and has a shorter warming up time. This valve is temperature controlled. The valve starts closing the bypass line to the oil cooler when the oil temperature is 105 °C and is fully closed at 116 . The valve has a safety function so that if the pressure rises in the oil cooler, the valve opens. The opening pressure is variable and is dependant on the oil temperature. At 118 °C, the opening pressure is 240 kPa and at 125 °C it is 270 kPa

5

The reduction valve controls the engine’s oil pressure and leads surplus oil back to the oil tank. The opening pressure is 4.8 bars.

6

Piston cooling valve 1 ensures that there is at least 3.0 bar in the gallery line before piston cooling starts. In this way the engine’s lubrication points are supplied with oil before oil is taken for piston cooling. The valve is a sliding valve whose spring force is exceeded at a pressure of 3.0 bars in the oil from the gallery line. When it opens, oil is released from both the gallery line and the by-pass filter to piston cooling.

7

Piston cooling valve 2 ensures that piston cooling pressure’s optimal value (1.5 bar) is maintained. The valve is a sliding valve whose spring pressure is exceeded at a piston cooling pressure of 1.5 bars. When it closes, the oil from the gallery line is shut off and the piston cooling receives only oil from the by-pass filter. Behind the piston cooling valves there is a spring chamber. Valve leakage flow is led back from the spring chamber to the crankcase. At low engine rpm and low loads, piston cooling valve 1 shuts off piston cooling to give priority to the lubrication of the engine. Valve closure is controlled by the control unit which sends a signal to the solenoid valve on the oil distribution housing. The solenoid valve then opens and admits oil from the gallery line to the discharge chamber. The spring force and the oil pressure are together sufficient to close piston cooling valve 1.

Oil cooler and oil pump

© Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

18 / 41

IMPACT 3.0

1. 2. 3. 4. 5. 6. 7. 8. 9.

Thursday, 20 September 2012

Oil cooler. Oil pump. Sump pump for crankcase. Sump pump for valve cover. From crankcase. From valve cover. To oil tank. From oil tank. To filter.

The oil cooler has seven plates as opposed to the earlier five. The oil cooler is screwed directly onto the cylinder block under the cover of the cylinder block’s coolant channel and is fully surrounded by coolant. The red arrows show the flow of oil and the blue arrows the flow of coolant in the oil cooler. The oil pumps are gear wheel types. The oil pump housing is manufactured of aluminium and bolted onto the engine’s front main bearing cap. The pump housing and cover are machined together and cannot be replaced separately. The suction pipe and the pressure pipe are manufactured of steel and are sealed with rubber seals towards the pump lid. The suction strainers are manufactured of aluminium.

Fuel system Fuel system Fuel system components

Fuel system

© Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

19 / 41

IMPACT 3.0

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.

Thursday, 20 September 2012

Fuel tank. Tank filter. Check valve. Fuel shut-off valve. Control unit. Distributor valve. Unit injectors. Feed pump. Switch, bleeding. Fuel filter. Fuel pre-filter with water separator.

The fuel system has electronically controlled unit injectors, one for each cylinder, which inject at very high pressure. The high pressure is generated from the overhead camshaft via the rocker arms. The injection volume and timing is regulated electronically by the engine control system. The figure shows the fuel flow. The suction side is shown in pink, the feed pressure is in red and the return fuel line is red and white. The feed pressure to the unit injectors is 3.5-4.5 bar. The feed pump sucks fuel through the tank filter, the fuel shut-off valve, the non-return valve, the control unit cooling coil and down to the suction side of the fuel filter. The fuel then passes further through the hand pump and water separator/course filter, the distribution valve and down to the feed pump. From the feed pump, the fuel is pressed through the fine filter and then to the fuel channel/injectors in the cylinder head. The return line is on the rear of the cylinder head, it leads the fuel via the overflow valve to the distribution valve. The fuel system also has a bleeding/return line. This bleeding/return line is connected between the feed pump, fuel filter and distribution valve, which is fitted with an overflow valve, to the return line to the fuel tank.

Fuel system components

© Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

20 / 41

IMPACT 3.0

Thursday, 20 September 2012

1

The feed pump is a gear-wheel pump driven from the crankshaft by an intermediate gear. The driveshaft has two seals that seal against fuel and oil respectively. The capacity of the feed pump is adapted to give the correct pressure and flow to all unit injectors. A relatively high pressure is required to ensure proper filling of the unit injectors. The flow must be sufficiently high to even out any temperature differences in the fuel in the cylinder head fuel channel. There are three valves in the feed pump. The reduction valve (A) allows the fuel to flow back to the suction side if the pressure becomes too high. The non-return valve (B) opens when the hand pump is used. Automatic bleeding back to the fuel tank is handled by the bleeding valve (C).

2

The fuel is filtered via a pre-filter with water separator and a fuel filter. The fuel filter is a spin-on filter with a six month replacement interval. The filter insert is made from special paper with very god filtering characteristics. The pre-filter with water separator is available in two versions, with and without heating. The water separator has a level sensor at the bottom, which indicates when it is time to drain. An electric fuel pump is mounted directly on the filter bracket and is used for draining water from the water separator and bleeding the fuel system. The sensor must indicate a high water level for water to be drained out of the water separator. The engine must be stationary and the starter key in drive position. Water is drained when the bleeding/draining switch is pressed in. The drain valve opens to release water while the electric pump applies pressure to the water. Draining takes around 30 seconds. The fuel system is bled by pressing in the button, which starts the electric pump. The button shall be held in for four minutes. Bleeding occurs when the fuel system is filled and the pressure in the system increases. Air is pressed out through the fuel line and then through the bleeding valve and back to the fuel tank via the return line, after which the engine can be started.

3

The control unit is screwed to the engine via vibration-absorbing rubber blocks. It is cooled by the suction side fuel that passes through the cooling coil, which is screwed onto the outside of the control unit.

4

The non-return valve is on the suction side, after the fuel tank, close to the engine.

5

The engine has six unit injectors, one for each cylinder. The unit injectors are a combination of © Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

21 / 41

IMPACT 3.0

Thursday, 20 September 2012

injection pump and injector. They can create a considerably higher pressure than a conventional injector. On an earlier engine version, the DH12CD, an E1 injector was used with an injection pressure of 1500 bar. The DH12E uses an E3 injector which provides an injection pressure of approx. 2000 bar. The injector gets is fuel directly from the fuel channel. The injection timing and fuel volume are decided by the control unit, which gives signals to the two solenoid valves that control the fuel valve. The force on the unit injector is transferred from a camshaft lobe via a rocker arm. You can read more about the unit injectors further on in the booklet. 6

The overflow valve inside the distribution valve (A) is integrated with the hollow bolt in the return line from the cylinder head. The bypass valve regulates the feed pressure in the fuel system. The opening pressure is 3.5 bar. The high feed pressure ensures good filling of the unit injectors. The fuel distribution housing also contains the bleeding valve (B) which allows automatic bleeding directly back to the fuel tank.

Inlet and exhaust system, turbo Injection system Unit injector E3 Unit injector spill phase Unit injector pressurising phase Unit injector injection phase Unit injector depressurising phase Turbocharger Exhaust pressure governor Compression brake Control valve SCR

Injection system

The control unit is the central component of the injection system. All buses with Euro4 specification are

© Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

22 / 41

IMPACT 3.0

Thursday, 20 September 2012

equipped with a new variant of the control unit, EMS2, which is a further development of the earlier variant EMS1. The control unit receives continuous information from the accelerator, the tachograph/the speedometer and a number of sensors on the engine to determine the fuel amount and at which point in time the fuel should be sprayed into the cylinders. Control signals to the unit injectors are transmitted via electrical cables to the unit injectors’ fuel valves. All cable connections for the control unit’s sensors have DIN standard connectors. The control unit stores information on any faults and deviations which occur in the system. Faults which arise sporadically are saved in the control unit so to they can be traced at a later occasion. The following sensors can be found on the engine: 1

Sensor for the fuel’s feed pressure after the fuel filter. Fitted to the filter bracket.

2

Combination sensor for charge air pressure and charge air temperature. Fitted to the intake pipe.

3

Sensor for camshaft position. Fitted to the upper timing gear cover.

4

Sensor for coolant level. Fitted to the expansion tank and connected to the vehicle control unit.

5

Combination sensor for air pressure and air temperature. Fitted to the connecting pipe between the air filter and turbo.

6

Sensor for coolant temperature. Fitted to the front edge of the cylinder head.

7

Sensor for flywheel position and rotational speed. Fitted to the flywheel cover.

8

Combination sensor for oil pressure and oil temperature. Fitted to the lubrication system main channel in the cylinder block.

9

Oil level sensor installed in the sump and registers oil level. The engine must have been shut off for at least 20 minutes before the correct value is shown on the display.

10

The crankcase ventilation sensor monitors the pressure in the crankcase and is fitted on the sump close to the dipstick.

11

External temperature sensor. Fitted to the bodywork, not shown in figure.

Unit injector E3

© Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

23 / 41

IMPACT 3.0

1. 2. 3. 4. 5. 6. 7.

Thursday, 20 September 2012

Spill valve. Solenoid valve. Solenoid valve. Needle control valve. Needle control piston. Needle. Electrical connection.

The new version of the unit injector, the E3, has the same appearance and is fitted in the same way, as the earlier version E1. It also functions in the same way as the E1 as far as fuel injection (volume and timing) is concerned, with a spill valve (1) and solenoid valve (2). In order to minimise smoke and particles in the exhaust, the E3 injector is equipped with a valve, the needle control valve (4), and is controlled by yet another solenoid valve (3). The needle control valve (4) and solenoid valve (3) make it possible to retain the injector needle (6), by applying a high fuel pressure to the needle control piston (5). In this way the injector opening pressure can be varied to give the best combination of engine speed and engine load and make it possible to obtain better fuel consumption and reduced exhaust emissions. The opening pressure of injector E3 varies between 250 and 2000 bar, compared with the earlier version E1 that had a fixed opening pressure of 1500 bar. The injector’s calibration code and spare parts number can be read off from the electrical connection. The injector hardware varies depending on horsepower output.

Unit injector spill phase

© Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

24 / 41

IMPACT 3.0

1. 2. 3. 4.

Thursday, 20 September 2012

Spill valve. Solenoid valve. Solenoid valve. Needle control valve.

During the injectors leak-off phase, both solenoid valves (2 and 3) are deactivated which leaves the leak-off valve (1) open and the needle control valve (5) closed. Despite the pump operating, no pressure is built up since the fuel is just circulated through the spill valve and cylinder head fuel channel. The injector is in this condition when the engine is shut off.

Unit injector pressurising phase

© Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

25 / 41

IMPACT 3.0

1. 2. 3. 4. 5. 6. 7. 8.

Thursday, 20 September 2012

Spill valve. Solenoid valve. Solenoid valve. Needle control valve. Needle control piston. Needle. High pressure channel. A hollow space.

The pressurising phase starts when the camshaft has turned to the position where the camshaft’s lobe (via the rocker arm) starts to press the pump piston down. The solenoid valve (2) is activated and the spill valve (1) closes. A high pressure is built up in the injector’s high pressure channel (7). Since the needle control valve (4) is still closed, a hydraulic pressure is built up in the cavity (8) which causes the needle control piston (5) to keep the injector needle closed and no injection occurs in this phase.

Unit injector injection phase

© Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

26 / 41

IMPACT 3.0

1. 2. 3. 4. 5. 6. 7. 8.

Thursday, 20 September 2012

Spill valve. Solenoid valve. Solenoid valve. Needle control valve. Needle control piston. Needle. High pressure channel. Hollow space.

The solenoid valve (2) was already activated during the pressurising phase, which holds the spill valve closed and causes the hydraulic pressure in the space (8) to hold the needle control (5) down, which keeps the injector needle closed. The engine control unit uses information from the engine’s sensors and other information via J1939, to calculate the pressure at which the injector should open. When this predetermined pressure is reached, the following process occurs; Solenoid valve (3) is also activated which releases the hydraulic pressure in the space (8), the needle control piston (5) is lifted by the injector needle (6) and injection occurs. In this way it is possible to achieve an opening pressure that can vary between 250 and 2000 bar.

Unit injector depressurising phase

© Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

27 / 41

IMPACT 3.0

1. 2. 3. 4. 5. 6. 7. 8.

Thursday, 20 September 2012

Spill valve. Solenoid valve. Solenoid valve. Needle control valve. Needle control piston. Needle. High pressure channel. Hollow space.

The depressurising phase starts when the control unit decides that the engine has received sufficient fuel volume and cuts the power supply to the solenoid valves (2 and 3). When the solenoid valve (2) is deactivated, the needle control valve return channel is closed which causes the injector needle to close. At the same time solenoid valve (2) is deactivated which opens the spill valve so that the fuel can flow back to the fuel channel. The injector has returned to the leak-off phase.

Turbocharger

© Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

28 / 41

IMPACT 3.0

1. 2. 3. 4. 5. 6. 7. 8.

Thursday, 20 September 2012

Air from the air cleaner. Compressor wheel. Compressed air to the engine. Exhaust gases from the engine. Turbine wheel. Exhaust gases to the exhaust system. Lubrication oil housing. Coolant housing.

The engine’s exhaust gases drive the turbocharger’s turbine wheel. The turbine wheel is on the same shaft as the compressor wheel. When the compressor wheel rotates, air is sucked in from the air cleaner and is compressed by the turbocharger. The compressed air is then forced in through the charge air cooler to the engine. The turbocharger has a water cooled bearing housing. Lubrication is with oil from the full flow filter. Compared to earlier engine alternatives, the DH12E engine’s turbocharger has a higher charge air pressure, especially at low engine speeds. As an example, the DH12C/D provides 155 kPa at 1400 rpm, compared with DH12E which provides 270 kPa at the same rpm. The turbocharger hardware varies depending on the engine output horsepower.

Exhaust pressure governor

© Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

29 / 41

IMPACT 3.0

1. 2. 3. 4. 5. 6. 7.

Thursday, 20 September 2012

Exhaust pressure governor. Shutter. Piston. Cylinder. Air valve. Solenoid valve. Two-way valve.

The standard version of the engine brake consists of the EPG (Exhaust Pressure Governor) exhaust brake, which is activated by an exhaust pressure governor. The exhaust pressure governor is located alongside the turbocharger turbine housing. It has two tasks, one of which is to act as an exhaust brake when driving downhill, and the other is to hold the engine warm during idling. The exhaust pressure governor is equipped with a shutter in the turbo’s exhaust outlet. The shutter is opened and is closed by a compressed air operated cylinder. The compressed air is taken from the bus’s compressed air system and is controlled by an air valve. The air valve AVU (Air Valve Unit) is a PWM valve (Pulse Width Modulated) which contains a solenoid valve and a printed circuit card. It is on the engine’s left side and is connected to the engine’s control unit via a cable with a DIN connector. When activating the exhaust brake, a signal is sent from the engine ECU (EECU) to the air valve. The valve opens in relation to the signal’s length and releases a specified pressure. Function: Position A

During normal driving, the AVU valve is not supplied with power. The shutter is fully open and the exhaust gases can freely flow past the EPG (the exhaust brake)

B

The exhaust brake is steplessly activated with the wheel brakes via the brake pedal. Dependent on the pulse width of the PWM signal from the control unit, the pressure from the AVU valve (air valve unit) to the exhaust brake increases. At a pulse width of 90%, the AVU valve opens and releases a pressure of about 7.5 bar to the cylinder.

© Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

30 / 41

IMPACT 3.0

Thursday, 20 September 2012

The shutter closes and a back pressure is built up in the exhaust gases. The shutter is balanced against the exhaust pulses and allows a small amount of exhaust past. The best braking effect is achieved when the engine speed is kept in the blue sector on the rev counter. Maximum braking power is up to 160 kW. If the exhaust brake is used with the VEB or other retarder, it is activated together with these, steplessly. C

Engine heating function. When the engine coolant temperature is less than 50 degrees C and the parking brake is applied, the engine control unit sends a PWM signal to the AVU valve with a pulse length of 25%. The AVU valve opens and releases a pressure of about 2 bar to the cylinder. The shutter is forced against the closed position and the engine works against a back pressure and therefore is warmed up more quickly. The shutter is in this case nearly fully closed such that there is an aperture of around 1 mm.

Compression brake

1. Control valve. 2. Camshaft. 3. Exhaust rocker arm. The VEB (Volvo Engine Brake) is available as an option. It consists of two different systems, the standard EPG exhaust brake and the VCB (Volvo Compression Brake), which is integrated in the engine valve system. The engine compression brake controls outlet valve opening during the engine’s compression stroke and outlet stroke so that high pressure is created in the combustion chamber. The high pressure generates a braking effect on the crankshaft. On the D12D engine, the exhaust brake (EPG) is supplemented with a new type of control valve, a so called AVU valve (Air Valve Unit). © Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

31 / 41

IMPACT 3.0

Thursday, 20 September 2012

The AVU valve steplessly controls the air pressure to the exhaust brake. The VEB can be activated either through a control (retarder lever) on the right side of the steering wheel or together with the wheel brakes using the foot brake. If the bus does not have a retarder stalk but does have VEB, then VEB is activated soley via the footbrake. In order to make it possible to turn off the VEB, there is a two-position switch on the instrument panel, where the position "0" indicates that braking is without VEB and position "1" which uses VEB together with the wheel brakes. The control function on the steering wheel connects VEB in the following stages: Position 0

VEB not activated, only EPG as back-pressure with cold engine for faster warm up, pressure EPG about 2 bar.

A

Automatic mode, if the speed is set with the cruise control, VEB will be activated and work when required. So-called "down-hill cruise". VEB can also be activated steplessly via the footbrake, up to full effect.

1

VEB engaged with EPG activated at 25% (about 2 bar)

2

VEB engaged with EPG activated at 50% (about 3.5 bar)

3

VEB engaged with EPG activated at 75% (about 4.5 bar)

4

VEB engaged with EPG activated at 100% (about 7.5 bar)

VEB starts working first when the following conditions are fulfilled: The accelerator pedal is released. The engine speed exceeds 1100 rpm. The clutch pedal is released. Engines with VEB have different camshafts and exhaust rocker arms compared with standard engines. In addition, there is a control valve for controlling the exhaust rocker arms using oil pressure. NOTE! If the ABS system is activated, VEB is disconnected automatically. NOTE! The VEB brake cannot be activated if the engine oil temperature is below +55°C. The INFO-lamp on the instrument panel flashes if the driver tries to engage the VEB brake in this condition. Engines without VEB have the ordinary exhaust brake EPG, which has two functions: Is activated when the engine is cold (less than 50 degrees C) but with a lower air pressure, about 2 bar, to warm up the engine faster, (Parking brake applied) Is activated steplessly together with the wheel brakes using the footbrake pedal.

Control valve

© Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

32 / 41

IMPACT 3.0

1. 2. 3. 4. 5. 6.

Thursday, 20 September 2012

Oil inlet. Solenoid valve. Piston. Spring. Oil outlet. Oil chamber.

The control valve is on the cylinder head under the valve cover. Its task is to regulate the oil pressure to the rocker arm mechanism. The inlet is connected to the lubrication oil channel in the cylinder block and therefore always has oil system pressure. The outlet is connected to the rocker arm shaft. The engine compression brake is activated by the solenoid valve which is controlled from the control unit. A

When the engine is running, the piston partly covers the oil outlet as it moves into a balanced position between the force in the spring and the oil pressure in the oil chamber on the opposite side of the piston. From here, the oil pressure then falls to around 1 bar after the control valve. This pressure is sufficient for lubrication of the camshaft bearing and the rocker mechanism.

B

When the engine compression brake is activated, voltage is applied to the solenoid valve and a drain valve is opened which the oil can flow out through. The spring force takes over and the piston is forced downwards. The entire oil outlet is opened and the oil pressure to the rocker arm shaft increases.

SCR

© Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

33 / 41

IMPACT 3.0

1. 2. 3. 4.

Thursday, 20 September 2012

Urea container. Dosing unit. Urea injector. Catalyst.

After-treatment of the exhaust gases is required in order to achieve Euro 4. The earlier Euro 3 engines have a particulate filter as an option. This type of basic engine specification reduces the occurrence of nitrous oxides (NOx), but increases the occurrence of particulates. It may be though strange that the difference in fuel consumption between a Euro 2 and a Euro 3 engine is so little, since one may think that a Euro 3 engine, which produces less NOx, should consume less fuel. The situation can be describes as ”adding more fuel to ensure that the fire burns more completely”. As named earlier, the occurrence of NOx is reduced, but the occurrence of particulates (which are captured by the particulate filter) increases. As far as the DH12E is concerned, less fuel and more air is added, which drastically reduces the occurrence of particles, which in turn means that a particulate filter is no longer necessary as an option. As previously mentioned, reducing the fuel mixture increases the occurrence of nitrous oxide (NOx). These nitrous oxides are treated with a urea solution which is added just before the catalytic converter, causing a chemical reaction that converts the nitrous oxides into harmless water vapour and nitrogen. The engine is not directly involved in the SCR process, since the addition of urea solution is first done after the exhaust gases have left the engine. The dosing unit activates the urea injector that injects a urea solution into the exhaust gases just prior to the catalytic converter, which is integrated in the silencer. The exhaust gases are forced to rotate in the catalytic converter, where the injected urea solution starts the chemical reaction that converts the nitrous oxides into harmless water vapour and nitrogen gas. © Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

34 / 41

IMPACT 3.0

Thursday, 20 September 2012

Cooling system Charge air cooling and preheating Cooling system Coolant circulation Coolant fan

Charge air cooling and preheating

1. Charge air cooler. 2. Starter element. The charge air cooler is located in front of the water cooler and is an air to air type. It reduces the inlet air temperature to around 100 . In this way the inlet air volume is reduced and more air can be forced into the cylinders. This will give higher engine power, higher torque and lower fuel consumption. The cooler air also reduces the stress on valves and pistons For markets with cold winters there is, on the inlet side, an electric preheater that heats the air in the inlet manifold. This is activated when the driver turns the ignition key to the preheater position and the engine’s coolant temperature is lower than +10 . Preheating and after heating times are controlled by the engine’s control unit. The hot air eases starting at low temperatures and reduces white smoke in the exhaust. There is an engine preheater lamp on the instrument panel. The lamp lights when the preheater is active, but not during after-heating. The lamp is also used to indicate if a fault has occurred in the element whilst driving. The following conditions must be fulfilled for preheater operation: The parking brake must be applied. Preheating times vary with temperature in the following way: With a coolant temperature above +10 there is no preheating. © Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

35 / 41

IMPACT 3.0

Thursday, 20 September 2012

With a coolant temperature +10 °C the preheating time is 25 seconds. With a coolant temperature below -15 °C the preheating time is 55 seconds. In the interval +10 to -15 the preheating time increases linearly. After heating time is always equal to the preheating time.

Cooling system

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17.

Thermostat, engine. Coolant pump. Radiator. Expansion tank. Level sensor. Cover with pressure valves. Coolant filter. Pressure retaining valve. To body builder’s outlet/heating. Thermostat, cabin heater. Connection, cabin heater. Connection, defroster heating. Return connection, heating/defroster. Coolant to retarder. Coolant from retarder. Air bleed nipple. Air bleed nipple.

The cooling system cools the engine. If the bus has a retarder, the cooling system also cools the oil in the retarder. The heated coolant is led to the body builder’s outlet for further transport to the cabin heater and defroster. © Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

36 / 41

IMPACT 3.0

Thursday, 20 September 2012

The radiator is made from aluminium and has end tanks made of plastic. There are two water cooler sizes dependent on engine power and cooling requirement. For power variant 340 hp, the radiator area is 5600 cm2 and for power variants 380 and 420 hp, the radiator area is 7000 cm2. The expansion tank is manufactured of transparent plastic and has a built in level sensor connected to the engine control unit. It has two filler caps, the upper one being equipped with two pressure valves. One of the valves is a safety valve which opens when the system’s basic pressure of 0.75 bar is exceeded. The other valve is a low pressure valve which admits air when there is a low pressure in the system. A coolant filter, a Perry-filter, is available as an option, placed beneath the hydraulic oil tank. A smaller amount of coolant is led to the filter where an anti-rust agent is released into the coolant. The anti-rust agent extends the coolant change interval. A bleeding nipple is located on the steel pipe between the engine/water pump and the radiator and an air bleeding nipple is located where the coolant comes from the engine and flows to the retarder and the turbo. On the B12M variant, there is a bleeding nipple on the steel pipe to the thermostat housing. The bleeding nipples are located by the retarder pipe and radiator. The basic pressure in the system has been increased from 0.5 bar to 0.75 bar, to allow a higher engine temperature and thus better efficiency. The coolant filter should be replaced every 6 months. The coolant should normally be changed after 24 months or 200,000 km, but with the coolant filter, the coolant only needs replacing after 48 months or 500,000 km. The coolant system must be bled as specified in instructions, as a special procedure is required. The system is filled from below using a pump. There is a great risk of the engine seizing if air pockets remain in the engine. To prevent an overdose of anti-rust agent, the filter should not be replaced at the same time as the coolant, but 6 months later. After which the filter should be replaced every 6 months until the next coolant replacement. The expansion tank on B12M is fitted in the maintenance area on power variant 340 hp and on the left side above the radiator on power variants 380 and 420 hp so that it is located above the larger radiator’s coolant level. On the B12B, the expansion tank is fitted farthest to the rear of the bus.

Coolant circulation

© Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

37 / 41

IMPACT 3.0

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14.

Thursday, 20 September 2012

Oil cooler. Cylinder liner. Cylinder head coolant jacket. Coolant thermostat. Coolant pump. Radiator. Expansion tank. Coolant for retarder Coolant to bodywork outlet. Thermostat for heater outlet. Pressure retaining valve. Coolant filter. Air bleed nipple. Air bleed nipple.

The coolant pump pumps the coolant into the engine via a pipe to the distribution jacket on the top of the cylinder block. The majority of the coolant is forced between the oil cooler’s flanges while a small part of the coolant is forced into the cylinder liners’ lower cooling jackets. The coolant is also fed to the turbo. After the oil cooler, the coolant is distributed via calibrating holes to the cylinders upper cooling jackets and to the cylinder head. The cylinder head also receives return coolant from the cylinder liner’s cooling jackets. After the engine, the coolant flows to the retarder. A part of the coolant to the retarder is taken out before the engine via a by-pass pipe, so that the retarder receives coolant which has not been heated. If there is no retarder, the coolant flows directly in return to the coolant pump or the radiator via the coolant thermostat. A

During engine warm up, the coolant thermostat is closed and the coolant is led back to the coolant pump.

B

When the engine achieves operating temperature, the coolant thermostat opens and a part of the coolant is led to the radiator where it is cooled to around 5-7 °C. The coolant is led from the radiator back to the coolant pump. The thermostat starts to open at 86 °C and is completely open at 96 °C.

© Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

38 / 41

IMPACT 3.0

Thursday, 20 September 2012

If the bus is intended for a hot market (HOTCLIM) there is another opening temperature on the thermostat. The thermostat starts to open at 76 °C and is completely open at 86 °C. When the coolant warms up it expands, and to make space in the cooling system the excess is pressed into the expansion tank. This also helps to remove any air bubbles that have been created in the coolant. Some of the hot coolant from the engine is fed out to the bodywork outlet for the defroster and cabin heater. A thermostat on the outlet prevents heat from being extracted before the engine is hot. It opens at 60 °C. The pressure retaining valve ensures that the coolant flows to the bodybuilder's outlet at idle. It is kept open by the coolant system base pressure. The low pressure at idle will not keep the pressure retaining valve completely open, instead it starts to close so that the flow to the coolant pump is partially choked.

The coolant pump is a gear wheel type and is driven by the crankshaft via an intermediary gear. The impeller is manufactured of aluminium. Its shaft is mounted in bearings with a double ball bearing and is lubricated using oil from the engine timing gears. Between the oil seal and the coolant seal there is a chamber with a drainage channel. The coolant thermostat is piston type and is fitted in a housing of die cast aluminium. If the engines coolant has been drained, it must be refilled via a valve located on the underside of the block. Once the engine coolant has been refilled, it must be bled according to the instructions in group 26 IMPACT. All handling of coolant shall be via special filling equipment that is available from Volvo's special tools system. If the engine's cooling system is not bled as instructed, there is a risk of piston seizure.

Coolant fan

© Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

39 / 41

IMPACT 3.0

1. 2. 3. 4. 5. 6. 7.

Thursday, 20 September 2012

Coolant fan. Hydraulic motor. Hydraulic pump. Hydraulic oil tanks. Hydraulic oil filter. Hydraulic oil cooler. RPM sensor.

The radiator fan drive system is hydraulic. The hydraulic pump draws oil from the hydraulic oil tank which it shares with the power steering system. Then, the hydraulic pump forces the oil to the hydraulic motor which drives the radiator fan. After the hydraulic motor, the oil passes through the hydraulic oil cooler which is cooled by the radiator fan. Finally the oil passes through the hydraulic oil filter which it shares with the control system. The radiator fan is manufactured of plastic. It is permanently fitted directly on the hydraulic motor shaft. The maximum speed varies depending on the engine horsepower. The hydraulic motor is a gear wheel motor. It is bolted onto a bracket on the fan shroud. The hydraulic pump is a piston pump with nine pistons and variable yoke angle. The hydraulic pump speed is dependent on the engine’s rpm, while its flow and working pressure, and therefore the radiator fan’s rotational speed, is dependant on the yoke angle. In the basic position, two springs hold the yoke at the maximum angle, and the hydraulic pump’s working pressure is therefore highest. The yoke angle is controlled by a proportional valve which counteracts the springs. The proportional valve is controlled from the engine’s control unit (EECU) and control is based on coolant temperature. The greater the PWM modulated voltage that the control unit feeds to the solenoid valve, the greater the solenoid valve pressure on the spring. The © Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

40 / 41

IMPACT 3.0

Thursday, 20 September 2012

yoke angle then reduces and a lower working pressure is obtained. This design guaranteed that the coolant fan will continue to function even if contact is lost with the control unit. The hydraulic pump is driven by the engine’s transmission. The system is also fitted with an inductive rpm sensor that measures the actual rpm of the cooling fan. The actual value is sent to the EECU, which allows the engine control unit to make fine adjustments to the cooling fan rpm. The hydraulic oil tank is of the cyclone type. It comprises an upper and a lower chamber separated by a diaphragm. The return oil passes through a hole in the diaphragm and rotates around in the lower chamber. Air bubbles are therefore removed from the oil. This minimises the oil volume necessary and the entire system therefore requires just 8 litres. There is an oil level sensor in the oil tank. An INFO light and a symbol are shown in the display on the instrument panel when the oil level falls below the permitted level. The coolant fan’s drive system draws oil from the oil tank at a higher level than the control system. If a leakage occurs in the radiator fan’s drive system, there will still be 1 litre of oil remaining in the oil tank for the control system. The hydraulic oil filter is a disposable filter comprising folded special paper with very fine filtering characteristics. There is a pressure drop indicator on the filter. If the oil pressure in the filter exceeds 1.25 bars the INFO light comes on, on the instrument panel and a symbol is shown in the display. If the oil pressure in the filter exceeds 1.7 bars, a by-pass valve opens and allows the hydraulic oil to by pass the filter.

© Copyright Volvo Group North America The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

41 / 41