GB2416812A

GB2416812A - Lubrication system for turbocharger

Info

Publication number: GB2416812A
Application number: GB0416815A
Authority: GB
Inventors: Damian M Packer; Russ Martin; Andrew John Mcfarlane; James Martin Oates
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2004-07-29
Filing date: 2004-07-29
Publication date: 2006-02-08
Anticipated expiration: 2024-07-29
Also published as: JP2006037965A; GB0416815D0; DE102005035731B4; GB2416812B; DE102005035731A1; CN1734066A; CN1734066B

Abstract

An internal combustion engine 8 is provided with a lubrication system for a turbocharger 3 fitted to the engine including an oil pump 2 to supply oil to one or more bearings of the turbocharger 3 from a main oil reservoir 6, a secondary reservoir to receive oil from the turbocharger bearings and a vacuum pump 5 to urge oil to flow from the turbocharger bearings into the secondary reservoir 4 and to pump the oil back from the secondary reservoir 4 to the primary reservoir 6. An additional feature of the invention is that the vacuum pump 5 used to pump oil back from the secondary reservoir can also be used as a source of vacuum for a vacuum operated system 9.

Description

An Internal Combustion Engine and a Lubrication System therefor This

invention relates to the lubrication of internal combustion engines and in particular to the lubrication of a turbocharger fitted to such an engine.

It is well known that the performance of an internal combustion engine can be improved by the use of an exhaust i0 gas turbocharger. It is further known to provide a lubrication system for such a turbocharger in which oil is supplied to the turbocharger by an oil feed from the engine and is returned by gravity to a sump of the engine. In order to prevent backup of oil in the drain pipe from such a turbocharger it is usual to mount the turbocharger as high as possible to provide as long a drain pipe as possible and to use a substantially vertical drain pipe to assist with drainage. This has the disadvantage that the bonnet line of the motor vehicle will often need to be higher than would otherwise be necessary.

Backup in the drain pipe from a turbocharger is a considerable problem as it can lead to oil back feeding into the turbocharger which will cause exhaust smoke and in the case of a diesel engine can also lead to engine runaway due to the induction of oil into the engine. In effect under such conditions the turbocharger acts as a small uncontrolled gas turbine engine and such runaway conditions will almost invariably result in failure of the turbocharger or of the engine itself.

One of the problems with a conventional gravity return system is that the level of the oil in the sump will vary during use of the motor vehicle due to the orientation and 3r, dynamic condition of the motor vehicle. For example, if the vehicle is cornering, the oil will be urged by the centrifugal force to one side of the sump where it will ride :: . .: . . . . . . . . ... . . 204-0196GB - 2 - up the side of the sump. This can be a problem if the lower end of the oil return or drain pipe from the turbocharger becomes covered as it will then prevent oil from draining back into the sump and so is likely to lead to oil backup in the return pipe. A further situation when this type of system is problematic is where the vehicle is used on steeply inclined terrain such as is encountered off-road.

This type of prior art situation can be understood better with reference to Figs. 6 and 7 of the accompanying drawing lo in which the lower end of a return or drain pipe 221 from a turbocharger (not shown) is shown projecting into a sump 206 of an engine (also not shown).

In Fig.6 the situation is shown with the vehicle on level ground and in Fig.7 is shown with the vehicle on an incline O. It can be seen that when the vehicle is on the incline the end of the drain pipe 221 is below the level of the oil and so backup of oil in the drain pipe 221 is likely.

It will be appreciated that the large change in level of oil in the sump 206 is partly due to the fact that a large volume of oil has to be stored in the sump to supply the needs of the engine. 2'

The inventors have realised that if there was a very small volume of oil in the sump then even if the angle of the vehicle is changed there is little risk of the drain tube being covered. However, it is not possible to use such a small volume of oil in a normal sump as it would lead to oil pick up problems and potentially oil starvation to the engine.

It is an object of this invention to provide an internal combustion engine having an improved lubrication system.

A. *:. ::e Hi- :e.e 204-0196GB According to a first aspect of the invention there is provided an internal combustion engine having at least one turbocharger and a lubrication system for the turbocharger, the lubrication system comprising a main oil reservoir for storing oil used to lubricate the or each turbocharger, an oil pump to supply oil from the main oil reservoir to the or each turbocharger, a secondary reservoir to receive oil from the or each turbocharger and a vacuum pump to return the oil received in the secondary reservoir to the main oil lo reservoir.

The oil pump may be an engine oil pump used to supply oil to the or each turbocharger and to the internal combustion engine.

The vacuum pump may be operable to create a partial vacuum in the secondary oil reservoir so as to assist the flow of oil from the or each turbocharger into the secondary reservoir.

During operation of the engine, the pumping rate of the vacuum pump may be at least the same as the flow rate of oil from the or all of the turbochargers connected to the secondary reservoir so that substantially no oil is stored in the secondary reservoir.

Preferably, the pumping rate is greater than the flow rate of oil from the or all of the turbochargers into the secondary reservoir.

The or each turbocharger may have a respective oil inlet port to receive oil from the oil pump and a respective oil outlet port to return oil from the respective turbocharger to the secondary reservoir by means of a return conduit.

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204-0196GB - 4 - Each turbocharger may be connected to the secondary reservoir by a respective return conduit and the secondary reservoir may be a closed volume having an outlet conr.sated to the vacuum pump, a like number of inlets as there are return conduits and a vent to prevent the creation of excessive vacuum in the secondary reservoir.

The vent may be connected to a crankcase region of the engine.

The secondary reservoir may be located within the main oil reservoir.

The main oil reservoir may be formed primarily as a one piece casting and the secondary reservoir may be formed as part of the one piece casting forming the main oil reservoir. In which case, at least part of the vent may be formed as a passageway cast into the one piece casting.

The engine may have at least one camshaft and the vacuum pump may be driven from one end of the or one o the camshafts of the engine.

At least one camshaft may be driven by a chain housed in a chaincase and the vacuum pump may have an outlet port arranged to return oil to the main oil reservoir by exhausting it into the chaincase.

The engine may have a first camshaft driven by th_ chain and a second camshaft driven by a geared drive from the first camshaft, in which case, the oil exhausted from the vacuum pump may impinge against at least one gear forming the geared drive between the first and second camshafts.

Preferably, the vacuum pump may be a rotary sliding vane pump.

I. : . .. 2..e 204-0196GB - 5 The engine may have two turbochargers and each of the turbochargers may have a return conduit connected to the secondary reservoir.

The engine may be a V engine having two banks of cylinders and one of the turbochargers may be arranged to exhaust gases from one of the two banks of cylinders and the other turbocharger may be arranged to receive exhaust gases lo from the other of the two banks of cylinders. In which case, each of the turbochargers may be positioned below the bank of cylinders from which it receives exhaust gasses.

The vacuum pump may be mounted above the or each i5 turbocharger.

According to a second aspect of the invention there is provided a motor vehicle having an engine in accordance with said first aspect of the invention.

The motor vehicle may have a vacuum system and the vacuum pump may be used to provide vacuum to the vacuum system and to assist with the flow of oil from the or each turbocharger.

The vacuum system may be a vacuum assisted braking system and the vacuum pump may be operable to produce a partial vacuum in a vacuum reservoir of a brake booster forming part of the vacuum assisted braking system. an)

The vacuum pump may be a rotary sliding vane vacuum pump having a first inlet connected to the vacuum system and a second inlet connected to the secondary reservoir.

The invention will now be described by way of example with reference to the accompanying drawing of which: 2.. : 2 2.

204-0196GB - 6 Fig.1 is a schematic drawing of a motor vehicle and internal combustion engine according to the invention; Fig.2 is an end view of an internal combustion engine according to the invention; Fig.3 is a scrap cross-section through a chaincase forming part of the engine shown in Fig.2; lo Fig.4 is a pictorial representation of part of a main oil reservoir of the engine shown in Fig.2; Fig.5 is a diagrammatic view of a vacuum pump for use in a lubrication system for the engine shown in Fig.2 with an end cover removed showing the location of the inlet and outlet ports) Fig.6 is a diagrammatic representation of a prior art oil reservoir of an engine and turbocharger drain pipe showing the level of oil when a vehicle to which the engine is fitted is on level ground; and Fig.7 is a representation similar to that shown in Fig.6 but showing the oil level when the vehicle is on an incline.

The invention will now be described with particular reference to F g.' which shows a motor vehicle 10 having an internal combustion engine 8. The engine 8 includes a crankcase 7 and a main oil reservoir or sump 6.

The engine 8 is fitted with a lubrication system to lubricate not only the various moving parts of the engine 8 but also a turbocharger 3 which is operatively connected to an exhaust manifold (not shown) of the engine 8 to provide improved engine performance.

it: . ...:. :: . . . : 204-0196GB - 7 - The lubrication system comprises of an oil pump 2 to pump lubricant in the form of oil from the main oil reservoir 6 to the turbocharger 3 and in particular to bearings of the turbocharger 3, a secondary reservoir 4 to receive oil from the turbocharger bearings and an engine driven vacuum pump 5 to provide a partial vacuum in the secondary reservoir 4 thereby urging oil to flow from the turbocharger bearings to the secondary reservoir 4 and also to pump any oil collected in the secondary reservoir 4 back lo to the main oil reservoir 6.

The secondary reservoir 4 is in the form of a closed volume having a return conduit or drain pipe from the turbocharger 3 attached thereto, an outlet conduit in the form of an oil return pipe from the vacuum pump 5 attached thereto and a vent connected by a vent pipe to the crankcase 7 of the engine 8.

The drain pipe is attached to an upper or top surface of the secondary reservoir 4 and has a lower end positioned near to the upper surface of the secondary reservoir 4 so that it is unlikely to be covered by any oil collected in the secondary reservoir 4. The vent pipe is also connected near to the upper surface of the secondary reservoir 4 so that if the pressure in the crankcase 7 is lower than the pressure in the secondary reservoir vapour from the oil returning from the turbocharger can be returned to the crankcase 7.

The function of the vent is to prevent excessive vacuum being formed in the secondary reservoir 4 by the pump 5.

Although it is desirable to maintain the secondary reservoir 4 at a pressure below atmospheric at all times during running of the engine 8 and certainly at a pressure which is lower than the pressure of the oil in the t turbocharger bearings it is undesirable for the pressure in the secondary reservoir to fall too low as this will tend to destroy the ë 2: .e' 2..

204-0196GB - 8 - oil film in the turbocharger bearings and cause premature bearing failure. For example and without limitation, if the pressure in the secondary reservoir is reduced below ??? N/m2 bearing failure is likely. It is an advantage of the invention that, by correctly sizing the vent and the oil return pipe to the vacuum pump 5, it is possible to maintain a low level vacuum within the secondary reservoir without any additional valves or controls.

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The vacuum pump 5 is also connected to a vacuum system in the form of a vacuum reservoir 9 for brake booster forming part of a vacuum assisted braking system. It is an advantage of this aspect of the invention that a single vacuum pump 5 is used to provide the vacuum to the secondary is reservoir and to provide a source of vacuum for any vacuum operated equipment on the motor vehicle 10. This is particularly advantageous if the engine of the motor vehicle is a diesel engine for in such a case it is usual to provide a vacuum pump to provide vacuum for the braking circuit and so the advantageous effects of the invention can be obtained without the need for an additional pump as the same vacuum pump normally used just to provide vacuum for the braking system can be used with obvious cost savings.

2- Operation of the system is as follows, upon start-up of the engine 8 it is likely that a small amount of oil will have drained back from the turbocharger 3 and collected in the secondary reservoir 4. As soon as the engine is running oil is pumped by the pump 2 from the main oil reservoir 6 to SO the turbocharger bearings and begins to flow from the turbocharger 3 to the secondary reservoir 4 through the drain pipe urged by the partial vacuum that has been formed in the secondary reservoir 4 by the pump 5. When the engine 8 is idling the flow rate of the pump 5 is substantially the 3- same as the flow rate of oil from the turbocharger 3 to the secondary reservoir 4 and the pressure in the secondary reservoir 4 is slightly below or substantially equal to .22.2. :.

:. - . :

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204-0196GB _ 9 _ atmospheric pressure but as soon as the speed of the engine 8 is increased the vacuum in the secondary reservoir 4 increases. This is because the vacuum pump 5 is driven by the engine 8 and so is affected by engine speed. It will be appreciated that the vacuum pump could alternatively be hydraulically or electrically driven in which case the flow rate of the pump would be independent of engine speed.

When the engine 8 is running above idle speed the flow rate of the pump 5 exceeds the flow rate of oil returning to the secondary reservoir 4 so that after a few minutes of running there is little or no oil remaining in the secondary reservoir 4.

This ensures that, within the limits of stability of the motor vehicle' the orientation of the vehicle will not have an adverse affect on the flow of oil from the turbocharger 3 and that oil cannot flow back into the turbocharger 3 from the drain pipe.

Any oil and vapour exiting the turbocharger 3 are drawn through the secondary reservoir 4 into the main reservoir 6 by the vacuum pump 5 in which they are separated for re-use.

The owl returned to the main oil reservoir 6 is reused to lubricate the engine 8 and turbocharger 3 and any entrained vapour or oil mist is fed to the crankcase where it is separated into gas and fluid. The gas from the vapour is then passed through a crankcase ventilation system in the normal manner and the fluid is allowed to drain back to the 3 main oil reservoir 6.

It an therefore be seen that a lubrication system according to the invention provides improved turbocharger lubrication at virtually no extra cost or complexity.

With reference to Figs 2 to 5 there is shown a preferred embodiment of the invention as applied a V8 diesel ire'' 2 2: . .'" 2'..

204-0196GB - 10 - engine 108 having two banks of cylinders. Each bank of cylinders has a turbocharger 103 arranged to receive exhaust gases from the engine 108 through an exhaust gas manifold.

Each of the turbochargers 103 is mounted below the bank of cylinders to which it is operatively connected thereby minimising the height of the engine 108.

Each of the turbochargers 103 is supplied with oil from an engine oil pump (not shown) which- is also used to supply lo oil to various other components of the engine 108. The oil is stored in a main oil reservoir or sump 106 fastened to the lower end of the engine 108 and is pumped by the engine oil pump from the sump 106 through various internal passageways formed in the engine 108. Each turbocharger 103 has a respective oil inlet port to receive oil from the engine oil pump via an internal oil feed formed in the engine (not shown) and a respective oil outlet port to return oil from the respective turbocharger to a secondary reservoir or turbo sump 104.

The oil inlet and outlet ports of each turbocharger 103 are connected to bearings located within the respective turbocharger 103 and are used to supply and return oil from the bearings of the turbocharger 103.

A return conduit in the form of a drain pipe 121 is connected between the outlet port of each turbocharger 103 and the turbo sump 104 to permit oil to be returned from the bearings to the turbo sump 104.

As best seen with reference to Fig.4 the main oil reservoir 106 is formed as a one piece casting and the secondary reservoir or turbo sump 104 is located within the main oil reservoir 106 and is formed as part of the one piece casting used to form the main oil reservoir 106.

ë, 2 vet ë 204-0196GB The turbo sump 104 as shown in Fig.4 is not complete as in use it is fitted with a lid so as to form a closed volume and has various pipes connected to it as discussed below.

The drain pipes 121 from the turbochargers 103 sealingly pass through respective apertures 140 formed in a wall of the casting used to form the main oil reservoir 106 and are sealingly attached to apertures 130 formed near to the top end of the turbo sump 104.

A vent for the turbo sump 104 is provided in the form of a passageway 142 cast into the casting forming the main oil reservoir 106. The passageway 142 cooperates in use with a further passageway (not shown) formed in the engine 108 which allows vapour to flow to and from a crankcase region of the engine 108. This connection limits the vacuum that can be formed in the turbo sump 104 because when the vacuum in the turbo sump 104 reaches a certain level gas and or oil vapour will tend to flow into the turbo sump 104 from the crankcase of the engine 108. It is important to limit the vacuum that can be produced in the turbo sump 104 because if too high a vacuum is produced the oil will tend to be sucked out from the turbocharger bearings causing the oil film that needs to be present in the bearings to break down thereby causing premature bearing failure.

A further aperture 150 is formed in the wall of the main oil reserve r 106 to which is sealingly connected an oil return pipe 122 used to transport oil and oil vapour from the turbo sump 104 to an engine driven rotary vacuum pump 105.

The oil return pipe 122 is connected to an aperture 151 near to the base of the turbo sump 104 so that substantially any oil collected in the turbo sump 104 can be pumped out by the vacuum pump 105 and be returned to the main oil reservoir 106.

2: , ' ' 2.

204-0196GB - 12 With particular reference to Figs 2, 3 and 5 the upper end of the oil return pipe 122 is connected to a second inlet to the rotary vacuum pump 105. As can be seen with reference to Fig.5 the rotary vacuum pump is of conventional form having a rotor 110 slidingly supporting a vane 112 within a chamber. A first inlet 113 to the chamber of the rotary pump 105 is connected in use to a vacuum system such as a vacuum assisted braking system (not shown). An outlet lo port 115 is provided to exhaust fluid and vapour from the chamber when the rotor 110 is rotated in the direction of the arrow "R". A reed valve (not shown) on the back of the pump 105 allows fluid to pass out but not in through the outlet port 115.

The pump 105 is fixed to a chaincase 120 used to enclose a chain 126 drivingly connecting a crankshaft (not shown) of the engine 108 to a camshaft 125. The position of the rotary vacuum pump 105 is such that it is mounted above the two turbochargers 103 so that any oil leaving the turbochargers 103 flows downwardly to the turbo sump 104 and then upwardly to the pump 105. In order to ensure that the vane 112 is able to correctly seal against the chamber a small supply of oil is provided from the engine 108 to the pump 105. However, because of the type of pump used no actual pump priming is required and the pump 105 will begin operating as soon as the rotor 110 starts rotating.

The chaincase 120 is sealingly attached to an end wall 124 of the engine 108 which supports the camshaft 125. The engine 108 has four camshafts in total, two per bank of cylinders and the outside camshaft 125 of the right hand bank of cylinders is used to directly drive the rotor 110 of the pump 105. The other camshaft (not shown) of the right hand bank of cylinders is driven by a gear 127 driveably attached to the end of the outside camshaft 125 which mates 2 '.' : . 2 ' ' ;,.

204-0196GB - 13 with a complementary gear (not shown) fastened to the inside camshaft.

The outlet port of the rotary pump 105 cooperates with an aperture 128 formed in the chaincase 120 so that oil and vapour leaving the pump 105 are urged into the chaincase and impinge against the gear 127. This is beneficial because under certain conditions the outflow from the vacuum pump approximates to a fine mist and the impingement against the lo gear 127 tends to increase the droplet size thereby assisting with collection and recirculation of the oil.

The oil expelled into the chaincase 120 flows down through the chaincase 120 under the effect of gravity and is is collected in the main oil reservoir 106 from where it can be re-used.

The engine 108 is fitted with a crankcase breather system to recirculate gasses extracted from any returning oil to an inlet manifold (not shown) of the engine 108.

In order to ensure that during running of the engine 108 substantially no oil is stored in the turbo sump 104 the pumping capacity of the vacuum pump 105 is selected to be ?5 slightly greater than the flow rate of oil from the two turbochargers 103 Lo the turbo sump 104. Although, due to gravity drain back during engine off conditions, there may be a small amount of oil in the turbo sump 104 at engine start-up, as soon as the engine starts to function this oil is quickly removed from the turbo sump 104 and returned to the main oil reservoir 106. The turbo sump 104 therefore provides a discontinuity in the flow path back from the turbochargers 103 to the main oil reservoir 106 as once oil enters the turbo sump it cannot be drawn back up the drain pipes 121.

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. . . . . . . . 204-0196GB - 14 When the engine is idling there is virtually no vacuum in the turbo sump because the flow capacity of the vent 142 is substantially the same as the flow rate of the pump 105 but as engine speed rises the flow rate of the pump increases and so it is able to increase the partial vacuum in the turbo sump 104. However because of the predetermined leak formed by the vent 142, the magnitude of the partial vacuum formed in the turbo sump 104 is never high enough to cause the oil film in the bearings of the turbochargers 103 lo to be destroyed.

It will be appreciated that with such an arrangement the overall height of the engine has remained unchanged and that because the vacuum pump used is the same as that often :5 used on a diesel engine to provide a source of vacuum the cost of implementing such as system is relatively low. In addition, the same pump can be used to assist with oil drainage from any turbochargers fitted to the engine and also to provide a source of vacuum for any vacuum operated systems fitted to the vehicle.

Because during running of the engine there is always a small pressure difference between the pressure of the oil in the turbocharger bearings and the lower pressure in the turbo sump 104 oil will always tend to flow towards the turbo sump 104 irrespective of the orientation of the engine 108.

Although in this preferred embodiment the vacuum pump JO is driven directly from the engine it need not be and could be driven by any suitable source of motive power.

Although the invention has been described and is particularly advantageous in respect of its use for an internal combustion engine fitted to a motor vehicle it will be appreciated that it could be used on any turbocharged engine.

e e e :::: .. :e:: ..

? 204-0196GB It will be appreciated by those skilled in the art that although the invention has been described by way of example with reference to a number of specific embodiments it is not limited to these embodiments and that various alternative embodiments or modifications to the disclosed embodiments could be made without departing from the scope of the invention.

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Claims

204-0196GB - 16 Claims 1. An internal combustion engine having at least

one turbocharger and a lubrication system for the turbocharger, the lubrication system comprising a main oil reservoir for storing oil used to lubricate the or each turbocharger, an oil pump to supply oil from the main oil reservoir to the or each turbocharger, a secondary reservoir to receive oil from the or each turbocharger and a vacuum pump to return the oil lo received in the secondary reservoir to the main oil reservoir.
2. An engine as claimed in claim 1 wherein the oil pump is an engine oil pump used to supply oil to the or each turbocharger and to the internal combustion engine.
3. An engine as claimed in claim 1 or in claim 2 wherein the vacuum pump is operable to create a partial vacuum in the secondary oil reservoir so as to assist the flow of oil from the or each turbocharger into the secondary reservoir.
4. An engine as claimed in any of claims 1 to 3 wherein, during operation of the engine, the pumping rate of the vacuum pump is at least the same as the flow rate of oil from the or all of the turbochargers connected to the secondary reservoir so that substantially no oil is stored in the secondary reservoir.
5. An engine as claimed in any of claims 1 to 4 wherein the or each turbocharger has a respective oil inlet port to receive oil from the oil pump and a respective oil outlet port to return oil from the respective turbocharger to the secondary reservoir by means of a return conduit.
6. An engine as claimed in claim 5 wherein each turbocharger is connected to the secondary reservoir by a . . . . 204-0196GB - 17 - respective return conduit and the secondary reservoir is a closed volume having an outlet connected to the vacuum pump, a like number of inlets as there are return conduits and a vent to prevent the creation of excessive vacuum in the secondary reservoir.
7. An engine as claimed in claim 6 wherein the vent is connected to a crankcase region of the engine.

lo
8. An engine as claimed in any of claims 1 to 7 wherein the secondary reservoir is located within the main oil reservoir.
9. An engine as claimed in claim 8 wherein the main oil reservoir is formed primarily as a one piece casting and the secondary reservoir is formed as part of the one piece casting forming the main oil reservoir.
10. An engine as claimed in claim 9 when claim 8 is dependent upon claim 6 or upon claim 7 wherein at least part of the vent is formed as a passageway cast into the one piece casting.
11. An engine as claimed in any of claims 1 to 10 wherein the engine has at least one camshaft and the vacuum pump IS driven from one end of the or one of the camshafts of the engine.
12. An engine as claimed in claim 11 wherein at least JO one camshaft is driven by a chain housed in a chaincase and the vacuum pump has an outlet port arranged to return oil to the main oil reservoir by exhausting it into the chaincase.
13. An engine as claimed in 12 in which the engine has a first camshaft driven by the chain and a second camshaft driven by a geared drive from the first camshaft wherein the oil exhausted from the vacuum pump impinges against at least . . e e 204-0196GB - 18 one gear forming the geared drive between the first and second camshafts.
14. An engine as claimed in any of claims 1 to 10 wherein the vacuum pump is a rotary sliding vane pump.
15. An engine as claimed in any of claims 1 to 16 wherein the engine has two turbochargers and each of the turbochargers has a return conduit connected to the lo secondary reservoir.
16. An engine as claimed in claim 15 wherein the engine is a V engine having two banks of cylinders and one of the turbochargers is arranged to exhaust gases from one of the two banks of cylinders and the other turbocharger is arranged to receive exhaust gases from the other of the two banks of cylinders.
17. An engine as claimed in claim 16 wherein each of the turbochargers is positioned below the bank of cylinders from which it receives exhaust gasses.
18. An engine as claimed in any of claims 1 to 17 wherein the vacuum pump is mounted above the or each 2r turbocharger.
19. A motor vehicle having an engine as claimed in any of claims 1 to 18.
20. A motor vehicle as claimed in claim 20 wherein the motor vehicle has a vacuum system and the vacuum pump is used to provide vacuum to the vacuum system and to assist with the flow of oil from the or each turbocharger.
21. A motor vehicle as claimed in claim 20 in which the vacuum system is a vacuum assisted braking system and the vacuum pump is operable to produce a partial vacuum in a . . . . . - . . . . . . 204-0196GB - 19 vacuum reservoir of a brake booster forming part of the vacuum assisted braking system.
22. A motor vehicle as claimed in claim 20 or in claim 21 wherein the vacuum pump is a rotary sliding vane vacuum pump having a first inlet connected to the vacuum system and a second inlet connected to the secondary reservoir.
23. An internal combustion engine substantially as lo described herein with reference to the accompanying drawing.
24. A motor vehicle substantially as described herein with reference to the accompanying drawing.

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