GB2571270A

GB2571270A - Exhaust manifold assembly

Info

Publication number: GB2571270A
Application number: GB1802771.4A
Authority: GB
Inventors: Jones Steve
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2018-02-21
Filing date: 2018-02-21
Publication date: 2019-08-28
Also published as: GB201802771D0; DE102019201874A1

Abstract

An exhaust manifold assembly 10 for an internal combustion engine comprises a conduit system 12 including a plurality of inlets 14 each for connection to a respective cylinder port (25, fig 3) within a cylinder head (42, fig 3) of the engine and an outlet 22 fluidly connected to the inlets. A cover plate 28 includes an aperture 30 for receiving the outlet of the conduit system and is mountable to the cylinder head. An exhaust system for an internal combustion engine comprises an engine cylinder head including a plurality of cylinder ports and the exhaust manifold assembly. A method of assembling the exhaust system comprises mounting the cover plate of the exhaust manifold system to the cylinder head such that the inlets of the conduit system are positioned within a respective cylinder port. A method of insulating an exhaust manifold assembly comprises injecting an insulating material into a cavity between the exhaust manifold assembly and a surrounding internal structure of an engine cylinder head.

Description

EXHAUST MANIFOLD ASSEMBLY

TECHNICAL FIELD

The present disclosure relates to an exhaust manifold assembly and particularly, but not exclusively, to an exhaust manifold assembly for mounting to a cylinder head of an internal combustion engine. Aspects of the invention relate to an exhaust manifold assembly, to an engine exhaust system, to a vehicle and to a method of insulating an exhaust manifold assembly.

BACKGROUND

Vehicle exhaust systems are configured to control the flow and treatment of exhaust gases that are expelled from a vehicle engine, before the exhaust gases are released into the atmosphere. Vehicle exhaust systems typically comprise an exhaust manifold that is configured to collect exhaust gases from the engine and directs the gases into downstream components of the exhaust system. More particularly, the exhaust manifold collects exhaust gases from multiple cylinders of the engine via multiple inlets and directs them into a single exhaust pipe from which they are released to the atmosphere.

An outlet of the exhaust manifold may be connected to a turbocharger assembly, which, in turn, is connected to a hot end of the exhaust pipe. Exhaust gases pass through the hot end of the exhaust pipe, before passing through a cold end of the exhaust system, and the gases are then expelled through an exhaust pipe outlet. The hot end of the exhaust system typically comprises aftertreatment devices, such as a catalytic converter which helps reduce harmful emissions into the environment.

Catalytic converters can only function effectively when the exhaust system reaches an optimal temperature. The point at which the system reaches this optimal temperature is called ‘catalytic light-off’.

Exhaust manifolds may have high thermal inertia which can increase the time the exhaust takes to reach catalytic light-off after the engine starts thereby increasing the level of harmful emissions from the engine during its first few minutes of operation.

In order to address this problem, ‘twin skin’ exhaust manifold assemblies have been developed in which the exhaust conduits of the exhaust manifold are covered with an additional ‘skin’, e.g. a thin layer of metal, which helps reduce the heat transfer from the inner exhaust conduit. However, such assemblies are very expensive to produce and often require additional support of the assembly within the exhaust system.

Another type of exhaust manifold assembly is a so-called ‘integrated exhaust manifold’ in which the exhaust manifold assembly forms part of the cylinder head, rather than being mounted outside thereof. Such assemblies are compact and allow a catalytic converter to be positioned close to the cylinder head. However, such assemblies require complex cooling systems such as water pumping systems to prevent the materials within the cylinder head from overheating and melting.

It is an aim of the present invention to address the above mentioned disadvantages associated with the prior art.

SUMMARY OF THE INVENTION

According to an aspect of the present invention there is provided an exhaust manifold assembly for an internal combustion engine. The exhaust manifold assembly comprises a conduit system including a plurality of inlets each for connection to a respective cylinder port within a cylinder head of the engine and an outlet fluidly connected to the inlets. The assembly further comprises a cover plate including an aperture for receiving the outlet of the conduit system, the cover plate being mountable to the cylinder head.

The invention therefore provides an exhaust manifold that can be mounted directly to a cylinder head such that the cover plate provides a single outlet of exhaust gases from the cylinder head. The majority of the conduit system can be contained within the cylinder head thereby requiring no external structural support.

The conduit system may be formed from a plurality of sections of pipe and the sections of pipe may be connected to each other via slip joints. Sections of pipe may be easy to form and the slip joints may allow for thermal expansion or contraction of the pipe sections relative to each other without transferring stress therebetween. Having a cover plate that can seal against a cylinder head allows flexibility in the design of the conduit system such that joints thereof need not be gas tight.

Each of the inlets may include a lip for sealing against an internal surface of the respective cylinder port. This may result in a fitting that is easy to assemble within a cylinder head.

The cover plate may include a further aperture for receiving a thermally insulating material thereby allowing a thermally insulating material to be added once the conduit system and cover plate are in position.

In embodiments, the conduit system may comprise a plurality of outlets each connected to respective inlets and the cover plate comprises a plurality of apertures each for receiving a respective outlet of the conduit system thus allowing a variety of exhaust flow arrangements.

The exhaust manifold assembly may further comprise a layer of thermally insulating material applied to an external surface of the conduit system.

According to an embodiment of the invention, an exhaust system for an internal combustion engine comprises an engine cylinder head including a plurality of cylinder ports and an exhaust manifold assembly as set forth in any of the embodiments above. The cover plate is mounted to the cylinder head and each of the inlets is connected to a respective cylinder port.

The exhaust system may further comprise a thermally insulating material surrounding the conduit system within the cylinder head. The insulating material may be a porous ceramic material and/or may fill a cavity between the conduit system and a surrounding region of the cylinder head. The thermally insulating material may be instead of or in addition to the layer of thermally insulating material as described above.

A vehicle may comprising the exhaust system of any of embodiments described above.

Accordingly to a further aspect of the invention, a method of assembling the exhaust system as set forth in any of embodiments described above comprises mounting the cover plate of the exhaust manifold system to the cylinder head such that the inlets of the conduit system are positioned within a respective cylinder port.

The method may further comprise injecting an insulating material through an aperture of the cover plate such that the insulating material fills a cavity between the conduit system and the cylinder head.

According to a further aspect of the invention a method of insulating an exhaust manifold assembly comprises injecting an insulating material into a cavity between the exhaust manifold assembly and a surrounding internal structure of an engine cylinder head.

The injected insulating material may hold the conduit system in position and act as a second insulating skin of the system. The method also allows quick and easy mounting of the conduit system prior to the addition of insulation.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a section view of an exhaust manifold assembly in accordance with an embodiment of the present invention;

Figure 2 is a section view of an exhaust manifold assembly in accordance with a further embodiment of the present invention;

Figure 3 shows an outlet side of a cylinder head for receiving an exhaust manifold assembly;

Figure 4 is a detail view of an inlet of the exhaust manifold assembly of Figure 1 in a cylinder port;

Figure 5 is a perspective view of an exhaust system according to an embodiment of the present invention;

Figure 6 is a section view of an exhaust manifold assembly according to an embodiment attached to a turbocharger assembly;

Figures 7a-c show an exhaust manifold assembly according to an embodiment at various stages of manufacture;

Figure 8a shows a conduit system for an exhaust manifold assembly according to a further embodiment of the invention; and

Figure 8b shows the cover plate mounted on a cylinder head according to the embodiment of Figure 8a.

DETAILED DESCRIPTION

With reference to Figure 1, an exhaust manifold assembly 10 in accordance with an embodiment of the invention comprises a conduit system 12 for directing exhaust gases from a plurality of cylinders of an internal combustion engine into a single outlet 22. The conduit system 12 has an inlet side 11 for receiving the exhaust gases and a outlet side 13 for delivering the gases to a further component of an exhaust system such as a turbocharger.

The conduit system 12 includes a plurality of inlet conduits 16 formed from sections of pipe 15 each having a respective inlet 14 on the inlet side thereof. The inlet conduits 16 are each fluidly connected to a plenum 18 such that exhaust gases flowing from the inlet 14 of each of the inlet conduits 16 combine in the plenum 18. The conduit system 12 includes a further section of pipe 15 forming an outlet conduit 20. The outlet conduit 20 has a first end 21 arranged toward the inlet side 11 and a second end 22 arranged towards the outlet side 13. The first end 21 is connected to the plenum 18 and the second end 22 forms an outlet of the exhaust manifold assembly 10. As such, the outlet 22 of the exhaust manifold assembly 10 is fluidly connected to the inlets 14 via the inlet conduits 16, plenum 18 and outlet conduit 20. Accordingly, exhaust gases enter the conduit system 12 at the inlets 14, pass through the inlet conduits 16 and mix in the plenum 18, pass into the outlet conduit 20 and exit the conduit system 12 via the outlet 22.

The conduit system 12 is formed from thin wall ferritic steel or austinitic hydroformed steel. More particularly, the conduit system 12 is formed from a plurality of sections of steel pipe 15. In alternative embodiments, the conduit system 12 may be formed from steel plate material which has been stamped and welded into pipes 15.

The sections of pipe 15 forming the conduit system 12 are connected to each other by slip joints 24. Slip joints 24 allow for thermal expansion or contraction of the pipe sections 15 relative to each other without transferring stress therebetween. The slip joints 24 need not necessarily be gas-tight and may allow a small amount of gas egress via the slip joints 24 to the extent that the flow properties of the exhaust gases through the conduit system 12 are not substantially affected.

The inlets 14 of the conduit system 12 are each configured for connection to a respective cylinder port 25 (shown in Figure 3) within a cylinder head of an internal combustion engine. The inlets 14 may be configured to loosely fit into the cylinder ports 25. A metal mesh seal (not shown) maybe required to ensure correct fitting however, the seal need not be gas-tight, as described with respect to the slip joints above. In an embodiment, the inlets 14 comprise press-fit steel inserts which are configured to be inserted into the ends of the cylinder ports 25.

The exhaust manifold assembly 10 further comprises a cover plate 28 attached to the conduit system 12 adjacent the outlet 22 thereof. The cover plate 28 is a rectangular sheet of cast metal configured for mounting to a cylinder head to secure the conduit system 12 in a desired position within the cylinder head. The cover plate 28 further provides a seal around an opening in the cylinder head to prevent exhaust gas from exiting the cylinder head via the opening.

The cover plate 28 includes an outlet aperture 30 for receiving the outlet 22 of the conduit system 12 such that exhaust gases exit the cylinder head via the outlet aperture 30. The outlet aperture 30 is positioned off-centre in the cover plate closer to a first edge 27 than a second edge 29 thereof. The outlet aperture 30 further includes a mounting feature 32 for mounting a turbocharger assembly (shown in Figure 6) thereto such that exhaust gases exiting the conduit system 12 are directed into the turbocharger assembly. The mounting feature 32 facilitates a gas-tight seal between the cover plate 28 and a turbocharger assembly.

The cover plate 28 further includes a seal member 34 for creating a gas-tight seal between the cover plate 28 and a cylinder head. The seal member 34 is in the form of a resilient gasket that is configured to seal against a corresponding seal land of a cylinder head.

The cover plate 28 includes a plurality of fastening means 36 for mounting the cover plate 28 to the cylinder head. In particular, the cover plate 28 includes two threaded bolts 36 provided either side of the outlet aperture 30. The bolts pass through fastening apertures 38 positioned in a periphery region of the cover plate 28, adjacent the seal member 34.

Figure 2 shows an alternative embodiment of an exhaust manifold assembly 110 according to the invention. The assembly 110 of Figure 2 is substantially the same as the assembly 10 of Figure 1 with the exception that the outlet 122 of the conduit system 112 and outlet aperture 130 are positioned on a different part of the cover plate 128. More particularly, the outlet 122 of this embodiment is positioned closer to a second side 129 than a first side 127 of the cover plate 128 i.e. on the opposite side of the cover plate 128 than shown in the embodiment of Figure 1. In alternative embodiments, the outlet pipe 128 may be located in a substantially central zone of the cover plate 128 as shown in phantom in Figure 2. More generally, the conduit system 112 may be configured such that the outlet pipe 128 is in any position within the cover plate 128 depending on the conduit system configuration, size and position of the cover plate and/or corresponding opening in the cylinder head. Accordingly, the cover plate 128 allows flexibility in positioning of the outlet 122 on the cylinder head to which the assembly 110 is mounted.

As a result of the flexibility in positioning of the outlet 122, the exhaust manifold assembly 110 of the present invention could be configured to accommodate a range of turbocharger mounting arrangements, thereby facilitating its use in a variety of engine models and layouts. For example, due to the simplicity of its construction the conduit system 112 could easily be rerouted such that the outlet conduit 120 is positioned centrally with in the cover plate 128 to accommodate multiple turbocharger positions with a single cylinder head.

The exhaust manifold assembly 10 of the above described embodiments further includes a thermally insulating material 40 (140 in Figure 2) surrounding the conduit system 12 within the cylinder head to which it is mounted. The thermally insulating material 40 is a porous ceramic material, more particularly a ceramic, gas-filled, set slurry such as those used to support catalyst ceramics. The thermally insulating material 40 supports the conduit system 12 and allows thermal expansion of other components of the exhaust manifold assembly 10 including the conduit system 12, without providing or transferring additional thermal stresses in the assembly 10. The thermally insulating material 40 may further provide noise, vibration and harshness (NVH) dampening.

One example of a commercially available material suitable for use as the thermally insulating material 40 is Fiberfrax® produced by Unifrax Limited (UK). Fiberfrax® products contain alumina-silicate fibres which exhibit high temperature stability resulting in low thermal conductivity, low heat storage, thermal shock resistance and low weight. The fibres are dispersed in high temperature binder, to form a wet slurry which can be pumped into a cavity around the conduit system 12. Upon drying, the material 40 produces a strong insulating structure with low thermal conductivity. Alternatively this material 40 may be moulded (e.g. vacuum formed) around pipes 15 of the conduit system 12 such that it holds the pipes 15 together during assembly into a cylinder head.

The conduit system 12 and the thermally insulating material 40 form a two layer exhaust manifold wherein the conduit system 12 forms an inner skin and the thermally insulating material 40 forms an outer layer thereof. Accordingly, the exhaust manifold system 10 of the present invention may have many of the advantages associated with twin skin manifolds.

The outside surface of the pipes 15 of the conduit system 12, the thermally insulating material 40 and cover plate 28, as well as the internal cylinder head cast surface, may additionally be painted with a thermally insulating material such as those containing microscopic Boroscillate ceramic micro-spheres.

Figure 3 shows a top view of a cylinder head 42 of an internal combustion engine into which the above described exhaust manifold assembly 10 may be mounted. The cylinder head 42 includes a plurality of cylinder ports 25 positioned within a cavity 50 of the cylinder head housing 51. The cylinder ports 25 are each associated with a respective combustion cylinder of the engine (not shown). In the illustrated embodiment, the engine is a three cylinder engine having two cylinder ports per cylinder and the cylinder head 42 therefore includes six cylinder ports 25 each associated with a respective one of the six combustion cylinders.

The cylinder head 42 further includes an opening 52 providing access to the cylinder ports 25 and the cavity 50. The opening 52 is sized to allow insertion of the conduit system 12 into the cavity 50 therethrough. A seal land 53 surrounds the opening for receiving the seal member 34 of the exhaust manifold assembly 10 as described above.

Figure 4 shows, a detailed sectional view of an inlet 14 of the conduit system 12, according to any of the embodiments described herein. The inlet 14 is positioned within a cylinder port 25, as shown in Figure 3, which forms an outlet of a combustion cylinder of an internal combustion engine. The inlet 14 is in the form of a so-called ‘Dplug’ and has been press-fit into the cylinder port 25. The inlet conduit 16 has a flared or frusto-conical shape having a maximum diameter at the inlet 14. At the inlet 14, the walls of the inlet conduit 16 include a circumferential lip 26 that curves radially outwards and axially backwards away from the inlet 14 to form a resilient sealing surface for mating with the inner wall of the cylinder port 25.

Figure 5 shows an exhaust system 60 comprising an exhaust manifold assembly 210 mounted into a cylinder head 42 the as described with reference to Figure 3 above. The exhaust manifold assembly 210 of this embodiment is substantially the same as the assemblies 10, 110 described in relation to Figures 1 and 2 above. In this embodiment, the outlet aperture 222 is positioned substantially centrally on the cover plate 228. The cover plate 228 further includes four apertures 238 for receiving mechanical fasteners (not shown) for securing the exhaust manifold assembly 210 in position relative to the cylinder head 42.

The exhaust manifold assembly 210 and cylinder head 42 together form an exhaust system 60, which may be connected to further exhaust components, such as a turbocharger assembly, to form a larger exhaust assembly. The conduit system 212 of the exhaust manifold assembly 210 (of which only the outlet 222 can be seen) is positioned within the cylinder head 42 such that the cylinder head 42 effectively has a single exhaust outlet corresponding to the conduit system outlet 222. Having the conduit system 212 within the cylinder head 42, as opposed to externally therefrom, results in a more compact arrangement and further means that no external support of the manifold assembly 210 is required thereby reducing the weight and complexity of the exhaust system 60.

Figure 6 shows an exhaust manifold assembly 310 according to an embodiment of the invention having a turbocharger assembly 46 attached thereto. The turbocharger assembly 46 includes an inlet port 48 for receiving hot exhaust gases from the exhaust manifold assembly 310. The turbocharger assembly 46 may be fabricated separately from the cover plate 328 and subsequently attached thereto by any means know in the art. For example, the turbocharger assembly 46 may be welded to the cover plate 328.

The exhaust manifold assembly 10, as described in relation to any of the embodiments above, may be assembled with a cylinder head 42 to form an exhaust system 60 according to the following method.

The conduit system 12 is provided with the cover plate 28 attached thereto. The assembly 10 does not yet comprise the thermally insulating material 40. The conduit system 12 is then inserted into the cavity 50 of the cylinder head 42 via the opening 52. Each of the inlets 14 is positioned within a cylinder port 25 as shown in Figure 4.

The cover plate 28 is then attached to the seal land 53 on the outside surface of the cylinder head 42 in order to hold the conduit system 12 in position and create a gastight seal for preventing exhaust gases escaping from within the cylinder head cavity 50.

Once the conduit system 12 is secured in position, the thermally insulating material 40 is injected into the cylinder head cavity 50 so that it substantially surrounds the conduit system 12. The thermally insulating material 40 is injected through an aperture of the cover plate, such as the injection aperture 341 shown in Figure 6. The injection aperture 341 may include a valve or other closing means such that the injection aperture 341 may be sealed after injection. The thermally insulating material 40 is then allowed to set such that it provides structural reinforcement, as well as thermal insulation, to the conduit system 12.

Figures 7a-c show a conduit system 412 for an exhaust manifold assembly according to a further embodiment of the invention during various stages of manufacture.

Figure 7a shows a pipe fitting 415 having a plenum 418, a plurality of inlet conduits 416 and an outlet conduit 420. The plenum 418, inlet conduits 416 and outlet conduit 420 are formed as a unitary structure. The outlet conduit 420 extends from the plenum 418 towards the outlet side 413 thereof and four inlet conduits 416 extend from the plenum 418 toward the inlet side 411 thereof. The inlet conduits 416 therefore are each fluidly connected to the outlet conduit 420 via the plenum 418.

Figure 7b shows the pipe fitting 415 of Figure 7a with the addition of a thermally insulating material 440 applied to the pipe fitting 415. The thermally insulating material 440 is a foam material attached to an outside surface of the pipe fitting 415.

Figure 7c shows a detail view of one of the four inlet conduits 416. An inlet fitting 417 providing two inlets 414 is mounted to the inlet conduit 416 on the inlet side 411 thereof. The inlets 414 of the inlet fitting 417 are joined to one another at a junction thereof. Exhaust flow from each of the inlets 414 combines at the junction and then enters the inlet conduit 416 via a joint 424, as such both ports of a single cylinder may be combined at inlet conduit 416. The joint 424 is a slip-joint as described with reference to the embodiments above.

An inlet fitting 417 may be mounted to each one of the inlet conduits 416 such that the conduit system 412 includes eight inlets 414. As such, the conduit system 412 may be suitable for attaching to an eight cylinder engine.

The conduit system 412 of Figures 7a-c may be attached to a cover plate and mounted to a cylinder head as described above. Further thermally insulating material may or may not be injected into the cylinder head cavity around the conduit system 412 as described in relation to the embodiments above, as required.

Figures 8a and 8b show a further embodiment of the invention in which the conduit system includes more than one outlet.

Figure 8a shows a conduit system 512 comprising eight inlet conduits 516 defining eight inlets 514 for connection to a four cylinder engine in the same manner as described in relation to any of the embodiments above. The inlets 514 include a first set of inlets 514a in fluid communication with a first outlet conduit 520a and a second set of inlets 514b in fluid communication with a second outlet conduit 520b such that the conduit system includes two outlets 522a, 522b fed by different inlets 514. Accordingly, the corresponding cover plate 528 requires two outlet apertures 530 as shown in Figure 8b.

The exhaust manifold assembly 510 of Figure 8b is substantially the same as described in relation to preceding embodiments with the exception of the alternative conduit system of Figure 8a. The cover plate 528 has also been modified to include two outlet apertures 530 for receiving corresponding outlets 522a, 522b of the conduit system 512. The cover plate 528 is mounted to the cylinder head as described in any of the foregoing embodiments and a thermally insulating material surrounds the conduit system as set out above. It will be appreciated that arrangements comprising any other number of inlets and/or outlets could be used without departing from the scope of the invention.

Several modifications to the above described examples are contemplated.

For example, the conduit system of the present invention may be formed by alternative means. In alternative embodiments of any of the above, the conduit system may be a unitary structure and therefore need not include the slip joints described above. In further embodiments, the conduit system is formed from sections of pipe that are fixed to one another by other means known in the art such as flexible couplings, welding/brazing, bolted flanges etc.

The conduit system may be attached to the cover plate by any means known in the art and/or described above. For example, the conduit system may be fastened, clipped, welded, brazed or adhered to the cover plate.

The embodiments described above include six or eight inlets, however it will be appreciated that other numbers of inlets may be present depending of the number of cylinders of the engine to which the manifold assembly is to be mounted. For example, the conduit system may include four inlets for connection to each of the cylinder ports of a two cylinder engine or may include ten inlets for connection to each of the cylinder ports of a five cylinder engine. In other embodiments, the conduit system may include two, twelve, fourteen or sixteen inlets, depending on the engine to which it is to be mounted.

Although the described embodiments include D-plug fittings at inlets, it will be appreciated that other fittings may be used without departing from the scope of the invention, for example alternative press-fit geometry or fittings with gaskets. In embodiments, the inlets or inlet conduits have any form that will allow press fitting of the conduit system inlets into the cylinder ports.

The cover plate need not be generally rectangular and may have any shape that substantially corresponds to an opening in the cylinder head through which the conduit system 12 is inserted. More generally, the cover plate is a sheet of material, for example metal plate or a sheet of material suitable for use in an engine exhaust system, sealed around the outlet of the conduit system and an opening in the cylinder head. The cover plate may be formed by alternative means to those described above, such as by hydroforming or post machining of metallic plate material.

In the embodiments, the cover plate is secured to the cylinder head via bolts, it will be appreciated that other fastening means could be used without departing from the scope of the invention. For example, the cover plate could be secured to the cylinder head via alternative mechanical fasteners such as screws, rivets, clips or clamps. Any number of fastening elements may be used depending on the geometry of the cover plate and mating structures. Alternatively, the cover plate may be welded or brazed onto the cylinder head or may be secured via adhesive or other bonding methods known in the art.

The seal between the cover plate and cylinder head may be formed by alternate means. For example, a gasket or sealing material may be mounted to the cylinder head and a corresponding seal land feature incorporated onto the cover plate. In embodiments where the cover plate is welded, brazed or otherwise adhered to the cylinder head, there may be no need for an additional sealing feature.

In the embodiments, the thermally insulating material comprises a porous ceramic material; however it will be appreciated that other insulating materials could be used. For example, the thermally insulating material could, additionally or alternatively, comprise a thermally insulating paint, moulded thick foam, silica woven tape and/or a closed cell intumescent foam rubber. In alternative embodiments, the thermally insulating material could comprise a multi-layer insulation system such as the ISOLITE Blanket ® system produced by ISOLITE, Germany.

As such it will be appreciated that modifications of the above described method may include attaching an insulating material to the conduit system before inserting the system into the cylinder head. Attaching the insulating material may involve applying a foam material or insulating tape and/or painting on an insulating paint.

Many modifications may be made to the above examples without departing from the scope of the present invention as defined in the accompanying claims.

Claims

1. An exhaust manifold assembly for an internal combustion engine, the exhaust manifold assembly comprising:

a conduit system including a plurality of inlets each for connection to a respective cylinder port within a cylinder head of the engine and an outlet fluidly connected to the inlets; and a cover plate including an aperture for receiving the outlet of the conduit system, the cover plate being mountable to the cylinder head.

2. The exhaust manifold assembly of claim 1, wherein the conduit system is formed from a plurality of sections of pipe.

3. The exhaust manifold assembly of claim 2, wherein the sections of pipe are connected to each other via slip joints.

4. The exhaust manifold assembly of any preceding claim, wherein each of the inlets includes a lip for sealing against an internal surface of the respective cylinder port.

5. The exhaust manifold assembly of any preceding claim, wherein the cover plate includes a further aperture for receiving a thermally insulating material.

6. The exhaust manifold assembly of any preceding claim, wherein the conduit system comprises a plurality of outlets each connected to respective inlets and the cover plate comprises a plurality of apertures each for receiving a respective outlet of the conduit system.

7. The exhaust manifold assembly of any preceding claim, further comprising a layer of thermally insulating material applied to an external surface of the conduit system.

8. An exhaust system for an internal combustion engine, the exhaust system comprising:

an engine cylinder head including a plurality of cylinder ports;

an exhaust manifold assembly as set forth in any preceding claim, wherein the cover plate is mounted to the cylinder head and each of the inlets is connected to a respective cylinder port.

9. The exhaust system of claim 8, further comprising a thermally insulating material surrounding the conduit system within the cylinder head.

10. The exhaust system of claim 9, wherein the insulating material is a porous ceramic material.

11. The exhaust system of claim 9 or 10, wherein the insulating material fills a cavity between the conduit system and a surrounding region of the cylinder head.

12. The exhaust system of any of claims 8 to 11, further comprising a layer insulating of material applied to an external surface of the conduit system.

13. A vehicle comprising the exhaust system of any of claims 8 to 12.

14. A method of assembling the exhaust system as set forth in any of claims 8 to 11 comprising:

mounting the cover plate of the exhaust manifold system to the cylinder head such that the inlets of the conduit system are positioned within a respective cylinder port.

15. The method of claim 14, further comprising injecting an insulating material through an aperture of the cover plate such that the insulating material fills a cavity between the conduit system and the cylinder head.

16. A method of insulating an exhaust manifold assembly comprising:

injecting an insulating material into a cavity between the exhaust manifold assembly and a surrounding internal structure of an engine cylinder head.