GB2535537A

GB2535537A - Exhaust manifold assembly

Info

Publication number: GB2535537A
Application number: GB1502978.8A
Authority: GB
Inventors: Turner James
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2015-02-23
Filing date: 2015-02-23
Publication date: 2016-08-24
Anticipated expiration: 2035-02-23
Also published as: GB2535537B; GB201502978D0

Abstract

An exhaust manifold assembly 2 for a multi-cylinder engine 1. The manifold assembly comprises a first portion which separates a first exhaust gas E1, E4, CE1 from one or more engine cylinders C1, C4 from a second exhaust gas E2, E3, CE2 from one or more engine cylinders C2, C3, and a second portion which selectively directs each of exhaust gases to either a first turbocharger T1 only, or to both first and second turbochargers T1, T2. Alternatively the second portion may direct at least a portion of each of the exhaust gases to the first turbocharger, and a third portion may optionally direct a portion of each of the exhaust gases to second and third turbochargers. Flow of exhaust gas to the second, and optionally third, turbochargers may be controlled by one or more valves V1, V2. The valve(s) may distribute an equal or unequal exhaust gas volume from the fist and second exhaust gases.

Description

EXHAUST MANIFOLD ASSEMBLY

TECHNICAL FIELD

The present disclosure relates to an exhaust manifold assembly particularly, but not exclusively, for an internal combustion engine having a pulse-divided, twin parallel-sequential twin scroll turbocharger arrangement. An embodiment of the invention could be applied to systems with two or more turbos.

Aspects of the invention relate to an exhaust manifold assembly, to an internal combustion engine, to a controller and to a vehicle.

BACKGROUND

It is known to provide a cylinder head exhaust manifold having "exhaust pulse division" to avoid unwanted gas exchange between cylinders during exhaust valve overlap events. As an example, in a conventional four stroke four cylinder engine having a 1, 3, 4, 2 firing order it is typical for the exhaust period to be around 240° of the crankshaft rotation, which can lead to unwanted gas mixing between cylinders. In this example for any given first cylinder reaching the end of its exhaust stroke, the cylinder which is next in the firing order discharges a high pressure pulse of exhaust gas into the manifold which can force unwanted hot burnt gas back into the first cylinder through the open exhaust port. For example cylinder 3 could push hot exhaust gas back into cylinder 1 in the above firing order example. This raises the residual exhaust gas content in the first cylinder and has an adverse effect on its combustion performance.

One solution to this is known as pulse division whereby the exhaust gases from cylinders 1 and 4 are kept separate from the exhaust gas from cylinders 2 and 3, assuming the 1, 3, 4, 2 firing order, between the exhaust ports in the cylinder head and the inlet of a twin scroll turbo or alternatively up to a point in the conventional exhaust for a naturally aspirated engine.

Twin scroll turbochargers can be used which have separate inlet ports designed to work in pulse divided manifold arrangements which carry the separated gases right into the turbine wheel, thereby minimising the possibility of inappropriate exhaust gas exchange between cylinders. In our example firing order as the gases from ports 1 and 3 are kept separate there is no chance of pressure pulses being able to transfer from cylinder 3 to cylinder 1.

Pulse division in this example gives 360° between the start of the exhaust events in the manifold, thus removing the potential for undesirable gas exchange between cylinders. Pulse division can be applied to engines having two or more cylinders.

An example of pulse division is discussed in US7,150,273 wherein the manifolds are clearly shown to have the necessary gas flow separation in the exhaust manifold arrangement for a single twin scroll turbo.

It is also known to provide parallel sequential turbocharger systems to modern engines in which a first turbocharger, which is of smaller flow capacity than if a single turbocharger were used for the full power output of the engine, connects to an exhaust manifold and operates continually. All exhaust gases flow through the first turbocharger for low engine loads as typically the exhaust gas flows are low. A second turbocharger, which can be isolated by a control valve from the exhaust gas stream shared by the first supercharger, may be used additionally to the first turbocharger in high engine load conditions as typically the exhaust gas flow can be higher at this operating point.

This arrangement seeks to provide efficient turbocharger sizing especially on downsized engines in an effort to reduce turbo spin up times and thus reduce lag effects on engine response. An example of parallel sequential turbochargers prior art is JPH07-26971A.

While parallel sequential turbochargers and pulse divided manifold technology are known independently, to date these technologies have not been used together because the complexity of the manifold systems limits their use within the available package space in the vehicle engine compartment.

The combination of parallel-sequential turbocharger and twin scroll twin turbo systems require advances in the field of manifold and valve integration because both turbochargers have to communicate with the same exhaust manifold and all of the cylinders, whilst having the capability of controlled gas flow separation when required. Embodiments of the present invention provide a novel and inventive exhaust manifold assembly that permits gas flow control within the vehicle packaging constraints.

SUMMARY OF THE INVENTION

Aspects of the invention relate to an exhaust manifold assembly, an internal combustion engine, a controller and a vehicle as claimed in the appended claims.

According to an aspect of the present invention there is provided an exhaust manifold assembly for an engine having a plurality of cylinders. The exhaust manifold assembly may comprise a first portion configured to separate a first exhaust gas exhausted by a first one or more cylinders of the engine from a second exhaust gas exhausted by a second one or more cylinders of the engine. The assembly may comprise a second portion configured selectively to direct each of the first exhaust gas and the second exhaust gas to either a first turbocharger only or to both a first turbocharger and a second turbocharger.

In an embodiment flow of exhaust gas to the second turbocharger is controlled by one or more valves located in the second portion of the exhaust manifold assembly.

In an embodiment the or each valve in the second portion of the exhaust manifold assembly comprises one or more of a butterfly valve, a globe valve, a gate valve, a ball valve or a controllable reed valve.

In an embodiment the valves in the second portion of the exhaust manifold assembly share a common actuator or have independent actuation means.

In an embodiment the or each valve in the second portion of the exhaust manifold assembly is configured to distribute exhaust gas volume from both the first exhaust gas and the second exhaust gas.

In an embodiment the or each valve in the second portion of the exhaust manifold assembly is configured to operate in parallel to distribute an equal exhaust gas volume from both the first exhaust gas and the second exhaust gas.

In an embodiment the or each valve in the second portion of the exhaust manifold assembly is configured to distribute an unequal exhaust gas volume from both the first exhaust gas and the second exhaust gas.

In an embodiment the second portion allows the first or second exhaust gases to flow to a first turbocharger alone, a first turbocharger and a second turbocharger, or a first turbocharger, a second turbocharger and a third turbocharger.

In an embodiment the valves in the second portion of the exhaust manifold assembly are configured to control exhaust gas flow to one or more of a first turbocharger, a second turbocharger and a third turbocharger if fitted.

According to another aspect of the invention there is provided an exhaust manifold assembly comprising a first portion configured to separate a first exhaust gas exhausted by a first one or more cylinders of an engine from a second exhaust gas exhausted by a second one or more cylinders of the engine, a second portion configured to maintain separation of the first and second exhaust gases and to direct at least a portion of said gases to a first turbocharger; and a third portion configured to maintain separation of the first and second exhaust gases and optionally to direct a portion of exhaust gas flow to a second turbocharger and a third turbocharger.

In an embodiment, flow of exhaust gas to the third turbocharger is controlled by one or more valves located in the second and/or third portions of the exhaust manifold assembly.

In an embodiment, flow of exhaust gas to the second turbocharger is controlled by one or more valves located in the second and/or third portions of the exhaust manifold assembly.

In an embodiment, flow of exhaust gas to the second turbocharger and/or the third turbocharger is controlled by one or more valves located in at least one of the turbochargers.

In an embodiment, flow of exhaust gas to the second turbocharger and/or the third turbocharger is determined by one or more valves located downstream of one or more turbochargers.

In an embodiment the exhaust manifold assembly is integrally formed with a cylinder head or an internal combustion engine.

According to another aspect of the invention there is provided a controller configured to control one or more valves in an exhaust manifold assembly according to any of the preceding aspects or embodiments.

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 shows a schematic representation of an exhaust gas flow for a four cylinder engine with a 1, 3, 4, 2 firing order, combining manifold pulse division and a parallel-sequential twin turbo arrangement turbos, according to an embodiment.

Figure 2 is a schematic representation of a side view of an exhaust manifold assembly with turbos according to the embodiment of Figure 1.

Figure 3 shows an end sectional view along the line S1 in Figure 2, in the direction of arrow A. Figure 4 shows an end sectional view along the line S2 in Figure 2, in the direction of arrow A. Figure 5 is a schematic representation of a side view of an exhaust manifold assembly according to another embodiment.

Figure 6 shows an end sectional view along the line S3 in Figure 5, in the direction of arrow B. Figure 7 is a schematic representation of an exhaust manifold assembly according to another embodiment.

DETAILED DESCRIPTION

Embodiments of an exhaust manifold assembly for an internal combustion engine with pulse division, suitable for use with a parallel sequential turbo arrangement, are described herein with reference to the accompanying Figures, in which like reference numerals indicate like parts.

Figure 1 shows an example schematic representation of an embodiment showing exhaust gas flows for a four cylinder engine combining manifold pulse division (MPD) and a parallel-sequential twin turbo (PSTT) arrangement including control valves (V1,V2). The example four cylinder engine (1) has cylinders (C1 to C4) each with a respective inlet valve and exhaust valve which may be controlled by conventional means. The inlet valves (11 to 14) are coupled to a suitable induction system and manifold (not shown) to provide a fuel air mixture to the engine (1) as required. The exhaust valves (01 to 04) are configured to allow hot exhaust gases to exit the engine after combustion in the conventional manner. After the exhaust gases leave the combustion chamber they exit the cylinder head and enter the exhaust manifold (2).

The exhaust manifold (2) initially comprises four fluidly separate exhaust pipes (El to E4) which then merge into 2 fluidly separate pipes (CE1,CE2) in a way that provides known pulse separation benefits as disclosed in, for example, prior art US7,150,273. In the illustrated example, pipes El and E4 are combined into a single pipe CE1, while pipes E2 and E3 are combined into a single pipe CE2.

Pipe (CE1), which is configured to transport gases from the exhausts of cylinders (C1) and (C4), then branches into two pipes (CE1A, CE1B), allowing the exhaust gas to flow to turbines of either a first turbo (T1), through pipe (CE1A), or a second turbo (T2), via pipe (CE1 B), a valve (V2) and a pipe (VP2). Similarly pipe (CE2), which is configured to transport gases from the exhausts of cylinders (C2) and (C3), branches into two pipes (CE2A, CE2B), allowing the exhaust gas to flow to either the first turbo (T1), through pipe (CE2A), or to the second turbo (T2) via a pipe (CE2B), a valve (V1) and a pipe (VP1).

In this example, for light engine loads valves (V1,V2) may be closed which forces all of the exhaust gases from the pipes (CD) and (CE2) to flow through Turbo (T1). On the other hand, when the engine is operated in the higher load and speed regions, valves (VI,V2) may be open so that exhaust gas flows through both turbos (T1 and T2). Gases flowing through turbos (T1,T2) exit through respective turbine exits (TE1,TE2) thereof and continue through the conventional exhaust system in the normal way. The twin-scroll turbos depicted in Figure 1 are merely examples of possible turbo configurations and other configurations are also beneficial.

While the inlets and outlets of the turbos (T1, T2) are similar in configuration to known PSTT arrangements, such as that shown in JPH07-26971A, it is the difficulty in combining PSTT and MPD which creates the necessity for the invention due to the packaging constraints dictated by available space in the vehicle engine compartment.

Figures 2 -4 illustrate schematically an example embodiment of the present invention which provides a unique manifold and valve arrangement to satisfy under-bonnet design requirements. Figure 2 is a side cross sectional view of the assembly (10) whilst Figures 3 and 4 are cross sectional views through the assembly (10) along the lines S1 and S2, respectively, in the direction of arrow A. As shown in Figure 2, the exhaust manifold assembly (10) is connected to the turbos (T1,T2). In this embodiment, exhaust gases from the exhaust pipes El and E4 and exhaust gases from the exhaust pipes E2 and E3 enter the exhaust manifold assembly (10) from the left hand side and are maintained fluidly separate by a first dividing wall (W1) which, as shown in Figure 3, defines, at least in part, the pipes (CE1,CE2). Pipe (CE1) is configured to receive and conduct exhaust gases from cylinders (C1, C4) and pipe (CE2) is configured to receive and conduct exhaust gases from cylinders (C2, C3). It will be understood that the gases from cylinders (C1, C4) cannot mix with the gases from cylinders (C2, C3) due to the presence of the first dividing wall (W1).

The exhaust gases flow from left to right in Figure 2 through the pipes (CE1, CE2) until the they reach the end (P1) of a second dividing wall (W2) which is formed within the assembly (10) and oriented substantially orthogonally to the first dividing wall (W1). The second dividing wall (W1) causes the exhaust gases flowing through the pipes (CE1, CE2) to be divided, respectively, into the pipes (CE1A, CE1B) and (CE2A, CE2B).

As shown in Figure 4, the first and second dividing walls (W1, W2) have the effect of defining, at least in part, the four fluidly separate pipes (CE1A,CE1B, CE2A,CE2B) within the manifold assembly (10) which are configured to permit the exhaust gases from pipes (CE1,CE2) to flow through pipes (CE1A, CE2A) to the turbo (T1) only or optionally additionally to be directed through pipes (CE1 B, CE2B) via valves (V1, V2) to the turbo (T2).

It will be understood that, in use, pulse division is still active in the manifold assembly (10) at section S2 as the gases in pipes (CE1A, CE1B) cannot mix with gases in pipes(CE2A, CE2B) due to the presence of the first dividing wall (W1).

Valves (V1, V2) control the gas flows into the twin scroll turbos (T1, T2) and may be operated in parallel according to known PSTT control methods as described in JPH07-26971A. Valves (V1, V2) could comprise butterfly valves or any other high temperature compliant valve capable of controlling the airflow. Other valve type examples could include, without limitation, gate valves, globe valves or ball valves.

Exhaust gases exit the turbos (T1, T2) via the turbine exits (TE1, TE2) to join a standard exhaust after treatment system (not shown) in a conventional manner.

Actuation of the valves (V1, V2) could be pneumatic, motor driven, hydraulic, electro hydraulic or mechanical and multiple valves could share actuators or each valve could have separate actuation mechanisms. As an example twin butterfly valves (V1,V2) as shown in Figure 4 could share a common pivot spindle (15) or independent drive mechanisms could be used for each valve (V1,V2). Independent drive for valves (V1, V2) could be beneficial if exhaust gas flow balancing between each scroll of the turbos (T1, T2) were required, perhaps due to differences in back pressure from the scrolls of the turbos (T1, T2).

The manifold assembly (10) could be cast from solid material or could be fabricated from sheet or tube materials using standard techniques. The pipes (CE1, CE2, CE1A, CE2A, CE1 B, CE2B) could all be cast or fabricated into one manifold assembly 00), including the valves (V1,V2) according to the embodiment or alternately the pipes (CE1, CE2, CE1A, CE2A, CE1 B, CE2B) could be formed in separate pipes and then connected to provide the same functionality as described in the invention.

The exhaust manifold assembly 00) could be fabricated from more than one part and multiple parts could be sleeved, bolted, welded, flanged, shrink-fitted or glued and assembled to make one exhaust manifold assembly.

In another embodiment the exhaust manifold assembly (10) could be formed as part of the cylinder head of the engine (1). The exhaust manifold assembly (10) could be fully integrated with the cylinder head by casting the cylinder head and exhaust manifold assembly (10) in a single step.

Turbo bypass valves (not shown) could be connected in a conventional manner to improve spooling-up time, reduce lag and prevent over-pressure situations according to known techniques.

A detailed four cylinder embodiment has been described but this concept could be applied to other cylinder arrangements also. A six cylinder embodiment as an example would be similar in its approach such that for a firing order of, say, 1-5-3-6-2-4, the first three cylinder exhausts (C1, C2, C3 not shown) in an in line arrangement could be flowed into the pipe (CE1) and the last three cylinder exhausts (C4, C5, C6 not shown) could be flowed into the pipe (CE2). Thereafter the system would be substantially identical to the four cylinder embodiment.

The PSTT detailed embodiment described considers two parallel turbochargers (T1,T2). However other combinations are possible, for example a triple turbocharger arrangement as shown in Figure 5.

The exhaust manifold assembly disclosed herein could be applied to all conventional internal combustion engines, including rotary engines, particularly those engines configured to combine exhaust pulse division and multiple parallel-sequential turbochargers.

Figures 5 and 6 represent a schematic illustration of another embodiment of the invention using three twin scroll turbos. Figure 5 represents a side view of the exhaust manifold assembly (25) connected to turbos (T1, T2, T3). The manifold assembly (25) is connected to the same type of four cylinder engine as that of Figure 2 having the same 1, 3, 4, 2 firing order.

In this embodiment, exhaust gases from the exhaust pipes El and E4 and exhaust gases from the exhaust pipes E2 and E3 enter the exhaust manifold assembly (25) from the left hand side and are maintained fluidly separate by a first dividing wall (W1) which, as shown in Figure 6, defines, at least in part, the pipes (CE1,CE2). Pipe (CE1) is configured to receive and conduct exhaust gases from cylinders (C1, C4) and pipe (CE2) is configured to receive and conduct exhaust gases from cylinders (C2, C3). It will be understood that the gases from cylinders (C1, C4) cannot mix with the gases from cylinders (C2, C3) due to the presence of the first dividing wall (W1), i.e. they are pulse divided.

The exhaust gases flow from left to right in Figure 5 through the pipes (CE1, CE2) until the they reach the ends (P2, P3) of respective second and third dividing walls (W2, W3) which are formed within the assembly (25). The second and third dividing walls (W2, W3) cause the exhaust gases flowing through the pipes (CE1, CE2) to be divided, respectively, into pipes (31, 33, 35) and pipes (32, 34, 36).

As shown in Figure 6, the manifold assembly (25) includes four butterfly valves (V1, V2, V3, V4) with associated pivot spindles (41, 42), and second and third dividing walls (W2, W3) oriented substantially orthogonally to the first dividing wall (W1) which, together with the wall (W1) at least partially define three possible routes for each flow of exhaust gases to flow into the turbos (T1,T2,T3). It will be thus understood that the internal pipe arrangement of the manifold assembly (25) changes from two pipes (CE1, CE2) into six separate pipes (31 -36) in a way that allows the gases from either pipes (CE1, CE2) to flow through pipes (31, 32) to the turbo (T1) only, or optionally additionally directed through pipes (33, 34) via valves (V1, V2) to the turbo (T2) and/or optionally additionally directed through pipes (35, 36) via valves (V3, V4) to the turbo (T3).

Exhaust gases exit the turbos (T1, T2, T3) via turbine exits (TE1, TE2, TE3) to join a standard exhaust after treatment system (not shown) in a conventional manner.

In the embodiment of Figure 5, it is possible to control the exhaust gas flow through only the first turbo (T1), during light engine loads by closing valves (V1, V2, V3, V4). Increasing engine load/speeds could necessitate valves (V1, V2) to be partially or fully opened thus allowing a portion of the exhaust gases to flow additionally through turbo (T2) in parallel to turbo (T1). At higher operating load/speeds it would be a further control option to partially or fully open valves (V3, V4) thus allowing a portion of the exhaust gas to flow through turbo (T3) in parallel to turbos (T1,T2). In this case all three turbos (T1, T2, T3) could be operational as and when required. Operation of the valves (V1, V2) and the valves (V3, V4) may be in the reverse order so as to bring turbo (T3) into operation before (T2) and the operation of turbo (T2) and turbo (T3) could be operated in parallel in certain high demand operating conditions. For example, under high throttle demand the turbos (T2, T3) could be commanded to open by the same amount (e.g. 80%) at the same time.

Figure 7 represents a side view of another example embodiment of the invention showing a distributed exhaust manifold assembly (35) connected to turbos (T1, T2, T3). In this example embodiment the exhaust gas flows from pipes (CE1, CE2) are pulse divided according to the previous embodiment and represents the exhaust gas output for the same four cylinder engine with the same 1, 3, 4, 2 firing order as in previous examples. Figure 7 shows an alternative distributed exhaust manifold assembly wherein the exhaust manifold comprises extended pipe branches which may suit under-bonnet package requirements. In this embodiment the pulse-divided gases entering the left side of Figure 7 through pipes (CE1,CE2) are always directed to twin scroll turbo (T1) and optionally to twin scroll turbos (T2, T3) by operation of the valves (VA1, VA2, VA3, VA4) which are housed within the distributed exhaust manifold assembly (35). Exhaust gases exit the turbos through (TE1, TE2, TE3) to join a standard exhaust after treatment system (not shown) in a conventional manner.

It may be that alternative valve positions are desirable within the distributed exhaust manifold assembly (35) to provide advantages in packaging, electrical connectivity or simply to position the valve actuator in an environment suitable for actuator operation.

Alternative example valve positions are indicated in the embodiment of Figure 7. For example, valves (VA5, VA6) located within the twin scroll turbo inlet could be used instead of valves (VA1, VA2), or a single alternative valve (VA9) could be used in the outlet side of twin scroll turbo (T2) where pulse division is no longer required and all cylinder gases are allowed to mix. Similarly alternative valve positions are indicated for twin scroll turbo (T3) where valves (VA7, VA8) located within the twin scroll turbo inlet could be used instead of valves (VA3, VA4), or a single alternative valve (VA10) could be used in the outlet side of twin scroll turbo (T3).

In another example embodiment the valves (VA9, VA10) could be located further downstream in the exhaust path after the twin scroll turbos (T2, T3), which may be dependent on under-bonnet packaging conditions. As the gases (CE1, CE2) are now mixed downstream of the twin scroll turbos, only one valve per turbo is required on the outlet side of the turbo, which may advantageously require less packaging space, reduced electrical connections and power consumption to operate the valves.

It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.

Claims

CLAIMS: 1. An exhaust manifold assembly (10) for an engine (1) comprising a plurality of cylinders, the exhaust manifold assembly (10) comprising: a first portion configured to separate a first exhaust gas exhausted by a first one or more cylinders of the engine from a second exhaust gas exhausted by a second one or more cylinders of the engine; and a second portion configured selectively to direct each of the first exhaust gas and the second exhaust gas to either a first turbocharger (T1) only or to both a first turbocharger (T1) and a second turbocharger (T2).
2. An exhaust manifold assembly (10) according to claim 1 wherein flow of exhaust gas to the second turbocharger (T2) is controlled by one or more valves located in the second portion of the exhaust manifold assembly.
3. An exhaust manifold assembly (10) according to claim 2 wherein the or each valve in the second portion of the exhaust manifold assembly comprises one or more of a butterfly valve, a globe valve, a gate valve, a ball valve or a controllable reed valve.
4. An exhaust manifold assembly (10) according to claim 2 or claim 3 wherein the valves in the second portion of the exhaust manifold assembly (10) share a common actuator or have independent actuation means.
5. An exhaust manifold assembly (10) as claimed in any one of claims 1 to 4 wherein the or each valve in the second portion of the exhaust manifold assembly is configured to distribute exhaust gas volume from both the first exhaust gas and the second exhaust gas.
6. An exhaust manifold assembly (10) as claimed in any one of claims 1 to 4 wherein the or each valve in the second portion of the exhaust manifold assembly is configured to operate in parallel to distribute an equal exhaust gas volume from both the first exhaust gas and the second exhaust gas.
7. An exhaust manifold assembly (10) as claimed in any one of claims 1 to 4 wherein the or each valve in the second portion of the exhaust manifold assembly is configured to distribute an unequal exhaust gas volume from both the first exhaust gas and the second exhaust gas.
8. An exhaust manifold assembly (10) according to any preceding claim wherein the second portion allows the first or second exhaust gases to flow to: a first turbocharger (T1) alone; a first turbocharger (T1) and a second turbocharger (T2); or a first turbocharger (T1), a second turbocharger (T2) and a third turbocharger (T3).
9. An exhaust manifold assembly (10) according to any preceding claim wherein the or each valve in the second portion of the exhaust manifold assembly (10) is configured to control exhaust gas flow to one or more of a first turbocharger (T1), a second turbocharger (T2) and a third turbocharger (T3) if fitted.
10. An exhaust manifold assembly (10) comprising: a first portion configured to separate a first exhaust gas exhausted by a first one or more cylinders of an engine from a second exhaust gas exhausted by a second one or more cylinders of the engine; a second portion configured to maintain separation of the first and second exhaust gases and to direct at least a portion of said gases to a first turbocharger (T1); and a third portion configured to maintain separation of the first and second exhaust gases and optionally to direct a portion of exhaust gas flow to a second turbocharger (T2) and a third turbocharger (T3).
11. An exhaust manifold assembly (10) as claimed in claim 10 wherein flow of exhaust gas to the third turbocharger (T3) is controlled by one or more valves located in the second and/or third portions of the exhaust manifold assembly.
12. An exhaust manifold assembly (10) as claimed in claim 10 or claim 11 wherein flow of exhaust gas to the second turbocharger (T2) is controlled by one or more valves located in the second and/or third portions of the exhaust manifold assembly (10).
13. An exhaust manifold assembly (10) as claimed in any one of claims 10 to 12 wherein flow of exhaust gas to the second turbocharger (T2) and/or the third turbocharger (T3) is controlled by one or more valves located in at least one of the turbochargers.
14. An exhaust manifold assembly (10) as claimed in any one of claims 10 to 13 wherein flow of exhaust gas to the second turbocharger (T2) and or the third turbocharger (T3) is determined by one or more valves located downstream of one or more turbochargers.
15. An exhaust manifold assembly (10) as claimed in any previous claim wherein the exhaust manifold assembly (10) is integrally formed with a cylinder head.
16. A controller configured to control one or more valves in an exhaust manifold assembly as claimed in any preceding claim.
17. An internal combustion engine (1) comprising a controller as claimed in claim 16 or a an exhaust manifold assembly (10) as claimed in any of claims 1 to 15.
18. A vehicle comprising an internal combustion engine (1) as claimed in claim 17.
19. An exhaust manifold assembly (10), a controller or a vehicle substantially as described herein and/or as shown in the accompanying drawings.