Patent Description:
Turbocharging has been used in relation to internal combustion engines for many years. In relatively recent years, twin volute (also known as twin scroll) turbochargers have been introduced in an effort to improve boost response, increase power throughout the power band, and at the same time improve fuel efficiency. These twin volute turbochargers have the turbine located in a housing whereby it receives exhaust flow from separate banks of cylinders in the engine in turn through the separate volutes. This alternating sequence of exhaust flow helps reduce lag and bring the improvements discussed above.

To further improve the performance of twin volute turbochargers it is also known to provide the turbocharger housing with a diverter valve which can selectively divert exhaust flow to one or both volutes depending upon engine state and performance requirements at any given time. In order to avoid a turbocharger overboost or overspeed event, the turbocharger housing is also provided with a wastegate, or exhaust bypass, which can be opened to allow exhaust flow to bypass the turbocharger when necessary. An example of such an arrangement in a turbocharger can be seen in <CIT>.

Providing both a diverter valve and wastegate as separate components increases the complexity and associated cost of the turbocharger. In addition, in EP'<NUM> and other prior art disclosures the twin volutes of the turbocharger receive the exhaust flow from a single inlet passage or turbine throat, so the exhaust flows from the separate banks of cylinders can interfere with one another in the throat, thus reducing the performance benefits of the twin volute turbocharger.

<CIT> discloses an exhaust gas turbocharger having a bypass operatively connected to an exhaust gas inlet to port exhaust gas around a twin scroll turbine housing to bypass a turbine wheel. The turbocharger also has a valve operatively positioned to control exhaust gas flow to each side of the twin scroll turbine housing and the bypass.

<CIT> discloses a turbocharger for an engine. The turbocharger has at least two inlet passages connected to respective manifold passages. A bypass channel is provided which extends between the two inlet passages. A rotary valve is also provided in one of the inlet passages, the valve switching between different exhaust gas flow modes which selectively direct exhaust flow through one or more of the inlet passages and bypass passage.

It is an aim of the present invention to obviate or mitigate one or more of these disadvantages.

According to a first aspect of the present invention, there is provided an exhaust manifold for an internal combustion engine as recited in claim <NUM>.

According to a second aspect of the invention, there is provided a twin volute turbocharger for an internal combustion engine as recited in claim <NUM>.

Preferred embodiments of the present invention will now be described, by way of example only, with reference to the following drawings:.

A first embodiment of an exhaust manifold for an internal combustion engine exhaust system is shown in schematic section views in <FIG>. Those figures illustrate various states of the manifold. <FIG> illustrates how in use the manifold would be connected between banks of cylinders of the engine and a twin volute, or twin scroll, turbocharger. However, those elements have been omitted from the other figures for clarity.

Referring to <FIG>, the manifold is generally designated <NUM> and comprises a first exhaust gas inlet <NUM>, which is connectable in a known manner to a first bank of cylinders <NUM> of an internal combustion engine <NUM>. The manifold <NUM> also comprises a second exhaust gas inlet <NUM>, which is connectable in the same way to a second bank of cylinders <NUM> of the engine <NUM>. Thus, the first and second exhaust gas inlets <NUM>,<NUM> receive the exhaust gas issuing from the first and second banks of cylinders, respectively. The engine may be a <NUM> or <NUM> cylinder engine, wherein each bank comprises <NUM> or <NUM> cylinders.

The manifold <NUM> also comprises separate first and second exhaust gas outlets <NUM>,<NUM> which are connectable in use to respective first and second volutes <NUM>,<NUM> of a twin volute turbocharger <NUM>. Twin volute turbochargers separate exhaust events so as to prevent exhaust pulse interference between cylinders.

Located between, and in fluid communication with, the exhaust inlets <NUM>,<NUM> and outlets <NUM>,<NUM> is an exhaust chamber <NUM> which has at least one wastegate outlet connectable to a passage which bypasses the turbocharger <NUM>. In the illustrated embodiment the chamber <NUM> has a pair of wastegate outlets <NUM>,<NUM>.

Also located in the chamber <NUM> is a diverter valve <NUM> which is adapted to control the flow of exhaust gas from the first and second exhaust gas inlets <NUM>,<NUM> to at least one of the first and second exhaust gas outlets <NUM>,<NUM> and the wastegate outlets <NUM>,<NUM>. The diverter valve <NUM> comprises a rotatable valve body having a base <NUM> shaped as a segment of a circle, where the base <NUM> may rotate under the power of a known actuator mechanism (e.g. solenoid) about an axis of rotation R. An upwardly projecting diverter plate <NUM> is mounted upon the rotatable base <NUM>, and it is this diverter plate which diverts the exhaust gas flow. The base <NUM> is also provided with at least one wastegate aperture whose shape preferably corresponds with that of the at least one wastegate outlet in the chamber <NUM>. As there are two wastegate outlets <NUM>,<NUM> in this embodiment there are a corresponding pair of wastegate apertures <NUM>,<NUM> in the base <NUM>. The wastegate apertures <NUM>,<NUM> preferably lie either side of the diverter plate <NUM>.

The three states of the manifold <NUM> shown in <FIG>, which are dictated by positions of the diverter valve <NUM>, will be described in detail below.

An alternative embodiment of exhaust manifold is shown in <FIG> and generally designated <NUM>. As with the first embodiment, this manifold <NUM> comprises a first exhaust gas inlet <NUM>, which is connectable in a known manner to a first bank of cylinders of an internal combustion engine. The manifold <NUM> also comprises a second exhaust gas inlet <NUM>, which is connectable in the same way to a second bank of cylinders of the engine.

The manifold <NUM> also comprises separate first and second exhaust gas outlets <NUM>,<NUM> which are connectable in use to respective first and second volutes of a twin volute turbocharger. Located between, and in fluid communication with, the exhaust inlets <NUM>,<NUM> and outlets <NUM>,<NUM> is an exhaust chamber <NUM> which has at least one wastegate outlet connectable to a passage which bypasses the turbocharger. In the illustrated embodiment the chamber <NUM> has a pair of wastegate outlets <NUM>,<NUM> which, when open, are in fluid communication with a generally annular wastegate chamber <NUM> which is arranged in the form of a jacket about the exterior of the exhaust chamber <NUM>. It is from the wastegate chamber <NUM> that the exhaust would flow to the bypass passage when the wastegate outlets <NUM>,<NUM> are open.

Also located in the chamber <NUM> is a diverter valve <NUM> which is adapted to control the flow of exhaust gas from the first and second exhaust gas inlets <NUM>,<NUM> to at least one of the first and second exhaust gas outlets <NUM>,<NUM> and the wastegate outlets <NUM>,<NUM>. The diverter valve <NUM> comprises a rotatable valve body <NUM> having a generally cylindrical shape, where the body <NUM> may rotate under the power of a known actuator mechanism (e.g. solenoid) about an axis of rotation R'. The body <NUM> and the axis of rotation R' lie generally perpendicular to the direction of flow of exhaust gas through the manifold. The interior of the valve body <NUM> is divided into two portions by a diverter plate <NUM> which runs the length of the valve body, and it is this diverter plate which diverts the exhaust gas flow. The cylindrical wall of the body <NUM> has a pair of exhaust inlet apertures <NUM>,<NUM> and a pair of exhaust outlet apertures <NUM>,<NUM> which permit exhaust gas to flow through the valve body <NUM> depending upon its rotational position. One exhaust inlet aperture and one exhaust outlet aperture are provided on either side of the diverter plate <NUM>. The body <NUM> also has at least one wastegate aperture whose shape and size preferably corresponds with that of the at least one wastegate outlet in the chamber <NUM>. As there are two wastegate outlets <NUM>,<NUM> in this embodiment there are a corresponding pair of wastegate apertures <NUM>,<NUM> in the base <NUM>.

A third embodiment of an exhaust manifold for an internal combustion engine exhaust system is shown in schematic section views in <FIG>. Those figures illustrate various states of the manifold which are equivalents to those described above in relation to the first embodiment of the manifold.

Referring to <FIG>, the manifold is generally designated <NUM> and comprises first and second exhaust gas inlets <NUM>,<NUM> which are connectable in a known manner to a first bank of cylinders of an internal combustion engine (not shown). The manifold <NUM> also comprises third and fourth exhaust gas inlets <NUM>,<NUM> which are connectable in the same way to a second bank of cylinders of the engine (not shown).

The manifold <NUM> also comprises separate first and second exhaust gas outlets <NUM>,<NUM> which are connectable in use to respective first and second volutes of a twin volute turbocharger (not shown). Located between, and in fluid communication with, the exhaust inlets <NUM>,<NUM>,<NUM>,<NUM> and outlets <NUM>,<NUM> is an exhaust chamber <NUM> which has at least one wastegate outlet connectable to a passage which bypasses the turbocharger. In the illustrated embodiment the chamber <NUM> has four wastegate outlets <NUM>.

Also located in the chamber <NUM> is a diverter valve which is adapted to control the flow of exhaust gas from the exhaust gas inlets <NUM>-<NUM> to at least one of the first and second exhaust gas outlets <NUM>,<NUM> and the wastegate outlets <NUM>. The diverter valve comprises a rotatable, cylindrical valve body <NUM> having an external wall <NUM>, where the body may rotate under the power of a known actuator mechanism (e.g. solenoid) about an axis of rotation which is generally perpendicular to the direct of exhaust flow through the manifold. The body is predominantly hollow and the external wall <NUM> includes a number of inlet and outlet apertures (not shown) which allow the exhaust gas to flow through the body <NUM>. The body <NUM> also includes a solid diverter portion <NUM> which fills approximately one third of the volume defined by the external wall <NUM>, as shown in the end on views of <FIG>. It is this diverter portion <NUM> which diverts the exhaust gas flow depending upon the rotational position of the valve body <NUM>. The body <NUM> is also provided with at least one wastegate aperture whose shape preferably corresponds with that of the at least one wastegate outlet in the chamber <NUM>. As there are four wastegate outlets <NUM> in this embodiment there are four corresponding wastegate apertures <NUM> in the body <NUM>. The diverter portion <NUM> also includes a cross-drilled wastegate passage <NUM>, which is in fluid communication with the third and fourth exhaust gas inlets <NUM>,<NUM> and the wastegate outlets <NUM> when the valve is in the third state shown in <FIG>. As will be described in more detail below, this wastegate passage <NUM> allows exhaust gas from the third and fourth inlets <NUM>,<NUM> to flow to the wastegate outlets <NUM> when the diverter portion <NUM> is keeping the exhaust flows from the first pair of inlets <NUM>,<NUM> and the second pair of inlets <NUM>,<NUM> separate.

A first embodiment of a twin volute turbocharger is shown in schematic section views in <FIG>. For reasons of clarity, only the inlet to the turbocharger is shown in the figures. The remainder of the turbocharger can be assumed to be of a known design.

Referring to <FIG>, the turbocharger is generally designated <NUM> and comprises a first exhaust gas inlet <NUM>, which is connectable in a known manner to a first exhaust gas outlet of an exhaust manifold (not shown). The turbocharger <NUM> also comprises a second exhaust gas inlet <NUM>, which is connectable in the same way to a second exhaust gas outlet of an exhaust manifold. The turbocharger <NUM> also comprises separate first and second volutes <NUM>,<NUM> which house the turbine over which the exhaust gas will flow.

Located between, and in fluid communication with, the exhaust inlets <NUM>,<NUM> and the volutes <NUM>,<NUM> is an exhaust chamber <NUM> which has at least one wastegate outlet connectable to a passage which bypasses the volutes. In the illustrated embodiment the chamber <NUM> has a pair of wastegate outlets <NUM>,<NUM>.

Also located in the chamber <NUM> is a diverter valve <NUM> which is adapted to control the flow of exhaust gas from the first and second exhaust gas inlets <NUM>,<NUM> to at least one of the first and second volutes <NUM>,<NUM> and the wastegate outlets <NUM>,<NUM>. The diverter valve <NUM> comprises a rotatable valve body having a base <NUM> shaped as a segment of a circle, where the base <NUM> may rotate under the power of a known actuator mechanism (e.g. solenoid) about an axis of rotation R. An upwardly projecting diverter plate <NUM> is mounted upon the rotatable base <NUM>, and it is this diverter plate which diverts the exhaust gas flow. The base <NUM> is also provided with at least one wastegate aperture whose shape preferably corresponds with that of the at least one wastegate outlet in the chamber <NUM>. As there are two wastegate outlets <NUM>,<NUM> in this embodiment there are a corresponding pair of wastegate apertures <NUM>,<NUM> in the base <NUM>. The wastegate apertures <NUM>,<NUM> preferably lie either side of the diverter plate <NUM>.

An alternative embodiment of twin volute turbocharger is shown in <FIG> and generally designated <NUM>. Again, only the inlet of the turbocharger is shown with the remainder of the turbocharger being of a known design. As with the first embodiment of <FIG>, this turbocharger <NUM> comprises a first exhaust gas inlet <NUM>, which is connectable in a known manner to a first exhaust gas outlet of an exhaust manifold (not shown). The turbocharger <NUM> also comprises a second exhaust gas inlet <NUM>, which is connectable in the same way to a second exhaust gas outlet of the manifold.

The turbocharger <NUM> also comprises separate first and second volutes <NUM>,<NUM>. Located between, and in fluid communication with, the exhaust inlets <NUM>,<NUM> and volutes <NUM>,<NUM> is an exhaust chamber <NUM> which has at least one wastegate outlet connectable to a passage which bypasses the volutes <NUM>,<NUM>. In the illustrated embodiment the chamber <NUM> has a pair of wastegate outlets <NUM>,<NUM> which, when open, are in fluid communication with a generally annular wastegate chamber <NUM> which is arranged in the form of a jacket about the exterior of the exhaust chamber <NUM>. It is from the wastegate chamber <NUM> that the exhaust would flow to the bypass passage when the wastegate outlets <NUM>,<NUM> are open.

Also located in the chamber <NUM> is a diverter valve <NUM> which is adapted to control the flow of exhaust gas from the first and second exhaust gas inlets <NUM>,<NUM> to at least one of the first and second volutes <NUM>,<NUM> and the wastegate outlets <NUM>,<NUM>. The diverter valve <NUM> comprises a rotatable valve body <NUM> having a generally cylindrical shape, where the body <NUM> may rotate under the power of a known actuator mechanism (e.g. solenoid) about an axis of rotation R'. The body <NUM> and the axis of rotation R' lie generally perpendicular to the direction of flow of exhaust gas through the manifold. The interior of the valve body <NUM> is divided into two portions by a diverter plate <NUM> which runs the length of the interior of the valve body, and it is this diverter plate which diverts the exhaust gas flow. The cylindrical wall of the body <NUM> has a pair of exhaust inlet apertures <NUM>,<NUM> and a pair of exhaust outlet apertures <NUM>,<NUM> which permit exhaust gas to flow through the valve body <NUM> depending upon its rotational position. One exhaust inlet aperture and one exhaust outlet aperture are provided on either side of the diverter plate <NUM>. The body <NUM> also has at least one wastegate aperture whose shape and size preferably corresponds with that of the at least one wastegate outlet in the chamber <NUM>. As there are two wastegate outlets <NUM>,<NUM> in this embodiment there are a corresponding pair of wastegate apertures <NUM>,<NUM> in the base <NUM>.

The manner in which the manifold and turbocharger of the present invention operate will now be described. It should be noted that the second embodiment of the manifold shown in <FIG> has the valve in the same position as in <FIG>, and is also able to move between first, second and third positions which are the same as those shown in <FIG>. Similarly, it should be noted that whilst the operation of the turbocharger is described with particular reference to the positions taken up by the first embodiment shown in <FIG> the second embodiment shown in <FIG> can also move between the same first, second and third positions.

There are three positions which the diverter valve in both the first and second embodiments of the manifold may take up, depending on the performance demands of the engine and boost pressure of the turbocharger. The diverter valve may default to the state shown in either <FIG> or <FIG>, with the exhaust flow remaining divided by the valve and with the wastegate closed or at least partially open. Most preferably, the valve defaults to the state shown in <FIG>, with full wastegating provided by the fully open wastegate outlets to prevent overspeed or overboost of the turbocharger. In use, the actuator which operates the diverter valve body will be in communication with a controller, which may be the main electronic control unit (ECU) of the engine or else a dedicated manifold controller which itself is in communication with the main ECU. The main ECU monitors acceleration demands placed upon the engine by the vehicle operator, which may be done via a position sensor on the accelerator pedal of the vehicle, for example. The main ECU also monitors the boost pressure being provided by the turbocharger to the engine.

Sensing arrangements for this purpose are well known, and will not be described in any more detail here.

When the operator places an acceleration demand via the accelerator pedal of the vehicle, rapid spooling up of the turbocharger is required so as to achieve the increase in engine power needed to meet the acceleration demand. To achieve this the controller instructs the valve actuator to move to the position shown in <FIG> (and <FIG>). In this first position, the diverter plate <NUM>,<NUM> of the valve <NUM>,<NUM> lies between the second exhaust inlet <NUM>,<NUM> and the second exhaust outlet <NUM>,<NUM> so as to perform a "converger" function. This means that the exhaust gas flow from both banks of cylinders converges on the first outlet <NUM>,<NUM> and flows on into the first volute <NUM> of the turbocharger. In this first position the wastegate outlets <NUM>,<NUM>,<NUM>,<NUM> are closed by the valve <NUM>,<NUM>. Directing all of the exhaust flow into a single volute in this way improves the response of the turbocharger by effectively halving the turbine flow capacity.

When there is no acceleration demand placed upon the engine, and the boost pressure of the turbocharger is under a pre-determined limit, the controller will instruct the actuator to move the valve <NUM> into a second "steady state" position shown in <FIG>. In the second position, the valve base <NUM> has rotated clockwise about the rotational axis R so that the diverter plate <NUM> now acts to keep the exhaust flow from the first and second inlets <NUM>,<NUM> separate. Thus, the exhaust flow from the first bank of cylinders enters the first inlet <NUM> and passes through the first outlet <NUM> into the first volute of the turbocharger. Similarly, the exhaust flow from the second bank of cylinders enters the second inlet <NUM> and passes through the second outlet <NUM> into the second volute of the turbocharger. As with the first position, the wastegate outlets <NUM>,<NUM> are still closed by the valve <NUM> in the second position.

At any point during the operation of the engine the controller may determine that the boost pressure, or speed, of the turbocharger has reached or exceeded the pre-determined limit. To relieve the pressure and/or reduce the speed, the controller instructs the actuator to move the valve <NUM> further clockwise about the axis R into the third position shown in <FIG>. In this third position the diverter plate <NUM> still keeps the two exhaust flows from the banks of cylinders separate as they pass through the manifold <NUM> into the respective volutes of the turbocharger. However, now the wastegate apertures <NUM>,<NUM> in the valve base <NUM> are aligned with the wastegate outlets <NUM>,<NUM> in the chamber <NUM> so that at least part of the exhaust flow on both sides of the manifold <NUM> now enters the wastegate passage and bypasses the turbocharger. Hence, the boost pressure or speed of the turbocharger is reduced and/or maintained at the pre-determined pressure limit.

For the avoidance of doubt, the same positions are also achieved in the second embodiment of the manifold shown in <FIG>. The only difference in the second embodiment being that the wastegate outlets <NUM>,<NUM> and wastegate apertures <NUM>,<NUM> are located upon the circumference of the chamber <NUM> and valve <NUM>, respectively.

As with the first two embodiments of the manifold, there are three positions which the diverter valve in the third embodiment of the manifold may take up. The diverter valve may default to the state shown in either <FIG> or <FIG>, with the exhaust flow remaining divided by the valve and with the wastegate closed or at least partially open. Most preferably, the valve defaults to the state shown in <FIG>, with full wastegating provided by the fully open wastegate outlets to prevent overspeed or overboost of the turbocharger. In use, the actuator which operates the diverter valve body will be in communication with a controller, which may be the main electronic control unit (ECU) of the engine or else a dedicated manifold controller which itself is in communication with the main ECU. The main ECU monitors acceleration demands placed upon the engine by the vehicle operator, which may be done via a position sensor on the accelerator pedal of the vehicle, for example. The main ECU also monitors the boost pressure being provided by the turbocharger to the engine.

When the operator places an acceleration demand via the accelerator pedal of the vehicle, rapid spooling up of the turbocharger is required so as to achieve the increase in engine power needed to meet the acceleration demand. To achieve this the controller instructs the valve actuator to move to the position shown in <FIG>. In this first position, the diverter portion <NUM> of the valve body <NUM> prevents exhaust gas flowing in from the first and second inlets <NUM>,<NUM> from flowing out through the first outlet <NUM>. Instead, the exhaust gas flow from both banks of cylinders converges on the second outlet <NUM> and flows on into the respective volute of the turbocharger. In this first position the wastegate outlets <NUM> are closed by the valve <NUM> as the wastegate apertures <NUM> are not even partially aligned with the wastegate outlets <NUM>.

When there is no acceleration demand placed upon the engine, and the boost pressure of the turbocharger is under a pre-determined limit, the controller will instruct the actuator to move the valve body <NUM> into a second "steady state" position shown in <FIG>. In the second position, the valve body <NUM> has rotated clockwise about its rotational axis so that the diverter portion <NUM> now acts to keep the exhaust flow from the first and second inlets <NUM>,<NUM> separate from that of the third and fourth inlets <NUM>,<NUM>. Thus, the exhaust flow from the first and second inlets <NUM>,<NUM> passes through the valve <NUM> to the first outlet <NUM> into the first volute of the turbocharger. Similarly, the exhaust flow from the third and fourth inlets <NUM>,<NUM> passes through the valve <NUM> to the second outlet <NUM> and on into the second volute of the turbocharger. As with the first position, the wastegate outlets <NUM> are still closed because the wastegate apertures <NUM> in the valve body <NUM> remain out of rotational alignment with the wastegate outlets <NUM>.

As with the preceding embodiments the controller may determine that the boost pressure, or speed, of the turbocharger has reached or exceeded the pre-determined limit. To relieve the pressure and/or reduce the speed, the controller instructs the actuator to rotate the valve body <NUM> further clockwise about the rotational axis into the third position shown in <FIG>. In this third position the diverter portion <NUM> in the body <NUM> still keeps the two exhaust flows from the pairs of exhaust inlets separate as they pass through the manifold <NUM> into the respective volutes of the turbocharger. However, now the wastegate apertures <NUM> in the valve body <NUM> are aligned with the wastegate outlets <NUM> in the chamber <NUM> so that at least part of the exhaust flow from the first and second exhaust inlets <NUM>,<NUM> now enters the wastegate and bypasses the turbocharger. In addition, the inlet of the wastegate passage <NUM> is now in fluid communication with the third and fourth exhaust inlets <NUM>,<NUM> such that a portion of that inlet flow also passes through the wastegate passage <NUM> in the diverter portion <NUM> and out via the wastegate outlets. Hence, the boost pressure or speed of the turbocharger is reduced and/or maintained at the pre-determined pressure limit.

As with the embodiments of the manifold there are three positions which the diverter valve in both the first and second embodiments of the turbocharger may take up, depending on the performance demands of the engine and boost pressure of the turbocharger. The diverter valve may default to the state shown in either <FIG>, with the exhaust flow remaining divided by the valve and with the wastegate closed or at least partially open. Most preferably, the valve defaults to the state shown in <FIG>, with full wastegating provided by the fully open wastegate outlets to prevent overspeed or overboost of the turbocharger. In use, the actuator which operates the diverter valve body will be in communication with a controller, which may be the main electronic control unit (ECU) of the engine or else a dedicated turbocharger controller which itself is in communication with the main ECU. The main ECU monitors acceleration demands placed upon the engine by the vehicle operator, which may be done via a position sensor on the accelerator pedal of the vehicle, for example. The main ECU also monitors the boost pressure being provided by the turbocharger to the engine.

When the operator places an acceleration demand via the accelerator pedal of the vehicle, rapid spooling up of the turbocharger is required so as to achieve the increase in engine power needed to meet the acceleration demand. To achieve this the controller instructs the valve actuator to move to the position shown in <FIG> (and <FIG>). In this first position, the diverter plate <NUM>,<NUM> of the valve <NUM>,<NUM> lies between the second exhaust inlet <NUM>,<NUM> and the second exhaust outlet <NUM>,<NUM> so as to perform a "converger" function. Hence, the exhaust gas flow from both inlets <NUM>,<NUM>,<NUM>,<NUM> converges on the first outlet <NUM>,<NUM> and flows on into the associated first volute of the turbocharger <NUM>. In this first position the wastegate outlets <NUM>,<NUM>,<NUM>,<NUM> are closed by the valve <NUM>,<NUM>.

When there is no acceleration demand placed upon the engine, and the boost pressure of the turbocharger is under a pre-determined limit, the controller will instruct the actuator to move the valve <NUM> into a second "steady state" position shown in <FIG>. In the second position, the valve base <NUM> has rotated clockwise about the rotational axis R so that the diverter plate <NUM> now acts to keep the exhaust flow from the first and second inlets <NUM>,<NUM> separate. Thus, the exhaust flow from the first inlet <NUM> passes through the first outlet <NUM> into the first volute of the turbocharger. Similarly, the exhaust flow from the second inlet <NUM> passes through the second outlet <NUM> into the second volute of the turbocharger. As with the first position, the wastegate outlets <NUM>,<NUM> are still closed by the valve <NUM> in the second position.

At any point during the operation of the engine the controller may determine that the boost pressure, or speed, of the turbocharger has reached or exceeded the pre-determined limit. To relieve the pressure and/or reduce the speed, the controller instructs the actuator to move the valve <NUM> further clockwise about the axis R into the third position shown in <FIG>. In this third position the diverter plate <NUM> still keeps the two exhaust inlet flows separate as they pass through the chamber <NUM> into the respective volutes <NUM>,<NUM> of the turbocharger <NUM>. However, now the wastegate apertures <NUM>,<NUM> in the valve base <NUM> are aligned with the wastegate outlets <NUM>,<NUM> in the chamber <NUM> so that at least part of the exhaust flow on both sides of the chamber <NUM> now enters the wastegate passage and bypasses the turbocharger volutes <NUM>,<NUM>. Hence, the boost pressure or speed of the turbocharger is reduced and/or maintained at the pre-determined pressure limit.

For the avoidance of doubt, the same positions are also achieved in the second embodiment of the turbocharger shown in <FIG>. The only difference in the second embodiment being that the wastegate outlets <NUM>,<NUM> and wastegate apertures <NUM>,<NUM> are located upon the circumference of the chamber <NUM> and valve <NUM>, respectively.

The present invention provides an exhaust manifold and turbocharger which are able to perform a converger function when an acceleration demand is placed upon the engine, as well as providing integrated wastegate functionality when an overboost is detected. Providing a manifold or turbocharger that performs both the converger and wastegating functions using a single valve arrangement reduces the complexity and cost of adding this functionality to the manifold or turbocharger. Furthermore, both the manifold and turbocharger of the present invention keep the exhaust flow from the banks of cylinders separate other than when in the first "converger" position. This means that there is no interference to either flow from the other, thereby maintaining the optimal gas flow into the twin volutes of the turbocharger.

As well as moving between the three specific positions described above, the controller and actuator may combine to move the valve to other positions which are intermediate the three shown. For example, to achieve partial wastegating of the turbocharger whilst still maintaining steady state operation the valve body may be rotated such that the wastegate outlets and the wastegate apertures in the valve body are partially aligned as opposed to being fully aligned.

The manifold or turbocharger of the present invention may have more than one or two wastegate outlets and respective wastegate apertures. For example, there may be four wastegate outlets and respective wastegate apertures. In addition, the wastegate apertures of the diverter valve may all be on the same side of the diverter plate rather than arranged on both sides of the plate.

Claim 1:
An exhaust manifold for an internal combustion engine, the manifold comprising:
at least one first exhaust gas inlet (<NUM>) connectable to a first bank of cylinders of the engine;
at least one second exhaust gas inlet (<NUM>) connectable to a second bank of cylinders of the engine;
first and second exhaust gas outlets (<NUM>,<NUM>) connectable to respective first and second volutes of a twin volute turbocharger;
at least one wastegate outlet (<NUM>) connectable to a bypass passage which bypasses the turbocharger; and
a diverter valve (<NUM>) located within the manifold (<NUM>), wherein the diverter valve is adapted to selectively direct exhaust gas from the first and second inlets (<NUM>,<NUM>) to at least one of the first and second exhaust gas outlets (<NUM>,<NUM>) and the wastegate outlet (<NUM>); wherein the diverter valve is adapted to selectively move between:
(i) a first position in which the valve (<NUM>) diverts all of the exhaust gas from each inlet (<NUM>,<NUM>) to the first exhaust gas outlet (<NUM>), and prevents gas flow through the at least one wastegate outlet (<NUM>);
(ii) a second position in which the valve (<NUM>) maintains separate flows of the exhaust gas from each inlet (<NUM>,<NUM>) to the first and second exhaust gas outlets (<NUM>,<NUM>), respectively, and prevents gas flow through the at least one wastegate outlet (<NUM>); and
(iii) a third position in which the valve (<NUM>) maintains the separate flows of the second position, and permits flow of exhaust gas through the at least one wastegate outlet (<NUM>).