Patent Publication Number: US-9422833-B2

Title: Camshaft assembly for an internal combustion engine

Description:
TECHNICAL FIELD 
     The disclosure generally relates to a camshaft assembly for an internal combustion engine. 
     BACKGROUND 
     Internal combustion engines (ICE) are often called upon to generate considerable levels of power for prolonged periods of time on a dependable basis. Many such ICE assemblies employ a supercharging device, such as an exhaust gas turbine driven turbocharger, to compress the airflow before it enters the intake manifold of the engine in order to increase power and efficiency. 
     Specifically, a turbocharger is a centrifugal gas compressor that forces more air and, thus, more oxygen into the combustion chambers of the ICE than is otherwise achievable with ambient atmospheric pressure. The additional mass of oxygen-containing air that is forced into the ICE improves the engine&#39;s volumetric efficiency, allowing it to burn more fuel in a given cycle, and thereby produce more power. 
     Additionally, ICE&#39;s are being methodically developed to consume smaller amounts of fuel. Various technologies are frequently incorporated into ICE&#39;s to generate on-demand power, while permitting the subject engine to operate in a more fuel-efficient mode. Such fuel saving technologies may shut off operation of some of the engine&#39;s cylinders when engine power requirement is reduced and even completely stop the engine when no engine power is required. 
     SUMMARY 
     A vehicle includes an internal combustion engine. The internal combustion engine includes an engine block, a plurality of valve stems, a first camshaft assembly, and a second camshaft assembly. The engine block defines a first set of cylinders and a second set of cylinders. The valve stems are configured to provide selective fluid communication with the first and second set of cylinders. 
     The first camshaft assembly and a second camshaft assembly each extend along, and are each rotatable about, a respective cam axis. The first and second camshaft assembly are each disposed in operative communication with at least one of the valve stems. 
     The first camshaft assembly is configured to provide lift to at least one of the respective valve stems to selectively allow air to enter at least one of the first and second set of cylinders in response to rotation of the first camshaft assembly about the respective cam axis. Likewise, the second camshaft assembly is configured to provide lift to the respective valve stems to selectively allow air to exit at least one of the first and second set of cylinders in response to rotation of the second camshaft about the respective cam axis. 
     Each camshaft assembly is configured to provide lift to at least one of a plurality of valve stems to selectively allow air to respectively enter and exit at least one of the first and second set of cylinders. 
     Each camshaft assembly includes a camshaft, a first lobe set, and a second lobe set. The camshaft extends along, and is rotatable about, a cam axis. The first lobe set is operatively attached to the camshaft such that the first lobe set surrounds the cam axis. The first lobe set includes a first lobe, a second lobe, and a third lobe. The first lobe, the second lobe, and the third lobe of the first type of first lobe set each have a different profile from one another. The first lobe set is movable along the cam axis between a first position, a second position, and a third position. The first position of the first lobe set corresponds to selection of the first lobe so that lift is provided to the respective valve stem as a function of the profile of the first lobe of the first lobe set as the camshaft rotates about the cam axis. The second position corresponds to selection of the second lobe so that lift is provided to the respective valve stem as a function of the profile of the second lobe of the first lobe set as the camshaft rotates about the cam axis. The third position corresponds to selection of the third lobe so that lift is provided to the selective valve stem of the first lobe set as the camshaft rotates about the cam axis. 
     The second lobe set is operatively attached to the camshaft such that the second lobe set surrounds the cam axis. The second lobe set includes a first lobe and a second lobe such that the second lobe set includes a fewer number of lobes than the first lobe set. The first lobe and the second lobe of the second lobe set each have a different profile from one another. The second lobe set is movable along the cam axis between a first position and a second position. The first position corresponds to selection of the first lobe so that lift is provided to the respective valve stem corresponding to the profile of the first lobe of the second lobe set as the camshaft rotates about the cam axis. The second position corresponds to selection of the second lobe so that lift is provided to the respective valve stem of the second lobe of the second lobe set as the camshaft rotates about the cam axis. 
     The above features and advantages and other features and advantages of the present disclosure are readily apparent from the following detailed description of the best modes for carrying out the disclosure when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagrammatic block diagram of a vehicle including an internal combustion engine with a single scroll turbocharger. 
         FIG. 2  is a schematic side view of a camshaft assembly of the internal combustion engine of  FIG. 1 . 
         FIG. 3  is a schematic end view of a lobe of the camshaft assembly of  FIG. 2 . 
         FIG. 4  is a schematic end view of another lobe of the camshaft assembly of  FIG. 2 . 
         FIG. 5  is a schematic side view of a first lobe set of the camshaft assembly of the internal combustion engine, illustrating positioning of lobes, relative to a poppet valve, in each of a first position, a second position, and a third position. 
         FIG. 6  is a schematic side view of a second lobe set of the camshaft assembly of the internal combustion engine, illustrating positioning of the lobes, relative to a poppet valve, in each of a first position and a second position. 
     
    
    
     DETAILED DESCRIPTION 
     Those having ordinary skill in the art will recognize that terms such as “above,” “below,” “upward,” “downward,” “top,” “bottom,” etc., are used descriptively for the figures, and do not represent limitations on the scope of the disclosure, as defined by the appended claims. 
     Referring to the Figures, wherein like numerals indicate like parts throughout the several views,  FIG. 1  illustrates a vehicle  20  employing a powertrain  22  for propulsion thereof via driven wheels  24 . As shown, the powertrain  22  includes an internal combustion engine  26 , such as a spark- or compression-ignition type, and a transmission assembly  28  operatively connected thereto. The powertrain  22  may also include one or more electric motor/generators, none of which are shown, but the existence of which may be envisioned by those skilled in the art. 
     With continued reference to  FIG. 1 , the engine  26  includes a cylinder block  30  with a plurality of cylinders  32  arranged therein and a cylinder head  31  that is coupled to the cylinder block  30 . The cylinder head  31  may be integrated into or cast together with the cylinder block  30 . The cylinder head  31  receives air and fuel from an intake system  36  to be used inside the cylinders  32  for subsequent combustion. The air and fuel or air alone is admitted into the cylinder head  31  for each individual cylinder  32  via appropriately configured valve(s) that are not shown, but known to those skilled in the art. 
     The cylinders  32  are separated into a first cylinder or set of cylinders  32 A and a second cylinder or set of cylinders  32 B. The engine  26  also includes a mechanism  38  configured to selectively activate and deactivate the first set of cylinders  32 A during operation of the engine  26 . 
     Each cylinder  32  includes a piston, which is not specifically shown, but known to those skilled in the art to reciprocate therein. Combustion chambers, which are not specifically shown, but known to those skilled in the art, are formed within the cylinders  32  between the bottom surface of the cylinder head  31  and the tops of the pistons. As known by those skilled in the art, each of the combustion chambers receive fuel and air from the cylinder head  31  that form a fuel-air mixture for subsequent combustion inside the subject combustion chamber. Each cylinder  32  includes an intake valve and an exhaust valve, which are not specifically shown, but known to those skilled in the art to respectively provide air to, and exhaust gasses from, the respective combustion chamber. Although an in-line four-cylinder engine is shown, nothing precludes the present disclosure from being applied to an engine having a different number and/or arrangement of cylinders. 
     In the case of the in-line four-cylinder engine  26  depicted in the figures, the first set of cylinders  32 A may include two individual cylinders, while the second set of cylinders  32 B may include the remaining two individual cylinders. The deactivation of the first set of cylinders  32 A via the mechanism  38  is intended to permit the engine  26  to operate on only the second set of cylinders  32 B when a load on the engine  26  is sufficiently low so that power from both the first and second sets of cylinders  32 A,  32 B is not required drive the vehicle  20 . For example, such low load operation may take place when the vehicle  26  is cruising at a steady state highway speed and the engine  26  is mostly used to overcome air drag and rolling resistance of the vehicle  20 . Accordingly, operation of the engine  26  on solely the second set of cylinders  32 B permits reduced consumption of fuel when engine power from the first set of cylinders  32 A is not required to drive the vehicle  20 . 
     The engine  26  also includes a crankshaft (not shown) configured to rotate within the cylinder block. As known to those skilled in the art, the crankshaft is rotated by the pistons, as a result of an appropriately proportioned fuel-air mixture being burned in each combustion chamber. After the air-fuel mixture is burned inside a specific combustion chamber, the reciprocating motion of a particular piston serves to exhaust post-combustion gasses from the respective cylinder  32 . The cylinder head  31  is also configured to exhaust post-combustion gasses from the combustion chambers to an exhaust system  42  via an exhaust manifold  44 . As shown in  FIG. 1 , the exhaust manifold  44  may be internally cast, i.e., integrated, into the cylinder head  31 . The exhaust manifold  44  defines at least part of a passage  46  that is in fluid communication with the cylinder head  31 . The first set of cylinders  32 A and the second set of cylinders  32 B discharge the post-combustion gasses into the passage  46 . The passage  46  includes an outlet  48  defined by the exhaust manifold  44 . Accordingly, the post-combustion gasses from each of the first and second sets of cylinders  32 A,  32 B may exit the exhaust manifold  44  via the outlet  48 . 
     The engine  26  also includes a turbocharging system  50  configured to develop boost pressure, i.e., pressurize an airflow that is received from the ambient, for delivery to the cylinders  32 . The turbocharging system  50  is configured as a single-stage forced induction arrangement for the engine  26 . The turbocharging system  50  includes a turbocharger  52  that is in fluid communication with the passage  46  and configured to be driven by the post-combustion gasses from the outlet  48 . The turbocharger  52  pressurizes and discharges the airflow to the cylinder head  31 , via passage  34 . When the first set of cylinders  32 A are deactivated via the mechanism  38 , the turbocharger  52  can be driven by the post-combustion gasses from only the second set of cylinders  32 B and supply the pressurized airflow to feed the second set of cylinders  32 B for combustion with an appropriate amount of fuel therein. 
     The turbocharger  52  includes a rotating assembly  54 . The rotating assembly  54  includes a turbine wheel  56  mounted on a shaft  58 . The turbine wheel  56  is rotated along with the shaft  58  by the post-combustion gasses. The turbine wheel  56  is disposed inside a turbine housing  60 . The turbine housing  60  includes an appropriately configured, i.e., designed and sized, turbine volute or scroll  62 , a relatively high-pressure inlet  64 , and a relatively low-pressure outlet (not shown in detail, but known to those skilled in the art), that, along with the turbine wheel  56 , provides a turbine subassembly, a.k.a., a turbine. The turbine scroll  62  of the turbine housing  60  receives the post-combustion gasses and directs the gasses to the turbine wheel  56 . The turbine scroll  62  is configured to achieve specific performance characteristics, such as efficiency and response, of the turbocharger  52 . 
     The rotating assembly  54  also includes a compressor wheel  68  mounted on the shaft  58 . The compressor wheel  68  is configured to pressurize the airflow being received from the ambient for eventual delivery to the cylinders  32 . The compressor wheel  68  is disposed inside a compressor cover  70 . The compressor cover  70  includes a compressor volute or scroll  72 , a relatively low-pressure inlet (not shown in detail, but known to those skilled in the art), and a relatively high-pressure outlet  78 , that, along with the compressor wheel  68 , generates a compressor subassembly, a.k.a., a compressor. As understood by those skilled in the art, the variable flow and force of the post-combustion gasses influences the amount of boost pressure that may be generated by the compressor wheel  68  of the turbocharger  52  throughout the operating range of the engine  26 . 
     Additionally, referring again to  FIG. 1 , the vehicle includes a programmable controller  82  configured to regulate operation of the engine  26 , such as by controlling an amount of fuel being injected into the cylinders  32  for mixing and subsequent combustion with the pressurized airflow. The physical hardware embodying the controller may include one or more digital computers having a processor  33  and a memory  35 , e.g., a read only memory (ROM), random access memory (RAM), electrically-programmable read only memory (EPROM), high speed clock, analog to digital (A/D) and digital to analog (D/A) circuitry, and input/output circuitry and devices (I/O) including one or more transceivers  37  for receiving and transmitting any required signals in the executing of a method, as well as appropriate signal conditioning and buffer circuitry. Any computer-code resident in the controller or accessible thereby, including the algorithm, can be stored in the memory and executed via the processor(s) to provide the functionality set forth below. 
     The controller  82  of  FIG. 1  may be configured as a single or a distributed control device. The controller  82  is electrically connected to, or otherwise in hard-wired or wireless communication with, the engine  26  via suitable control channels, e.g., a controller area network (CAN) or serial bus, including for instance any required transfer conductors, whether hard-wired or wireless, sufficient for transmitting and receiving the necessary electrical control signals for proper power flow control and coordination aboard the vehicle  20 . 
     With reference to  FIGS. 1 and 2 , the engine  26  includes a first camshaft assembly  84 A and a second camshaft assembly  84 B. Each camshaft assembly  84 A,  84 B includes a camshaft  86  and a plurality of lobe sets  88  operatively attached to the camshaft  86 . Each camshaft  86  is rotatable about a respective cam axis  90 . The lobe sets  88  may be slidably attached to the camshaft  86  for axial movement along the camshaft  86 , and for rotation with the camshaft  86  about the cam axis  90 . 
     For a four-cylinder engine  26 , each camshaft assembly  84 A,  84 B includes two types of lobe sets  88 , i.e., a first lobe set  88 A and a second lobe set  88 B. The first lobe set  88 A corresponds to the first set of cylinders  32 A and the second lobe set  88 B corresponds to the second set of cylinders  32 B. A pair of the first lobe sets  88 A corresponds to the pair of the first set of cylinders  32 A and a pair of the second lobe sets  88 B corresponds to the pair of the second set of cylinders  32 B. As such, for each camshaft assembly  84 A,  84 B, each one of the first and second type lobe sets  88 A,  88 B corresponds to a respective one of the four cylinders  32 . It should be appreciated, however, there may be more or less lobe sets  88 A,  88 B, so as to correspond to a respective number of cylinders  32  in the engine  26 . 
     Referring specifically to  FIG. 2 , each lobe set  88 A,  88 B includes a plurality of lobes. The plurality of lobes of the first lobe set  88 A includes a first lobe  88 A- 1 , a second lobe  88 A- 2 , and a third lobe  88 A- 3 . Likewise, the plurality of lobes of the second lobe set  88 B includes only a first lobe  88 B- 1  and a second lobe  88 B- 2 . Each of the first, second, and third lobes  88 A- 1 ,  88 A- 2 ,  88 A- 3  defines a different profile from one another, which is perpendicular to the cam axis  90 . Similarly, each of the first and second lobes  88 B- 1 ,  88 B- 2  defines a different profile from one another. The respective lobes  88 A- 1 ,  88 A- 2 ,  88 A- 3  of the first lobe set  88 A and the respective lobes  88 B- 1 ,  88 B- 2  of the second lobe set  88 B are arranged in series along the cam axis  90 . Referring to  FIGS. 1 and 2 , the first lobe sets  88 A may be arranged adjacent one another on the cam axis  90  such that the first lobe sets  88 A are sandwiched between the second lobe sets  88 B. Alternatively, the second lobe sets  88 B are arranged adjacent one another on the cam axis  90  such that the second lobe sets  88 B are sandwiched between the first lobe sets  88 A. Further, it should be appreciated that the profile of the first lobes  88 A- 1 ,  88 B- 1  of the types of the lobe sets  88 A,  88 B may be identical to one another and the profile of the second lobes  88 A- 2 ,  88 B- 2  of the types of lobe sets  88 A,  88 B may be identical to one another. 
     The intake valves are configured to selectively move to an open position, in response to actuation by one of the lobes  88 A- 1 ,  88 A- 2 ,  88 B- 1 ,  88 B- 2  of a respective lobe set  88 A,  88 B, and thereby allow air into the respective cylinder  32 . Likewise, the exhaust valve stem is configured to selectively move to an open position, in response to actuation by one of the lobes  88 A- 1 ,  88 A- 2 ,  88 B- 1 ,  88 B- 2  of a respective lobe set  88 A,  88 B, and thereby exhaust gasses from the cylinder  32 . 
     For the first lobe set  88 A and the second lobe set  88 B, the profile of each of each first lobe  88 A- 1 ,  88 B- 1  is configured to provide a maximum lift and the profile of each second lobe  88 A- 2 ,  88 B- 2  is configured to provide a minimum lift. For the first lobe set  88 A, the profile of each third lobe  88 A- 3  is configured to provide zero lift. 
     Each lobe set  88 A,  88 B is movable along the respective cam axis  90 , relative to the camshaft  86 , between a number of positions corresponding to the number of lobes in the respective lobe set  88 A,  88 B. Therefore, the first lobe set  88 A is configured to move along the cam axis  90  between a first position  92 A, a second position  92 B, and a third position  92 C. The first position  92 A corresponds to the selection of the first lobe  88 A- 1 , the second position  92 B corresponds to the selection of the second lobe  88 A- 2 , and the third position  92 C corresponds to the selection of the third lobe  88 A- 3 . Likewise, the second lobe set  88 B is configured to move along the cam axis  90  between only the first position  92 A and the second position  92 B. Similarly, the first position  92 A corresponds to the selection of the first lobe  88 B- 1  and the second position  92 B corresponds to the selection of the second lobe  88 B- 2 . 
     The engine  26  includes a cam mechanism  112 , in operative communication with the controller  82 . The cam mechanism  112  is configured to selectively move one or more lobe sets  88 A,  88 B along the cam axis  90 , into a required position  92 A,  92 B,  92 C. The lobe sets  88 A,  88 B are configured to be axially slid relative to the camshaft  86  between the three positions  92 A,  92 B,  92 C and two positions  92 A,  92 B, respectively. Movement of the lobe sets  88 A,  88 B, relative to the camshaft  86 , allows each lobe set  88 A,  88 B to be positioned relative to the respective valve stem. By changing the axial positions of one or more of the sets of lobes, relative to the camshaft, a lift for each valve stem may be altered, as a function of the selected lobes  88 A- 1 ,  88 . 
     Each lobe  88 A- 1 ,  88 A- 2 ,  88 A- 3 ,  88 B- 1 ,  88 B- 2  for the first and second lobe sets  88 A,  88 B is configured to provide valve timing by opening the respective valve at the proper time, while giving the valve proper lift, by keeping the valve open for a sufficient amount of time, and by allowing the valve to close at the proper time. Referring to  FIGS. 3 and 4 , the profile for each lobe  88 A- 1 ,  88 A- 2 ,  88 A- 3 ,  88 B- 1 ,  88 B- 2  dictates the valve timing. The profile for each lobe  88 A- 1 ,  88 A- 2 ,  88 A- 3 ,  88 B- 1 ,  88 B- 2  has a base circle  96  having a base radius R 1 . With reference to  FIG. 3 , the center C 1  of the base circle  96  is operatively disposed on the cam axis  90 . In order to create the required lift during rotation of the first lobe  88 A- 1 ,  88 A- 2  or second lobe  88 B- 1 ,  88 B- 2  about the cam axis  90 , a ramp  100  extends from the base circle  96 , to a peak  104 . Since the third lobe  88 A- 3  (shown in  FIG. 4 ) does not provide any lift, the third lobe  88 A- 3  only includes the base circle  96 . 
     Referring again to the first lobe  88 A- 1 ,  88 A- 2  and second lobe  88 B- 1 ,  88 B- 2  (shown in  FIG. 3 ), a peak distance D 1  is defined between the peak  104  and the center C 1  of the base circle  96 . Referring to  FIGS. 5 and 6 , a follower or poppet  106  is operatively disposed between the respective first and second lobe set  88 A,  88 B and a valve stem  108 , as known to those in the art. As each first lobe  88 A- 1 ,  88 A- 2  or second lobe  88 B- 1 ,  88 B- 2  rotates about the cam axis  90 , the respective lobe  88 A- 1 ,  88 A- 2 ,  88 B- 1 ,  88 B- 2  converts rotation into a linear or vertical motion by using the follower  106  to lift an associated valve stem. The lift is a function of a lift distance D 2 , as illustrated in  FIG. 3 , which is defined as the distance beyond the base radius R 1  of the circle, i.e., a difference between the peak distance D 1  and the base radius R 1 . The lift of the respective valve stem eventually rises to its peak, i.e., a highest point beyond the base radius R 1  for the circle. Therefore, the difference between the peak distance D 1  and the base radius R 1  of each first lobe  88 A- 1 ,  88 A- 2  and second lobe  88 B- 1 ,  88 B- 2  is the lift component of the first and second lobes  88 A- 1 ,  88 A- 2 ,  88 B- 1 ,  88 B- 2 . The lift is created as the follower  106 , which is in contact with the circumference of the lobe  88 A- 1 ,  88 A- 2 ,  88 B- 1 ,  88 B- 2 , gradually moves from the base circle  96 , i.e., base radius R 1 , to the peak  104 , i.e., the peak distance D 1 . 
     With reference to  FIGS. 5 and 6 , for each lobe set  88 A,  88 B, the peak distance D 1  of the first lobes  88 A- 1 ,  88 B- 1  is greater than the peak distance D 1  of the second lobes  88 A- 2 ,  88 B- 2 . As such, the first lobes  88 A- 1 ,  88 B- 1  are configured to generate more lift than the second lobes  88 A- 2 ,  88 B- 2 . Further, since the third lobe  88 A- 3  has only the base circle  96  with the base radius R 1 , zero lift is generated. 
     Referring to  FIG. 1 , in combination with  FIGS. 5 and 6 , the controller  82  is configured to receive input (arrow S 110 ) from a plurality of sensors  110  and then determine a required position of one or more of the lobe sets, i.e., the first position  92 A, the second position  92 B, and/or the third position  92 C, along the cam axis  90 . The required position(s)  92 A,  92 B,  92 C of each of the lobe sets  88 A,  88 B is output as a signal (arrow S 112 ) to the respective cam mechanism  112 . The cam mechanisms  112  may be a slide cam mechanism and the like. Each cam mechanism  112  is operatively attached to the respective lobe set  88 A,  88 B to individually slide the desired lobe set(s)  88 A,  88 B along the camshaft  86 , to a required position. 
     During engine  26  operation, the controller  82  determines vehicle  20  and engine  26  parameters including, but not limited to, a vehicle speed, an engine load, a throttle position, exhaust temperature, and the like. The controller  82  may determine the required position(s) of each lobe set  88 A,  88 B, as a function of the vehicle  20  and engine  26  parameters. In one embodiment, the controller  82  may determine that the vehicle speed and engine load are such that only the second set of cylinders  32 B are required for operation of the engine  26 . As a result, the controller  82  may send a signal (arrow S 112 ) to the cam mechanisms  112  to move the first lobe sets  88 A to the third position  92 C, as illustrated in  FIG. 5 . When the first lobe set  88 A is in the third position  92 C, zero lift is provided to the associated poppet valve  106 , resulting in the first set of cylinders  32 A being deactivated. As a result of the deactivation of the first set of cylinders  32 A, fuel may be saved and fuel economy of the vehicle  20  may be improved. 
     The controller  82  may further determine that when the first lobe set  88 A is required to be in the third position  92 C, the second lobe sets  88 B are required to be in either the first position  92 A or the second position  92 B, as illustrated in  FIG. 6 . More specifically, the controller  82  may determine that each of the second lobe sets  88 B are required to be in the second position  92 B, to provide minimum lift, when the vehicle speed and engine load are no greater than a minimum load threshold. Therefore, the controller  82  may send a signal (arrow S 112 ) to the cam mechanisms  112  to move the second lobe sets  88 B to the second position  92 B. This configuration of the lobe sets  88 A,  88 B thus provides a maximum fuel economy for the vehicle. 
     However, the controller  82  may determine that when the first lobe set  88 A is required to be in the third position  92 C, the second lobe sets  88 B are required to be in the first position  92 A, to provide maximum lift, when the vehicle speed and engine load are greater than the minimum load threshold and less than a maximum load threshold. As such, the controller  82  may also send a signal (arrow S 112 ) to the cam mechanisms  112  to move the second lobe sets  88 B to the first position  92 A. 
     Additionally, the controller  82  may determine that, based on the vehicle  20  and engine  26  parameters, the required position of each of the first and second lobe sets  88 A,  88 B is the first position  92 A. This configuration is required when the controller  82  determines a wide-open throttle (WOT) position is required to maximize engine torque. As a result, the controller  82  may send a signal (arrow S 112 ) to the cam mechanisms  112  to move the first lobe sets  88 A and second lobe sets  88 B to the first position  92 A. 
     Further, the use of lobe sets  88 A having three lobes  88 A- 1 ,  88 A- 2 ,  88 A- 3  allow the use of a high-lift configuration (i.e., the first lobes  88 A- 1  are in the first position  92 A) and low-lift configuration (i.e., the second lobes  88 A- 2  are in the second position  92 B) for an improved torque and transient response, and also providing a zero lift option to deactivate the first set of cylinders  32 A for improved fuel economy, all while using only a single scroll turbocharger  52 . It should be appreciated that the engine  26  is not limited to having only two cylinders  32 A deactivated, as more cylinders may be deactivated, as desired. Further, this configuration provides for an optimized peak torque for the single scroll turbo, i.e., the configuration reduces a low-end compromise of a single valve event. Further, by providing the three lobes  88 A- 1 ,  88 A- 2 ,  88 A- 3  on both camshaft assemblies  84 A,  84 B, inlet and exhaust valvetrain designs may be commonized. 
     While the best modes for carrying out the disclosure have been described in detail, those familiar with the art to which this disclosure relates will recognize various alternative designs and embodiments for practicing the disclosure within the scope of the appended claims.