Patent Publication Number: US-7717078-B2

Title: Intake manifold regulators for internal combustion engines

Description:
RELATED APPLICATIONS 
   This application is a continuation of co-pending U.S. patent application Ser. No. 11/639,764 filed on Dec. 15, 2006, the entire content of which is incorporated herein by reference. 

   FIELD OF THE INVENTION 
   This invention relates generally to internal combustion engines, and more particularly to intake manifold regulators for internal combustion engines. 
   BACKGROUND OF THE INVENTION 
   Regulators are often used to reduce the power output of an internal combustion engine. When used in combination with carbureted engines, such regulators are configured to not be easily removable. 
   SUMMARY OF THE INVENTION 
   The present invention provides, in one aspect, an engine system configured to provide a plurality of engines having different power outputs at the same selected speed. The engine system includes a first engine having a first power output at the selected speed. The first engine includes a first engine housing, a first crankshaft rotatably supported in the first engine housing, a first cylinder, a first piston movable within the first cylinder, a first combustion chamber in fluid communication with the first cylinder, a first fuel system configured to provide fuel to the first combustion chamber, a first passageway configured to provide a fluid (e.g., air, fuel, or an air/fuel mixture) to the first combustion chamber, and a first regulator at least partially positioned in the first passageway. A slot is positioned in the interior wall adjacent the first passageway. The first regulator is selected such that the first engine operates at the first power output at the selected speed. The first regulator has an end disposed in the slot. The first engine also includes a first coupling device configured to maintain the first regulator in the first passageway. The first coupling device is also configured to enable removal of the first regulator without disassembly of the first passageway. The engine system also includes a second engine having a second power output at the selected speed different from the first power output. The second engine includes a second engine housing, a second crankshaft rotatably supported in the second engine housing, a second cylinder, a second piston movable within the second cylinder, a second combustion chamber in fluid communication with the second cylinder, a second fuel system configured to provide fuel to the second combustion chamber, a second passageway configured to provide a fluid (e.g., air, fuel, or an air/fuel mixture) to the second combustion chamber, and a second regulator at least partially positioned in the second passageway. A second slot is positioned in the interior wall of the second passageway. The second regulator has an end disposed in the second slot. The second regulator is selected such that the second engine operates at the second power output at the selected speed, with the second power output being different from the first power output. The second engine also includes a second coupling device configured to maintain the second regulator in the second passageway. The second coupling device is also configured to enable removal of the second regulator without disassembly of the second passageway. 
   Such an engine system may be used to manufacture engines, each engine having a distinct desired power output selectable from a range of power outputs, from a common engine configuration utilizing the same fuel calibration and the same fuel systems. For example, first and second production runs of engines, including substantially identical engine housings, crankshafts, cylinders, pistons, combustion chambers, fuel systems, and intake passageways may yield a first power output at a selected speed and a second power output (different than the first power output) at the selected speed, respectively, due to the differently-sized regulators chosen for the first and second production runs of engines. Therefore, costs relating to tooling, down time, and assembly line set-up changes to incorporate different crankshafts, camshafts, pistons, connecting rods, cylinder heads, or fuel systems to change the power output of the engines may be reduced. The engines may be pre-built and stored in inventory, with their respective regulators being added or changed later. 
   The present invention provides, in another aspect, an internal combustion engine including an engine housing, a crankshaft rotatably supported in the engine housing, a cylinder, a piston movable within the cylinder, a combustion chamber in fluid communication with the cylinder, a carburetor configured to provide fuel to the combustion chamber, an intake passageway configured to provide an air/fuel mixture to the combustion chamber, and a first regulator at least partially positioned in the intake passageway. A slot is positioned in the interior wall adjacent the intake passageway, and the first regulator has an end disposed in the slot. The first regulator is selectable from a plurality of regulators. The engine also includes a coupling device configured to maintain the first regulator in the intake passageway. The first regulator is configured to be removed and replaced by a second regulator from the plurality of regulators without disassembly of the intake passageway. 
   The present invention provides, in yet another aspect, an intake manifold assembly configured for use with an internal combustion engine having a carburetor and a cylinder head. The intake manifold assembly comprises an intake manifold that includes an inlet configured to receive an air/fuel mixture from the carburetor, an outlet configured to discharge the air/fuel mixture into the cylinder head, and an interior wall defining an intake passageway fluidly communicating the inlet and the outlet. The intake passageway has a cross-sectional open area. A slot is positioned in the interior wall adjacent the intake passageway. A first regulator is at least partially positioned in the intake passageway to effectively decrease the cross-sectional open area of the intake passageway. The first regulator has an end disposed in the slot. The first regulator is selectable from a plurality of regulators configured to each be at least partially positionable in the intake passageway. The first regulator is configured to be removed and replaced by a second regulator from the plurality of regulators without disassembly of the intake manifold from the carburetor and the cylinder head. 
   Other features and aspects of the invention will become apparent by consideration of the following detailed description and accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of an internal combustion engine of the present invention. 
       FIG. 2   a  is a partial cross-sectional view of the engine of  FIG. 1  through section  2   a - 2   a  in  FIG. 1 . 
       FIG. 2   b  is a partial cross-sectional view similar to  FIG. 2   a , illustrating a second engine having substantially the same configuration of the engine of  FIG. 1 . 
       FIG. 3  is an exploded perspective view of a portion of the engine of  FIG. 1 , illustrating a first construction of an intake manifold and a first construction of a group or family of differently-sized intake manifold regulators. 
       FIG. 4  is an exploded perspective view of the intake manifold and one regulator, chosen from the group or family of differently-sized regulators in  FIG. 3 . 
       FIG. 5  is an assembled plan view of the intake manifold and regulator of  FIG. 4 , illustrating a partial cutaway of the intake manifold to expose the regulator positioned in an intake passageway. 
       FIG. 6  is a cross-sectional view of the intake manifold of  FIG. 5  through section  6 - 6  in  FIG. 5 . 
       FIG. 7  is a cross-sectional view of the intake manifold and regulator of  FIG. 5  through section  7 - 7  in  FIG. 5 . 
       FIG. 8  is an exploded perspective view of a portion of the engine of  FIG. 1 , illustrating a second construction of an intake manifold and a second construction of one of a group or family of differently-sized intake manifold regulators. 
       FIG. 9  is an exploded perspective view of a portion of the engine of  FIG. 1 , illustrating a third construction of an intake manifold and a third construction of one of a group or family of differently-sized intake manifold regulators. 
       FIG. 10  is a perspective view of a fourth construction of one of a group or family of differently-sized intake manifold regulators. 
       FIG. 11  is an assembled view of the regulator of  FIG. 10  and a fourth construction of an intake manifold, illustrating a partial cutaway of the intake manifold to expose the regulator positioned in an intake passageway of the intake manifold. 
       FIG. 12  is a perspective view of a fifth construction of an intake manifold assembly according to the present invention. 
       FIG. 13  is a top view of the intake manifold used in the fifth construction. 
       FIG. 14  is an exploded perspective view of the fifth construction, and illustrates a group or family of differently-sized intake manifold regulators used in the fifth construction. 
       FIG. 15  is a side cross sectional view of the fifth construction, taken along line  15 - 15  of  FIG. 12 . 
   

   Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. 
   DETAILED DESCRIPTION 
     FIG. 1  illustrates a small, air-cooled, four-stroke internal combustion engine  10  having a single cylinder  12  (see  FIG. 2   a ) and a vertically-oriented crankshaft or output shaft  14 . The engine  10  also includes a piston  15  coupled to the output shaft  14  by a connecting rod  17  for reciprocating movement in the cylinder  12 , and a combustion chamber  16  in fluid communication with the cylinder  12 . The engine  10  may be configured to operate, among other things, engine-driven outdoor power equipment (e.g., lawn mowers, lawn tractors, snow throwers, generators, pressure washers, etc.). When used in combination with a walk-behind lawn mower, for example, the engine  10  may be supported by a mower deck and the output shaft  14  may be coupled to a blade positioned beneath the mower deck. It should be understood that alternative constructions of the engine  10  may also include multiple-cylinder configurations or a horizontal output shaft configuration. 
   With continued reference to  FIG. 1 , the engine  10  also includes a blower housing  18  for providing a cooling airflow over the external components of the engine  10  (e.g., an outer housing or engine housing  22  and a cylinder head  26 ), an air cleaner  30  coupled to the blower housing  18  for providing a filtered airflow to the engine  10 , a fuel system including a carburetor  34  that receives the filtered airflow from the air cleaner  30  and adds fuel to the filtered airflow to create a fuel/air mixture, and an intake manifold  38  coupled to the carburetor  34  for delivering the fuel/air mixture to the cylinder head  26 . It should also be understood that the engine  10  may include any of a number of different configurations of blower housings for providing the cooling airflow over the external components of the engine and/or air cleaners for providing the filtered airflow to the engine  10 . 
   With reference to  FIGS. 3 and 4 , the intake manifold  38  includes an inlet  42  configured to receive the fuel/air mixture from the carburetor  34 , an outlet  46  configured to discharge the fuel/air mixture into the cylinder head  26 , an interior wall  48 , and an intake passageway  50  defined by the interior wall  48 , through which the fuel/air mixture passes, extending between the inlet  42  and the outlet  46 . With additional reference to  FIG. 5 , the intake passageway  50  has a non-linear longitudinal axis  54 , such that the fuel/air mixture passing through the intake passageway  50  travels a substantially arcuate flow path moving from the inlet  42  to the outlet  46 . Alternative constructions of the intake manifold  38  may include any of a number of different configurations, in which the longitudinal axis  54  of the intake passageway  50  is substantially arcuate or substantially straight or linear. 
   With reference to  FIG. 3 , a family or a group  58  of interchangeable, differently-sized regulators is shown, any of which may be at least partially positioned in an airflow passageway or a fuel/air mixture passageway in the engine  10 . In the illustrated construction of the engine  10 , any regulator from the group  58  may be coupled to the intake manifold  38 . Alternatively, any regulator from the group  58  may be positioned in an airflow passageway in the engine  10  upstream of the carburetor  34 . For example, any regulator from the group  58  may be positioned in an airflow passageway in the air cleaner  30 , or any regulator from the group  58  may be positioned in an airflow passageway between the air cleaner  30  and the carburetor  34 . As such, the term “intake passageway” should not be limited to the passageway through the intake manifold  38 , but rather should include any airflow passageway upstream of the carburetor  34 , or any fuel/air mixture passageway through the carburetor  34  or downstream of the carburetor  34 . Further, rather than selecting a single regulator from the group  58 , a combination of two or more regulators from the group  58  (or from other groups of regulators) may be positioned in an airflow passageway in the engine  10  upstream of the carburetor  34  or a fuel/airflow passageway in the engine  10  downstream of the carburetor  34  to achieve a desired decrease in power output by the engine  10 . 
   With reference to  FIGS. 1 and 2   a , the engine  10  is shown having one of the regulators  62  from the group  58  coupled to the intake manifold  38 . The engine  10 , therefore, is operable to achieve a first power output at a selected speed. With reference to  FIG. 2   b , a second engine  10   a  which may have—but need not have—substantially similar internal components as the first engine  10 , is shown. Specifically, the second engine  10   a  includes a second cylinder  12   a  that may be substantially similar to the cylinder  12 , a second output shaft  14   a  that may be substantially similar to the output shaft  14 , a second piston  15   a  that may be substantially similar to the piston  15 , a second connecting rod  17   a  that may be substantially similar to the connecting rod  17 , a second engine housing  22   a  that may be substantially similar to the engine housing  22 , a second cylinder head  26   a  that may be substantially similar to the cylinder head  26 , and a second air cleaner  30   a  that may be substantially similar to the air cleaner  30 . Second fuel system or carburetor  34   a  is preferably substantially similar to the carburetor  34 . Second intake manifold  38   a  may be substantially similar to the intake manifold  38 . The second engine  10   a , however, utilizes a different regulator  62   a  from the group  58  than the engine  10 . The engine  10   a , therefore, is operable to achieve a second power output different from the first power output of the engine  10  at the same selected speed. As will be discussed in greater detail below, other components of the engine  10   a , such as the cylinder  12   a , the output shaft  14   a , the piston  15   a , the connecting rod  17   a , the engine housing  22   a , the cylinder head  26   a , the air cleaner  30   a , the carburetor  34   a , and the intake manifold  38   a  may be changed, either individually or in combination, to achieve the second or another different power output. 
   With reference to  FIG. 3 , the intake manifold  38  includes a wall  64  defining an aperture  66 , positioned between the inlet  42  and the outlet  46 , exposed to the intake passageway  50  for receiving one regulator selected from the group  58  (see also  FIG. 5 ). In the illustrated construction of the intake manifold  38  and group  58  of regulators, the aperture  66  is configured as a stepped aperture  66  for receiving different portions of the regulator. Each of the regulators in the group  58  includes an interior portion (e.g., interior portions  70 ,  70   a  of regulators  62 ,  62   a ) that is at least partially positioned within the intake passageway  50 , and a base or an exterior portion  74  that is external to the intake passageway  50 . As shown in  FIG. 5 , the exterior portion  74  includes a groove  78  extending around the outer periphery of the exterior portion  74 , in which a seal  82  (e.g., an O-ring) is received to seal against the wall  64  to inhibit outside air from leaking into the intake passageway  50  through the aperture  66 . Alternative constructions of the intake manifold  38  and the regulators may include stepped or non-stepped apertures and corresponding stepped or non-stepped surfaces on the regulators. 
   With reference to  FIGS. 3 and 4 , both the interior portions (e.g., interior portions  70 ,  70   a ) and the exterior portions  74  of the respective regulators have a generally cylindrical shape. Particularly, the interior portions (e.g., interior portions  70 ,  70   a ) of the respective regulators are configured as cylinders having a spherical or dome-shaped distal end  84 , a longitudinal axis  86 , a length dimension D 1  along the longitudinal axis  86 , and a width dimension D 2  transverse to the longitudinal axis  86  (see  FIG. 5 ). Because the interior portions are configured as cylinders having a curved outer surface (e.g., curved outer surface  90  of the regulator  62 ), the width dimension D 2  is equal to the outer diameter of the interior portions  70  (see also  FIG. 3 ). 
   Alternative constructions of the regulators may include interior portions having any of a number of different shapes. For example, alternative constructions of the regulators may include interior portions, or portions of the regulators exposed to the intake passageway  50 , configured as substantially flat plates oriented substantially transversely to the longitudinal axis  54  of the intake passageway  50 . In such a configuration, the regulator and/or the intake manifold may include an alignment feature to ensure proper alignment and orientation of the regulator in the intake passageway  50 . Also, alternative constructions of the regulators may include substantially conical-shaped interior portions having a longitudinal axis generally aligned with the longitudinal axis  54  of the intake passageway  50 . Many other configurations of regulators can be used, because it is the effective regulator surface area exposed (i.e., the portion of the regulator that comes into contact with the airflow or air/fuel mixture) to the airflow compared to the total cross-sectional area of the intake passageway  50 , not the shape of the regulator, which primarily determines the change in engine power output. 
   As shown in  FIG. 3 , the diameter or the width dimension D 2  of each of the interior portions (e.g., interior portions  70 ,  70   a ) of the respective regulators in the group  58  is substantially equal, while the length dimension D 1  (see  FIG. 5 ) of each of the interior portions of the respective regulators in the group  58  is different. Further, each of the exterior portions  74  of the respective regulators in the group  58  is substantially the same size. As such, any one of the regulators in the group  58  may be selected to be received within the stepped aperture  66  because the regulators share commonly-shaped exterior portions  74 , and interior portions (e.g., interior portions  70 ,  70   a ) may have a common width dimension D 2  that conform to the shape of the stepped aperture  66 . A visual indicator (e.g., a distinctive color, a symbol, etc.) may be utilized on the regulators to differentiate the regulators according to their respective restriction on engine power output. 
   With reference to  FIG. 5 , one of the regulators (e.g. the regulator  62 ) from the group  58  is selected to be received within the stepped aperture  66 . The interior portion  70  is oriented within the intake passageway  50  such that the longitudinal axis  86  of the interior portion  70  is substantially transverse to the longitudinal axis  54  of the intake passageway  50 . As a result, at least a portion of the air/fuel mixture passing through the intake passageway  50  must pass over the dome-shaped distal end  84  and the curved outer surface  90  of the interior portion  70  of the regulator  62  before being discharged from the outlet  46  of the intake manifold  38 . 
   In other words, the presence of the interior portion  70  of the regulator  62  in the intake passageway  50  effectively decreases the width or height of the intake passageway  50 , causing a localized restriction in the flow path of the air/fuel mixture as it passes from the inlet  42  to the outlet  46 . The spherical or dome-shaped distal ends  84  allow the regulators, particularly those in the group  58  having the longest length dimensions D 1 , to be positioned in close proximity to the interior wall  48 . By configuring the regulators in the group  58  with the spherical or dome-shaped distal ends  84 , as opposed to flat ends with sharp corners that disrupt flow, tighter control of the pressure drop over the interior portions (e.g., interior portions  70 ,  70   a  of  FIG. 3 ) may be achieved. Tighter control of the power output of the engine (e.g., engines  10 ,  10  of  FIGS. 2   a  and  2   b , respectively) and more precise control of the power output of the engine may be achieved utilizing the regulators with the spherical or dome-shaped distal ends  84  because of the absence of sharp corners (which can disrupt flow) on the interior portions. 
   With reference to  FIG. 6 , a cross-section of the intake passageway  50  at a location upstream of the regulator  62  is shown. In the illustrated construction of the intake manifold  38   a ,  38   b , the intake passageway  50  is configured with a substantially circular cross-sectional shape through a plane  94  positioned upstream of the regulator  62  and oriented substantially transversely to the longitudinal axis  54  of the intake passageway  50 . The substantially circular cross-sectional shape of the intake passageway  50  with respect to the plane  94  defines a cross-sectional open area A 1 . Alternative constructions of the intake manifold  38   a ,  38   b  may include an intake passageway  50  having any of a number of different cross-sectional shapes. 
     FIG. 7  illustrates a cross-section of the intake passageway  50  and regulator  62 , taken through a plane  98  containing the longitudinal axis  86  of the interior portion  70  and oriented substantially transversely to the longitudinal axis  54  of the intake passageway  50 . As discussed above, the presence of the interior portion  70  of the regulator  62  in the intake passageway  50  effectively decreases the cross-sectional open area A 1  of the intake passageway  50 . Specifically, the presence of the interior portion  70  of the regulator  62  in the intake passageway  50  defines a cross-sectional open area A 2  substantially less than the cross-sectional open area A 1 . In one combination of the intake manifold  38  and one of the regulators selected from the group  58 , the cross-sectional open area A 2  may be no more than about 60 percent of the cross-sectional open area A 1 . In another combination of the intake manifold  38  and one of the regulators selected from the group  58 , the cross-sectional open area A 2  may be between about 25 percent and about 85 percent of the cross-sectional open area A 1 . 
   With reference to  FIGS. 3 and 4 , a coupling device  102  may be utilized to secure one of the regulators selected from the group  58  to the intake manifold  38  and maintain the interior portion of the regulator (e.g., the interior portion  70  of the regulator  62 ) in the intake passageway  50 . Particularly, in the construction of the intake manifold  38  and regulators of  FIGS. 3 and 4 , the coupling device  102  includes a coupler or a finger  106  extending from the exterior portion  74  of the regulator  62  and a groove or slot  110  formed in the intake manifold  38  around the aperture  66  and configured to receive the finger  106 . In positioning the regulator  62  in the intake passageway  50 , the regulator  62  is oriented such that the finger  106  is aligned with an opening  114  that leads into the slot  110 , the regulator  62  is inserted through the aperture  66 , and the finger  106  is passed through the opening  114  and into the slot  110 . To secure the regulator  62  to the intake manifold  38 , the regulator  62  may be rotated about its longitudinal axis  86 , causing the finger  106  to move within the slot  110  away from the opening  114 . An abutment surface  118  at least partially defining the slot  110 , therefore, inhibits the unintentional removal of the regulator  62  from the intake manifold  38  without the required rotation of the regulator  62  to align the finger  106  with the opening  114  in the slot  110 . 
   With reference to  FIG. 8 , another construction of a regulator  162  with another construction of a coupling device  122  is shown, with like features and components having like reference numerals. The coupling device  122  includes a coupler or a resilient tab  126 , having an abutment surface  128 , extending from the exterior portion  74  of the regulator  162 , and an abutment surface  130  on the intake manifold  38  configured to be engaged by the abutment surface  128  of the resilient tab  126  to inhibit unintentional removal of the regulator  162  from the aperture  66 . In positioning the regulator  162  in the intake passageway  50 , the regulator  162  is oriented such that the resilient tab  126  is aligned with the abutment surface  130  and the regulator  162  is inserted through the aperture  66 . To secure the regulator  162  to the intake manifold  38 , continued insertion of the regulator  162  causes the resilient tab  126  to deflect by sliding contact between a ramp surface  134  on the resilient tab  126  and an engagement surface  138  on the intake manifold  38 . When the regulator  162  is fully inserted into the stepped aperture  66 , the resilient tab  126  snaps back to its undeflected shape, such that mutual abutment of the surfaces  128 ,  130  on the resilient tab  126  and the intake manifold  38  inhibit unintentional removal of the regulator  162  from the intake manifold  38 . 
   With respect to  FIG. 9 , yet another construction of a regulator  262  with another construction of a coupling device  142  is shown for securing the regulator  262  to the intake manifold  38 , with like features and components having like reference numerals. The coupling device  142  includes an insert  146  coupled to the intake manifold  38 , a coupler or a mounting flange  150  extending from the exterior portion  74  of the regulator  262 , and a fastener  154  (e.g., a bolt or screw) inserted through an aperture  158  in the mounting flange  150  to threadably engage the insert  146  in the intake manifold  38 . Therefore, threading the fastener  154  into the insert  146  to some predetermined torque value inhibits unintentional removal of the regulator  262  from the intake manifold  38 . In the illustrated construction of the coupling device  142  in  FIG. 9 , the insert  146  is molded into the intake manifold  38 . In an alternative construction of the coupling device  142 , the insert  146  may be omitted such that the fastener  154  is threaded directly into a threaded aperture or bore in the intake manifold  38 . 
   Alternatively, the coupling devices  102 ,  122 ,  142  may be omitted, and an interference fit between the exterior portion  74  and/or the interior portion  70  of the regulator  62 ,  162 , or  262  and the stepped aperture  66  may be utilized to maintain the interior portion  70  of the regulator  62 ,  162 , or  262  in the intake passageway  50 . As a further alternative, the O-ring  82  may provide the interference fit with the stepped aperture  66 , such that the coupling devices  102 ,  122 ,  142  may be omitted. 
   With reference to  FIGS. 10 and 11 , another construction of an intake manifold  338  and a regulator  362  is shown. The intake manifold  338  is similar to the intake manifold  38  of  FIGS. 3-7 , with like features having like reference numerals. The regulator  362  includes an interior portion  370  that is at least partially positioned within the intake passageway  50 , and an exterior portion  374  that is external to the intake passageway  50 . The exterior portion  374  includes a groove  378  extending around the outer periphery of the exterior portion  374 , in which a seal  382  (e.g., an O-ring, see  FIG. 11 ) is received to seal against a wall  364  of the intake manifold  338  to inhibit outside air from leaking into the intake passageway  50  through a non-stepped aperture  366  defined by the wall  364 . The groove  378  and seal  382  also separates the interior portion  370  from the exterior portion  374  of the regulator  362 . Although the regulator  362  is illustrated with a portion of the coupling device  102  (i.e., the finger  106 ), the regulator  362  may be configured to utilize any of the coupling devices  122 ,  142  illustrated in  FIGS. 8 and 9 , respectively. 
   With continued reference to  FIGS. 10 and 11 , the regulator  362  includes an axial locating post  368  extending from a spherical or dome-shaped end  384  of the interior portion  370 . The post  368  includes a substantially flat distal end  370  that is engageable with the interior wall  48  of the intake manifold  338  (see  FIG. 11 ). The post  368  has a length dimension D 3  that, when the regulator  362  is inserted through the aperture  366 , determines how much of the interior portion  370  is exposed to the air/fuel mixture in the intake passageway  50 . Like the family or group  58  of regulators illustrated in  FIG. 3 , the regulator  362  may be one of a family or group of regulators having axial locating posts of different length dimensions D 3  to provide different amounts of restriction within the intake passageway  50 . 
   By providing the axial locating post  368 , rather than a combination of differently-sized bases or exterior portions (e.g., exterior portions  74  in  FIG. 3 ) and interior portions (e.g., interior portions  70 ,  70   a  in  FIG. 3 ), the tolerance stack-up of the resulting open area at the restriction may be reduced. In other words, the tolerance of the open area (e.g., open area A 2  of  FIG. 7 ) is affected by a single value—the tolerance of the length dimension D 3  of the axial locating post  368 —rather than multiple values (e.g., the length dimension D 1  of the interior portion  70  in  FIG. 5 , the counter-bore depth of the stepped aperture  66  in  FIG. 5 , and the location of the shoulder between the interior and exterior portions  70 ,  74  in  FIG. 5 ). As a result, tighter and more precise control of the power output of the engine (e.g., the engines  10 ,  10   a  of  FIGS. 2   a  and  2   b , respectively) may be achieved. 
   With reference to  FIG. 3 , the regulators in the family or group  58  may be sized to decrease the net horsepower of the unrestricted engine  10  between about 5 percent and about 25 percent or more. Such a reduction in the power output of the engine  10  is a function of the exposed area (i.e., the portion of the regulator  62  that comes into contact with the airflow or fuel/air mixture) of the regulator  62  in the intake passageway  50 —i.e., as the length dimension D 1  increases, the cross-sectional open area A 2  (see  FIG. 7 ) decreases, thus restricting the amount of fuel/air mixture that can be effectively consumed by the engine  10  during operation. Such a reduction in power output may be achieved without any modifications to the calibration of the carburetor  34  or other fuel system, and without replacing the carburetor or other fuel system. In other words, no changes in the amount of fuel metered to the airflow by the carburetor  34  would be necessary to achieve the resultant decreases in power output for each engine-regulator combination. 
   With reference to  FIG. 3 , one regulator from the group  58  may be selected to achieve a power output of the engine  10  that is less than the unrestricted power output of the engine  10 . In deciding which of the regulators in the group  58  to select, the unrestricted power output of the engine  10  is determined, and a desired or a restricted power output is determined. Then, knowing the horsepower drop caused by each of the regulators in the group  58  from empirical testing performed on an engine having the same configuration as the engine  10 , a particular regulator may be selected to achieve the desired power output of the engine  10 , without altering or changing the fuel calibration of the carburetor  34  and without changing the engine castings. It is also desirable to use the same configuration of the engine housing  22 . While the same configurations of pistons  15 , connecting rods  17 , crankshafts  14 , and the valve train may also be used, different configurations of the pistons, connecting rods, crankshafts, and the valve train may alternatively be used to achieve a greater number of variations of power output for the engine  10 . 
   Another method or process of using the family or group  58  of regulators with the engine  10  includes measuring the power output of the engine  10  using a first regulator from the group  58 . If the measured power output of the restricted engine  10  does not match a desired power output, then the first regulator may be removed from the intake manifold  38  without disassembling the engine  10  or removing the intake manifold  38  from the cylinder head  26  or the carburetor  34 . A second regulator from the group  58  may then be chosen to replace the first regulator in the intake manifold  38 . This method or process of using the group  58  of regulators reduces the repair time or the rebuild time necessary for changing the power output of the engine  10 . Rather than changing internal components of the engine  10  (e.g., the crankshaft  14 , the piston  15 , the connecting rod  17 , the valve train, the camshaft, the cylinder head  26 , etc.) to change the power output of the engine  10 , which often requires a relatively large amount of time, the existing regulator in the engine  10  may be replaced with another regulator from the group  58  to change the power output of the engine  10 . 
   As used herein, “disassembly of the intake passageway” includes removing or disconnecting any component forming a portion of the intake passageway, including the carburetor  34  and the intake manifold  38 . In other words, the first regulator may be removed and replaced by the second regulator merely by disconnecting the coupling device  102 ,  122 , or  142 , removing the first regulator from the aperture  66  along the longitudinal axis  86  of the first regulator, inserting the second regulator into the aperture  66  along the longitudinal axis  86  of the second regulator, and re-connecting the coupling device  102 ,  122 , or  142 . These steps to exchange the first regulator for the second regulator may occur without removing or disconnecting the carburetor  34  or the intake manifold  38 , for example, from the engine  10 . 
   These processes may be used to manufacture engines  10 , each having a distinct desired power output, selectable from a range of power outputs available from installing one of the regulators in the group  58 , from a common engine configuration utilizing the intake manifold  38  and the same fuel calibration in the carburetor  34 . For example, first and second production runs of engines  10 , including substantially identical engine housings  22 , output shafts  14 , cylinders  12 , pistons  15 , combustion chambers  16 , carburetors  34 , and intake manifolds  38 , may yield a first power output at a selected speed and a second power output (different than the first power output) at the selected speed, respectively, due to the differently-sized regulators chosen for the first and second production runs of engines  10 . Also, an existing production run of engines  10  incorporating one of the regulators from the group  58  may be re-worked to remove the existing regulators from the engines  10 , which allowed the engines  10  to generate the first power output at the selected speed, and replace them with differently-sized regulators, which would allow the engines  10  to generate the second power output at the selected speed. In embodiments of the regulators utilizing visual indicators (e.g., distinctive colors, symbols, etc.) on the regulators in the group  58  to distinguish between the first and second regulators, the visual indicators may facilitate identification of the regulators on an assembly line during a production run or during re-work (i.e., repairing or rebuilding) of already-assembled engines so that the correct regulator is coupled to the engine. Therefore, costs relating to tooling, assembly line set-up changes, down time, and re-work of already-assembled engines to change-out crankshafts, camshafts, pistons, connecting rods, cylinder heads, or carburetors to change the power output of the engines may be reduced. 
     FIGS. 12-15  depict another construction of the present invention. Referring to  FIGS. 12-15 , intake manifold assembly  438  includes a main body  439  having an inlet  442  and an outlet  443 . Body  439  includes an intake passageway  450  defined by a wall  448 . 
   Intake assembly manifold assembly  438  also includes a regulator  462  that is disposed in a slot or aperture  466  (See  FIG. 13 ) formed within wall  464 . In this construction, regulator  462  has a substantially planar outer surface  463  as part of its exterior portion  474 , and an interior portion  470  having a fluid flow aperture  471  therein. Interior portion  470  is configured as a plate-like member in the depicted embodiment, although other constructions could be used. 
   As best shown in  FIGS. 12 and 15 , regulator  462  is retained by a coupling device that interconnects the exterior portion  474  of the regulator  462  to the intake manifold body  439 . The coupling device includes a post  435  having a ramped surface  434  attached to body  439 . Post  435  receives an aperture  430  of a resilient tab  426  that extends from exterior portion  474 , and more particularly from outer surface  463  of regulator  462 . As best shown in  FIGS. 14 and 15 , a seal  482  (such as an o-ring) is received in a groove  478  formed in the end or exterior portion  474  of regulator  462 . 
   The regulator  462  is retained in place by having its end  484  disposed within a slot or recess  485 , which in turn is formed in intake manifold body  439 . See  FIG. 15 . This configuration reduces the tolerance stack-up issues discussed above in connection with the construction of  FIGS. 8-11 . 
     FIG. 14  depicts a group or family  458  of regulators, each designed to achieve a different horsepower for the engine by varying the size of the effective fluid flow aperture  471  in the interior portion  470 . The larger the size of the aperture, the less restriction there is to fluid flow through intake passageway  450 . Conversely, the smaller the size of the aperture  471 , the greater the surface area of the solid portion of interior portions  470 , and consequently the greater the restriction to fluid flow through the intake passageway  450 . 
   Although reference is made to a fluid flow aperture as part of the interior portion, it is apparent that the aperture as shown is more accurately depicted as a cylinder in that it has a length in the direction of fluid flow. Of course, non-cylindrical apertures could also be used, such as conical or polygonal shaped-openings; in general, it is the total amount of restriction to fluid flow which determines the amount of regulation, not the particular shape or configuration of the aperture. 
   Referring again to  FIG. 14 , the group or family of regulators  462  is comprised of regulators  462   a  through  462   h . Each of these regulators  462   a  through  462   h  has respective interior portions  470   a  through  470   h . Each of the interior portions has formed therein a respective aperture  471   a  through  471   h . Each of the apertures  471   a  through  471   h  has a different size, as clearly shown in  FIG. 14 . Thus, each of the regulators  462   a  through  462   h  results in a different horsepower for the engine. 
   Various features of the invention are set forth in the following claims.