Intake manifold regulators for internal combustion engines

The present invention provides 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 fuel system configured to provide fuel to the combustion chamber, an intake passageway configured to provide a fluid to the combustion chamber, and a first regulator at least partially positioned in the intake passageway. 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.

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. The first regulator is selected such that the first engine operates at the first power output at the selected speed. 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. 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 fuel system configured to provide fuel to the combustion chamber, an intake passageway configured to provide a fluid (e.g., air, fuel, or an air/fuel mixture) to the combustion chamber, and a first regulator at least partially positioned in the intake passageway. 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, a regulator adapted to be received within an aperture near an intake passageway in an internal combustion engine. The regulator includes a first portion configured to be exposed to an airflow in the intake passageway and selected such that the engine operates at a first power output at a selected speed when the first portion is exposed to the airflow, and a second portion configured to be received within the aperture and removably coupled to the engine without disassembly of the intake passageway.

DETAILED DESCRIPTION

FIG. 1illustrates a small, air-cooled, four-stroke internal combustion engine10having a single cylinder12(seeFIG. 2a) and a vertically-oriented crankshaft or output shaft14. The engine10also includes a piston15coupled to the output shaft14by a connecting rod17for reciprocating movement in the cylinder12, and a combustion chamber16in fluid communication with the cylinder12. The engine10may 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 engine10may be supported by a mower deck and the output shaft14may be coupled to a blade positioned beneath the mower deck. It should be understood that alternative constructions of the engine10may also include multiple-cylinder configurations or a horizontal output shaft configuration.

With continued reference toFIG. 1, the engine10also includes a blower housing18for providing a cooling airflow over the external components of the engine10(e.g., an outer housing or engine housing22and a cylinder head26), an air cleaner30coupled to the blower housing18for providing a filtered airflow to the engine10, a fuel system including a carburetor34that receives the filtered airflow from the air cleaner30and adds fuel to the filtered airflow to create a fuel/air mixture, and an intake manifold38coupled to the carburetor34for delivering the fuel/air mixture to the cylinder head26. It should also be understood that the engine10may 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 engine10.

With reference toFIGS. 3 and 4, the intake manifold38includes an inlet42configured to receive the fuel/air mixture from the carburetor34, an outlet46configured to discharge the fuel/air mixture into the cylinder head26, an interior wall48, and an intake passageway50defined by the interior wall48, through which the fuel/air mixture passes, extending between the inlet42and the outlet46. With additional reference toFIG. 5, the intake passageway50has a non-linear longitudinal axis54, such that the fuel/air mixture passing through the intake passageway50travels a substantially arcuate flow path moving from the inlet42to the outlet46. Alternative constructions of the intake manifold38may include any of a number of different configurations, in which the longitudinal axis54of the intake passageway50is substantially arcuate or substantially straight or linear.

With reference toFIG. 3, a family or a group58of 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 engine10. In the illustrated construction of the engine10, any regulator from the group58may be coupled to the intake manifold38. Alternatively, any regulator from the group58may be positioned in an airflow passageway in the engine10upstream of the carburetor34. For example, any regulator from the group58may be positioned in an airflow passageway in the air cleaner30, or any regulator from the group58may be positioned in an airflow passageway between the air cleaner30and the carburetor34. As such, the term “intake passageway” should not be limited to the passageway through the intake manifold38, but rather should include any airflow passageway upstream of the carburetor34, or any fuel/air mixture passageway through the carburetor34or downstream of the carburetor34. Further, rather than selecting a single regulator from the group58, a combination of two or more regulators from the group58(or from other groups of regulators) may be positioned in an airflow passageway in the engine10upstream of the carburetor34or a fuel/airflow passageway in the engine10downstream of the carburetor34to achieve a desired decrease in power output by the engine10.

With reference toFIGS. 1 and 2a, the engine10is shown having one of the regulators62from the group58coupled to the intake manifold38. The engine10, therefore, is operable to achieve a first power output at a selected speed. With reference toFIG. 2b, a second engine10awhich may have—but need not have—substantially similar internal components as the first engine10, is shown. Specifically, the second engine10aincludes a second cylinder12athat may be substantially similar to the cylinder12, a second output shaft14athat may be substantially similar to the output shaft14, a second piston15athat may be substantially similar to the piston15, a second connecting rod17athat may be substantially similar to the connecting rod17, a second engine housing22athat may be substantially similar to the engine housing22, a second cylinder head26athat may be substantially similar to the cylinder head26, and a second air cleaner30athat may be substantially similar to the air cleaner30. Second fuel system or carburetor34ais preferably substantially similar to the carburetor34. Second intake manifold38amay be substantially similar to the intake manifold38. The second engine10a, however, utilizes a different regulator62afrom the group58than the engine10. The engine10a, therefore, is operable to achieve a second power output different from the first power output of the engine10at the same selected speed. As will be discussed in greater detail below, other components of the engine10a, such as the cylinder12a, the output shaft14a, the piston15a, the connecting rod17a, the engine housing22a, the cylinder head26a, the air cleaner30a, the carburetor34a, and the intake manifold38amay be changed, either individually or in combination, to achieve the second or another different power output.

With reference toFIG. 3, the intake manifold38includes a wall64defining an aperture66, positioned between the inlet42and the outlet46, exposed to the intake passageway50for receiving one regulator selected from the group58(see alsoFIG. 5). In the illustrated construction of the intake manifold38and group58of regulators, the aperture66is configured as a stepped aperture66for receiving different portions of the regulator. Each of the regulators in the group58includes an interior portion (e.g., interior portions70,70aof regulators62,62a) that is at least partially positioned within the intake passageway50, and a base or an exterior portion74that is external to the intake passageway50. As shown inFIG. 5, the exterior portion74includes a groove78extending around the outer periphery of the exterior portion74, in which a seal82(e.g., an O-ring) is received to seal against the wall64to inhibit outside air from leaking into the intake passageway50through the aperture66. Alternative constructions of the intake manifold38and the regulators may include stepped or non-stepped apertures and corresponding stepped or non-stepped surfaces on the regulators.

With reference toFIGS. 3 and 4, both the interior portions (e.g., interior portions70,70a) and the exterior portions74of the respective regulators have a generally cylindrical shape. Particularly, the interior portions (e.g., interior portions70,70a) of the respective regulators are configured as cylinders having a spherical or dome-shaped distal end84, a longitudinal axis86, a length dimension D1along the longitudinal axis86, and a width dimension D2transverse to the longitudinal axis86(seeFIG. 5). Because the interior portions are configured as cylinders having a curved outer surface (e.g., curved outer surface90of the regulator62), the width dimension D2is equal to the outer diameter of the interior portions70(see alsoFIG. 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 passageway50, configured as substantially flat plates oriented substantially transversely to the longitudinal axis54of the intake passageway50. 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 passageway50. Also, alternative constructions of the regulators may include substantially conical-shaped interior portions having a longitudinal axis generally aligned with the longitudinal axis54of the intake passageway50. 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 passageway50, not the shape of the regulator, which primarily determines the change in engine power output.

As shown inFIG. 3, the diameter or the width dimension D2of each of the interior portions (e.g., interior portions70,70a) of the respective regulators in the group58is substantially equal, while the length dimension D1(seeFIG. 5) of each of the interior portions of the respective regulators in the group58is different. Further, each of the exterior portions74of the respective regulators in the group58is substantially the same size. As such, any one of the regulators in the group58may be selected to be received within the stepped aperture66because the regulators share commonly-shaped exterior portions74, and interior portions (e.g., interior portions70,70a) may have a common width dimension D2that conform to the shape of the stepped aperture66. 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 toFIG. 5, one of the regulators (e.g. the regulator62) from the group58is selected to be received within the stepped aperture66. The interior portion70is oriented within the intake passageway50such that the longitudinal axis86of the interior portion70is substantially transverse to the longitudinal axis54of the intake passageway50. As a result, at least a portion of the air/fuel mixture passing through the intake passageway50must pass over the dome-shaped distal end84and the curved outer surface90of the interior portion70of the regulator62before being discharged from the outlet46of the intake manifold38.

In other words, the presence of the interior portion70of the regulator62in the intake passageway50effectively decreases the width or height of the intake passageway50, causing a localized restriction in the flow path of the air/fuel mixture as it passes from the inlet42to the outlet46. The spherical or dome-shaped distal ends84allow the regulators, particularly those in the group58having the longest length dimensions D1, to be positioned in close proximity to the interior wall48. By configuring the regulators in the group58with the spherical or dome-shaped distal ends84, as opposed to flat ends with sharp corners that disrupt flow, tighter control of the pressure drop over the interior portions (e.g., interior portions70,70aofFIG. 3) may be achieved. Tighter control of the power output of the engine (e.g., engines10,10ofFIGS. 2aand2b, 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 ends84because of the absence of sharp corners (which can disrupt flow) on the interior portions.

With reference toFIG. 6, a cross-section of the intake passageway50at a location upstream of the regulator62is shown. In the illustrated construction of the intake manifold38a,38b, the intake passageway50is configured with a substantially circular cross-sectional shape through a plane94positioned upstream of the regulator62and oriented substantially transversely to the longitudinal axis54of the intake passageway50. The substantially circular cross-sectional shape of the intake passageway50with respect to the plane94defines a cross-sectional open area A1. Alternative constructions of the intake manifold38a,38bmay include an intake passageway50having any of a number of different cross-sectional shapes.

FIG. 7illustrates a cross-section of the intake passageway50and regulator62, taken through a plane98containing the longitudinal axis86of the interior portion70and oriented substantially transversely to the longitudinal axis54of the intake passageway50. As discussed above, the presence of the interior portion70of the regulator62in the intake passageway50effectively decreases the cross-sectional open area A1of the intake passageway50. Specifically, the presence of the interior portion70of the regulator62in the intake passageway50defines a cross-sectional open area A2substantially less than the cross-sectional open area A1. In one combination of the intake manifold38and one of the regulators selected from the group58, the cross-sectional open area A2may be no more than about 60 percent of the cross-sectional open area A1. In another combination of the intake manifold38and one of the regulators selected from the group58, the cross-sectional open area A2may be between about 25 percent and about 85 percent of the cross-sectional open area A1.

With reference toFIGS. 3 and 4, a coupling device102may be utilized to secure one of the regulators selected from the group58to the intake manifold38and maintain the interior portion of the regulator (e.g., the interior portion70of the regulator62) in the intake passageway50. Particularly, in the construction of the intake manifold38and regulators ofFIGS. 3 and 4, the coupling device102includes a coupler or a finger106extending from the exterior portion74of the regulator62and a groove or slot110formed in the intake manifold38around the aperture66and configured to receive the finger106. In positioning the regulator62in the intake passageway50, the regulator62is oriented such that the finger106is aligned with an opening114that leads into the slot110, the regulator62is inserted through the aperture66, and the finger106is passed through the opening114and into the slot110. To secure the regulator62to the intake manifold38, the regulator62may be rotated about its longitudinal axis86, causing the finger106to move within the slot110away from the opening114. An abutment surface118at least partially defining the slot110, therefore, inhibits the unintentional removal of the regulator62from the intake manifold38without the required rotation of the regulator62to align the finger106with the opening114in the slot110.

With reference toFIG. 8, another construction of a regulator162with another construction of a coupling device122is shown, with like features and components having like reference numerals. The coupling device122includes a coupler or a resilient tab126, having an abutment surface128, extending from the exterior portion74of the regulator162, and an abutment surface130on the intake manifold38configured to be engaged by the abutment surface128of the resilient tab126to inhibit unintentional removal of the regulator162from the aperture66. In positioning the regulator162in the intake passageway50, the regulator162is oriented such that the resilient tab126is aligned with the abutment surface130and the regulator162is inserted through the aperture66. To secure the regulator162to the intake manifold38, continued insertion of the regulator162causes the resilient tab126to deflect by sliding contact between a ramp surface134on the resilient tab126and an engagement surface138on the intake manifold38. When the regulator162is fully inserted into the stepped aperture66, the resilient tab126snaps back to its undeflected shape, such that mutual abutment of the surfaces128,130on the resilient tab126and the intake manifold38inhibit unintentional removal of the regulator162from the intake manifold38.

With respect toFIG. 9, yet another construction of a regulator262with another construction of a coupling device142is shown for securing the regulator262to the intake manifold38, with like features and components having like reference numerals. The coupling device142includes an insert146coupled to the intake manifold38, a coupler or a mounting flange150extending from the exterior portion74of the regulator262, and a fastener154(e.g., a bolt or screw) inserted through an aperture158in the mounting flange150to threadably engage the insert146in the intake manifold38. Therefore, threading the fastener154into the insert146to some predetermined torque value inhibits unintentional removal of the regulator262from the intake manifold38. In the illustrated construction of the coupling device142inFIG. 9, the insert146is molded into the intake manifold38. In an alternative construction of the coupling device142, the insert146may be omitted such that the fastener154is threaded directly into a threaded aperture or bore in the intake manifold38.

Alternatively, the coupling devices102,122,142may be omitted, and an interference fit between the exterior portion74and/or the interior portion70of the regulator62,162, or262and the stepped aperture66may be utilized to maintain the interior portion70of the regulator62,162, or262in the intake passageway50. As a further alternative, the O-ring82may provide the interference fit with the stepped aperture66, such that the coupling devices102,122,142may be omitted.

With reference toFIGS. 10 and 11, another construction of an intake manifold338and a regulator362is shown. The intake manifold338is similar to the intake manifold38ofFIGS. 3-7, with like features having like reference numerals. The regulator362includes an interior portion370that is at least partially positioned within the intake passageway50, and an exterior portion374that is external to the intake passageway50. The exterior portion374includes a groove378extending around the outer periphery of the exterior portion374, in which a seal382(e.g., an O-ring, seeFIG. 11) is received to seal against a wall364of the intake manifold338to inhibit outside air from leaking into the intake passageway50through a non-stepped aperture366defined by the wall364. The groove378and seal382also separates the interior portion370from the exterior portion374of the regulator362. Although the regulator362is illustrated with a portion of the coupling device102(i.e., the finger106), the regulator362may be configured to utilize any of the coupling devices122,142illustrated inFIGS. 8 and 9, respectively.

With continued reference toFIGS. 10 and 11, the regulator362includes an axial locating post368extending from a spherical or dome-shaped end384of the interior portion370. The post368includes a substantially flat distal end370that is engageable with the interior wall48of the intake manifold338(seeFIG. 11). The post368has a length dimension D3that, when the regulator362is inserted through the aperture366, determines how much of the interior portion370is exposed to the air/fuel mixture in the intake passageway50. Like the family or group58of regulators illustrated inFIG. 3, the regulator362may be one of a family or group of regulators having axial locating posts of different length dimensions D3to provide different amounts of restriction within the intake passageway50.

By providing the axial locating post368, rather than a combination of differently-sized bases or exterior portions (e.g., exterior portions74inFIG. 3) and interior portions (e.g., interior portions70,70ainFIG. 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 A2ofFIG. 7) is affected by a single value—the tolerance of the length dimension D3of the axial locating post368—rather than multiple values (e.g., the length dimension D1of the interior portion70inFIG. 5, the counter-bore depth of the stepped aperture66inFIG. 5, and the location of the shoulder between the interior and exterior portions70,74inFIG. 5). As a result, tighter and more precise control of the power output of the engine (e.g., the engines10,10aofFIGS. 2aand2b, respectively) may be achieved.

With reference toFIG. 3, the regulators in the family or group58may be sized to decrease the net horsepower of the unrestricted engine10between about 5 percent and about 25 percent or more. Such a reduction in the power output of the engine10is a function of the exposed area (i.e., the portion of the regulator62that comes into contact with the airflow or fuel/air mixture) of the regulator62in the intake passageway50—i.e., as the length dimension D1increases, the cross-sectional open area A2(seeFIG. 7) decreases, thus restricting the amount of fuel/air mixture that can be effectively consumed by the engine10during operation. Such a reduction in power output may be achieved without any modifications to the calibration of the carburetor34or 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 carburetor34would be necessary to achieve the resultant decreases in power output for each engine-regulator combination.

With reference toFIG. 3, one regulator from the group58may be selected to achieve a power output of the engine10that is less than the unrestricted power output of the engine10. In deciding which of the regulators in the group58to select, the unrestricted power output of the engine10is determined, and a desired or a restricted power output is determined. Then, knowing the horsepower drop caused by each of the regulators in the group58from empirical testing performed on an engine having the same configuration as the engine10, a particular regulator may be selected to achieve the desired power output of the engine10, without altering or changing the fuel calibration of the carburetor34and without changing the engine castings. It is also desirable to use the same configuration of the engine housing22. While the same configurations of pistons15, connecting rods17, crankshafts14, 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 engine10.

Another method or process of using the family or group58of regulators with the engine10includes measuring the power output of the engine10using a first regulator from the group58. If the measured power output of the restricted engine10does not match a desired power output, then the first regulator may be removed from the intake manifold38without disassembling the engine10or removing the intake manifold38from the cylinder head26or the carburetor34. A second regulator from the group58may then be chosen to replace the first regulator in the intake manifold38. This method or process of using the group58of regulators reduces the repair time or the rebuild time necessary for changing the power output of the engine10. Rather than changing internal components of the engine10(e.g., the crankshaft14, the piston15, the connecting rod17, the valve train, the camshaft, the cylinder head26, etc.) to change the power output of the engine10, which often requires a relatively large amount of time, the existing regulator in the engine10may be replaced with another regulator from the group58to change the power output of the engine10.

As used herein, “disassembly of the intake passageway” includes removing or disconnecting any component forming a portion of the intake passageway, including the carburetor34and the intake manifold38. In other words, the first regulator may be removed and replaced by the second regulator merely by disconnecting the coupling device102,122, or142, removing the first regulator from the aperture66along the longitudinal axis86of the first regulator, inserting the second regulator into the aperture66along the longitudinal axis86of the second regulator, and re-connecting the coupling device102,122, or142. These steps to exchange the first regulator for the second regulator may occur without removing or disconnecting the carburetor34or the intake manifold38, for example, from the engine10.

These processes may be used to manufacture engines10, each having a distinct desired power output, selectable from a range of power outputs available from installing one of the regulators in the group58, from a common engine configuration utilizing the intake manifold38and the same fuel calibration in the carburetor34. For example, first and second production runs of engines10, including substantially identical engine housings22, output shafts14, cylinders12, pistons15, combustion chambers16, carburetors34, and intake manifolds38, 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 engines10. Also, an existing production run of engines10incorporating one of the regulators from the group58may be re-worked to remove the existing regulators from the engines10, which allowed the engines10to generate the first power output at the selected speed, and replace them with differently-sized regulators, which would allow the engines10to 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 group58to 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. 12-15depict another construction of the present invention. Referring toFIGS. 12-15, intake manifold assembly438includes a main body439having an inlet442and an outlet443. Body439includes an intake passageway450defined by a wall448.

Intake assembly manifold assembly438also includes a regulator462that is disposed in a slot or aperture466(SeeFIG. 13) formed within wall464. In this construction, regulator462has a substantially planar outer surface463as part of its exterior portion474, and an interior portion470having a fluid flow aperture471therein. Interior portion470is configured as a plate-like member in the depicted embodiment, although other constructions could be used.

As best shown inFIGS. 12 and 15, regulator462is retained by a coupling device that interconnects the exterior portion474of the regulator462to the intake manifold body439. The coupling device includes a post435having a ramped surface434attached to body439. Post435receives an aperture430of a resilient tab426that extends from exterior portion474, and more particularly from outer surface463of regulator462. As best shown inFIGS. 14 and 15, a seal482(such as an O-ring) is received in a groove478formed in the end or exterior portion474of regulator462.

The regulator462is retained in place by having its end484disposed within a slot or recess485, which in turn is formed in intake manifold body439. SeeFIG. 15. This configuration reduces the tolerance stack-up issues discussed above in connection with the construction ofFIGS. 8-11.

FIG. 14depicts a group or family458of regulators, each designed to achieve a different horsepower for the engine by varying the size of the effective fluid flow aperture471in the interior portion470. The larger the size of the aperture, the less restriction there is to fluid flow through intake passageway450. Conversely, the smaller the size of the aperture471, the greater the surface area of the solid portion of interior portions470, and consequently the greater the restriction to fluid flow through the intake passageway450.

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 toFIG. 14, the group or family of regulators462is comprised of regulators462athrough462h. Each of these regulators462athrough462hhas respective interior portions470athrough470h. Each of the interior portions has formed therein a respective aperture471athrough471h. Each of the apertures471athrough471hhas a different size, as clearly shown inFIG. 14. Thus, each of the regulators462athrough463hresults in a different horsepower for the engine.