Engine with closely-coupled catalyst

Abstract

An engine assembly includes an engine block including a first cylinder and an exhaust outlet, a crankshaft extending from the engine block and defining a crankshaft axis, a blower assembly coupled to the engine block and configured to provide cooling air to the engine block, and an exhaust assembly. The exhaust assembly includes a catalytic converter assembly coupled to the exhaust outlet, and a muffler arranged downstream of the catalytic converter assembly. The catalytic converter assembly includes a catalytic converter body that defines a converter axis, and the muffler defines a muffler axis that is parallel to the converter axis.

Description

ENGINE WITH CLOSELY-COUPLED CATALYSTBACKGROUND

[0001] Small air-cooled internal combustion engines are typically installed on chore products or outdoor power equipment to power various implements (e.g., pumps, blades, augers, wheels, etc.).SUMMARY

[0002] At least one embodiment relates to an engine assembly that includes an engine block having a first cylinder and an exhaust outlet, a crankshaft extending from the engine block and defining a crankshaft axis, a blower assembly coupled to the engine block and configured to provide cooling air to the engine block, and an exhaust assembly. The exhaust assembly includes a catalytic converter assembly coupled to the exhaust outlet, and a muffler arranged downstream of the catalytic converter assembly. The catalytic converter assembly includes a catalytic converter body that defines a converter axis, and the muffler defines a muffler axis that is parallel to the converter axis.

[0003] At least one embodiment relates to an engine assembly that includes an engine block having a first cylinder and an exhaust outlet, a crankshaft extending from the engine block and defining a crankshaft axis, a blower assembly coupled to the engine block and configured to provide cooling air to the engine block, and an exhaust assembly. The exhaust assembly includes a catalytic converter assembly coupled to the exhaust outlet, and a muffler coupled to the catalytic converter body and defining a muffler axis. The catalytic converter assembly includes a catalytic converter body that defines a converter axis, and the muffler axis is arranged closer to the crankshaft axis than the converter axis.

[0004] At least one embodiment relates to outdoor power equipment that includes a frame, an exhaust chamber, and an engine assembly supported on the frame. The engine assembly includes an engine block having a first cylinder and an exhaust outlet, a crankshaft extending from the engine block and defining a crankshaft axis, a blower assembly coupled to the engine block and configured to provide cooling air to the engine block, and an exhaust assembly arranged within the exhaust chamber. The exhaust assembly includes a catalytic converter assembly coupled to the exhaust outlet, and a muffler arranged downstream of the catalytic converter assembly. The catalytic converter assembly includesa catalytic converter body that defines a converter axis, and the muffler defines a muffler axis that is parallel to the converter axis.|0005] This summary is illustrative only and is not intended to be in any way limiting. Other aspects, inventive features, and advantages of the devices or processes described herein will become apparent in the detailed description set forth herein, taken in conjunction with the accompanying figures, wherein like reference numerals refer to like elements.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The disclosure will become more fully understood from the following detailed description, taken in conjunction with the accompanying figures, wherein like reference numerals refer to like elements, in which.|0007] FIG. 1 is a perspective view of an engine assembly including a vertical-shaft engine, according to some embodiments.

[0008] FIG. 2 is a rear view of the engine assembly of FIG. 1.|0009] FIG. 3 is a side view of the engine assembly of FIG. 1.10010] FIG. 4 is a perspective view of a catalytic converter assembly, according to an exemplary embodiment.

[0011] FIG. 5 is a top view of the catalytic converter assembly of FIG. 4.

[0012] FIG. 6 is a side view of the catalytic converter assembly of FIG. 4.

[0013] FIG. 7 is a rear view of the catalytic converter assembly of FIG. 4.

[0014] FIG. 8 is a perspective wireframe view of the catalytic converter assembly of FIG. 4.

[0015] FIG. 9 is a top wireframe view of the catalytic converter assembly of FIG. 4

[0016] FIG. 10 is a perspective view of an engine assembly including the engine of FIG. 1 and the catalytic converter assembly of FIG. 4, according to an exemplary embodiment.

[0017] FIG. 11 is a rear view of the engine assembly of FIG. 10.

[0018] FIG. 12 is a side view of the engine assembly of FIG. 10.

[0019] FIG. 13 is a partial rear view of a zero-turn radius lawnmower frame including the engine assembly of FIG. 1, according to an exemplary embodiment.(0020] FIG. 14 is a partial side section view of the zero-turn radius lawnmower frame of FIG. 13.|0021] FIG. 15 is a partial top view of the zero-turn radius lawnmower frame of FIG. 13.1 022] FIG. 16 is a partial rear view of a zero-turn radius lawnmower frame including the engine assembly of FIG. 10, according to an exemplary embodiment.

[0023] FIG. 17 is a partial side section view of the zero-turn radius lawnmower frame of FIG. 16.

[0024] FIG. 18 is a partial top view of the zero-turn radius lawnmower frame of FIG. 16.[00251 FIG. 19 is a perspective view of an engine assembly including a horizontal-shaft engine, according to an exemplary embodiment.

[0026] FIG. 20 is a side view of the engine assembly of FIG. 19.

[0027] FIG. 21 is a front view of the engine assembly of FIG. 19.

[0028] FIG. 22 is a perspective view of an engine assembly including the horizontal-shaft engine of FIG. 19 and the catalytic converter assembly of FIG. 4, according to an exemplary embodiment.|0029] FIG. 23 is a side view of the engine assembly of FIG. 22.|0030] FIG. 24 is a front view of the engine assembly of FIG. 22.

[0031] FIG. 25 is a perspective view of a catalytic converter assembly, according to an exemplary embodiment.10032] FIG. 26 is a top view of the catalytic converter assembly of FIG. 25.10033] FIG. 27 is a rear view of the catalytic converter assembly of FIG. 25.

[0034] FIG. 28 is a side view of the catalytic converter assembly of FIG. 25.

[0035] FIG. 29 is a perspective wireframe view of the catalytic converter assembly of FIG. 25.

[0036] FIG. 30 is a perspective view an engine assembly with the catalytic converter assembly of FIG. 25 coupled to an engine, according to an exemplary embodiment.10037] FIG. 31 is a rear view of the engine assembly of FIG. 30.|0038] FIG. 32 is a side view of the engine assembly of FIG. 30.

[0039] FIG. 33 is a side view a zero-turn radius lawnmower frame including the engine assembly of FIG. 30, according to an exemplary embodiment.

[0040] FIG. 34 is a side view of the zero-turn radius lawnmower frame and the engine assembly of FIG. 33, where the zero-turn lawnmower frame is transparent.[0041 [ FIG. 35 is a rear view of the zero-turn radius lawnmower frame and the engine assembly of FIG. 33, where the zero-turn lawnmower frame is transparent.[0042| FIG. 36 is a top view of the zero-turn radius lawnmower frame and the engine assembly of FIG. 33, where the zero-turn lawnmower frame is transparent.

[0043] FIG. 37 is a cross-sectional view the zero-turn radius lawnmower frame and the engine assembly of FIG. 33, taken along line 37-37 in FIG. 36.DETAILED DESCRIPTION10044] Before turning to the figures, which illustrate the exemplary embodiments in detail, it should be understood that the application is not limited to the details or methodology set forth in the description or illustrated in the figures. It should also be understood that the terminology is for the purpose of description only and should not be regarded as limiting.[0045| The use herein of the term “axial” and variations thereof refers to a direction that extends generally along an axis of symmetry, a central axis, or an elongate direction of a particular component or system. For example, axially extending features of a componentmay be features that extend generally along a direction that is parallel to an axis of symmetry or an elongate direction of that component.10046] The use of the terms “downstream” and “upstream” herein are terms that indicate direction relative to the flow of a fluid. The term “downstream” corresponds to the direction of fluid flow, while the term “upstream” refers to the direction opposite or against the direction of fluid flow.[0047| Referring to the figures generally, the engines and engine assemblies described herein may be used in chore products, including outdoor power equipment, standby generators, portable jobsite equipment, or other appropriate uses. Outdoor power equipment may include lawn mowers, riding tractors, snow throwers, pressure washers, portable generators, tillers, log splitters, zero-turn radius mowers, walk-behind mowers, wide-area walk-behind mowers, riding mowers, standing mowers, industrial vehicles such as forklifts, utility vehicles, etc. Outdoor power equipment may, for example, use an internal combustion engine to drive an implement, such as a rotary blade of a lawn mower, a pump of a pressure washer, an auger of a snow thrower, the alternator of a generator, and / or a drivetrain of the outdoor power equipment. Portable jobsite equipment includes portable light towers, mobile industrial heaters, and portable light stands.

[0048] A “chore product” as used herein refers to any type of equipment, machine, or vehicle that may be used to perform a chore (e.g., an outdoor chore, an indoor chore, lawn care, etc.). For example, a chore product may include a motor, a pump, an actuator, a compressor, and / or another device that is electrically powered to operate some function of the chore product to facilitate performing a chore. In some embodiments, a chore is a task performed, either by a user or autonomously, at or near a household, a farm, an agricultural facility, a building, a sidewalk, a park, a parking lot, a forest, a field, and / or a lawn. In some embodiments, a chore product transports an operator and performs a chore. In some embodiments, a chore product autonomously operates to perform a chore without an operator being present on the chore product or physically / manually manipulating the chore product.(0049] Small engines may include cooling systems. Common cooling system configurations for small engines include air cooling. An air-cooled system generally includes a blower system having a blower housing and a fan within the blower housing.Each of the cylinders of the engine includes fins, which increase the surface area of the cylinders to maximize the heat transfer from the cylinder to the surrounding air. A fan blows the air surrounding the cylinders to remove heat from the engine.

[0050] Different government regulatory bodies have emissions standards for small engines. Federal agencies, such as the Environmental Protection Agency (EP A) have emission standards for small engines, limiting the hydrocarbon (HC) and nitrogen oxides (NOx) amounts that an engine can emit into the environment. Other regulatory bodies also set forth emissions standards. California, which has one of the largest state populations in the United States of America, sets its own regulations, which have often been stricter than those set forth by the EPA. The California Air Resource Board (“CARB”) provides regulations for small off-road engines, which it defines as spark-ignition engines rated at or below 19 kilowatts (25.4794 horsepower) (“SORE”). Often, small engines are able to meet the applicable emissions standards without the use of catalytic converters. Larger engines (e.g., automotive engines) are similarly regulated by government regulatory bodies and have stricter emissions standards, requiring, for example, that engine emissions are reduced by 99%. To meet these emission requirements, catalytic converters are typically used in larger engines. Catalytic converters may be included in the exhaust system of an engine to reduce toxic gases and pollutants (e.g., hydrocarbons and nitrogen oxides) produced by combustion and found within the exhaust of the engine.[0051 [ The use of a catalytic converter on a small engine reduces certain emissions. If used, for example, a catalytic converter may reduce the emissions of a small engine by 70- 90%. It would be advantageous for engine manufacturers to use a catalytic converter that is cost-effective to manufacture and can be installed in the exhaust system of existing small engine models with no or limited redesign of those engine models to enable manufacturing of the updated engines with catalytic converters.[0052 [ Typically, a catalytic converter includes a substrate and a catalyst. The substrate creates a structure (e.g., a honeycomb structure) having an increased surface area compared to the cross-section of the catalytic converter. The substrate is typically constructed from a ceramic or metal material. The catalyst is then disposed on the substrate. A catalytic converter may further include a washcoat to further increase the surface area of the catalytic converter. The washcoat may be made from a material (e.g., aluminum oxide, titaniumoxide, silicon dioxide, a silica and / or alumina mixture, etc.) that can form a rough coating on the substrate. The catalyst is suspended in the washcoat, and then the mixture is applied to the substrate. An engine produces exhaust gases (e.g., nitrogen oxides (N0x), carbon monoxide (CO), and hydrocarbons (HC)) during combustion. The exhaust gases flow through the catalytic converter, the catalyst causes the exhaust gases to undergo chemical reactions (e.g., oxidation and reduction reactions). The reactions convert the exhaust gases to products that are less harmful to the environment (e.g., nitrogen (N2), carbon dioxide (CO2), water (H2O), etc.) which are emitted from the catalytic converter. A three-way catalytic converter (TWC) has three simultaneous reactions occurring. A TWC reduces nitrogen oxides (NOx) to nitrogen (N2), oxidizes carbon monoxide (CO) to carbon dioxide (CO2), and oxidizes unburnt hydrocarbons (HC) to carbon dioxide (CO2) and water (H2O). Precious metals, such as platinum, palladium, iridium, and rhodium are typical catalysts used in a catalytic converter. Ruthenium-based or primarily ruthenium catalysts may also be used. Platinum, palladium, iridium, and rhodium each actively react with exhaust gases and produce a cleaner exhaust. Platinum, palladium, iridium, and rhodium also remain stable in a variety of engine operation conditions (e.g., rich and lean conditions). Other metals, such as cerium, iron, manganese, nickel, and copper can also be used as a catalyst. Some catalytic converters use combinations of different metals.[00531 Referring to the FIGURES generally, described herein are small engine assemblies with integrated catalytic converters. The catalytic converters may be directly coupled to and positioned adjacent the engine. The engine may be a small air-cooled engine that may be used in outdoor power equipment. Because the catalytic converter is integrated with and closely coupled to the engine, the outdoor power equipment may not require a separate exhaust system. The engine may replace an existing engine in outdoor power equipment that does not include a catalytic converter, which may reduce harmful emissions from the outdoor power equipment.|0054J Referring to FIGS. 1-3, an engine assembly 10 is shown according to an exemplary embodiment. The engine assembly 10 may include an engine 12, which may be a conventional air-cooled small engine 12. The engine 12 includes pistons moveable within cylinders 13 formed in an engine block 17 along a cylinder axis. The reciprocating motion of the pistons rotates a crankshaft 14 about a crankshaft axis 16 (see FIG. 3). In the illustrated embodiment, the engine 12 is a vertical-shaft configuration with the crankshaft14 extending along a vertical direction (e.g., up and down from the perspective of FIG. 3). In some embodiments, the engine 12 may be in a horizontal-shaft configuration, as described herein. A flywheel 18 is coupled to the crankshaft 14 and is positioned near the top of the engine 12, above the engine block 17. The engine 12 may include two cylinders 13 arranged in a V-twin configuration. However, a broad range of engines may benefit from the teachings disclosed herein. For example, the engine may include a single cylinder or three or more cylinders in any of a number of different configurations (e.g., inline, horizontally opposed, etc.), or may have a two-stroke cycle. The engine 12 may be configured to power a broad range of equipment, including walk-behind lawn mowers, zero-turn radius mowers, lawn tractors, pressure washers, electric generators, snow throwers, and other outdoor power equipment.

[0055] The engine 12 further includes a blower assembly 19 configured to direct air to the engine block 17 to cool the engine 12 by removing waste heat from the engine block 17. The blower assembly 19 includes a blower housing 20 (e.g., engine cover, engine shroud, etc.) coupled to the top of the engine 12. The blower housing 20 includes a central portion 22 including an opening 24 through which the air passes to the engine block 17. According to an exemplary embodiment, the blower housing 20 is configured for use with the engine 12 having a V-twin arrangement and may be shaped to generally conform with the shape of the engine block 17. The central portion 22 is aligned with the crankshaft 14. The blower housing 20 may therefore further include two angled arms 25 extending outward from the central portion 22 that are generally aligned with the cylinders of the engine 12.Alternatively, for a single-cylinder engine, the blower housing 20 may include a single arm 25.

[0056] The blower assembly 19 may be an active system with components that draw air in through a static cover 30 and the blower housing 20 to cool the engine 12 (e.g., provide cooling to the cylinders 13 and / or the engine block 17). The blower assembly 19 may include a blower fan, shown as a centrifugal fan 26 coupled to the flywheel 18. The centrifugal fan 26 rotates about the crankshaft axis 16, like the flywheel 18. The centrifugal fan 26 includes a multitude of fan blades configured to discharge a cooling airflow through an airspace defined between the engine block 17 and the blower housing 20. The fan blades each include an inner or leading edge defining a central inlet through which axially directed air is drawn. The cooling airflow is discharged from the centrifugal fan 26 in a radiallyoutward direction past the trailing edges of the respective fan blades and into the airspace between the engine block 17 and the blower housing 20.|0057] The engine assembly 10 may include a muffler 32 that is directly coupled to the exhaust outlets 34 of the engine 12 by two inlet pipes 36. Each exhaust outlet 34 may output exhaust from one of the two cylinders 13. The muffler 32 may have an muffler body 38 with a longitudinal axis 33 that is substantially perpendicular to a plane containing the crankshaft axis 16 of the crankshaft 14. The muffler 32 may be positioned near the bottom of the engine 12 and to one side of the engine 12. The muffler 32 may be somewhat spaced apart from the engine 12, which may improve heat dissipation. For example, an air gap is positioned between the muffler 32 and the engine block 17, which aids in preventing heat transfer between the engine block 17 and the muffler 32. The muffler 32 may reduce noise generated by the engine 12, as exhaust gases enter the muffler 32 via the inlet pipes 36, pass through the muffler body 38, and are output via the exhaust port 40.10058] Referring now to FIGS. 4-9, a catalytic converter assembly 100 is shown, according to some embodiments. The catalytic converter assembly 100 includes a catalytic converter body 102 including an inlet 104 and an outlet 106. The inlet 104 is coupled to two exhaust ports 108, 110 via a first exhaust pipe 112 and a second exhaust pipe 114, respectively, that merge into a combined exhaust pipe 116 that is directly coupled to the inlet 104 and delivers exhaust gas to the inlet 104. In some embodiments, the engine block 17 may include only one cylinder 13, and the catalytic converter assembly 100 may include a single exhaust pipe (e.g., only the first exhaust pipe 112 or only the second exhaust pipe 114), which may be connected directly to the inlet 104 of the catalytic converter body 102. The ends of the two exhaust pipes 112, 114 may each be coupled (e.g., welded, bolted, integrally formed with, etc.) with a mounting bracket 118. Each mounting bracket 118 may include one or more openings 120 through which a fastener may be inserted to couple the exhaust ports 108, 110 to an engine block. The engine block may include mounting features matching the openings 120 to which the fasteners may be coupled. The outlet 106 of the catalytic converter body 102 may be coupled to an outlet pipe 122 with an outlet port 124 configured to output catalyzed exhaust gases. The end of the outlet pipe 122 may be coupled to another mounting bracket 118, which may couple the outlet pipe to a muffler.

[0059] The catalytic converter assembly 100 may include an oxygen sensor 126 coupled to and extending into the combined exhaust pipe 116 upstream of the inlet 104 of the catalytic converter body 102. The oxygen sensor 126 may be configured to measure the oxygen concentration of the exhaust upstream of the catalytic converter assembly 100. The oxygen sensor 126 may be coupled to a cable 128 containing one or more wires, which may carry signals from the oxygen sensor 126. The wires may be coupled to an adapter or connector 130, which may be coupled to a corresponding adapter on the engine or a CAN network, allowing for an electrical and communicative connection between the oxygen sensor 126 and an engine control unit of the engine.[00601 In use, the catalytic converter assembly 100 is configured to receive exhaust from the cylinders of the engine via the exhaust ports 108, 110. For example, the engine may include two cylinders, and each exhaust port 108, 110 may be configured to receive the exhaust from one of the cylinders. The exhaust may travel through the exhaust pipes 112, 114, 116 to the inlet 104 of the catalytic converter body 102. The catalytic converter body 102 may include catalyst, such as platinum, palladium, iridium, ruthenium and / or rhodium catalysts, positioned on a substrate. As the exhaust passes through the substrate, hydrocarbons, carbon monoxide, and nitrogen oxides may be converted to less harmful gases, such as carbon dioxide, nitrogen gas, and water due to their interaction with the catalyst. After passing through the catalytic converter body 102 and undergoing these chemical reactions, the resulting gas may be referred to as catalyzed exhaust. The catalyzed exhaust may be output via the outlet 106 of the catalytic converter body 102 and travel through the outlet pipe 122 and out of the outlet port 124 to the muffler. The direction of flow through the catalytic converter body 102 (e.g., from the inlet 104 to the outlet 106) may define a longitudinal axis of the catalytic converter body 102. As shown in FIGS. 8 and 9, the catalytic converter body 102 may include a heat shield 132 surrounding and spaced apart from an inner chamber 134 containing the substrate and catalyst. The oxygen sensor 126 may measure the oxygen content of the exhaust gases in the combined exhaust pipe 116, and signals from the oxygen sensor 126 may be transmitted via the cable 128 and connector 130 to the engine control unit. The engine control unit may use the measurements from the oxygen sensor 126 to control the supply of fuel or air to the engine.

[0061] Referring now to FIGS. 10-12, an engine assembly 300 including the catalytic converter assembly 100 is shown, according to an exemplary embodiment. The engineassembly 300 may include the engine 12 shown and described with respect to FIGS. 1-3 but with the catalytic converter assembly 100 integrated into the engine 12; however, the muffler 32 may not be directly coupled to the engine 12. Instead, the catalytic converter assembly 100 may be directly coupled to the engine 12 (e.g., to the engine block 17), and the muffler 32 may be coupled to the catalytic converter assembly 100. For example, the catalytic converter assembly 100 may be arranged upstream of the muffler 32, such that exhaust gases from the engine 12 flow through the catalytic converter assembly 100 to the muffler 32 rather than directly from the engine 12 to the muffler 32. In some embodiments, the catalytic converter assembly 100 and the muffler 32 may combine to form an exhaust assembly that is coupled to the exhaust outlets 34 of the engine 12. In some embodiments, the muffler 32 may be coupled to the engine block 17 only through the catalytic converter assembly 100, such that the muffler 32 does not come into direct contact with the engine block 17. As discussed above with respect to FIGS. 4-9, the exhaust pipes 112, 114 of the catalytic converter assembly 100 may be coupled (e.g., directly coupled) to the exhaust outlets 34 of the engine block 17, such that the exhaust ports 108, 110 receive exhaust gases from respective cylinders 13. The catalytic converter assembly 100 may be coupled to the engine block 17 in the same way and in the same location that the muffler 32 is coupled to the engine in the engine assembly 10 of FIGS. 1-2. After the exhaust gases pass through the catalytic converter body 102, the catalyzed exhaust may be output via the outlet pipe 122 to the muffler 32. As discussed above, a mounting bracket 118 may be coupled to the muffler 32 to couple the outlet pipe 122 to the muffler 32 (e.g., to a muffler inlet 212). The outlet pipe 122 and the muffler inlet 212 may be coupled to the muffler 32 on substantially the opposite side of the muffler body 38 from the exhaust port 40, such that catalyzed exhaust travels substantially the entire length of the muffler body 38 through the muffler 32 and is expelled from the muffler exhaust port.10062] The catalytic converter body 102 may be positioned near the bottom of the engine 12 and to one side of the engine 12. It should be noted that the engine assembly 300 is shown in FIGS. 10-12 in its ordinary operating orientation, with the crankshaft 14 extending downward from the engine block 17 (e.g., a vertical crankshaft or PTO shaft orientation). The catalytic converter body 102 may be oriented such that the direction of flow of gases through the catalytic converter body 102 (e.g., a longitudinal or converter axis 103 of the catalytic converter body 102) is substantially parallel to a longitudinal or muffler axis 33 of a cylindrical body of the muffler 32. Further, the catalytic converter body 102 may bepositioned close to the engine block 17. For example, the diameter of the heat shield 132 may be larger than the distance from the heat shield 132 to the engine block 17, as can be seen in FIG. 12. The muffler 32 may be positioned in substantially the same spatial position as the muffler 32 (e.g., relative to the engine block 17) in the engine assembly 10 shown in FIGS. 1-3, near the bottom of the engine and off to one side. In some embodiments, the muffler 32 may be moved downward and towards the crankshaft axis 16 to accommodate the catalytic converter assembly 100. The catalytic converter body 102 may be positioned adjacent to the muffler 32, in a position higher than the muffler 32 (e.g., when the engine 12 is arranged such that the crankshaft 14 extends downward from the engine block 17, as shown) and farther from the crankshaft axis 16 of the crankshaft 14 than the muffler 32. For example, the longitudinal axis 103 of the catalytic converter body 102 is arranged vertically above the longitudinal axis 33 of the muffler 32 (e.g., in a direction parallel the crankshaft axis 16), and the longitudinal axis 33 of the muffler 32 is arranged closer than the longitudinal axis 103 of the catalytic converter body 102 to the crankshaft axis 16 of the crankshaft 14 (see FIG. 12). The engine 12 defines a cylinder plane P that is arranged perpendicular to the crankshaft axis 16 and includes a cylinder axis defined along a centerline of at least one of the cylinders 13. With specific reference to FIG. 12, the longitudinal axis 103 of the catalytic converter body 102 is arranged between the cylinder plane P and the longitudinal axis 33 of the muffler 32.

[0063] The arrangement of the catalytic converter assembly 100 and the muffler 32 allows for the catalytic converter assembly 100 to be integrated in an engine assembly without a catalytic converter (e.g., the engine assembly 10 or another existing engine assembly that did not conventionally include a catalytic converter) without requiring a larger mounting envelope for to accommodate the additional of the catalytic converter. For example, the engine assembly 300 may occupy substantially the same amount of space as the engine assembly 10 so that the engine assembly 300 can be utilized in a chore product that is configured to include the engine assembly 10. For example, the engine assembly 300 may have substantially the same mounting or installation volume, when measured at the largest outer width, length, and height of the engine assembly 300, as the engine assembly 10. Stated another way, the engine assembly 300 may have substantially the same outermost width, length, and height as the engine assembly 10. This may allow chore products that can be assembled interchangeably with the engine assembly 10 or the engine assembly 300 without having to modify the design of the core product to interface with either engineassembly 10, 300. So, for example, where stricter emissions standards are in place (e.g., in California), a chore product may be assembled and sold including the engine assembly 300, while in other locations with less strict emissions standards, the chore product may include the engine assembly 10. However, in either case, the other components of the chore product (e.g., the chassis / frame and blades of a zero-turn radius (ZTR) lawnmower) may not need to be modified to interface with either engine assembly 10, 300. In some embodiments, the engine assembly 300 and the engine assembly 10 may be referred to as different configurations of an engine assembly. In a first configuration (e.g., corresponding to the engine assembly 10), the engine assembly may not include the catalytic converter assembly 100. In a second configuration (e.g., corresponding to the engine assembly 300), the engine assembly may include the catalytic converter assembly 100.

[0064] Referring now to FIGS. 13-15, a portion of a ZTR lawnmower 400 is shown, which incorporates the engine assembly 10 (e.g., without the catalytic converter assembly 100). The ZTR lawnmower 400 includes a chassis or frame 401 and an exhaust chamber 402 that surrounds the lower portion of the engine 12 and the muffler 32. In general, the engine 12 is supported on the chassis 12. The exhaust chamber 402 includes a rear opening 404 through which exhaust gases from the muffler 32 can be expelled, and cooling air can flow in and out. Several bars 406 extend across the rear opening 404. In general, the exhaust chamber 402 may define at least a portion of a mounting envelope within which the exhaust components (e.g., the muffler 32 and its associated connecting pipes and mounting linkages) of the engine assembly 10 are mounted. For example, the mounting envelope may be defined by the bars 406, the engine block 17, and an exhaust plate 408 of the frame 401. In some embodiments, the mounting envelope defined by the bars 406, the engine block 17, and the exhaust plate 408 defines a volume within which the exhaust components of the engine assembly 10 are enclosed when mounted.

[0065] Referring now to FIGS. 16-18, a portion of the ZTR lawnmower 400 incorporating the engine assembly 300 is shown, according to an exemplary embodiment. The ZTR lawnmower 400 of FIGS. 16-18 may be substantially the same as the ZTR lawnmower 400 of FIGS. 13-15, except that the ZTR lawnmower includes the engine assembly 300 rather than the engine assembly 10. In general, the engine assembly 300 including the catalytic converter assembly 100 may be positioned within the same mounting envelope as the engine assembly 10 because of the compact incorporation of the catalytic converterassembly 100 on the engine 12. For example, the longitudinal axis 103 of the catalytic converter body 102 is arranged vertically above the longitudinal axis 33 of the muffler 32 (e.g., in a direction along the crankshaft axis 16), and the longitudinal axis 33 of the muffler 32 is arranged closer than the longitudinal axis 103 of the catalytic converter body 102 to the crankshaft axis 16 of the crankshaft 14. This arrangement of the catalytic converter body 102 and the muffler 32 orients or offsets these components along a diagonal direction (e.g., the axes 33 and 103 are offset both in a first or vertical direction and in a second or horizontal direction that is perpendicular to the first direction) relative to the crankshaft axis 16. Orienting the catalytic converter body 102 and the muffler 32 along the diagonal direction relative to the crankshaft axis 16 aids in containing the catalytic converter assembly 100 and the muffler 32 within the mounting envelope, without requiring the mounting envelope to change shape or size.

[0066] Referring now to FIGS. 19-21, an engine assembly 500 is shown, according to an exemplary embodiment. The engine assembly 500 includes an engine 510 with a crankshaft 514. In the illustrated embodiment, the engine 510 is a horizontal-shaft configuration with the crankshaft 514 extending along a horizontal direction (e.g., left and right from the perspective of FIG. 20). The engine 510 includes pistons moveable within cylinders 513 formed in an engine block 517. The reciprocating motion of the pistons rotates the crankshaft 514 about a crankshaft axis 516. The engine 510 may include two cylinders 513 arranged in a V-twin configuration. For example, the engine may include a single cylinder or three or more cylinders in any number of different configurations (e.g., inline, horizontally opposed, etc.), or may have a two-stroke cycle.

[0067] The engine 510 further includes a blower assembly 519 configured to direct air to the engine block 517 to cool the engine 510 by removing waste heat from the engine block 517 and / or the cylinders 513. The engine 510 may be configured to power a broad range of equipment, including walk-behind lawnmowers, zero-turn radius mowers, lawn tractors, pressure washers, electric generators, snow throwers, and other outdoor power equipment. The engine assembly 500 further includes a muffler 532 directly coupled to the exhaust outlets 504 of the engine 510, similar to the connection of the muffler 32 to the exhaust outlets 34 of the engine 12 of the vertical-shaft engine assembly 10. The muffler 532 may be positioned above the crankshaft 514 and the engine block 517 in the vertical direction (as shown) and may extend away from the engine block 517 in the same lateral direction as thecrankshaft 514. In some embodiments, an air gap is positioned between the muffler 532 and the engine block 517, which aids in preventing heat transfer between the engine block 517 and the muffler 532. The muffler 532 may be oriented such that the longitudinal axis 533 of the muffler body 538 is substantially perpendicular to a plane containing the crankshaft axis 516.[0068 | Referring now to FIGS. 22-24, an engine assembly 600 including the catalytic converter assembly 100 is shown, according to an exemplary embodiment. The engine assembly 600 may include the engine 510 shown and described with respect to FIGS. 19- 21, but with the catalytic converter assembly 100 directly coupled to the engine 510 upstream of the muffler 532, and the muffler 532 may be coupled to the catalytic converter assembly 100. The exhaust pipes 112, 114 of the catalytic converter assembly 100 may be coupled to the exhaust outlets 504 of the engine 510, such that the exhaust ports 108, 110 receive exhaust gases from the cylinders 513. Thus, the catalytic converter assembly 100 may be coupled to the engine block 517 in the same way and in the same location that the muffler 532 is coupled to the engine 510 in the engine assembly 500 of FIGS. 19-21.[0069| After the exhaust gases pass through the catalytic converter body 102, the catalyzed exhaust may be output via the outlet pipe 122 to the muffler 532. The catalytic converter body 102 may be positioned near the top of the engine 510 and to one side of the engine 510. For example, the catalytic converter body 102 may be positioned on the same side of the engine 510 as the crankshaft 514 extends out from the engine block 517.[0070| It should be noted that the engine assembly 600 is shown in FIGS. 22-24 in its ordinary operating orientation, with the engine block 517 and crankshaft 514 positioned near the bottom of the engine assembly 600 and the catalytic converter body 102 is positioned above the crankshaft 514. The catalytic converter body 102 may be oriented such that the direction of flow of gases through the catalytic converter body 102 (e.g., the longitudinal axis 103 of the catalytic converter body 102) is substantially parallel to the longitudinal axis 533 of the muffler 532 and substantially perpendicular to the crankshaft axis 516 of the crankshaft 514. The muffler 532 may be positioned in substantially the same position as the muffler 532 in the engine assembly 500 shown in FIGS. 19-21, near the top of the engine and off to one side. The catalytic converter body 102 may be positioned adjacent the muffler 532, in a position farther than the muffler 532 from thecrankshaft axis 516 and closer than the muffler 532 to the engine block 517 in the lateral direction (as shown). For example, the longitudinal axis 103 of the catalytic converter body 102 is arranged vertically above the longitudinal axis 533 of the muffler 532 (e.g., in a direction perpendicular to the crankshaft axis 516), and the longitudinal axis 533 of the muffler 532 is arranged closer than the longitudinal axis 103 of the catalytic converter body 102 to the crankshaft axis 516 of the crankshaft 514. The engine 510 defines a cylinder plane P that is arranged perpendicular to the crankshaft axis 516 and includes a cylinder axis defined along a centerline of at least one of the cylinders 513. With specific reference to FIG. 23, the longitudinal axis 103 of the catalytic converter body 102 is arranged between the cylinder plane P and the longitudinal axis 533 of the muffler 532.[00711 This arrangement of the catalytic converter body 102 and the muffler 532 orients these components along a diagonal direction (e.g., the axes 533 and 103 are offset both in a first or vertical direction and in a second or horizontal direction that is perpendicular to the first direction) relative to the crankshaft axis 516. Orienting the catalytic converter body 102 and the muffler 532 along the diagonal direction relative to the crankshaft axis 516 aids in containing the catalytic converter assembly 100 and the muffler 532 within a mounting envelope that includes the exhaust components of the engine assembly 500 when the catalytic converter assembly 100 is not installed, without requiring the mounting envelope to change shape or size.[00721 Referring to FIGS. 25-29, the catalytic converter assembly 100 is shown, according to an exemplary embodiment. The catalytic converter assembly 100 of FIGS. 25-29 is similar to the catalytic converter assembly 100 of FIGS. 4-9, with like features identified using the same reference numerals, except as described herein or apparent from the figures. As shown in FIGS. 25-29, the first exhaust pipe 112 and the second exhaust pipe 114 are kept as separate pipes for a longer length prior to being combined in the combined exhaust pipe 116. That is, the combined exhaust pipe 116 defines a V-shaped adapter that is directly upstream of the inlet 104 to the catalytic converter body 102, and the first exhaust pipe 112 and the second exhaust pipe 114 are both maintained as separate / independent exhaust flows until they are combined in the combined exhaust pipe 116. In the illustrated embodiment, the first exhaust pipe 112 completes an approximately one hundred and eighty degree bend prior to entering the combined exhaust pipe 116, and the second exhaust pipe 114 completes an approximately ninety degree bend prior to entering the combined exhaust pipe 116. Inthis way, for example, the combined exhaust pipe 116 does not bend along the curves defined by the first exhaust pipe 112 and the second exhaust pipe 114 upstream of the combined exhaust pipe 116, and the location where the first exhaust pipe and the second exhaust pipe 114 mix occurs much closer to the inlet 104 of the catalytic converter body 102 (e.g., when compared to the catalytic converter assembly 100 of FIGS. 4-9). The separate / independent exhaust flows provided by the first exhaust pipe 112 and the second exhaust pipe 114, and the lengths of the first exhaust pipe 112 and the second exhaust pipe 114 shown in FIGS. 25-29 provides improved engine performance (e.g., pressure pulse tuning).[00731 The catalytic converter assembly 100 of FIGS. 25-29 further includes a mounting bracket 140 that is coupled between the first exhaust pipe 112 and the outlet pipe 122. For example, the mounting bracket 140 is coupled to the first exhaust pipe 112 at an interface that is arranged adjacent to the exhaust port 108 (e.g., closer to the exhaust port 108 than an interface between the first exhaust pipe 112 and the combined exhaust pipe 116), and the mounting bracket 140 is coupled to the outlet pipe 122 at a location that is adjacent to the outlet 106 of the catalytic converter body 102 (e.g., closer to the outlet 106 than the outlet port 124). The mounting bracket 140 includes a flange 142 that facilitates coupling the mounting bracket 140, and thereby the catalytic converter assembly 100, to a portion of an engine (see, e.g., FIGS. 30, 31, and 35), which provides mounting support in addition to the couplings formed between the exhaust ports 108, 110 and an engine (e.g., the engine 12).

[0074] Referring now to FIGS. 30-32, the catalytic converter assembly 100 of FIGS. 25-29 is shown integrated into the engine assembly 300, according to an exemplary embodiment. For example, the catalytic converter assembly 100 of FIGS. 25-29 is arranged upstream of the muffler 32, such that exhaust gases from the engine 12 flow through the catalytic converter assembly 100 to the muffler 32 rather than directly from the engine 12 to the muffler 32. In some embodiments, the catalytic converter assembly 100 and the muffler 32 may combine to form an exhaust assembly that is coupled to the exhaust outlets 34 of the engine 12. The engine assembly 300 shown in FIGS. 30-32 is similar to the engine assembly 300 of FIGS. 10-12, with like features identified using the same reference numerals, except as described herein or apparent from the figures. In the illustrated embodiment, the outlet port 124 is coupled to the muffler 32 (e.g., at the muffler inlet 212) on the same side of the muffler as the exhaust port 40. Additionally, the muffler 32 includesa tailpipe 310 coupled to the exhaust port 40. In some embodiments, the tailpipe 310 may be shaped to direct the exhaust flow from the muffler 32 through an existing port or cutout formed on a chore product (e.g., the frame 401).

[0075] In general, the orientation of the catalytic converter body 102 and the muffler 32 on the engine assembly 300 of FIGS. 30-32 is similar to the engine assembly 300 of FIGS. 10- 12. For example, the catalytic converter body 102 may be positioned near the bottom of the engine 12 and to one side of the engine 12. It should be noted that the engine assembly 300 is shown in FIGS. 30-32 in its ordinary operating orientation, with the crankshaft 14 extending downward from the engine block 17 (e.g., a vertical crankshaft or PTO shaft orientation). The catalytic converter body 102 may be oriented such that the direction of flow of gases through the catalytic converter body 102 (e.g., the longitudinal or converter axis 103 of the catalytic converter body 102) is substantially parallel to the longitudinal or muffler axis 33 of a cylindrical body of the muffler 32. Further, the catalytic converter body 102 may be positioned close to the engine block 17. For example, the diameter of the heat shield 132 may be larger than the distance from the heat shield 132 to the engine block 17, as can be seen in FIG. 32. In some embodiments, the muffler 32 may be moved downward and towards the crankshaft axis 16 to accommodate the catalytic converter assembly 100. The catalytic converter body 102 may be positioned adjacent to the muffler 32, in a position higher than the muffler 32 (e.g., when the engine 12 is arranged such that the crankshaft 14 extends downward from the engine block 17, as shown) and farther from the crankshaft axis 16 of the crankshaft 14 than the muffler 32. For example, the longitudinal axis 103 of the catalytic converter body 102 is arranged vertically above the longitudinal axis 33 of the muffler 32 (e.g., in a direction parallel the crankshaft axis 16), and the longitudinal axis 33 of the muffler 32 is arranged closer than the longitudinal axis 103 of the catalytic converter body 102 to the crankshaft axis 16 of the crankshaft 14 (see FIG. 32). The engine 12 defines a cylinder plane P that is arranged perpendicular to the crankshaft axis 16 and includes a cylinder axis defined along a centerline of at least one of the cylinders 13. With specific reference to FIG. 32, the longitudinal axis 103 of the catalytic converter body 102 is arranged between the cylinder plane P and the longitudinal axis 33 of the muffler 32.

[0076] The arrangement of the catalytic converter assembly 100 and the muffler 32 allows for the catalytic converter assembly 100 to be integrated in an engine assembly without acatalytic converter (e.g., the engine assembly 10 or another existing engine assembly that did not conventionally include a catalytic converter) without requiring a larger mounting envelope for to accommodate the additional of the catalytic converter. For example, the engine assembly 300 of FIGS. 30-32 may occupy substantially the same amount of space as the engine assembly 10 so that the engine assembly 300 can be utilized in a chore product that is configured to include the engine assembly 10.

[0077] Referring to FIGS. 33-37, the engine assembly 300 of FIGS. 30-32 is shown installed within the portion of the ZTR lawnmower 400, according to an exemplary embodiment. In general, the engine assembly 300 of FIGS. 30-32 including the catalytic converter assembly 100 of FIGS. 25-29 may be positioned within the same mounting envelope as the engine assembly 10 because of the compact incorporation of the catalytic converter assembly 100 on the engine 12. For example, the longitudinal axis 103 of the catalytic converter body 102 is arranged vertically above the longitudinal axis 33 of the muffler 32 (e.g., in a direction along the crankshaft axis 16), and the longitudinal axis 33 of the muffler 32 is arranged closer than the longitudinal axis 103 of the catalytic converter body 102 to the crankshaft axis 16 of the crankshaft 14. This arrangement of the catalytic converter body 102 and the muffler 32 orients these components along a diagonal direction (e.g., the axes 33 and 103 are offset both in a first or vertical direction and in a second or horizontal direction that is perpendicular to the first direction) relative to the crankshaft axis 16. Orienting the catalytic converter body 102 and the muffler 32 along the diagonal direction relative to the crankshaft axis 16 aids in containing the catalytic converter assembly 100 and the muffler 32 within the mounting envelope, without requiring the mounting envelope to change shape or size.

[0078] In the illustrated embodiment, the frame 401 further includes an exhaust cutout 410 formed in a lateral side of the frame 401 (see, e.g., FIGS. 33 and 34). The exhaust cutout 410 extends through a portion of the frame 401 to provide fluid communication between the exhaust chamber 402 and the external environment. In some embodiments, the exhaust cutout 410 may be a predetermined location where exhaust is vented from the muffler 32 when the catalytic converter assembly 100 is not installed on the engine 12. The incorporation of the tailpipe 310 enables the catalytic converter assembly 100 to be installed on the engine assembly 300 within the frame 401 without needing to move the position of the exhaust cutout 410. For example, the tailpipe 310 is shaped to extend from the exhaustport 40 on the muffler 32 through the exhaust cutout 410, which removes the need to alter the existing design of the frame 401 to incorporate the catalytic converter assembly 100 of FIGS. 25-29.

[0079] As utilized herein with respect to numerical ranges, the terms “approximately,” “about,” “substantially,” and similar terms generally mean + / - 10% of the disclosed values. When the terms “approximately,” “about,” “substantially,” and similar terms are applied to a structural feature (e.g., to describe its shape, size, orientation, direction, etc.), these terms are meant to cover minor variations in structure that may result from, for example, the manufacturing or assembly process and are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and claimed are considered to be within the scope of the disclosure as recited in the appended claims.

[0080] It should be noted that the term “exemplary” and variations thereof, as used herein to describe various embodiments, are intended to indicate that such embodiments are possible examples, representations, or illustrations of possible embodiments (and such terms are not intended to connote that such embodiments are necessarily extraordinary or superlative examples).

[0081] The term “coupled” and variations thereof, as used herein, means the joining of two members directly or indirectly to one another. Such joining may be stationary (e.g., permanent or fixed) or moveable (e.g., removable or releasable). Such joining may be achieved with the two members coupled directly to each other, with the two members coupled to each other using one or more separate intervening members, or with the two members coupled to each other using an intervening member that is integrally formed as a single unitary body with one of the two members. If “coupled” or variations thereof are modified by an additional term (e.g., directly coupled), the generic definition of “coupled” provided above is modified by the plain language meaning of the additional term (e.g., “directly coupled” means the joining of two members without any separate intervening member), resulting in a narrower definition than the generic definition of “coupled” provided above. Such coupling may be mechanical, electrical, or fluidic. For example,circuit A communicably “coupled” to circuit B may signify that the circuit A communicates directly with circuit B (i.e., no intermediary) or communicates indirectly with circuit B (e.g., through one or more intermediaries).

[0082] References herein to the positions of elements (e.g., “top,” “bottom,” “above,” “below,” “between,” etc.) are merely used to describe the orientation of various elements in the figures unless otherwise noted. It should be noted that the orientation of various elements may differ according to other exemplary embodiments, and that such variations are intended to be encompassed by the present disclosure.|0083] Although only a few embodiments of the present disclosure have been described in detail, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited. For example, elements shown as integrally formed may be constructed of multiple parts or elements. It should be noted that the elements and / or assemblies of the components described herein may be constructed from any of a wide variety of materials that provide sufficient strength or durability, in any of a wide variety of colors, textures, and combinations. Accordingly, all such modifications are intended to be included within the scope of the present inventions. Other substitutions, modifications, changes, and omissions may be made in the design, operating conditions, and arrangement of the preferred and other exemplary embodiments without departing from scope of the present disclosure or from the spirit of the appended claims.

Claims

WHAT IS CLAIMED IS:

1. An engine assembly comprising: an engine block including a first cylinder and an exhaust outlet; a crankshaft extending from the engine block and defining a crankshaft axis; a blower assembly coupled to the engine block and configured to provide cooling air to the engine block; and an exhaust assembly including: a catalytic converter assembly coupled to the exhaust outlet; and a muffler arranged downstream of the catalytic converter assembly, wherein the catalytic converter assembly includes a catalytic converter body that defines a converter axis, and wherein the muffler defines a muffler axis that is parallel to the converter axis.

2. The engine assembly of claim 1, wherein the catalytic converter assembly includes a first exhaust pipe coupled to the engine block and configured to receive exhaust from the first cylinder.

3. The engine assembly of claim 2, wherein the engine block includes a second cylinder.

4. The engine assembly of claim 3, wherein the catalytic converter assembly includes a second exhaust pipe coupled to the engine block and configured to receive exhaust from the second cylinder.

5. The engine assembly of claim 4, wherein the first exhaust pipe and the second exhaust pipe join at a combined exhaust pipe, and wherein the combined exhaust pipe is coupled to an inlet of the catalytic converter body so that exhaust from the first exhaust pipe and the second exhaust pipe are directed into the catalytic converter body.

6. The engine assembly of claim 5, further comprising an oxygen sensor coupled to the combined exhaust pipe and configured to measure an oxygen concentration upstream of the inlet of the catalytic converter body.

7. The engine assembly of claim 5, wherein the first exhaust pipe and the second exhaust pipe are separated until the combined exhaust pipe.

8. The engine assembly of claim 1, wherein the catalytic converter assembly includes an outlet pipe coupled to an outlet of the catalytic converter body, and wherein the outlet pipe is coupled to the muffler.

9. The engine assembly of claim 1, wherein the converter axis is substantially perpendicular to the crankshaft axis.

10. The engine assembly of claim 9, wherein the muffler axis is closer to the crankshaft axis than the converter axis.

11. The engine assembly of claim 10, wherein the converter axis is arranged between a cylinder plane and the muffler axis.

12. The engine assembly of claim 1, wherein the catalytic converter body is diagonally offset from the muffler so that the converter axis is offset from the muffler axis in a first direction relative to the crankshaft axis and a second direction relative to the crankshaft axis that is perpendicular to the first direction.

13. An engine assembly comprising: an engine block including a first cylinder and an exhaust outlet; a crankshaft extending from the engine block and defining a crankshaft axis; a blower assembly coupled to the engine block and configured to provide cooling air to the engine block; and and exhaust assembly including: a catalytic converter assembly coupled to the exhaust outlet, wherein the catalytic converter assembly includes a catalytic converter body that defines a converter axis; and a muffler coupled to the catalytic converter body and defining a muffler axis, wherein the muffler axis is arranged closer to the crankshaft axis than the converter axis.

14. The engine assembly of claim 13, wherein the converter axis is arranged between a cylinder plane and the muffler axis.

15. The engine assembly of claim 13, wherein the catalytic converter body is diagonally offset from the muffler so that the converter axis is offset from the muffler axis in a first direction relative to the crankshaft axis and a second direction relative to the crankshaft axis that is perpendicular to the first direction.

16. The engine assembly of claim 13, wherein the catalytic converter assembly includes a first exhaust pipe coupled to the engine block and configured to receive exhaust from the first cylinder and a second exhaust pipe coupled to the engine block and configured to receive exhaust from a second cylinder.

17. The engine assembly of claim 16, wherein the first exhaust pipe and the second exhaust pipe join at a combined exhaust pipe, and wherein the combined exhaust pipe is coupled to an inlet of the catalytic converter body so that exhaust from the first exhaust pipe and the second exhaust pipe are directed into the catalytic converter body.

18. The engine assembly of claim 17, further comprising an oxygen sensor coupled to the combined exhaust pipe and configured to measure an oxygen concentration upstream of the inlet of the catalytic converter body.

19. Outdoor power equipment compri sing : a frame; an exhaust chamber; an engine assembly supported on the frame and including: an engine block including a first cylinder and an exhaust outlet; a crankshaft extending from the engine block and defining a crankshaft axis; a blower assembly coupled to the engine block and configured to provide cooling air to the engine block; and an exhaust assembly arranged within the exhaust chamber and including: a catalytic converter assembly coupled to the exhaust outlet; and a muffler arranged downstream of the catalytic converter assembly, wherein the catalytic converter assembly includes a catalytic converter body that defines a converter axis, and wherein the muffler defines a muffler axis that is parallel to the converter axis.

20. The outdoor power equipment of claim 19, wherein the muffler axis is arranged closer to the crankshaft axis than the converter axis.

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