The present disclosure relates to exhaust systems for vehicles. More particularly, the present disclosure relates to an auxiliary exhaust system for influencing (e.g., enhancing or amplifying) a sound output generated by a combustion engine of a vehicle (e.g., a motorcycle).
Background
[0002] Vehicles that operate on combustion engines may typically have stock exhaust systems to channel the exhaust released from the combustion engine into the outside environment. A stock exhaust system generally includes exhaust pipes and a muffler (e.g., a stock muffler) for damping or muffling a sound output generated by the combustion engine and carried onward by the exhaust flowing therethrough.
[0003] Nowadays, the sound output of the vehicles act as a crucial factor that multiplies the driving pleasure of the drivers, particularly motorcycle enthusiasts. For that, several aftermarket exhaust systems are available in the market. An aftermarket exhaust system may include an aftermarket muffler designed and manufactured to complement (e.g., enhance or amplify) the output sound carried onward by the exhaust passing therethrough. Due to already limited space available on the vehicle to install the stock exhaust system, installing the aftermarket exhaust system onto the vehicle along with the stock exhaust system may be cumbersome, time-consuming, and costly. Therefore, the drivers tend to completely replace the stock exhaust systems pre-installed on their vehicles with the aftermarket exhaust systems to attain such enhanced or amplified output sound.
Summary of the Invention
[0004] In one aspect, the disclosure relates to an auxiliary exhaust system for a motorcycle having an internal combustion engine with an exhaust port and an exhaust pipe having a first end removably coupled to the exhaust port and a second end removably coupled to a stock muffler. The exhaust pipe defines an inlet pipe

portion extending away from the first end of the exhaust pipe and configured to receive exhaust from the exhaust port, an intermediate pipe portion located downstream of the inlet pipe portion, an outlet pipe portion located downstream of the intermediate pipe portion and extending towards the stock muffler to meet the second end of the exhaust pipe, and a bypass opening defined at the inlet pipe portion. The auxiliary exhaust system includes a bypass duct and an acoustic muffler. The bypass duct defines an upstream duct end coupled to the bypass opening to receive the exhaust from the inlet pipe portion and a downstream duct end. The acoustic muffler is fluidly connected to the bypass duct to receive the exhaust from the bypass duct and amplify a sound output associated with the exhaust passing therethrough.
[0005] In another aspect, the disclosure is directed to a motorcycle. The motorcycle includes an internal combustion engine with an exhaust port, a stock muffler, an exhaust pipe, and an auxiliary exhaust system. The internal combustion engine is configured to expel exhaust from the exhaust port. The stock muffler is configured to receive the exhaust expelled from the internal combustion engine and attenuate a sound output of the exhaust. The exhaust pipe defines a first end removably coupled to the exhaust port of the internal combustion engine and a second end removably coupled to the stock muffler. The exhaust pipe further defines an inlet pipe portion, an intermediate pipe portion, an outlet pipe portion, and a bypass opening. The inlet pipe portion extends away from the first end of the exhaust pipe and is configured to receive the exhaust from the exhaust port, the intermediate pipe portion is located downstream of the inlet pipe portion, and the outlet pipe portion is located downstream of the intermediate pipe portion and extends toward the stock muffler to meet the second end of the exhaust pipe. The bypass opening is defined at the inlet pipe portion. The auxiliary exhaust system includes a bypass duct and an acoustic muffler. The bypass duct defines an upstream duct end coupled to the bypass opening to receive the exhaust from the inlet pipe portion and a downstream duct end. The acoustic muffler is fluidly connected to the bypass duct to receive the exhaust from the bypass duct and amplify a sound output associated with the exhaust passing therethrough.

Brief Description of the Drawings
[0006] The accompanying drawings, similar reference numerals, may refer to
identical or functionally similar elements. These reference numerals are used in the
detailed description to illustrate various embodiments and to explain various
aspects and advantages of the present disclosure.
[0007] FIG. 1 is a side view of an exemplary motorcycle including an auxiliary
exhaust system, in accordance with an embodiment of the present disclosure;
[0008] FIG. 2 is a perspective view of the auxiliary exhaust system coupled to an
exhaust pipe of the motorcycle, in accordance with an embodiment of the present
disclosure;
[0009] FIG. 3 is an exploded view of the auxiliary exhaust system, in accordance
with an embodiment of the present disclosure; and
[0010] FIG. 4 is a cross-sectional view of the auxiliary exhaust system, in
accordance with an embodiment of the present disclosure.
[0011] Persons skilled in the art will appreciate that elements in the figures are
illustrated for simplicity and clarity and may have not been drawn to scale. For
example, the dimensions of some of the elements in the figure may be exaggerated
relative to other elements to help to improve understanding of various embodiments
of the present disclosure.
Detailed Description
[0012] Reference will now be made in detail to specific embodiments or features, examples of which are illustrated in the accompanying drawings. Generally, corresponding reference numbers may be used throughout the drawings to refer to the same or corresponding parts, e.g., 1, V, V\ 101 and 201 could refer to one or more comparable components used in the same and/or different depicted embodiments.
[0013] Referring to FIG. 1, a motorcycle 100 is shown. The motorcycle 100 includes a frame 104, a combustion engine 108, a stock exhaust system 112, and an auxiliary exhaust system 114. The frame 104 may be supported by ground engaging

members, namely a front ground engaging member, illustratively wheel 116, and a rear ground engaging member, illustratively wheel 120. It will be appreciated that while the motorcycle 100 is illustrated as a two-wheel vehicle, various embodiments of the present teachings are also operable with three, four, six etc. wheeled vehicles.
[0014] The ground-engaging members (i.e., wheel 116 and wheel 120) may be powered by the combustion engine 108 to operate, and to propel the motorcycle 100 along the ground. The combustion engine 108 is mounted onto the frame 104. The combustion engine 108 includes an exhaust port 124. The combustion engine 108 is configured to combust air-fuel mixture to generate power required to propel the motorcycle 100 and expel exhaust from the exhaust port 124. In the present embodiment, the combustion engine 108 is a single cylinder four-stroke internal combustion engine.
[0015] Further, the motorcycle 100 may include other components (or assemblies) such as - a transmission assembly 110, fuel tank assembly 118, a steering assembly 122, and a seat assembly 126. Such components (or assemblies) and their functionality are known in the art, and therefore, they are not discussed, for the sake of brevity.
[0016] Referring to FIGS. 1 and 2, the stock exhaust system 112 is discussed. The stock exhaust system 112 may include a stock muffler 128 and an exhaust pipe 132. The stock muffler 128 is configured to receive the exhaust expelled from the combustion engine 108 and attenuate a sound output of the exhaust. Details regarding the stock muffler and its functionality are known in the art, and therefore are not discussed, for the sake of brevity.
[0017] The exhaust pipe 132 fluidly connects the stock muffler 128 with the exhaust port 124 of the combustion engine 108. For that, the exhaust pipe 132 defines a first end 136 and a second end 140 (please see FIG. 2). The first end 136 is configured to be removably coupled to the exhaust port 124 of the combustion engine 108. The second end 140 is located downstream of the first end 136. The second end 140 is configured to be removably coupled to the stock muffler 128. In that manner, the exhaust pipe 132 is configured to receive the exhaust expelled from

the combustion engine 108 (via exhaust port 124) and supply the exhaust to the stock muffler 128.
[0018] Further, the exhaust pipe 132 defines an inlet pipe portion 144, an intermediate pipe portion 148, an outlet pipe portion 152, and a bypass opening 156. The inlet pipe portion 144 extends away from the first end 136 of the exhaust pipe 132 to define an inlet downstream end 160. Further, the inlet pipe portion 144 may be a curved pipe portion (e.g., elbow pipe portion 144') defining a curved longitudinal axis 'Al'. Also, the inlet pipe portion 144 defines a length 'LI' extending between the first end 136 and the inlet downstream end 160 along the curved longitudinal axis 'Al'. The inlet pipe portion 144 is configured to receive the exhaust, passing through the exhaust port 124, and change a flow direction of the exhaust (i.e., exhaust flowing from the first end 136 towards the inlet downstream end 160) within the exhaust pipe 132.
[0019] The intermediate pipe portion 148 is located downstream of the inlet pipe portion 144. The intermediate pipe portion 148 extends away from the inlet downstream end 160 to define an intermediate downstream end 164. The intermediate pipe portion 148 may be a linear pipe portion 148" defining a linear longitudinal axis 'A2'. The intermediate pipe portion 148 defines a length 'L2' extending between the inlet downstream end 160 and the intermediate downstream end 164 along the linear longitudinal axis 'A2'. The intermediate pipe portion 148 is configured to fluidly connect the inlet pipe portion 144 with the outlet pipe portion 152. In that manner, the intermediate pipe portion 148 receives the exhaust, passing through the inlet downstream end 160 of the inlet pipe portion 144, and allows the exhaust to flow therethrough towards the outlet pipe portion 152. [0020] The outlet pipe portion 152 is located downstream of the intermediate pipe portion 148. The outlet pipe portion 152 extends away from the intermediate downstream end 164 towards the stock muffler 128 to meet the second end 140 of the exhaust pipe 132. Further, the outlet pipe portion 152 may be a curved pipe portion (e.g., an elbow pipe portion 152) defining a curved longitudinal axis 'A3'. Also, the outlet pipe portion 152 defines a length 'L3' extending between the intermediate downstream end 164 and the second end 140 along the curved

longitudinal axis 'A3'. The outlet pipe portion 152 is configured to receive the exhaust, passing through the intermediate downstream end 164, and change the flow direction of the exhaust (i.e., exhaust flowing from the intermediate downstream end 164 towards the second end 140 within the exhaust pipe 132) to deliver the exhaust to the stock muffler 128.
[0021] The exhaust pipe 132 may have a total length 'L' equal to a sum of the lengths 'LI', 'L2', and 'L3' of the inlet pipe portion 144, the intermediate pipe portion 148, and the outlet pipe portion 152, respectively. In the present embodiment, a ratio of the length 'LI' of the inlet pipe portion 144 and the total length 'L' of the exhaust pipe 132 is in a range of about 0.25 to 0.35. For example, the total length 'L' of the exhaust pipe is about 800 mm and the total length 'LI' of the inlet pipe portion 144 is about 200 mm. In another example, the total length 'L' of the exhaust pipe is about 700 mm and the total length 'LI' of the inlet pipe portion 144 is about 250 mm.
[0022] The bypass opening 156 is defined at the inlet pipe portion 144 of the exhaust pipe 132. In the present embodiment, the bypass opening 156 is located proximal to the first end 136 of the exhaust pipe 132 and distal to the inlet downstream end 160 of the inlet pipe portion 144. In an example, if the length 'LI' of the inlet pipe portion 144 is about 250 mm, the bypass opening 156 is defined at a distance of about 100 mm from the first end 136 (when measured along the curved longitudinal axis 'Al') and about 150 mm from the inlet downstream end 160 (when measured along the curved longitudinal axis 'Al').
[0023] In another embodiment, the bypass opening 156 may be formed proximal to the inlet downstream end 160 of the inlet pipe portion 144 and distal to the first end 136 of the exhaust pipe 132. In yet another embodiment, the bypass opening 156 may be equidistant from the first end 136 of the exhaust pipe 132 and the inlet downstream end 160 of the inlet pipe portion 144. Further, the bypass opening 156 is configured to fluidly connect the inlet pipe portion 144 with the auxiliary exhaust system 114. In that manner, the bypass opening 156 may direct the exhaust from the inlet pipe portion 144 towards the auxiliary exhaust system 114.

[0024] Referring to FIGS. 2, 3, and 4, the auxiliary exhaust system 114 is discussed. The auxiliary exhaust system 114 includes a bypass duct 168 and an acoustic muffler 172. The bypass duct 168 defines an upstream duct end 176 and a downstream duct end 180 (see FIG. 3). The upstream duct end 176 is configured to be coupled (e.g., welded, bolted, etc.) to the bypass opening 156 (see FIG. 2). In that manner, the upstream duct end 176 fluidly connects the bypass duct 168 with the inlet pipe portion 144 and enables the bypass duct 168 to receive the exhaust from the inlet pipe portion 144. The downstream duct end 180 is located downstream of the upstream duct end 176. The downstream duct end 180 is configured to deliver the exhaust, passing through the bypass duct 168, to the acoustic muffler 172.
[0025] Further, the bypass duct 168 may be an elbow duct 168" (see FIG. 3) defining a curved longitudinal axis 'A4'. Also, the bypass duct 168 may define a length 'L4' extending between the upstream duct end 176 and the downstream duct end 180 along the curved longitudinal axis 'A4'. In the present embodiment, the length 'L4' of the bypass duct is in a range of about 80 mm to 120 mm. Further, the bypass duct 168 is configured to change the flow direction of the exhaust flowing therethrough between the upstream duct end 176 and the downstream duct end 180.
[0026] The acoustic muffler 172 is configured to receive the exhaust from the inlet pipe portion 144, via the bypass duct 168, and amplify a sound output associated with the exhaust passing therethrough. For that, the acoustic muffler 172 may include a housing 184, an inner mesh 188, an outer mesh 192, a valve assembly 196, and a tailpipe 200. The housing 184 may at least partially enclose the inner mesh 188 and the outer mesh 192. In the present embodiment, the housing completely encloses the inner mesh 188 and the outer mesh 192. [0027] The housing 184 may be a hollow cylindrical body defining a longitudinal axis ' A5', an upstream housing end 208 and a downstream housing end 212. Also, the housing 184 may define a length 'L5' extending along the longitudinal axis ' A5' between the upstream housing end 208 and the downstream housing end 212. In the present embodiment, the length 'L5' of the housing 184 is in a range of about

140 mm to 170 mm. The upstream housing end 208 may be configured to be coupled (e.g., welded, bolted, etc.) to the downstream duct end 180 of the bypass duct 168 to fluidly connect the acoustic muffler 172 with the bypass duct 168 to receive the exhaust from the bypass duct 168. In addition, the acoustic muffler 172 may be oriented at an acute angle with respect to the stock muffler 128 when the acoustic muffler 172 gets coupled to the downstream duct end 180 of the bypass duct 168.
[0028] The inner mesh 188 may be a perforated cylindrical body 188" defining a longitudinal axis 'A6', an inner mesh upstream end 216 and an inner mesh downstream end 220. Also, the inner mesh 188 may define a length 'L6' extending along the longitudinal axis 'A6' between the inner mesh upstream end 216 and the inner mesh downstream end 220. In the present embodiment, the length 'L6' of the inner mesh 188 is in a range of about 80 mm to 120 mm. Further, the inner mesh 188 may define a plurality of apertures 224 between the inner mesh upstream end 216 and the inner mesh downstream end 220. In addition, the inner mesh 188 may include a cap 228 disposed at the inner mesh upstream end 216. In the present embodiment, the cap 228 is a hemispherical cap. The inner mesh 188 is configured to allow the exhaust to pass through the apertures 224 and absorbs the vibration or pressure associated with the exhaust passing therethrough.
[0029] Similar to the inner mesh 188, the outer mesh 192 may be a perforated cylindrical body 192' defining a longitudinal axis 'A7', an outer mesh upstream end 232 and an outer mesh downstream end 236. Also, the outer mesh 192 may define a length 'L7' extending along the longitudinal axis 'A7' between the outer mesh upstream end 232 and the outer mesh downstream end 236. In the present embodiment, the length 'L7' of the outer mesh 192 is in a range of about 90 mm to 130 mm. Further, the outer mesh 192 may define a plurality of apertures 240 between the outer mesh upstream end 232 and the outer mesh downstream end 236. The apertures 240 may be sized to allow the exhaust to pass therethrough. The outer mesh 192 may be configured to at least partially enclose the inner mesh 188. In the present embodiment, the outer mesh 192 fully encloses the inner mesh 188. Further, the outer mesh 192 and the inner mesh 188 are concentrically arranged

about the longitudinal axis 'A5' within the housing 184. Accordingly, the longitudinal axes 'A5', 'A6', and 'A7' may coincide each other when the outer mesh 192 and the inner mesh 188 are disposed within the housing 184. Furthermore, the outer mesh 192 is configured to allow the exhaust to pass through the apertures 240 towards the inner mesh 188 and absorbs the vibration or pressure associated with the exhaust passing therethrough.
[0030] The valve assembly 196 is coupled to the housing 184 (e.g., at the downstream housing end 212). The valve assembly 196 includes a valve housing 244, a valve shaft 248, a valve 252, and a valve actuator 256. The valve housing 244 may define an exhaust passageway 260 for allowing the exhaust to pass therethrough. The valve shaft 248 may be rotatably supported by the valve housing 244. The valve 252 may be coupled to the valve shaft 248 and may be positioned within the exhaust passageway 260. In that manner, the valve 252 may selectively restrict or allow the exhaust to flow through the exhaust passageway 260, and hence, through the acoustic muffler 172. In an example, the valve 252 may move to a first position (e.g., completely closed position) to restrict the exhaust to flow through the acoustic muffler 172. In another example, the valve 252 may move to a second position (e.g., completely open position) to allow the exhaust to flow through the acoustic muffler 172. In the present embodiment, the valve 252 is a butterfly valve 252'.
[0031] The valve actuator 256 may be coupled to the valve shaft 248. The valve actuator 256 is configured to actuate (e.g., pivot or rotate) the valve shaft 248 to move the valve 252 between the first position (e.g., completely closed position) and the second position (e.g., completely open position). For that, the valve actuator 256 is configured to receive a cable 264 which may be further connected to an input device 268 (e.g., a button or a switch installed at the steering assembly 122 of the motorcycle 100) (see FIG. 2). In other embodiments, the valve actuator 256 may be electrically or electronically controlled to move the valve 252 between the first position and the second position.
[0032] The tailpipe 200 may be a hollow cylindrical pipe 200' defining a longitudinal axis ' A8', an upstream tailpipe end 272 and a downstream tailpipe end

276. Also, the tailpipe 200 may define a length 'L8' extending along the longitudinal axis ' A8' between the upstream tailpipe end 272 and the downstream tailpipe end 276. In the present embodiment, the length 'L8' of the tailpipe 200 is in a range of about 170 mm to 260 mm. Also, the tailpipe 200 may have a bore diameter of about 30 mm to 100 mm.
[0033] The tailpipe 200 may be located downstream of the housing 184. Also, the tailpipe 200 may be located downstream of the valve assembly 196 (or the valve 252). In the present embodiment, the tailpipe 200 is coupled (e.g., welded) to the valve housing 244. The tailpipe 200 is configured to receive the exhaust passing through the exhaust passageway 260 and discharge the exhaust into the outside atmosphere. Also, the tailpipe 200 is configured to shape sound nodes of the sound output associated with the exhaust passing therethrough (e.g., in accordance with a traditional thump sound output).
[0034] In some embodiments, the acoustic muffler 172 may include a catalytic converter 280 (please see FIG. 3). The catalytic converter 280 may be positioned within the housing 184. In addition, the catalytic converter 280 may be located downstream of the downstream duct end 180 of the bypass duct 168 and upstream of the outer mesh upstream end 232 of the outer mesh 192. The catalytic converter 280 may be configured to adsorb and store NOx contained in the exhaust passing therethrough.
Industrial Applicability
[0035] During riding the motorcycle 100, a driver of the motorcycle 100 may desire to switch the operation of the motorcycle 100 from an attenuated mode (in which the exhaust is allowed to pass through the stock exhaust system 112 to attain attenuated sound output associated with the exhaust, e.g., about 40 decibel at 2000 rpm engine speed) to an amplified mode (in which the exhaust is allowed to pass through the auxiliary exhaust system 114 to attain amplified sound output decibel associated with the exhaust, e.g., about 70 decibel at 2000 rpm engine speed). In this regard, the driver may manipulate/actuate the input device 268 (e.g., a switch

installed on the steering assembly 122 of the motorcycle 100) to actuate the valve actuator 256.
[0036] In response to the manipulation/actuation of the input device 268, the valve actuator 256 may move (e.g., rotate or pivot) the valve shaft 248 and the valve 252 from the first position (e.g., closed position) to the second position (e.g., open position), thereby allowing the exhaust to bypass the stock exhaust system 112 and flow through the auxiliary exhaust system 114. Accordingly, the exhaust passing through the inlet pipe portion 144 may enter the bypass duct 168 from the upstream duct end 176 and flow towards the downstream duct end 180 (see FIG. 4). Further, the exhaust may flow through the downstream duct end 180 and enter the housing 184.
[0037] Within the housing 184, the exhaust may flow through the catalytic converter 280 such that the catalytic converter 280 may adsorb and store NOx contained in the exhaust passing therethrough. Further, the exhaust may flow through the apertures 240 of the outer mesh 192 towards the inner mesh 188. Next, the exhaust may flow through the apertures 224 of the inner mesh 188 towards the exhaust passageway 260. Additionally, a fraction of the exhaust may strike the cap 228 of the inner mesh 188. During the passage of the exhaust through the outer mesh 192 and the inner mesh 188, the vibration and/or the sound pressure carried by the exhaust may be absorbed by the apertures 240 of the outer mesh 192, and the apertures 224 and the cap 228 of the inner mesh 188. Next, the exhaust may pass through the exhaust passageway 260 to enter the tailpipe 200. Within the tailpipe 200, the exhaust may flow from the upstream tailpipe end 272 toward the downstream tailpipe end 276 to get discharged to the outside atmosphere. [0038] While riding the motorcycle 100, the driver of the motorcycle 100 desires to switch back the operation of the motorcycle 100 from the amplified mode to the attenuated mode. Accordingly, the driver may manipulate/actuate the input device 268 to actuate the valve actuator 256 in a manner to move the valve shaft 248 and the valve 252 from the second position (i.e., open position) to the first position (i.e., closed position). At the first position, the valve 252 may restrict the exhaust to flow through the acoustic muffler 172 (or the auxiliary exhaust system 114).

Accordingly, the exhaust may flow through the exhaust pipe 132 (i.e., through the inlet pipe portion 144, the intermediate pipe portion 148, and the outlet pipe portion 152) to enter the stock muffler 128 from where the exhaust may be discharged to the outside atmosphere.
[0039] The auxiliary exhaust system 114 may be easily retrofitted on the existing stock exhaust systems (such as the stock exhaust system 112 of the motorcycle 100) with limited modifications, in turn, providing sound output alternatives to the drivers. Also, the auxiliary exhaust system 114 provides a cost-efficient solution for influencing (e.g., enhancing or amplifying) the sound output generated by the combustion engines (similar to the combustion engine 108) of the vehicles (like the motorcycle 100).
[0040] It will be apparent to those skilled in the art that various modifications and variations can be made to the method and/or system of the present disclosure without departing from the scope of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the method and/or system disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalent.

LIST OF ELEMENTS
TITLE: AUXILIARY EXHAUST SYSTEM FOR INFLUENCING ENGINE SOUND OUTPUT OF VEHICLES

100 motorcycle
104 frame
108 combustion engine
110 transmission assembly
112 stock exhaust system
114 auxiliary exhaust system
116 wheel
118 fuel tank assembly
120 wheel
122 steering assembly
124 exhaust port
126 seat assembly
128 stock muffler
132 exhaust pipe
136 first end
140 second end
144 inlet pipe portion
148 intermediate pipe portion
152 outlet pipe portion
156 bypass opening
160 inlet downstream end
164 intermediate downstream end
168 bypass duct
172 acoustic muffler
176 upstream duct end
180 downstream duct end

184 housing
188 inner mesh
192 outer mesh
196 valve assembly
200 tailpipe
208 upstream housing end
212 downstream housing end
216 inner mesh upstream end
220 inner mesh downstream end
224 aperture
228 cap
232 outer mesh upstream end
236 outer mesh downstream end
240 aperture
244 valve housing
248 valve shaft
252 valve
256 valve actuator
260 exhaust passageway
264 cable
268 input device
272 upstream tailpipe end
276 downstream tailpipe end
280 catalytic converter
Al axis
A2 axis
A3 axis
A4 axis
A5 axis
A6 axis
A7 axis

A8 axis
LI length
L2 length
L3 length
L4 length
L5 length
L6 length
L7 length
L8 length

We Claim:

1. An auxiliary exhaust system for a motorcycle having an internal combustion
engine with an exhaust port and an exhaust pipe having a first end removably
coupled to the exhaust port and a second end removably coupled to a stock
muffler, the exhaust pipe defining an inlet pipe portion extending away from
the first end of the exhaust pipe and configured to receive exhaust from the
exhaust port, an intermediate pipe portion located downstream of the inlet
pipe portion, an outlet pipe portion located downstream of the intermediate
pipe portion and extending towards the stock muffler to meet the second end
of the exhaust pipe, and a bypass opening defined at the inlet pipe portion, the
auxiliary exhaust system comprising:
a bypass duct defining an upstream duct end coupled to the bypass opening to receive the exhaust from the inlet pipe portion and a downstream duct end; and
an acoustic muffler fluidly connected to the bypass duct to receive the exhaust from the bypass duct and amplify a sound output associated with the exhaust passing therethrough.
2. The auxiliary exhaust system as claimed in claim 1, wherein the acoustic
muffler includes:
an inner mesh having an inner mesh upstream end and an inner mesh downstream end, the inner mesh defining a plurality of apertures between the inner mesh upstream end and the inner mesh downstream end and a cap disposed at the inner mesh upstream end;
an outer mesh having an outer mesh upstream end and an outer mesh downstream end, the outer mesh defining a plurality of apertures between the outer mesh upstream end and the outer mesh downstream end, the outer mesh is configured to at least partially enclose the inner mesh;
a housing coupled to the downstream duct end of the bypass duct and configured to enclose the outer mesh and the inner mesh; and

a tailpipe located downstream of the housing.
3. The auxiliary exhaust system as claimed in claim 2, wherein the acoustic muffler includes a valve assembly coupled to the housing, the valve assembly including a valve configured to move between a first position to restrict the exhaust to flow through the acoustic muffler and a second position to allow the exhaust to flow through the acoustic muffler.
4. The auxiliary exhaust system as claimed in claim 3, wherein the valve is located downstream of the inner mesh.
5. The auxiliary exhaust system as claimed in claim 1, wherein the bypass duct is an elbow duct defining a curved longitudinal axis, the bypass duct is configured to change a flow direction of the exhaust flowing therethrough between the upstream duct end and the downstream duct end.
6. The auxiliary exhaust system as claimed in claim 1, wherein the acoustic muffler is oriented at an acute angle with respect to the stock muffler when the acoustic muffler is coupled to the downstream duct end of the bypass duct.
7. A motorcycle comprising:
an internal combustion engine with an exhaust port and configured to expel exhaust from the exhaust port;
a stock muffler configured to receive the exhaust expelled from the internal combustion engine and attenuate a sound output of the exhaust;
an exhaust pipe having a first end removably coupled to the exhaust port of the internal combustion engine and a second end removably coupled to the stock muffler, the exhaust pipe defining:
an inlet pipe portion extending away from the first end of the exhaust pipe and configured to receive the exhaust from the exhaust port;
an intermediate pipe portion located downstream of the inlet pipe portion;

an outlet pipe portion located downstream of the intermediate pipe portion and extending towards the stock muffler to meet the second end of the exhaust pipe; and
a bypass opening defined at the inlet pipe portion; and
an auxiliary exhaust system including:
a bypass duct defining an upstream duct end coupled to the bypass opening to receive the exhaust from the inlet pipe portion and a downstream duct end; and
an acoustic muffler fluidly connected to the bypass duct to receive the exhaust from the bypass duct and amplify the sound output associated with the exhaust passing therethrough.
8. The motorcycle as claimed in claim 7, wherein the acoustic muffler includes:
an inner mesh having an inner mesh upstream end and an inner mesh downstream end, the inner mesh defining a plurality of apertures between the inner mesh upstream end and the inner mesh downstream end and a cap disposed at the inner mesh upstream end;
an outer mesh having an outer mesh upstream end and an outer mesh downstream end, the outer mesh defining a plurality of apertures between the outer mesh upstream end and the outer mesh downstream end, the outer mesh is configured to at least partially enclose the inner mesh;
a housing coupled to the downstream duct end of the bypass duct and configured to enclose the outer mesh and the inner mesh;
a tailpipe located downstream of the housing; and
a valve assembly coupled to the housing, the valve assembly including a valve located downstream of the inner mesh and configured to move between a first position to restrict the exhaust to flow through the acoustic muffler and a second position to allow the exhaust to flow through the acoustic muffler.
9. The motorcycle as claimed in claim 7, wherein the bypass duct is an elbow
duct defining a curved longitudinal axis, the bypass duct is configured to

change a flow direction of the exhaust flowing therethrough between the upstream duct end and the downstream duct end.
10. The motorcycle as claimed in claim 7, wherein the acoustic muffler is oriented at an acute angle with respect to the stock muffler when the acoustic muffler is coupled to the downstream duct end of the bypass duct.