Patent Publication Number: US-2023160325-A1

Title: Exhaust system tuner tube to reduce standing wave

Description:
FIELD 
     The present disclosure relates to an exhaust system for a vehicle engine emitting exhaust gas, and particularly to an exhaust system with a tuner tube to reduce a standing wave. 
     BACKGROUND 
     This section provides background information related to the present disclosure which is not necessarily prior art. 
     An internal combustion engine can generate a substantial amount of combustion noise, which is transferred through an exhaust system and is audible as tailpipe noise. Mufflers are used within exhaust systems to reduce this noise and/or tune the exhaust sound characteristics to desired sound qualities. An electronic exhaust valve may be implemented within the exhaust system to control flow through a primary pipe of the muffler. The exhaust system may exhibit a drone or standing wave in the exhaust system when the electronic exhaust valve is closed, but no standing wave is created when the electronic exhaust valve is open. The present disclosure provides a tuner tube connected to the primary pipe to attenuate the standing wave. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     In accordance with one aspect of the present disclosure, a muffler assembly for an exhaust system for a vehicle engine emitting exhaust gas is provided. The exhaust system includes a collector and an exhaust conduit providing exhaust gas to the muffler assembly. The muffler assembly includes a housing, a primary pipe, a valve, a resonance length, a secondary pipe, a tuner tube, and a bleed port. The housing defines an enclosed volume. The primary pipe includes a primary pipe inlet and a primary pipe outlet. The primary pipe extends through the enclosed volume of the muffler. The valve is operable to restrict flow through the primary pipe. The resonance length is defined by a length of the exhaust system that extends from the collector of the vehicle engine to the valve. The secondary pipe includes a secondary pipe inlet and a secondary pipe outlet. The secondary pipe inlet is positioned in fluid communication with the enclosed volume. The secondary pipe outlet is positioned outside of the enclosed volume. The tuner tube includes an open tuner tube end and a closed tuner tube end. The open tuner tube end is in fluid communication with the primary pipe. The closed tuner tube end is opposite to the open tuner tube end. The tuner tube has a tuner tube length substantially one quarter of the resonance length. A bleed port is formed in the primary pipe and is in fluid communication with the enclosed volume. The bleed port is positioned downstream from the open tuner tube end. 
     In some configurations of the muffler assembly of the above paragraph, the muffler assembly includes a first baffle and a second baffle. The first baffle cooperates with the housing to define a first chamber. The second baffle cooperates with the housing to define a third chamber. A second chamber is positioned between the first and second baffle. Each of the first and second baffles including at least one perforation allowing the second chamber to be in fluid communication with the first chamber and the third chamber. 
     In some configurations of the muffler assembly of any one or more of the above paragraphs, the tuner tube is positioned within the first and second chambers. 
     In some configurations of the muffler assembly of any one or more of the above paragraphs, the bleed port is positioned within the first chamber. 
     In some configurations of the muffler assembly of any one or more of the above paragraphs, the secondary pipe inlet is positioned within the third chamber. 
     In some configurations of the muffler assembly of any one or more of the above paragraphs, at least one baffle is disposed within the housing and cooperating with the housing to define a plurality of chambers within the housing. The at least one baffle includes at least one perforation allowing fluid communication between adjacent chambers. 
     In some configurations of the muffler assembly of any one or more of the above paragraphs, the open tuner tube end is spaced from the collector at a distance of about 0% to about 10% of the resonance length. 
     In some configurations of the muffler assembly of any one or more of the above paragraphs, the open tuner tube end is spaced from the valve at a distance of about 0% to about 10% of the resonance length. 
     In some configurations of the muffler assembly of any one or more of the above paragraphs, the muffler assembly includes a bleed tube. The bleed tube includes a first bleed tube end in fluid communication with the primary pipe and a second bleed tube end. The bleed port is disposed at the second bleed tube end. 
     In some configurations of the muffler assembly of any one or more of the above paragraphs, the bleed port is at least one perforation. 
     The present disclosure also provides a muffler assembly that includes a housing, a primary pipe, a first valve, a first resonance length, a secondary pipe, a tertiary pipe, a first tuner tube, and a first bleed port. The housing defines an enclosed volume. The primary pipe includes a primary pipe inlet and a primary pipe outlet. The primary pipe extends through the enclosed volume. The first valve is operable to restrict flow through the primary pipe. The first resonance length is defined by a length of the exhaust system that extends from the collector of the vehicle engine to the valve. The secondary pipe includes a secondary pipe inlet and a secondary pipe outlet. The secondary pipe inlet is positioned in fluid communication with the enclosed volume. The secondary pipe outlet is positioned outside of the enclosed volume. The tertiary pipe includes a tertiary pipe inlet and a tertiary pipe outlet. The tertiary pipe extending through the enclosed volume. The first tuner tube includes an open first tuner tube end in fluid communication with the primary pipe and a closed first tuner tube end that is opposite the open tuner tube end. The first tuner tube has a first tuner tube length of substantially one-quarter of the first resonance length. The first bleed port is formed in the primary pipe and is in fluid communication with the enclosed volume. The first bleed port is positioned downstream from the open first tuner tube end. 
     In some configurations of the muffler assembly of any one or more of the above paragraphs, the muffler assembly further includes a second valve, a second resonance length, a second tuner tube, and a second bleed port. The second valve is operable to restrict flow through the tertiary pipe. The second resonance length is defined by a length of the exhaust system that extends from the collector of the vehicle engine to the second valve. The second tuner tube includes an open second tuner tube end that is in fluid communication with the tertiary pipe and a closed second tuner tube end that is opposite the open second tuner tube end. The second tuner tube has a second tuner tube length of substantially one-quarter of the second resonance length. The second bleed port is formed in the tertiary pipe tube and is in fluid communication with the enclosed volume. The second bleed port is positioned downstream from the open second tuner tube end. 
     In some configurations of the muffler assembly of any one or more of the above paragraphs, the muffler assembly further includes a quaternary pipe. The quaternary pipe includes a quaternary pipe inlet positioned in fluid communication with the enclosed volume and a quaternary pipe outlet positioned outside of the enclosed volume. 
     In some configurations of the muffler assembly of any one or more of the above paragraphs, a third distance between the tertiary pipe inlet and second bleed port is greater than a fourth distance between the tertiary pipe inlet and the open second tuner tube end. 
     In some configurations of the muffler assembly of any one or more of the above paragraphs, a first distance between the primary pipe inlet and the first bleed port is greater than a second distance between the primary pipe inlet and the open first tuner tube end. 
     In some configurations of the muffler assembly of any one or more of the above paragraphs, the muffler assembly further a first baffle and a second baffle. The first baffle cooperates with the housing to define a first chamber. The second baffle cooperates with the housing to define a third chamber. A second chamber is positioned between the first and second baffles. Each of the first and second baffles includes at least one perforation, allowing the second chamber to be in fluid communication with the first chamber and the third chamber. 
     The present disclosure also provides a muffler assembly that includes a housing, a first baffle, a second baffle, a primary pipe, a valve, a resonance length, a secondary pipe, a tuner tube, and a bleed port. The housing defines an enclosed volume. The first baffle cooperates with the housing to define a first chamber. The second baffle cooperates with the housing to define a third chamber. A second chamber is positioned between the first and second baffles. Each of the first and second baffles includes at least one perforation, allowing the second chamber to be in fluid communication with the first chamber and the third chamber. The primary pipe includes a primary pipe inlet and a primary pipe outlet. The primary pipe extends through the enclosed volume. The valve is operable to restrict flow through the primary pipe. The resonance length is defined by a length of the exhaust system that extends from the collector of the vehicle engine to the valve. The secondary pipe includes a secondary pipe inlet positioned in fluid communication with the enclosed volume and a secondary pipe outlet positioned outside of the enclosed volume. The tuner tube includes an open tuner tube end in fluid communication with the primary pipe and a closed tuner tube end that is opposite the open tuner tube end. The tuner tube has a tuner tube length of substantially one-quarter of the resonance length. The bleed port is formed in the primary pipe and is in fluid communication with the enclosed volume. The bleed port is positioned downstream from the open tuner tube end. 
     In some configurations of the muffler assembly of any one or more of the above paragraphs, the open tuner tube end is positioned in the first chamber and the closed tuner tube end is positioned in the second chamber. 
     In some configurations of the muffler assembly of any one or more of the above paragraphs, the valve is positioned within the enclosed volume. 
     In some configurations of the muffler assembly of any one or more of the above paragraphs, the valve is positioned outside of the enclosed volume. 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG.  1    is a schematic representation of a vehicle engine and exhaust system having a muffler assembly according to the principles of the present disclosure. 
         FIG.  2    is a front view of the exemplary muffler assembly. 
         FIG.  3    is a perspective view of the exemplary muffler assembly shown in  FIG.  2   , where the housing is transparent. 
         FIG.  4    is an exploded perspective view of the exemplary muffler assembly shown in  FIGS.  2  and  3   , where portions of the primary and secondary pipes are removed and the housing is removed. 
         FIG.  5    is a schematic of another exemplary muffler assembly according to the principles of the present disclosure, where arrows are included to illustrate a closed valve flow path, an open valve flow path, and an intermediately open valve flow path. 
         FIG.  6    is a schematic of yet another exemplary muffler assembly according to the principles of the present disclosure, where additional arrows are included to illustrate a closed valve flow path, an open valve flow path, an intermediately open valve flow path, a second closed valve flow path, a second open valve flow path, and a second intermediately open valve flow path. 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail. 
     The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. 
     When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments. 
     Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     With reference to  FIGS.  1  and  2   , a vehicle engine  10  is provided and operable to emit exhaust gas into an exhaust system  12 . The vehicle engine  10  may include a first bank of cylinders and a second bank of cylinders positioned opposite from the first bank of cylinders. In-line cylinder configurations are also common. 
     The exhaust system  12  may include one or more exhaust manifolds  14 , collectors  16 , exhaust conduits  18 , and muffler assemblies  20 . Typically, one exhaust manifold  14  is mounted to the vehicle engine  10  in fluid communication with either of the first or second bank of cylinders. The exhaust manifold may extend between a mounting surface  22  or a mounting flange  24  and an exhaust manifold outlet end  26 . The collector  16  may be integrally formed with the exhaust manifold  14  at the exhaust manifold outlet end  26  or may be a separate component disposed at the exhaust manifold outlet end  26 . The collector  16  is the portion of the exhaust system  12  that merges the flow from each individual cylinder of the vehicle engine  10  into an exhaust passageway  28  of the exhaust conduit  18 . The collector  16  may extend between a collector inlet  30  and a collector outlet  32 . 
     More specifically, each exhaust manifold  14  may include a branch  34  associated with each cylinder. In the exemplary vehicle engine  10  depicted, which is a V8 engine, each exhaust manifold includes a first, second, third and fourth branch  36 ,  38 ,  40 ,  42 . The first branch  36  extends between the mounting flange  24  and the collector  16 . Each of the second, third and fourth branches  38 ,  40 ,  42 , also extend from the mounting flange  24  to the collector  16 . The mounting flange  24  abuts the vehicle engine  10  to place the first, second, third and fourth branches  36 ,  38 ,  40 ,  42  of the exhaust manifold  14  in fluid communication with the bank of cylinders (not shown) of the vehicle engine  10 . In some configurations, the first branch  36 , and the second branch  38  may be joined in fluid communication with one another upstream of the collector inlet  30 . The third branch  40  and the fourth branch  42  may also be joined together in fluid communication with one another upstream of the collector inlet  30 . Regardless, all cylinders of the representative cylinder bank are in fluid communication with one another inside the collector  16 . The opposite bank of cylinders is equipped with another exhaust manifold  14  that is substantially a mirror image of the previously described exhaust manifold  14 . 
     The exhaust conduit  18  is positioned downstream from the collector  16  and receives gas exiting the collector  16 . The exhaust conduit  18  extends between the collector outlet  32  and the muffler assembly  20 . The exhaust conduit  18  may include a catalytic converter  44 , one or more flexible bellows  46 , and/or additional connecting pipes  48 . If the vehicle is so equipped, the catalytic converter  44  treats exhaust gases and the flexible bellow  46  absorbs movements in the exhaust system  12 . Gas exiting the exhaust conduit  18  is provided to the muffler assembly  20 . 
     The muffler assembly  20  may be shaped to fit within a given available space on a vehicle (not shown). For example, in some configurations, the muffler assembly  20  may be shaped to fit around a spare tire well of the vehicle and/or other components at or near an undercarriage of the vehicle. 
     The muffler assembly includes a housing  50 , a primary pipe  52  extending through at least one wall  54  of the housing  50 , a secondary pipe  56  extending through at least one wall  54  of the housing  50 , and a valve  58 . The primary pipe  52  may extend through the housing  50  between a primary pipe inlet  60  and a primary pipe outlet  62 . The primary pipe inlet  60  is in fluid communication with the collector  16 , via the exhaust conduit  18 . In other words, the primary pipe inlet  60  receives exhaust gas from the exhaust conduit  18 . The valve  58  is operable to restrict exhaust gas flow through the primary pipe  52 . The valve  58  may be an electrically operated valve and have a range of operating positions from a full open position to a full closed position. The exact position of the valve  58  is dependent on the desired performance characteristics of the muffler assembly  20 . A full open position of the valve  58  allows exhaust gas to freely pass through the primary pipe  52  and exit the primary pipe outlet  62 . A full closed position of the valve  58  restricts the flow of exhaust gas through the primary pipe outlet  62  and redirects exhaust gas flow through the muffler assembly  20 . In the configuration shown in the figures, the valve  58  is positioned downstream and outside of the housing  50 . Alternatively, the valve  58  may be positioned inside of the housing  50 . 
     The figures depict a closed-closed system which is defined when the primary pipe outlet  62  is closed via the valve  58 . More specifically, a closed-closed system may be present when the valve  58  is in the full closed position at one end of the system and the exhaust manifold  14  is disposed at the opposite end of the system. A standing wave may be developed in a closed-closed system when two waves move in opposite directions. The standing wave may extend from the collector outlet  32  to the valve  58 . A resonance length  66  is defined as the distance from the collector outlet  32  to the valve  58  along the centerline of the exhaust conduit  18  and the primary pipe  52 . The standing wave may result in an audible frequency that displeases customers. Thus, there is a need to attenuate, eliminate or otherwise reduce and minimize the standing wave. 
     With reference to  FIGS.  2  to  4   , the muffler assembly  20  is operable to reduce noise and tune the exhaust sound characteristics to desired sound qualities. In the configuration shown in the figures, the housing  50  includes an inner housing surface  68 , an outer housing surface  70 , a first shell  72  and a second shell  74 . The first shell  72  may be welded, mechanically locked, or otherwise sealingly fixed to the second shell  74  to define an enclosed volume  76 . Additionally, the housing  50  may include an inlet opening  78 , a first outlet opening  80  and a second outlet opening  82 . A one-piece housing is also contemplated. 
     The muffler assembly includes a tuner tube  84 . The tuner tube  84  has a tuner tube length  86  substantially one-quarter of the resonance length  66 . In this instance, “substantially one-quarter” refers to a length that need not be exactly one-quarter of the resonance length  66  but within a tolerance of plus or minus 5% of the resonance length  66 . The tuner tube  84  has an outer tuner tube surface  88  and a tuner tube diameter  90 . 
     The tuner tube  84  extends between an open tuner tube end  92  and a closed tuner tube end  94 . The tuner tube  84  may include one or more bends or curves. The open tuner tube end  92  is open into the primary pipe  52  and allows for fluid communication between the tuner tube  84  and the primary pipe  52 . The closed tuner tube end  94  is sealed by a tube cap  96 . The tuner tube  84  is operable to attenuate the standing wave. The optimal position of the open tuner tube end  92  is at a high acoustic pressure position within the exhaust system  12 . More specifically, the position of the open tuner tube end  92  is optimal when spaced from the valve  58  at a distance of about 0% to about 10% of the resonance length  66 . Alternatively, the position of the open tuner tube end  92  is optimal when spaced from the collector outlet  32  at a distance of about 0% to about 10% of the resonance length  66 . 
     The muffler assembly  20  may also include a bleed tube  100 . The bleed tube  100  extends between a first bleed tube end  102  and a second bleed tube end  104 . The bleed tube  100  may include one or more bends or curves. The bleed tube has an outer bleed tube surface  106  and a bleed tube diameter  108 . 
     The first bleed tube end  102  is open into the primary pipe  52  and allows for fluid communication between the primary pipe  52  and bleed tube  100 . The second bleed tube end  104  defines a bleed port  110  such that the second bleed tube end  104  is in fluid communication with the enclosed volume  76 . The first bleed tube end  102  is positioned downstream from the open tuner tube end  92 . A first distance  112  is defined between the primary pipe inlet  60  and the first bleed tube end  102 . A second distance  114  is defined between the primary pipe inlet  60  and the open tuner tube end  92 . The bleed tube  100  is positioned downstream from the open tuner tube end  92  when the first distance  112  is greater than the second distance  114 . In other words, the tuner tube  84  is positioned upstream from the bleed tube  100 . 
     The primary pipe  52  has an outer primary pipe surface  116  and a primary pipe diameter  118 . The primary pipe  52  may include one or more bends or curves. In the configuration shown, the primary pipe  52  may include a primary inlet pipe  120 , a primary connection pipe  122 , and a primary outlet pipe  124 . The primary connection pipe  122  may extend between a first connection end  126  and a second connection end  128 . The primary inlet pipe  120  may be positioned outside of the housing  50  and fluidly coupled with the first connection end  126  of the primary connection pipe  122  at the inlet opening  78  of the housing  50 . The primary connection pipe  122  may be disposed within the enclosed volume  76 . The primary outlet pipe  124  may be positioned outside of the housing  50  and fluidly coupled to the second connection end  128  of the primary connection pipe  122  at the first outlet opening  80  of the housing  50 . Gas may enter the housing  50  from the exhaust conduit  18  via the primary inlet pipe  120 , flow through the housing  50  via the primary connection pipe  122 , and exit the housing  50  via the primary outlet pipe  124 . The primary outlet pipe  124  may be open to the ambient environment surrounding the muffler assembly  20 , or may be coupled to another exhaust system component outside of the muffler assembly  20  such as a tailpipe (not shown). 
     The secondary pipe  56  has an outer secondary pipe surface  130  and a secondary pipe diameter  132 . The secondary pipe  56  may extend between a secondary pipe inlet  134  and a secondary pipe outlet  136 . The secondary pipe inlet  134  is open to and in fluid communication with the enclosed volume  76  and the secondary pipe outlet  136  is positioned outside of the housing  50 . The secondary pipe  56  may include one or more bends or curves. The secondary pipe  56  may include a secondary inlet pipe  138 , a secondary communication pipe  140 , and a secondary outlet pipe  142 . The secondary communication pipe  140  may extend between a third connection end  144  and a fourth connection end  146 . The third connection end  144  of the secondary communication pipe  140  may be fluidly coupled to the secondary inlet pipe  138 . The fourth connection end  146  of the secondary communication pipe  140  may be fluidly coupled to the secondary outlet pipe  142  at the second outlet opening  82 . The secondary outlet pipe  142  may be open to the ambient environment surrounding the muffler assembly  20 , or may be coupled to another exhaust system component outside of the muffler assembly  20  such as a tailpipe (not shown). 
     The shapes and diameters of the pipes may be tailored to achieve a desired range of sounds and desired performance characteristics over a given range of engine speeds. For instance, the embodiment shown in  FIGS.  2  to  4    depicts the tuner tube diameter  90  as being greater than the bleed tube diameter  108 . Additionally, the primary pipe diameter  118  is greater than the tuner tube diameter  90 , the bleed tube diameter  108 , and the secondary pipe diameter  132 . Because of the difference between the primary pipe diameter  118  and bleed tube diameter  108 , a greater flow rate of exhaust gas may be emitted from the primary pipe outlet  62  versus traveling into the enclosed volume  76  via the bleed tube  100  when the valve  58  is open. 
     The muffler assembly  20  may have a baffle  148  disposed within the enclosed volume  76  and cooperating with the housing  50  to define one or more chambers  150  within the enclosed volume  76 . The number of baffles, number of chambers, and/or volume of the chambers may not influence the performance of the tuner tube  84 . Rather, the number and placement of the one or more baffles  148  may be dependent on the mechanical support required by the housing  50  and/or the desired performance characteristics of the muffler assembly  20 . As shown in  FIGS.  3  and  4   , a first baffle  152  and a second baffle  154  are disposed within the enclosed volume  76 . The second baffle  154  is spaced apart from the first baffle  152 . Each of the first and second baffle  152 ,  154  may include an outer periphery  156 , which is shaped to generally match the contours of the inner housing surface  68 . The outer periphery  156  may be welded, mechanically locked, or otherwise sealingly fixed to the inner housing surface  68 . 
     The first and second baffles  152 ,  154  may divide the enclosed volume  76  into a first chamber  158 , a second chamber  160 , and a third chamber  162 . The first chamber  158  may be defined by the first baffle  152 , the first shell  72 , and the second shell  74 . The second chamber  160  may be defined by the first baffle  152 , the second baffle  154 , the first shell  72  and the second shell  74 . The third chamber  162  may be defined by the second baffle  154 , the first shell  72 , and the second shell  74 . Therefore, the second chamber  160  may be positioned between the first and third chambers  158 ,  162 . 
     Each of the first and second baffles  152 ,  154  may include one or more perforations  164  to allow fluid communication among adjacent chambers. The number and placement of the one or more perforations  164  may be dependent on the desired performance of the muffler assembly  20 . A greater number of perforations allow for a more fluid flow of gases between adjacent chambers, whereas a reduced number of perforations has the ability to restrict flow of gases between the adjacent chambers. In the configuration shown in  FIGS.  3  and  4   , the first and second baffles  152 ,  154  contain a plurality of the perforations  164 . The perforations  164  in the first baffle  152  allow for fluid communication between the first and second chambers  158 ,  160 . The perforations  164  in the second baffle  154  allow for fluid communication between the second and third chambers  160 ,  162 . Additionally, each of the first and second baffles  152 ,  154  may include one or more baffle openings  166  for pipes to extend through the first, second and third chambers  158 ,  160 ,  162 . The one or more baffle openings  166  are coupled to the respective pipes and may not allow for fluid communication of the enclosed volume  76  between adjacent chambers. The first baffle  152  may include a first and second baffle opening  168 ,  170 . The second baffle  154  may include a third baffle opening  172 . 
     The primary pipe  52  and bleed tube  100  may be positioned within the first chamber  158 . The tuner tube  84  may extend from the first chamber  158 , through the first baffle  152  via the first baffle opening  168 , and into the second chamber  160 . Thus, the open tuner tube end  92  may be positioned within the first chamber  158  and the closed tuner tube end  94  may be positioned within the second chamber  160 . Next, the bleed tube  100  may be positioned within the first chamber  158 . Lastly, the secondary pipe  56  may extend through the second baffle  154  between the third chamber  162  and the second chamber  160  via the third baffle opening  172  and through the first baffle  152  between the second chamber  160  and first chamber  158  via the second baffle opening  170 . Thus, the secondary pipe inlet  134  may be open to and in fluid communication with the third chamber  162 . 
     One or more brackets  174  may be disposed within the housing  50  to provide additional support between components. In the configurations shown in the figures, a first bracket  176 , a second bracket  178 , and a third bracket  180  is provided. The first bracket  176  may be disposed within the first chamber  158  and extends between a first bracket end  182  and a second bracket end  184 . The first bracket end  182  may be contoured to the general shape of the outer bleed tube surface  106  and abuts the outer bleed tube surface  106 . The second bracket end  184  may be contoured to the general shape of the outer tuner tube surface  88  and abuts the outer tuner tube surface  88 . The second bracket  178  may also disposed within the first chamber  158  and extend between a third bracket end  186  and a fourth bracket end  188 . The third bracket end  186  may be contoured to the general shape of the outer primary pipe surface  116 . The fourth bracket end  188  may be contoured to the general shape of the outer secondary pipe surface  130 . The third bracket end  186  abuts the outer primary pipe surface  116  and the fourth bracket end  188  abuts the outer secondary pipe surface  130 . Lastly, the third bracket  180  may be disposed within the second chamber  160 . The third bracket  180  extends between a fifth bracket end  190  and a sixth bracket end  192 . The fifth bracket end  190  abuts a first insert  194  of the first baffle  152  and the sixth bracket end  192  abuts a second insert  196  of the second baffle  154 . The first, second, third, fourth, fifth, and sixth bracket ends  182 ,  184 ,  186 ,  188 ,  190 ,  192  may be welded, mechanically locked, or otherwise sealingly fixed to the respective component. 
     As shown in  FIGS.  5  and  6   , the muffler assembly of the present disclosure may be constructed in a number of different ways. Many of the elements of the muffler assembly  20  previously described are the same or substantially the same amongst the multiple embodiments. More specifically, the structure, position, and function of these components may be similar or identical to that of the corresponding components of the muffler assembly  20  described above. Therefore, the common components are not described again in detail. Equivalent elements shared between the embodiments have corresponding reference numbers. For example, reference number  50  in  FIGS.  2  to  4    corresponds to reference number  250  in  FIGS.  5  and  450    in  FIG.  6   . Additionally, reference number  110  in  FIGS.  2  to  4    corresponds to reference number  310  in  FIG.  5    and reference number  510  in  FIG.  6   . 
     Referring now to  FIG.  5   , another muffler assembly  220  is provided. Like the muffler assembly  20  of the previous embodiment, the muffler assembly  220  includes a housing  250 , a primary pipe  252 , a valve  258 , a tuner tube  284  with a tuner tube length  286 , and a secondary pipe  256 . 
     The shapes of the pipes may be tailored to achieve a desired range of sounds and desired performance characteristics over a given range of engine speeds. In the configuration shown, the primary pipe outlet  262  and secondary pipe outlet  336  are positioned at opposite ends of the housing  250 . 
     A bleed port  310  is formed in the primary pipe  252  as at least one perforation  364 . In the configuration shown, a plurality of perforations  364  are disposed through the primary pipe  252  and positioned circumferentially. The bleed port  310  is open to and in fluid communication with the enclosed volume  276  via the perforations  364 . The bleed port  310  is positioned downstream from the open tuner tube end  292 . A first distance  312  is defined as the distance between the primary pipe inlet  260  and the bleed port  310 . A second distance  314  is defined between the primary pipe inlet  260  and the open tuner tube end  292 . The bleed port  310  is positioned downstream from the open tuner tube end  292  when the first distance  312  is greater than the second distance  314 . In other words, the open tuner tube end  292  is positioned upstream from the bleed port  310 . 
     A closed valve flow path  200  is defined when the valve  258  is in the full closed position. In the closed valve flow path  200 , gas from the exhaust conduit  18  enters the primary pipe  252  of the muffler assembly  220  via the primary pipe inlet  260 . Gas from the primary pipe inlet  260  flows to the bleed port  310  for entry into the enclosed volume  276 . Meanwhile, sound waves may travel to the tuner tube  284  for attenuating the standing wave. Gas from the enclosed volume  276  flows into the secondary pipe  256  via the secondary pipe inlet  334 . Gas from the secondary pipe inlet  334  travels to the secondary pipe outlet  336  for emission. 
     An open valve flow path  202  and also intermediately open valve flow path  204  are defined when the valve  258  is in the full open position or partially open position, respectively. In the open and intermediately open valve flow paths  202 ,  204 , exhaust gas from the exhaust conduit  18  enters the primary pipe  252  via the primary pipe inlet  260 . Exhaust gas from the primary pipe inlet  260  flows to the primary pipe outlet  262  for emission. Meanwhile, exhaust gas from the primary pipe inlet  260  flows to the bleed port  310  for entry into the enclosed volume  276 . Gas from the enclosed volume  276  flows into the secondary pipe  256  via the secondary pipe inlet  334 . Gas from the secondary pipe inlet  334  flows to the secondary pipe outlet  336  for emission. 
     Referring now to  FIG.  6   , another muffler assembly  420  is provided. Like the muffler assemblies  20 ,  220  of the previous embodiments, the muffler assembly  420  includes a housing  450 , a primary pipe  452 , a valve  458 , a tuner tube  484  with a tuner tube length  486 , a bleed port  510 , and a secondary pipe  456  with a closed valve flow path  400 , an open valve flow path  402 , and an intermediately open valve flow path  404 . Like the tuner tubes  84 ,  284  of the previous embodiments, the tuner tube  484  has a tuner tube length  486  of substantially one-quarter of the resonance length  466 . In this instance, “substantially one-quarter” refers to a length that need not be exactly one-quarter of the resonance length  466  but within a tolerance of plus or minus 5% of the resonance length  466 . 
     The muffler assembly  420  further includes a tertiary pipe  598 , a second valve  600 , a second tuner tube  602 , a second bleed port  604 , and a quaternary pipe  606 . The tertiary pipe  598  may extend through the housing  450  between a tertiary pipe inlet  608  and a tertiary pipe outlet  610 . The tertiary pipe inlet  608  is in fluid communication with the collector  16  via the exhaust conduit  18 . In other words, the tertiary pipe inlet  608  receives gas from the exhaust conduit  18 . The second valve  600  is operable to restrict flow through the tertiary pipe  598 . A full open position of the second valve  600  allows gas to freely pass through the tertiary pipe  598  and exit the tertiary pipe outlet  610 . A full closed position of the second valve  600  redirects gas through the enclosed volume  476  of the housing  450  and restricts emission of gas through the tertiary pipe outlet  610 . In the configuration shown in the figures, the second valve  600  is positioned downstream and outside of the housing  450 . Alternatively, the second valve  600  may be positioned inside of the housing  450 . 
     A closed-closed system is defined when both tertiary pipe outlet  610  and collector outlet  32  are in a closed state. More specifically, a closed-closed system may be present when the second valve  600  is in the full closed position at one end of the system and the exhaust manifold  14  is disposed at the opposite end of the system. A standing wave may extend from the collector outlet  32  to the second valve  600  and define a second resonance length  612  measured from the collector outlet  32  to the second valve  600  along the centerline of the exhaust conduit  18  and tertiary pipe  598 . 
     The second tuner tube  602  has a second tuner tube length  614  of substantially one-quarter of the second resonance length  612 . In this instance, “substantially one-quarter” refers to a length that need not be exactly one-quarter of the second resonance length  612  but within a tolerance of plus or minus 5% of the second resonance length  612 . The second tuner tube  602  extends between an open second tuner tube end  616  and a closed second tuner tube end  618 . The open second tuner tube end  616  allows for fluid communication between the second tuner tube  602  and tertiary pipe  598 . The closed second tuner tube end  618  is sealed by the tube cap  496 . The second tuner tube  602  is operable to attenuate the standing wave. The optimal position of the second tuner tube  602  is where there is high acoustic pressure within the exhaust system. More specifically, the position of the open second tuner tube end  616  is optimal when spaced from the second valve  600  at another distance of about 0% to about 10% of the second resonance length  612 . Alternatively, the position of the open second tuner tube end  616  is optimal when spaced from the collector outlet  32  at another distance of about 0% to about 10% of the second resonance length  612  (not shown). 
     The second bleed port  604  may include a plurality of perforations  564  that are disposed through the tertiary pipe  598  and positioned circumferentially. The second bleed port  604  is open to and in fluid communication with the enclosed volume  476  via the perforations  564 . The second bleed port  604  must be positioned downstream from the open second tuner tube end  616 . A third distance  622  is defined between the tertiary pipe inlet  608  and the second bleed port  604 . A fourth distance  624  is defined between the tertiary pipe inlet  608  and the open second tuner tube end  616 . The second bleed port  604  is positioned downstream from the open second tuner tube end  616  when the third distance  622  is greater than the fourth distance  624 . In other words, the open second tuner tube end  616  is positioned upstream from the second bleed port  604 . 
     The quaternary pipe  606  extends between a quaternary pipe inlet  626  and a quaternary pipe outlet  628 . The quaternary pipe inlet  626  is open to and in fluid communication with enclosed volume  476  and the quaternary pipe outlet  628  is positioned outside of the housing  450 . The quaternary pipe outlet  628  may be open to the ambient environment surrounding the muffler assembly  420 , or may be coupled to another exhaust system component outside of the muffler assembly  420  such as a tailpipe (not shown). 
     The shapes of the pipes may be tailored to achieve a desired range of sounds and desired performance characteristics over a given range of engine speeds. In the configuration shown, the tertiary pipe outlet  610  and secondary pipe outlet  536  is positioned on the same end of the housing  450 . The primary pipe outlet  462  and quaternary pipe outlet  628  is positioned on the same end of the housing  450 . The primary pipe outlet  462  and the tertiary pipe outlet  610  is positioned on opposite ends of the housing  450 . Similarly, the secondary pipe outlet  536  and quaternary pipe outlet  628  is positioned on opposite ends of the housing  450 . 
     A second closed valve flow path  630  is defined when the second valve  600  is in the full closed position. In the second closed valve flow path  630 , gas from the exhaust conduit  18  enters the tertiary pipe  598  via the tertiary pipe inlet  608 . Gas from the tertiary pipe inlet  608  flows to the second bleed port  604  for entry into the enclosed volume  476 . Meanwhile, sound waves may travel to the second tuner tube  602  for attenuating the standing wave. Gas from the enclosed volume  476  flows into the secondary pipe  456  via the secondary pipe inlet  534  and into the quaternary pipe  606  via the quaternary pipe inlet  626 . Gas from the secondary pipe inlet  534  flows to the secondary pipe outlet  536  for emission and gas from the quaternary pipe inlet  626  flows to the quaternary pipe outlet  628  for emission. 
     A second open valve flow path  632  and also a second intermediately open valve flow path  634  are defined when the second valve  600  is in the full open position or partially open position, respectively. In the second open valve flow path  632  and second intermediately open valve flow path  634 , gas from the exhaust conduit  18  enters the tertiary pipe  598  via the tertiary pipe inlet  608 . Gas from the tertiary pipe inlet  608  flows to the tertiary pipe outlet  610  for emission. Gas from the tertiary pipe inlet  608  also flows to the second bleed port  604  for entry into the enclosed volume  476 . Gas from the enclosed volume  476  flows into the secondary pipe  456  via the secondary pipe inlet  534  and into the quaternary pipe  606  via the quaternary pipe inlet  626 . Gas from the secondary pipe inlet  534  flows to the secondary pipe outlet  536  for emission and gas from the quaternary pipe inlet  626  flows to the quaternary pipe outlet  628  for emission. 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.