MOTORCYCLE EXHAUST ENHANCEMENT DEVICE

Abstract

Embodiments of the present invention provide an exhaust enhancement device that allows a motorcyclist to achieve a desired engine sound while also achieving improved engine performance by reducing exhaust reversion. More particularly, embodiments of the present invention provide for an exhaust enhancement device having a cylindrical tubular body portion configured to be disposed within a motorcycle exhaust pipe so that exhaust gasses may flow therethrough. The exhaust enhancement device further includes a frustoconical screen extending from an end of the cylindrical tubular body portion. The frustoconical screen has an array of holes in its wall for allowing exhaust gasses to pass therethrough. The exhaust enhancement device may further include one or more washer-like members disposed therein and configured to alter the flow of exhaust gasses so that reversion is reduced.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No. 11/005,655 filed Dec. 7, 2004, which in turn is a continuation-in-part of U.S. application Ser. No. 10/408,860 filed Apr. 7, 2003, now U.S. Pat. No. 6,848,252 granted Feb. 1, 2005, which claims priority from U.S. provisional application No. 60/387,005 filed Jun. 6, 2002.

FIELD OF THE INVENTION

Embodiments of the invention relate generally to exhaust enhancement devices for motorcycles.

BACKGROUND OF THE INVENTION

Motorcyclists are always seeking the right blend of sound and performance from their motorcycles. Often the sound is inextricably intertwined with the horsepower and performance of the engine. For example, using an aftermarket exhaust pipe to gain horsepower and performance may change the sound of the motorcycle. Furthermore, many motorcyclists prefer a particular type of sound for their motorcycle. For example, many motorcyclists try to achieve a “deep,” “rich,” and “throaty” sound. Motorcyclists, however, must also be aware of the many noise ordinances that have been put in place around the country. Many motorcyclists have, therefore, strived to create aftermarket exhaust pipes that achieve a proper balance of sound, volume, and performance. It would therefore be desirable to have an exhaust system that produces a quality sound without sacrificing performance. It would also be desirable to have an exhaust system that produces quality sound and performance at an acceptable volume level. It would also be desirable if such a device could be adjustable, customizable, or in some way changeable such that the motorcyclist can change the sound and performance of the motorcycle depending on the motorcyclists preferences or intended uses.

BRIEF SUMMARY OF THE INVENTION

In general terms, embodiments of the present invention provide an exhaust enhancement device for a motorcycle exhaust pipe. The exhaust enhancement device may include a cylindrical tubular body portion configured to be received within a motorcycle exhaust pipe. The exhaust enhancement device may further include foraminous screen extending from said first end of the cylindrical tubular body portion. The formanious screen has a frustoconical configuration converging as it extends away from the body portion to define an open first end of a diameter generally corresponding to the diameter of said first end of the body portion and an open opposite second end of a smaller diameter. At least one obstruction is positioned within the cylindrical tubular body portion or the frustoconical screen in the flow path of exhaust gases passing through the enhancement device. In some advantageous embodiments of the invention, the at least one obstruction comprises a flat circular member oriented in a plane perpendicular to the longitudinal axis of the cylindrical tubular body portion. The flat circular member may suitably have a central opening and may be positioned coaxially of the longitudinal axis of the cylindrical body portion. According to one exemplary embodiment of the invention, the flat circular member is positioned within the frustoconical screen. In another exemplary embodiment, the flat circular member is positioned within the tubular body portion.

In some embodiments, the exhaust enhancement device has two flat circular members, one flat circular member positioned within the tubular body portion and another flat circular member positioned within the frustoconical screen. In general, the outside diameter of at least a portion of the cylindrical tubular body portion is approximately equal to the inside diameter of the motorcycle exhaust pipe. In one embodiment, the cylindrical tubular body portion includes a reduced-diameter center chamber between its two opposite ends. In such an embodiment, a flat circular member may be positioned within one of the opposing cylindrical ends.

Embodiments of the present invention further provide a motorcycle exhaust system having an exhaust pipe for expelling exhaust from an engine; a cylindrical tubular body portion disposed within the exhaust pipe; a frustoconical screen extending from one end of the cylindrical tubular body portion, the frustoconical screen generally converging as it extends away from the cylindrical tubular body portion, and the frustoconical screen having at least one opening therethrough; and a flat circular member positioned within the cylindrical tubular body portion or the frustoconical screen in the path of the exhaust gasses. The frustoconical screen may extend from the end of the cylindrical tubular body portion generally toward an engine end of the exhaust pipe or may extend from the end of the cylindrical tubular body portion generally toward an exit end of the exhaust pipe.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

FIG. 1a schematically illustrates a motorcycle engine with a pair of exhaust pipes and shows where the exhaust enhancement devices may be located in the exhaust pipes, in accordance with an embodiment of the present invention;

FIG. 1b schematically illustrates how the exhaust enhancement device may be located in the exhaust pipe in accordance with another embodiment of the present invention;

FIGS. 2a and 2b illustrate a perspective sectional view and an exploded view, respectively, of an exhaust enhancement device in accordance with an embodiment of the present invention;

FIGS. 3a and 3b illustrate a perspective sectional view and an exploded view, respectively, of an exhaust enhancement device in accordance with another embodiment of the present invention; and

FIG. 4 is a cross-sectional view of an exhaust pipe having an exhaust enhancement device disposed therein in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the inventions are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.

FIG. 1a schematically illustrates a motorcycle engine 1 with a pair of exhaust pipes 2, and shows where the exhaust enhancement devices 10 may be located in the exhaust pipes 2, in accordance with an embodiment of the present invention. As shown in FIG. 1, an exhaust enhancement device 10 may be installed inside the motorcycle exhaust pipe 2 proximate its discharge end. In general, the exhaust enhancement device 10 includes a cylindrical tubular body portion 20 and a frustoconical screen 30. The cylindrical tubular body portion 20 is generally coupled to the frustoconical screen 30, and the frustoconical screen 30 generally tapers or “converges” as it extends away from the cylindrical tubular body portion 20. As used herein and in the claims, the term “conical” refers to conical and frusto-conical shapes, as well as other converging or funnel-like shapes including funnel-like shapes having polygonal cross-sections. Furthermore, as used herein and in the claims the term “converge” is used to describe the tapering sides of the conical shape and do not necessarily require that the sides completely merge together at a single point in space. In fact, as described herein, in the preferred embodiments, the sides of the conical portion do not completely merge together and in fact terminate at an opening opposite the base of the conical shape.

FIG. 1a illustrates the exhaust enhancement device 10 positioned in the exhaust pipe 2 such that the frustoconical screen 30 is on the “downstream” end of the cylindrical tubular body portion 20, which is the end of the cylindrical tubular body portion 20 positioned closer to the exit of the exhaust pipe 2. In another embodiment, however, the exhaust enhancement device 10 may be positioned such that the frustoconical screen 30 is on the “upstream” end of the cylindrical tubular body portion 20, which is the end that is closer to the engine side of the exhaust pipe 2. Such an embodiment is illustrated in FIG. 1b.

In general, embodiments of the exhaust enhancement device 10 create a unique rich and throaty sound at an appealing volume when the exhaust enhancement device 10 is installed in a motorcycle's exhaust pipe 2. However, changing the orientation of the exhaust enhancement device 10 from the orientation shown in FIG. 1a to the orientation shown in FIG. 1b generally changes the sound and the performance of the motorcycle. In this way, the user may use the exhaust enhancement device 10 to produce at least two different sounds. The user may also be able use the exhaust enhancement device 10 to bring the engine's power band (or “sweet spot”) in at different RPMs simply by reversing the exhaust enhancement device 10 in the exhaust pipe 2. In this regard, embodiments of the present invention may be configured to reduce reversion in the engine and the exhaust system. Since the reversion of exhaust gasses (caused, for example, by valve overlap during the engine cycle) dilutes the charge entering the combustion chamber, reducing the amount of reversion generally increases the horsepower and/or the responsiveness of the engine. Therefore, by installing an exhaust enhancement device 10 that is configured to reduce reversion of exhaust gasses in the exhaust pipe, the rider will often experience improved throttle response, a deeper sound, more midrange power, and more torque than the rider would have experienced without the exhaust enhancement device 10 installed in the exhaust pipe 2.

FIGS. 2a and 2b illustrate a perspective sectional view and a perspective exploded view, respectively, of an exhaust enhancement device 10 in accordance with an embodiment of the present invention. As illustrated in FIGS. 2a and 2b, the exhaust enhancement device 10 includes a cylindrical tubular body portion 20 and a frustoconical screen 30.

In the illustrated embodiment, the cylindrical tubular body portion 20 has two cylindrical end portions 24 and 25 on either side of a reduced diameter center chamber portion 22. The cylindrical tubular body portion 20 has a longitudinal axis 15 extending through the center of the cylindrical portions 24 and 25. The two cylindrical end portions 24 and 25 are generally configured to have an outside diameter that is approximately equal to or just less than the inside diameter of the exhaust pipe 2 for which the exhaust enhancement device 10 is designed. In this way, the exhaust from the exhaust pipe 2 is forced through the exhaust enhancement device 10 when the exhaust enhancement device 10 is installed inside the exhaust pipe 2.

For example, in an exemplary embodiment, a 1.75-inch diameter tube is cut to a length of approximately 4.5 inches to use in the formation of the cylindrical tubular body portion 20. Each end of the tubing may then be swaged or expanded to various diameters (dependent on the exhaust pipe 2 into which it will be installed) to form the cylindrical end portions 24 and 25 of substantially uniform diameter, leaving the reduced diameter center chamber portion 22 of approximately 2 inches in length and 1.75 inches in outside diameter. In an exemplary embodiment, the cylindrical tubular body portion 20 is made from high carbon steel tubing and is dipped in a black oxide solution to heat treat the cylindrical portion 20 and to make it more rust and corrosion resistant. It should be noted that the dimensions described herein are merely examples of dimensions that may be typical for an exhaust enhancement device configured for a typical exhaust pipe. The actual dimensions (e.g., the length and diameter of the cylindrical portion 20) of the exhaust enhancement device 10 may depend on the particular exhaust pipe 2 in which the exhaust enhancement device 10 is to be installed.

As illustrated in FIGS. 2a and 2b, the cylindrical tubular body portion 20 may include an anti-reversion member 40 located within the cylindrical portion 20. The anti-reversion member 40 located in the enhancer 10 generally acts to create a vortex which allows the exhaust gases to exit the pipe more efficiently and helps lessen reversion. As described above, lessening any reversion in the exhaust system may increase the horsepower and the responsiveness of the engine.

In the illustrated embodiment, the anti-reversion member 40 includes a circular member 42 centrally located within the cylindrical portion 20. The circular member 42 may be, for example, a flat washer-like piece of metal having a central opening 43. A shaft 44 may be used to couple the circular member 42 to an inside wall of the cylindrical portion 20. In an exemplary embodiment, the shaft is configured to hold the circular member 42 such that the circular member 42 is oriented in a plane extending perpendicular to the longitudinal axis 15 of the cylindrical portion 20. The circular member 42 may also be oriented such that the center of the central opening 43 is located substantially coincident with the longitudinal axis 15 of the cylindrical portion 20.

As illustrated in FIG. 2a, in one embodiment the anti-reversion member 40 is disposed within the cylindrical end portion 25 located opposite the conical portion 30. As such, the anti-reversion member 40 may be disposed on the upstream end or the downstream end of the cylindrical portion 20 depending upon the orientation of the exhaust enhancement device 10 in the exhaust pipe 2. In other embodiments, the anti-reversion member 40 may be disposed within the cylindrical end portion 24 located on the same side of the cylindrical portion 20 as the conical portion 30. Additionally or alternatively, the anti-reversion member 40 may be disposed within the center chamber portion 22 of the cylindrical portion 20. In still other embodiments, the exhaust enhancement device 10 may be used without an anti-reversion member 40 disposed in the cylindrical portion 20, or, in some embodiments, the exhaust enhancement device 10 may have a plurality of anti-reversion members 40 of the same or different sizes located at various places within the cylindrical portion 20.

In some embodiments of the present invention, the cylindrical tubular body portion 20 is comprised of an embodiment of the exhaust enhancement device described in co-owned U.S. Pat. No. 6,848,252 or co-pending U.S. patent application Ser. No. 11/005,655, which are incorporated herein by reference. Similarly, the anti-reversion member 40 of embodiments of the present invention may be configured in a manner similar to the baffling/anti-reversion pieces described in these co-owned references.

As illustrated in FIGS. 2a and 2b, the frustoconical screen 30 of the exhaust enhancement device 10 may be coupled to the cylindrical end 24 of the cylindrical portion 20. In the illustrated embodiment, the frustoconical screen 30 has a circular cross-section that reduces in diameter as the cross-section is located further from the end of the cylindrical portion 20. In other words, the walls of the conical portion 30 generally converge in a funnel-like manner as they extend away from the cylindrical portion 20. In the illustrated embodiment, the conical portion 30 has a longitudinal axis that is defined by an imaginary line drawn through the center of the circular cross-sections. In the illustrated embodiment, the walls of the conical portion 30 taper uniformly on all sides such that a longitudinal axis of the conical portion is coincident with the longitudinal axis 15 of the cylindrical portion 20.

At one end (e.g., the “base” end of the conical portion), the cross-section of the conical portion 30 has an outside diameter that is approximately equal to or slightly less than the inside diameter of the cylindrical end 24 of the cylindrical portion 20. In the illustrated embodiment, the conical portion 30 has a cylindrical end 31 having an outside diameter approximately equal to the inside diameter of the cylindrical end 24 so that conical portion 30 may be coupled to the cylindrical portion 20 by coupling the cylindrical end 31 of the conical portion 30 to the cylindrical end 24 of the cylindrical portion 20. At the other end of the conical portion 30, the conical portion 30 typically has an opening 32 for permitting exhaust to travel therethrough. In this regard, the conical portion 30 generally has a frusto-conical shape. In addition to the opening 32 in the end of the conical portion 30, the conical portion 30 may have a plurality of other openings or holes in the walls of the conical portion 30 that also permit exhaust to travel therethrough. In this regard, in one embodiment, the conical portion 30 is perforated with an array of holes and may be manufactured, for example, from a metallic foraminous screen. As with the cylindrical portion 20, the conical portion 30 may be dipped in or otherwise coated with a black oxide solution to heat treat the conical portion 20 and to make it more rust and corrosion resistant.

As described above, the conical portion 30 may be coupled to the cylindrical portion 20 by coupling the conical portion's cylindrical end 31 to the cylindrical portion 20. In this regard, in one embodiment the outside surface of the conical portion's cylindrical end 31 is welded, soldered, or otherwise adhered to the inside surface of the cylindrical end 24 of the cylindrical portion 20. In other embodiments, a screw or bolt is used to couple the cylindrical end 31 of the conical portion 30 to the cylindrical portion 20. In other embodiments, the cylindrical end 31 of the conical portion 30 has a diameter that is greater than the end of the cylindrical portion 20 such that the inside surface of the cylindrical end 31 of the conical portion 30 may be coupled to the outside surface of the cylindrical portion 20. In still other embodiments, the conical portion 30 may not have a cylindrical end 31 and may be coupled to the cylindrical portion 20 in other ways apparent to a person skilled in the art in view of this disclosure.

As illustrated in FIGS. 2a and 2b, the conical portion 30 may include an anti-reversion member 45 located within the conical portion 30. Like the anti-reversion member 40, described above, the anti-reversion member 45 may act to reduce reversion of exhaust gasses. As described above, lessening the reversion in the exhaust system may increase the horsepower and the responsiveness of the engine.

In the illustrated embodiment, the anti-reversion member 45 is embodied as a circular member 47 centrally located within the conical portion 30. The circular member 47 may be, for example, a flat washer-like piece of metal having a central opening 48. In the illustrated embodiment, the circular member 47 is positioned in the conical portion 30 such that the circular member 47 is perpendicular to the longitudinal axis 15 of the conical portion 30. As also illustrated in FIG. 2a, the circular member 47 may be positioned at a location in the conical portion 30 where the outside diameter of the circular member 47 is approximately equal to the inside diameter of the frustoconical screen's cross-section. In such an embodiment, the circular member 47 may be coupled to the conical portion 30 by welding, soldering, or otherwise adhering the outside edge of the circular member 47 to the inside surface of the conical portion 30. As illustrated in FIGS. 2a and 2b, the circular member 47 may be oriented such that the center of the central opening 48 is located substantially coincident with the longitudinal axis 15 of the conical portion 30.

In other embodiments of the present invention, other means may be used to couple the circular member 47 to the conical portion 30 and the circular member 47 may be located and positioned differently in the conical portion 30. For example, in one embodiment, a shaft may be used to couple the circular member 47 to an inside wall of the conical portion 30. In some embodiments, the conical portion 30 may be configured with more than one anti-reversion member 45 located therein, while, in other embodiments, the conical portion 30 may be used without an anti-reversion member 45.

FIGS. 3a and 3b illustrate a perspective sectional view and an exploded view, respectively, of an exhaust enhancement device 110 in accordance with another embodiment of the present invention. This embodiment of the present invention is generally similar to the embodiment depicted in FIGS. 2a and 2b in that the exhaust enhancement device 110 includes a cylindrical tubular body portion 120 having a frustoconical screen 130 extending therefrom. The exhaust enhancement device also has an anti-reversion member 140 located within the cylindrical portion 120. As in the embodiments described above, the anti-reversion member 140 may include a flat circular member 142 having a circular central opening 143. The anti-reversion member 140 may be configured such that circular member 142 is positioned perpendicular to the longitudinal axis 115 of the cylindrical portion 120. The circular member 142 may also be positioned such that the center of the central opening 143 is located substantially coincident with the longitudinal axis 115. A shaft 144 may be used to couple the circular member 142 to an inside wall of the cylindrical portion 120.

The embodiment of the exhaust enhancement device 110 depicted in FIGS. 3a and 3b differs from the embodiment previously described with respect to FIGS. 2a and 2b primarily in that the tubular body of the cylindrical tubular body portion 120 is of uniform diameter throughout. In general, the diameter of the cylindrical tubular body portion 120 is approximately equal to or just less than the inside diameter of the exhaust pipe 2 for which the exhaust enhancement device 110 is designed. In this way, the exhaust from the exhaust pipe 2 is forced through the exhaust enhancement device 110 when the exhaust enhancement device 110 is installed inside the exhaust pipe 2.

FIGS. 3a and 3b also illustrate an embodiment of the exhaust enhancement device where only one flat circular member 142 is positioned within the path of the exhaust gasses. In other embodiments, however, such as the embodiment illustrated previously with respect to FIGS. 2a and 2b, the exhaust enhancement device 110 may include more than one flat circular member 142 and the flat circular member 142 may be positioned within frustoconical screen 130 in addition to or as an alternative to a flat circular member being positioned within the cylindrical tubular body portion 120.

FIG. 4 is a cross-sectional view of an exhaust pipe 2 illustrated in FIG. 1a, the exhaust pipe 2 having an exhaust enhancement device 10 disposed therein in accordance with an embodiment of the present invention. FIG. 4 illustrates how the exhaust enhancement device 10 may be coupled to the exhaust pipe 2 in an exemplary embodiment of the invention. Specifically, one or more holes may be punched in the walls of the cylindrical tubular body portion 20, such as in the walls of the cylindrical ends 24 or 25 that are adjacent to the exhaust pipe walls when the exhaust enhancement device 10 is disposed within the exhaust pipe 2. A weld nut 13 can then be spot welded to the interior surface of the cylindrical portion's wall at each punched hole. A corresponding hole can be punched in the exhaust pipe 2 and a bolt 17 can be placed through the holes and threaded through the weld nut 13 to secure the exhaust enhancement device 10 within the exhaust pipe 2. Of course, other means of securing the exhaust enhancement device 10 within the exhaust pipe 2 will be apparent to a person skilled in the art in view of this disclosure.

FIG. 4 also illustrates how an embodiment of the anti-reversion member 240 may be coupled to the exhaust enhancement device 10 in accordance with an embodiment of the invention. In one embodiment, the shaft of the anti-reversion member 240 is made from a threaded screw or bolt 244 and the flat circular member 242 is made from a washer. For example, a ¼ 20 Allen head screw may be used with a 316 stainless steel washer that is heliarc welded to the top of the Allen screw using stainless steel rod. Once the washer is welded to the screw, they may then be polished to harden and smooth them. In the illustrated embodiment, a weld nut 13 is welded to the interior surface of the wall of the cylindrical tubular body portion 20 and the threaded shaft 244 of the anti-reversion member 240 is threaded into the weld nut 13. When the shaft 244 is threaded into the weld nut 13 such that the washer is oriented and positioned as desired within the path of the exhaust gasses, the anti-reversion member 240 may be secured in position by tightening a lock nut 18 against the weld nut 13. In one embodiment, holes are punched through the cylindrical portion 20 and/or the exhaust pipe 2 so that the shaft 244 can extend therethrough. In such an embodiment, the shaft 244 in conjunction with the holes and the weld nut 13 may be used to secure the exhaust enhancement device 10 within the exhaust pipe 2.

In other embodiments of the present invention, the anti-reversion member may be fabricated from a single piece of metal and may be welded to the body of the exhaust enhancement device 10. For example, in one embodiment, the anti-reversion piece may be fabricated from a standard eye-type electrical terminal of the kind commonly used for connecting an automotive battery cable to a battery. The flat circular-shaped portion of the anti-reversion piece is formed by the eye portion of the terminal and shaft portion of the anti-reversion is formed by the lug portion of the terminal which, when used as an electrical connector, is designed to be crimped onto the battery cable. The one end of the shaft portion may then be welded to the interior of the tubular body. The opposite end of the shaft portion terminates in the above-noted flat circular portion, which is position centrally of the cylindrical tubular body. More particularly, the flat circular shaped portion is in the shape of a flat washer having a central opening with a center located substantially coincident with the longitudinal axis of the tubular body. FIGS. 2a through 3b illustrate anti-reversion members 40 and 140 that are generally of the type formed from an eye-type electrical terminal, in accordance with one embodiment of the invention.

Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. An exhaust enhancement device for a motorcycle exhaust pipe comprising:

a cylindrical tubular body portion configured to be received within a motorcycle exhaust pipe for receiving the flow of exhaust gases therethrough, said body portion having first and second open opposite ends and a cylindrical wall extending therebetween;

a formanious screen extending from said first end of the cylindrical tubular body portion, said screen having a frustoconical configuration converging as it extends away from the body portion and defining an open first end of a diameter generally corresponding to the diameter of said first end of the body portion and an open opposite second end of a smaller diameter; and

at least one obstruction positioned within the cylindrical tubular body portion or the frustoconical screen in the flow path of exhaust gases passing through the enhancement device.

2. The exhaust enhancement device of claim 1, wherein the at least one obstruction comprises a flat circular member.

3. The exhaust enhancement device of claim 2, wherein the flat circular member is oriented in a plane perpendicular to the longitudinal axis of the cylindrical tubular body portion.

4. The exhaust enhancement device of claim 3, wherein the flat circular member has a central opening and is positioned coaxially of the longitudinal axis of the cylindrical body portion.

5. The exhaust enhancement device of claim 4, wherein the flat circular member is positioned within the frustoconical screen.

6. The exhaust enhancement device of claim 5, wherein outer peripheral edges of the flat circular member are connected to the interior surface of the frustoconical screen to secure the flat circular member in place.

7. The exhaust enhancement device of claim 4, wherein the flat circular member is positioned within the cylindrical tubular body portion.

8. The exhaust enhance device of claim 7, including a shaft having a first end connected to the flat circular member and a second end connected to the interior surface of the cylindrical wall of the tubular body portion.

9. The exhaust enhancement device of claim 1, wherein the at least one obstruction comprises a first flat circular member oriented in a plane perpendicular to the longitudinal axis of the cylindrical tubular body portion and positioned within the frustoconical screen and a second flat circular member oriented in a plane perpendicular to the longitudinal axis of the cylindrical tubular body portion and positioned within the cylindrical tubular body portion.

10. The exhaust enhancement device of claim 9, wherein said first and second flat circular members each have a central opening and are positioned coaxially of the longitudinal axis of the cylindrical body portion.

11. The exhaust enhancement device of claim 1, wherein the frustoconical screen includes a cylindrical first end portion adjacent said open first end which is received within and secured to said cylindrical wall of said cylindrical tubular body portion and a frustoconical tapering second portion extending from said first end portion to said open second end of the frustoconical screen.

12. The exhaust enhancement device of claim 1, wherein an outside diameter of the cylindrical tubular body portion is approximately equal to the inside diameter of the motorcycle exhaust pipe.

13. The exhaust enhancement device of claim 1, wherein the wall of said cylindrical tubular body portion includes a reduced-diameter center chamber between said first and second opposite ends.

14. The exhaust enhancement device of claim 13, wherein the at least one obstruction comprises a flat circular member oriented in a plane perpendicular to the longitudinal axis of the cylindrical tubular body portion and located adjacent one of said ends.

15. A motorcycle exhaust system comprising:

an exhaust pipe for expelling exhaust from an engine;

a cylindrical tubular body portion received within said exhaust pipe for receiving the flow of exhaust gases therethrough, said body portion having first and second open opposite ends and a cylindrical wall extending therebetween;

a formanious screen extending from said first end of the cylindrical tubular body portion, said screen having a frustoconical configuration converging as it extends away from the body portion and defining an open first end of a diameter generally corresponding to the diameter of said first end of the body portion and an open opposite second end of a smaller diameter; and

at least one obstruction positioned within the cylindrical tubular body portion or the frustoconical screen in the flow path of exhaust gases passing through the enhancement device.

16. The exhaust system of claim 15, wherein the at least one obstruction comprises a flat circular member oriented in a plane perpendicular to the longitudinal axis of the cylindrical tubular body portion.

17. The exhaust system of claim 16, wherein the flat circular member has a central opening and is positioned coaxially of the longitudinal axis of the cylindrical body portion.

18. The exhaust system of claim 15, wherein the open second end of the frustoconical screen is oriented toward an engine end of the exhaust pipe.

19. The exhaust system of claim 15, wherein the open second end of the frustoconical screen is oriented toward an exit end of the exhaust pipe.

20. The exhaust system of claim 15, wherein the outside diameter of at least a portion of the cylindrical tubular body portion corresponds approximately to the inside diameter of the exhaust pipe.