WO2010064256A1

WO2010064256A1 - Automotive exhaust system

Info

Publication number: WO2010064256A1
Application number: PCT/IN2009/000221
Authority: WO
Inventors: Rajeev Madhukar Ranadive
Original assignee: Rajeev Madhukar Ranadive
Priority date: 2008-12-04
Filing date: 2009-04-01
Publication date: 2010-06-10

Abstract

The present invention relates to an Automotive Exhaust System, herein after referred to as Switchable High Performance Exhaust system, having exhaust header tubes (2) attached to the exhaust ports of a multi-cylinder engine at one end and terminating in to an expansion chamber (1) at the other end, which expansion chamber (1) is provided with two types of outlets (34). One type of outlet or outlets (3,4) is connected to the "legally Compliant Exhaust System". The other type of outlet or outlets (3, 4), called auxiliary outlet (3) or outlets (3), are openable and closeable at will, to enable the vehicle to be driven in "High Performance Mode" when the said auxiliary outlets are open. It also enables the vehicle to be driven in "Legally Compliant Mode" when the auxiliary outlets (3) are closed. Due to this system, the engine performs more efficiently, developing more power and/ or reducing the first consumption.

Description

Automotive exhaust system

Technical field: The present invention relates to an Automotive Exhaust System, herein after referred to as Switchable High Performance Exhaust system, having exhaust header tubes attached to the exhaust ports of a multi-cylinder engine at one end and terminating in to an expansion chamber at the other end, which expansion chamber is provided with two types of outlets. One type of outlet or outlets is connected to the "legally Compliant Exhaust System". The other type of outlet or outlets, called auxiliary outlet or outlets, are openable and closeable at will, to enable the vehicle to be driven in "High Performance Mode" when the said auxiliary outlets are open. It also enables the vehicle to be driven in "Legally Compliant Mode" when the auxiliary outlets are closed.

Definitions: a) Legally Compliant Exhaust system:

There are certain requirements with respect to the exhaust system which are required to be met while driving the vehicle on the road. The requirements are as follows:

• The exhaust gases from an engine are required to be cleaned of toxic or hazardous matter before such gases are allowed to escape to the atmosphere. This is achieved by passing the gases through devices commonly called "After Treatment Devices", examples of which are Catalytic Converter and Particulate filters.

• The law requires that the sound emitted from the vehicle shall not exceed certain loudness limit. This is achieved by routing the exhaust gases through what is commonly called a "silencer" or a "Muffler", before the exhaust gases are released to the atmosphere. • In addition, the law requires that the exhaust gases be released from a specific location with respect to the vehicle, and that they should be released in a defined direction.

The exhaust system which complies with the rule given above is called as "Legally Compliant". The manufacturer provides such an exhaust system duly fitted with the vehicle.

b) Street Legal Mode (Referred to as legally compliant mode hereinafter):

As stated herein above, the invention provides for one or more outlets for the expansion chamber, which either comply with the law, or are connectable to the outlets capable of compliance with the law.

As such whenever stated auxiliary outlets are closed, the exhaust gases can pass only through the "Legally compliant" passage or outlet. Whenever the vehicle operates with the auxiliary outlets closed, it is referred to as the vehicle is operating in the "legally compliant mode".

c) High Performance Mode:

Whenever the auxiliary outlets are opened, which are intended to enhance the performance of the engine, and when the vehicle is driven with these auxiliary outlets open, it is said to be operating in "High Performance Mode".

d) Legally Compliant Outlets:

The outlets provided to the expansion chamber, which comply with the above stated requirements, or are connectable to passages which will comply with the above stated requirements is/ are therefore referred to as "legally Compliant Outlets"

e) Auxiliary Outlets:

The second type of outlets are referred to as "Auxiliary Outlets" which are fitted to the expansion chamber and are characterized by provision of a device, such as a valve, or a plug which will enable the said auxiliary outlets to be opened and closed at will.

f) Header:

Header is a cluster or assembly of tubes or hollow tubular passages of any cross section, made of materials such as mild or stainless steel, cast steel etc. They are also referred to as exhaust manifold, primary tubes etc. These tubes are connected to the exhaust port of an engine at one end, and the other end may be connected to the subsequent part of the exhaust system, such as the catalytic converter, muffler and the like. In the proposed embodiment, the header tubes are connected to an expansion chamber, either directly or indirectly, as defined below.

g) Expansion Chamber Having Header Tubes and Two Types of Outlets:

The expansion Chamber is a cavity, the shape of which may depend on factors such as packaging requirement of the vehicle on which it is installed; the pressure/ velocity/ direction of the gases entering into this cavity, and the outlet passages connected thereto. The expansion chamber are used for various proposes in different embodiments. Accordingly, the expansion chamber shape can vary depending on the vehicle on which it is fitted, the 80 space available, and the flow requirements of the engine. Variation in the shape of the expansion chamber has no limitation. The cylindrical shape shown in the illustration is only to explain the principle behind the invention.

The objective of terminating the header pipes into the expansion chamber is 85 to enable the exhaust gases exiting the header pipes to expand spontaneously, as explained here under. The objective of providing the auxiliary outlet or outlets to the said expansion chamber is to provide additional route for the exhaust gases to escape to the atmosphere from the expansion chamber, thereby reduce the pressure building up inside the 90 expansion chamber. This reduction in pressure enables quicker and more complete evacuation of the exhaust gases from the engine of the vehicle, so that the engine develops more power, whenever the auxiliary outlets are opened.

95 The purpose for which the expansion chamber is utilized in the proposed embodiment is to provide appropriate volume to enable the exhaust gases exiting from the engine's exhaust port through the header tubes to expand and promote evacuation of exhaust gases from the engine. More over, it is intended to prevent exhaust gases exiting from one exhaust header tube port

100 to interfere with evacuation of the exhaust gases from the other header tube port.

To achieve this above stated objective, the expansion chamber is connected to the header tubes. 105 The invention also provides that such an expansion chamber shall be equipped with two distinct types of outlets for the exhaust gases to escape from the expansion chamber to the atmosphere. These two types of outlets are as said above: Legally Compliant Outlets, Auxiliary Outlets 110

Background of the Invention and the Prior Art: Prior Art Employed By Vehicle Manufacturers

• The "Headers" of multi-cylinder engines provided by the vehicle manufacturers, or available in the market as a part of "High Performance

115 Exhaust" and/ or covered by the patents, do not terminate into an expansion chamber, but merge with each other, before terminating into an expansion chamber and/ or muffler.

• Vehicle manufacturers are required to equip vehicles sold by them with the exhaust systems which will comply with the legal provisions with

120 respect to cleansing of the toxic or environmentally harmful gases, keeping the noise level below specified limit and locating the exhaust gas outlet with respect to the vehicle as required by the law.

• The devices installed by the manufacturer to meet the above requirements result in causing restriction to the flow of the exhaust gases, thereby

125 resulting in loss of power available from the engine to propel the vehicle.

• The vehicle manufacturers also have to limit the power of the engine to ensure that the engines do not produce exhaust gases with toxic substances beyond the limit specified by law.

• The exhaust systems provided by the manufacturer are designed to meet 130 the exhaust gas flow requirements of the engine with the above limitations of meeting the law, and permissible power. • The exhaust system supplied by the manufacturer therefore imposes limitation in enabling the engine to attain it's full potential of developing power.

135 • The exhaust system supplied with the vehicle with the manufacturer is commonly referred to as the 'Original Exhaust System".

Prior Art With Respect To The Modifications Carried out by motor-sports enthusiasts- 140A- "High Performance" Exhaust systems

• Commercially sold vehicles are modified by motor-sports enthusiasts, for participating into various competitions and/ or sporting events.

• During such events, compliance to the laws concerning exhaust emissions or noise emissions may not be applicable.

145 • One of the objectives of modifications is to enable the engine to develop maximum possible power.

• The exhaust system, provide by the manufacturer, which imposes limitation on the power of the engine therefore becomes a target of modification.

150 • Exhaust systems designed to improve evacuation of exhaust gases are available in the market, for which several researchers have obtained patents.

• These exhaust systems enable the engine to "breath" better, thereby improving availability of air in the engine, thereby enabling more fuel

155 to be burnt and thereby enhancing the power the engine is capable of developing • Such exhaust systems are commonly known as high performance exhaust systems.

• Such exhaust systems do away with some or all parts of the original 160 exhaust system, and therefore may not remain legally compliant to the laws concerning exhaust systems explained above.

• Moreover, it is very difficult, expensive and time consuming to remove the "High Performance Exhaust System" from a vehicle, and re-install the original exhaust system on to the vehicle, after the motor sports

165 event.

B- "Switchable'' Performance Enhancement Exhaust Systems

• In order to enable the engine to develop more power than what is possible with the original exhaust system, several researchers have

170 developed devices, to achieve either or all of the following. Such systems are referred to as "Switchable Performance Enhancement Systems" herein below, to distinguish them from the "High Performance exhaust Systems" described above, which do not have ability to switch between "Performance Mode" and "Street Legal

175 Mode".

• Enable "Bypassing" of some of the devices, such as muffler, of the original exhaust system, by provision of pipes running parallel to such elements of the original exhaust. Since the original elements such as a muffler causes restriction to the flow of exhaust gases in order to

180 reduce noise emitted by the exhaust gases, when the flow is diverted through a parallel pipe, the restriction to the flow of the exhaust gases is reduced. Suitable valve arrangement is used to "Switch" the flow of the exhaust gases either through the original element, or through the parallel pipe.

185 • Replace the muffler fitted in the original exhaust system by the manufacturer of the vehicle to comply with the law, with a muffler having multiple passages. Such a replacement muffler is equipped with a valve, which divers the exhaust gases from one passage to another. One of the passages directs the exhaust gases through more

190 effective muffler to reduce the noise level compliant with the law, the other passage bypasses some or the entire muffler to reduce restriction to the flow of the gases.

• Provide a valve or a plug after the header, and release exhaust gases directly to the atmosphere, from the header. 195

Disadvantages of Prior Art:

Disadvantages of the Exhaust System Fitted By Vehicle Manufacturers: As explained hereinabove, the original exhaust system is not aimed at enabling the engine to develop maximum power, but is aimed at meeting the 200 legal provisions related to the exhaust system explained hereinabove. Moreover, the power of the engine is restricted by such exhaust system deliberately to ensure that the engine does not produce excessive pollutants.

As such, this original exhaust system is not considered suitable during 205 motorsports evens. The motorsports enthusiasts therefore replace the original exhaust system, with another exhaust system, in order to enable the engine of the vehicle to develop more power. Disadvantage of "High Performance" exhaust system:

• This type of exhaust system described hereinabove, when installed on the 210 vehicle, enables the engine to develop more power, but renders the vehicle operable only in the "High Performance Mode". Such systems do not possess any means, which will enable them to also operate in "Street Legal Mode" by "Switching".

• To make the vehicle "Street Legal", after it has been modified, it is 215 necessary to remove the high performance exhaust system, and re-install the original system. This process is tedious, difficult and expensive.

Disadvantage of "Switchable" Performance Enhancement Exhaust Systems: The "Switchable Performance enhancement exhaust systems" reduce

220 restriction to the flow of the exhaust gases caused by devices fitted by the vehicle manufacturer to meet the law, such as muffler which is fitted in the original system, by providing means to bypass such devices when desired. Alternately, the "Switchable" exhaust systems provide for two passages within a device such as a muffler, one passage being compliant to the legal

225 requirement, the other passage provided to bypass the legally compliant passage Therefore, the performance enhancement achievable is limited to that achieved by reduction of restriction. Therefore, such systems are not as effective in enhancing performance of the engine to the extent possible by use of the "High Performance Exhaust Systems"

230 Patents regarding Switchable Performance Enhancement Systems are as follows:

U.S. PATENT 922,563 DATED MAY 25, 1909

The invention provides for a valve to bypass exhaust muffler, and let out the 235 exhaust gases from the valve fitted before the muffler

US Patent 1,794,642 March 31931

The invention provides for an aperture to enable exhaust gases to escape from the exhaust manifold. This aperture is provided with a valve. Opening 240 of the valve enables bypassing the muffler

US Patent 4,674,278 Dated June 23, 1987

The embodiment provides a bypass valve to enable exhaust gases to escape into the atmosphere without passing through flame trap 245

US Patent 4,913,260 April 3 ,1990

The embodiment presents bypass valve within muffler.

US Patent 4,920747 May 1, 1990

250 The embodiment provides for a bypass port at the junction at the header assembly.

US Patent 4,939,898 JuI 10, 1990

The embodiment provides for a valve to change cross section of the exhaust 255 passage. US Patent 5,452578 Sep 26, 1995

The embodiment provides for Exhaust Cutout device, enabling exhaust gases to escape to atmosphere without passing through the muffler. 260

US Patent 5,692,374 Dec 2, 1997

The embodiment provided for a bypass valve within muffler.

US Patent 5,712,454 Jan 27, 1998 265 The embodiment provides for a bypass valve within the muffler.

US Patent 5,739,483 April 141998

The embodiment provided for a bypass valve within the muffler

270 US Patent 5,744,762 Apr 28, 1998

The embodiment provides for a bypass valve which opens additional outlet from the muffler.

US Patent 5,743,088 Apr 28, 1998

275 The embodiment provides for a valve to enable exhaust gases to escape from larger outlet.

US Patent 6,178,745 Jan30, 2001

The embodiment provides for a valve within a muffler to alter damping 280 characteristics. US Patent 6,584,767 JuI 1, 2003

285 The embodiment provides for a bypass valve, before the muffler, which connects to a parallel pipe, allowing the exhaust gases to bypass the muffler completely.

US Patent 6,598,390 B2 JuI 29, 2003

290 The embodiment provides for a valve before the muffler, to enable release of exhaust gases from a smaller or larger pipe through the muffler.

US Patent 6,612,400 B2 Sep 2, 2003

The embodiment provides for an electronically controlled valve, within the 295 muffler, to bypass some of the muffler elements to change the sound.

US Patent 6,662,554 B2 Dec 16, 2003

The embodiment provides for a valve, which can direct the exhaust gases from either a normal muffler or a low restriction muffler. 300

US Patent 6,915,876 B2 July 12, 2005

The embodiment provides for an electronically controlled valve installed on the muffler, which allows the exhaust gases to escape to the atmosphere without passing through all the muffler elements. 305

US Patent 6,938,729 B2 Sep 62005

A combination of valves enables use of one or more mufflers to alter muffling effect or flow resistance.

310 US Patent 7,040,451 B2 May 9, 2006

The embodiment provides a muffler device with plurality of mufflers and a valve to change flow resistance.

315 US Patent 7,121,088 B2 Oct 17, 2006

Valve assembly disposed within the muffler to select passage of exhaust gases through the muffler.

US Patent 7,171,804 B2 Feb 6, 2007

320 Exhaust system of a multi-cylinder engine, having header pipes terminating into a valve, which enables control of area of passage of exhaust gases, depending on engine speed.

US Patent 7,210,289 B2 May 1, 2007

325 Engine exhaust control system, comprising of a valve fitted within the exhaust pipe, with electronic control.

US Patent 7,267,195 B2 Sep 11, 2007

Exhaust device with two controllable outputs, one classical exhaust system, 330 and the other incorporating means to dilute and reduce visible, sound and infrared signature of the vehicle.

US 7,347,045 B2

The present invention provides a method of operating a dynamic exhaust

335 system of a motorcycle engine. The method includes providing a valve in the exhaust system that is movable to direct exhaust gases between a first flow path through the exhaust system and a second flow path through the exhaust system depending on the speed of the vehicle.

340 US 7,040,451 B2

The present invention provides a muffler device of a motor vehicle, with a plurality of mufflers and an actuator for changing the flow resistance to the exhaust gases flowing through the mufflers.

345 EP 1.739.287 Bl 13 Feb 2008

Method of actuating a switchover mechanism to select between two paths of the exhaust system depending on the speed/ load of the motor vehicle

EP 1.321.639 A225™ June 2003

350 Valve assembly installed at the muffler to enable the exhaust gases to bypass some of the muffler elements.

Objects of the present invention:

The object of the present invention is to create an exhaust system, which 355 combines benefits of the original exhaust system in terms of compliance to the legal requirements, benefits of the "High Performance Exhaust System" with respect to it's ability to enhance the performance of the engine, and also have ability to switch between the "Street Legal Mode" to "High Performance Mode" and back again, with minimum effort, cost and time. 360

Another object of the present invention is to improve performance of the engine, not only when the vehicle is operating in "High Performance Mode" but also while the vehicle operates in the "Street Legal Mode". 365 Yet another object of the present invention is to improve evacuation of the exhaust gases, to increase the fuel efficiency in the performance mode as well as in street legal mode.

A further object of the present invention is to improve the appeal of the 370 vehicle to the motor sports enthusiasts, as well as the novices by enabling them to use the same vehicle for Motor Sports Occasions as well as for daily use.

Statement of the invention:

375 The said exhaust system is designed such that the exhaust gases from individual cylinders are conveyed by individual pipes, called headers as defined above. The length and diameter of the headers can be 'tuned' to use pressure energy of the exhaust gases to assist the expulsion of the exhaust gases.

380 The header tubes remain independent of each other, till they terminate into an expansion chamber, as defined above. The dimensions and shape of the container is so designed that the exhaust gases entering the expansion chamber from the header tube expand. Due to the expansion of the exhaust gases, their pressure and temperature at the point of termination of the

385 header tube drops. This drop in pressure and temperature of the exhaust gases helps in more complete evacuation of the cylinder and reduces the energy lost by the engine in driving out the burnt gases from the cylinder. As a result, the engine sucks in more fresh air, performs more efficiently, developing more power and/ or reducing the fuel consumption. 390 The said expansion chamber, into which the exhaust gases are received from the header tube, and which provides for volume for their expansion, are also provided with two types of outlets, to provide for exit route for the incoming exhaust gases. One or more outlets of one type, called "Legally compliant outlet" is

395 compliant to or connectable to a "legally compliant passage for the exhaust gases, such that any toxic substance present in the exhaust gases are removed or reduced, noise emitting from the exhaust gases is brought down to the specified legal limit, and the exhaust gases are released at the appropriate point prescribed by the law.

400 In addition, the expansion chamber is also provided with one or more outlets, which may not comply with the law. These outlets are termed as auxiliary outlets, and characterized by provision of devices to open or close these outlets. The auxiliary outlet or outlets is/ are provided with device such as valve or

405 plug, to enable opening and closing of the said auxiliary outlet. Opening of the said auxiliary outlet creates plurality of outlet passages, substantially increasing the aperture area for the exhaust gases to escape into the atmosphere. The plurality of the apertures also helps by providing for escape routes for the exhaust gases at several locations, which results into reducing

410 the restriction to the flow of the exhaust gases, thereby increasing the power of the engine.

Opening of the outlets provide additional escape route for the exhaust gases, which enables more rapid evacuation of the exhaust gases from the

415 expansion chamber. Such rapid evacuation enables the engine to develop more power, whenever such more power is desired and laws with respect to the release of exhaust gases is not applicable. Example: during a motor sport event.

Closure of these auxiliary outlets compels the exhaust gases to pass only

420 through the legally compliant passage.

Moreover, the invention enables expansion of the exhaust gases at the point where the header pipes terminate, so as to enable the exhaust gases to be evacuated from the cylinder more easily, which also results into improvement of power, even when the auxiliary apertures are closed, and the

425 vehicle is operating in the street legal mode.

Detailed description of the invention:

The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art, techniques and approaches are

430 overcome by the present invention as described below in the preferred embodiment.

This invention is illustrated in the accompanying drawings, through out which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the following description

435

Figure 1: The preferred embodiment is shown with four header tubes (2) terminating into an expansion chamber (1), which expansion chamber is shown with two auxiliary outlets (3) on either side of the expansion chamber and one outlet connectable to legally compliant outlet (4) is shown in the

440 centre. Figure 2: The preferred embodiment is shown with four header tubes (2) terminating into an expansion chamber (1), which expansion chamber is shown with one auxiliary outlets (3) in the centre of the expansion chamber 445 and two outlets connectable to legally compliant outlet (4) are shown on either side of the expansion chamber.

Figure 3: The preferred embodiment is shown with four header tubes (2) terminating into an expansion chamber (1), which expansion chamber is 450 shown with two auxiliary outlets (3) on either side of the expansion chamber and one outlet connectable to legally compliant outlet (4) is shown in the centre. In addition, this preferred embodiment is shown with sound absorption material (5) positioned opposite header tube apertures.

455 Figure 4: The preferred embodiment is shown with four header tubes (2) terminating into an expansion chamber (1), which expansion chamber is shown with two auxiliary outlets (3) on either side of the expansion chamber and one outlet connectable to legally compliant outlet (4) is shown in the centre. In addition, the preferred embodiment is shown with sound

460 absorption and or emission control device fitment (6) to auxiliary outlet.

Figure 5: The preferred embodiment is shown with four header tubes (2) terminating into an expansion chamber (1), which expansion chamber is shown with two auxiliary outlets (3) on either side of the expansion chamber 465 and one outlet connectable to legally compliant outlet (4) is shown in the centre. In addition, the preferred embodiment is shown with a junction box (7) in between the expansion chamber and the header tubes, in which headers terminate. Such a Junction box (7) may also provide for space to install sound absorption or emission control devices. 470

Figure 6: The preferred embodiment is shown with the said header pipes (2) are so oriented in the expansion chamber (1) that they protrude inside the expansion chamber.

475 The exhaust system is designed such that the exhaust gases from individual cylinders are conveyed by Header tubes (2). These tubes remain independent of each other, till they terminate into Expansion chamber (1), or a junction box (7). The dimensions and shape of the expansion chamber (1) is so designed that the exhaust gases entering the expansion chamber (1) from the header

480 tube (2) expand, as a result of which their pressure and temperature drops. This drop in pressure and temperature of the exhaust gases after reaching the said expansion chamber (1) causes more complete evacuation of the cylinder and reduces the energy lost by the engine in driving out the burnt gases from the cylinder. As a result, the engine performs more efficiently, developing

485 more power and/ or reducing the fuel consumption.

The said expansion chamber (1) is provided with one or more legally compliant outlets (4), which are connectable to one or more legally compliant exhaust passages. In addition, the said expansion chamber is also provided with Auxiliary outlets (3). Such auxiliary outlets render themselves suitable

490 for fitment of valves of several types including "One Way Valves", operable through any means such as manual, mechanical, electro-mechanical, hydraulic, pneumatic, vacuum assisted, and the like. Opening of the said auxiliary outlet creates plurality of outlet passages, substantially increasing the aperture area for the exhaust gases to escape into the atmosphere. The

495 plurality of the apertures also helps by providing for escape routes for the exhaust gases at several locations, which results into reducing the restriction to the flow of the exhaust gases, thereby increasing the power of the engine. It is also possible for the auxiliary outlets to be fitted with or perform as various types of nozzles, tubes, resonance chambers or similar devices used for

500 "Tuning" the pulsation of the escaping exhaust gases.

In one of the preferred embodiments as shown in Fig. 6, the said header pipes (2) are so oriented in the expansion chamber (1) that they protrude inside the expansion chamber. As a result, chances of "Reversal" of the pressure wave 505 moving backward into the header pipe through which they exited, and/ or entry into any of the adjoining header pipes is eliminated, or reduced drastically.

In one of the embodiments explained with help of Fig 4, sound absorbing 510 material (5) is positioned opposite the header tubes (2). Commonly used materials for this purpose are rock wool, ceramic wool, and the like. As a result, the exhaust gases exiting the said tubes impinge on to the said noise /sound absorption material, positioned on and/ or inside the expansion chamber, in such a manner that considerable sound energy is expended 515 closer to the source of the sound, without causing obstruction to the flow of the exhaust gases. The construction of the expansion chamber can possess perforated sheets and similar material such as wire mesh, to keep the absorption material in place, and to provide "Communicating Passage" between the volume of the expansion chamber and the absorbent, which 520 together assist in absorbing the sound pressure energy.

In one of the preferred embodiments, the said expansion chamber is so located that it is cooled by the air flow caused by the motion of the vehicle, to further reduce the temperature and therefore pressure of the exhaust gases, 525 which helps in improvement of performance of the engine and reduction of the unwanted sound or noise. To enhance cooling, it is possible to equip the expansion chamber with fins or similar arrangement, to increase area of expansion chamber exposed to the air flow caused by motion of the vehicle.

530 The auxiliary outlets may or may not comply with the legal requirements. The said auxiliary outlets may or may not possess emission control and/ or silencing devices.

The said auxiliary outlets render themselves self suitable for fitment of 535 several types of apertures, so that the engine performance can be "tuned" to achieve desired shape of "Torque Curve"

The said auxiliary outlets render themselves suitable for fitment of one-way pressure relief system, such as a reed valve, so that when the pressure in the 540 expansion chamber pulsates above the atmospheric pressure, the exhaust gases shall have additional outlet to escape, but when the pressure in the expansion chamber pulsates below the atmospheric pressure, the outside air shall be prevented from entering the expansion chamber, thereby helping in reducing the mean pressure in the expansion chamber. 545 Although four header tubes are shown, the numbers of header tubes may vary according to the design of the engine and the installation on the vehicle of the engine requirement.

Similarly, although cylindrical shape is shown as the expansion chamber, 550 such a shape has no relation with the purpose served by the expansion chamber. The expansion chamber may be of any shape more dependent on ease of fitment on the vehicle, location of the header tubes, auxiliary outlets

^"and the legally compliant outlets.

Similarly, although cylindrical shape is shown as the header tube, the legally 555 compliant outlet, the auxiliary outlet, such a shape has no relation with the purpose served by the items mentioned herein. These items may have any shape or cross section.

Any outlet, whether legally compliant or auxiliary, may have single or multiple 'orifices'. Similarly, it is possible to have more than one outlet of 560 each type, legally compliant or auxiliary.

While multiple embodiments are disclosed, still other embodiments of the present invention will become apparent to those skilled in the art from the embodiments and description. As will be realized, the invention is capable of 565 modifications without departing from the spirit of the invention.

The exhaust system is capable of switching operation between legally Compliant Mode^/ and Ηigh Performance Mode' as follows:

• The said expansion chamber, which receives exhaust gases from the said header tubes, is provided with two types of outlets. One type being

575 "Legally Compliant Outlet" the other type being "Auxiliary Outlet"

• The said auxiliary outlets, in the preferred configuration, possess a suitable device to enable closure of these outlets. Under this condition of operation, the exhaust gases shall be led through the legally compliant outlet only. As such, when the vehicle is operated with the auxiliary

580 outlets closed, it will comply with the laws concerning the exhaust system, and therefore operation of a vehicle with the auxiliary aperture closed is termed as "Operation In Legally Compliant Mode"

• Opening the said auxiliary outlets shall enable the exhaust gases to escape to the atmosphere from the auxiliary outlets also, thereby improving the

585 evacuation of the exhaust gases, reducing back pressure and resulting in higher performance of the engine, as and when such high performance is desired, and when the law and/ or rules permit such release of exhaust gases without passing through noise reducing or exhaust after treatment devices. Operation of the vehicle, with the auxiliary aperture open is

590 therefore termed as "Operation In High Performance Mode"

• The above description of operation of the exhaust system explains the manner in which the exhaust system is capable of switching between the "Legally Compliant Mode and "High Performance Mode"

Claims

595 I claim:

1. An automotive exhaust system, for improving performance of the engine, wherein the said exhaust system comprising of an exhaust header tubes attached to the exhaust ports of a multi-cylinder engine

600 at one end and terminating into an expansion chamber at the other end, wherein the said expansion chamber is provided with two types of outlets wherein one type of outlet or outlets is connected to the "legally Compliant Exhaust System" and other type of outlet or outlets, called auxiliary outlet or outlets, are openable and closeable at

605 will, to enable the vehicle to be driven in ""High Performance Mode" when the said auxiliary outlets are open and it enables the vehicle to be driven in "Legally Compliant Mode" when the auxiliary outlets are closed.

610 2. As claimed in claiml, the said auxiliary outlets being equipped with valve or valves of any suitable type, operable through any means such as manual, mechanical, electro-mechanical, hydraulic, pneumatic, vacuum -assisted and the like.

615 3. As claimed in claiml, an automotive exhaust system wherein the said header pipes are terminated to the said expansion chamber through a junction box.

4. An automotive exhaust system as claimed in claim 1, wherein the said 620 expansion chamber is so located that it is cooled by the air flow caused by motion of the vehicle, to further reduce the temperature and therefore the pressure of the exhaust gases.

5. An automotive exhaust system as claimed in claim 1, wherein the said 625 header pipe protrudes into the said expansion chamber in such a way that as soon as the exhaust gases exit from the header pipes into expansion chamber the said exhaust gases are prevented to re-enter the header pipe exited by them or other header pipe or pipes present in the expansion chamber. 630

6. An automotive exhaust system as claimed in claims 1 wherein sound absorption material such as rock wool, ceramic wool, and the like is positioned opposite the exit point of the header tubes, in the said expansion chamber.

635

7. An automotive exhaust system as claimed in claims 1 wherein the said outlets of legally compliant and auxiliary outlets are at three independent orientations in respect to the vehicle and the said header pipes in central part of said expansion chamber.

640

8. An automotive exhaust system as claimed in claims 1 having two legally compliant outlets on either side of the expansion chamber and one central auxiliary outlet, which lay out is more suitable for, but not limited to rear engined vehicles.

9. An automotive exhaust as claimed in all the above claims, provided with sound absorption or emission control means provided to the said auxiliary outlet for sound absorption and/ or for emission control.