FORM-2 THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE
Specification
(See Section 10 and Rule 13)
INTAKE MANIFOLD WITH FLAP VALVE FOR AUTOMOTIVE
VEHICLES
MAHINDRA TWO WHEELERS LIMITED
an Indian Company
of D-l block, Plot no. 18/2, Chinchwad,
Pune - 411019, Maharashtra, India.
INVENTORS:
1. DURAIARASAN SARAVANAN
2. GOKHALEANISH
3. NAVANEETHAKRISHNAN KARTHIKEYAN
4. KHAN SHAHNAWAZ
5. GURURAJAN ARUNPRASATH
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE NATURE OF THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

This application is a divisional application to Indian Patent Application No. 1936/MUM/2013 issued on June 3, 2013, the entire contents of which, is specifically incorporated herein by reference.
FIELD OF THE DISCLOSURE
The present disclosure relates to internal combustion gasoline engines.
More specifically, the present disclosure relates to an intake system for internal
combustion gasoline engines using a carburetor per cylinder.
BACKGROUND
An intake system for internal combustion engines includes an air filter, a connecting tube, a carburetor, an intake manifold and an intake port which leads the air and fuel mixture to combustion chamber. The power and torque required for driving a motor vehicle and the like, is developed in the cylinder of the engine by combustion of the fuel. The requirement of power and torque during engine operating condition depends on load encountered, for example, in the case of motor vehicles the load depends upon various factors like road conditions and weight of the vehicle and the like. To cater the power requirements at different load conditions, the intake conditions has to be varied by accelerator control as the power and the torque developed by the engine, largely depends upon the amount of charge taken in the cylinder through the plunger opening.
Conventionally, the plunger position of carburetor determines the engine operating range. The engine operating range is determined by the mechanical movement of a plunger that regulates the power and torque generated by the engine. Particularly, in case of motor vehicles the requirement of power and torque such as in normal city driving conditions is achieved at lower engine speeds at a part open throttle condition and such as on highways it is achieved at higher engine speeds at a wide open throttle condition. The engine power and the torque developed throughout the travel of carburetor plunger depend on various factors; one among them being the length and geometry of the intake manifold.

Various efforts have been made to achieve two peaks of the torque, one occurring at lower engine speed and one occurring at higher engine speed by changing e.g. the exhaust system characteristics. Also, efforts have been made to provide twin passages in the intake manifold wherein the flow to one of the passage is controlled with the help of a butterfly valve actuated through an external means. This however adds to cost, increased complexity, increased number of moving parts, decreased reliability, restriction in the flow path and the like.
Hence, there is felt a need for a system that can provide higher torque at both part open throttle conditions and at wide open throttle condition.
OBJECTS
Some of the objects of the system of the present disclosure, which at least one embodiment herein satisfies, are as follows:
An object of the present disclosure is to provide an intake system that enables good spread of torque throughout the engine operating range.
Another object of the present disclosure is to provide an intake system that is simple
in construction.
Further, an object of the present disclosure is to provide a system that is reliable.
Yet another object of the present disclosure is to provide a system that involves
minimal moving parts.
An added object of the present disclosure is to provide a system that facilitates
improved combustion of fuel within an IC engine.
Another object of the present disclosure is to provide a system that is adaptable in
compact space.
Other objects and advantages of the present disclosure will be more apparent from the
following description when read in conjunction with the accompanying figures, which
are not intended to limit the scope of the present disclosure.

SUMMARY
In accordance with the present disclosure there is provided an intake manifold for conveying air-fuel mixture from an inlet to an outlet, the inlet and the outlet being connected to the carburetor and the cylinder head of the engine respectively, the manifold characterized by:
• a long duct fluidly communicating between the inlet and the outlet;
• a short duct fluidly communicating between the inlet and the outlet;
• a junction defined at fluid connection between the long duct and the short duct, the junction configured downstream of the inlet;
• a flap valve disposed at the junction, a flap of the flap valve is displaceable between a first position in which the flap defines a first flow-path of the air-fuel mixture wherein the air-fuel mixture passes through the long duct circumventing the flap when the engine operates at a lower speed, and a second position in which the flap defines a second flow-path of the air-fuel mixture wherein the air-fuel mixture passes through the short duct without passing through the long duct when the engine operates at a lower speed. The flap further adapted to be disposed between the first position and the second position to define a third flow-path of the air-fuel mixture wherein the air-fuel mixture partially flows through the long duct and the remaining air-fuel mixture flows through the short duct; and
• a pneumatic actuator adapted to regulate the movement of the flap of the flap valve between the first position, the second position and an intermediate position between the first position and the second position.
Typically, the inlet is configured with a plunger that moves to regulate opening of the inlet and defining a completely closed configuration in which the air fuel mixture is restricted from entry into the manifold and a completely open configuration of the inlet in which the air-fuel mixture is directed to pass through the short duct, the plunger further adapted to be displaced to an intermediate position in which the inlet is

blocked by 50% or more, and the air-fuel mixture is directed to flow through the long duct.
The flap valve prevents exit of air-fuel mixture through the short duct in the first position of the flap of the flap valve.
The flap valve prevents exit of air-fuel mixture through the long duct in the second position of the flap of the flap valve.
Typically, the pneumatic actuator comprises:
• a chamber;
• a diaphragm partitioning the chamber into a first section and a second section, the first section having an opening communicating with the atmosphere, the second section being in fluid communication with the internal environment of the manifold, such that, the pressure within the manifold is communicated directly to the second section;
• a compression spring adapted to bias the displacement of the diaphragm;
• a connecting rod cooperating with the diaphragm at one end. the connecting rod adapted to reciprocate along with diaphragm corresponding to the pressure difference between the first section and the second section; and
• a flap operating linkage adapted to translate the reciprocating movement of the connecting rod to angularly displace the flap valve between the first position and the second position.
Typically, the second section is in fluid communication with the internal environment of the manifold via a communicating tube.
Alternatively, the diaphragm is a deformable diaphragm to amplify the reciprocating movement of the connecting rod.
Typically, the flap operating linkage consists of:

• a flap supporting element adapted to support the flap valve, the flap supporting element adapted to rotate about an axis substantially perpendicular to the connecting rod; and
• a link adapted to displace the flap supporting element, the link adapted to cooperate with the connecting rod via a coupler element, the link being adapted to translate the linear movement of the connecting rod to the angular displacement of the flap valve.
The flap of the flap valve is angularly displaceable between the first position and the second position.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
The intake system for automotive vehicles of the present disclosure will now be
described with the help of accompanying drawings, in which:
Figure 1 illustrates a perspective view of a typical intake system for internal
combustion engine in accordance with an embodiment of the present disclosure;
Figure 2 illustrates a perspective view of the intake manifold of Figure 1;
Figure 3 illustrates a cross-sectional perspective view of the intake manifold of
Figure 2;
Figure 4 illustrates a perspective view a pneumatic actuator of the intake manifold of
Figure 2;
Figure 5 illustrates the pneumatic actuator cooperating with the short duct of the
intake manifold of Figure 2;
Figure 6 illustrates a cross sectional view of pressure switch of the pneumatic actuator
of Figure 2;
Figure 7 illustrates a cross-sectional perspective view of the intake system of Figure
2 depicting the flow of the air-fuel mixture through a long duct;
Figure 8 illustrates a cross-sectional perspective view of the intake system of Figure
2 depicting the flow of the air-fuel mixture through short duct path; and

Figure 9 illustrates a graphical representation depicting the variation of Torque in Newton-meter with respect to engine speed in revolution per minute (rpm) for the intake system of Figure 1.
DETAILED DESCRIPTION
A system of the present disclosure will now be described with reference to the embodiments which do not limit the scope and ambit of the disclosure. The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The intake system for automotive vehicles in accordance with the present disclosure is described herein below with respect to Figure 1 wherein the key components of the intake system are generally referenced by numerals as indicated. Figure 1 illustrates a perspective view of an intake system 1000 for an internal combustion engine. The intake system 1000 includes a carburetor 100, an intake manifold 200, a cylinder head 300 including an intake port and an air filter member 400.
The carburetor 100 includes a plunger "P", a fuel reservoir and a mounting provision for mounting the carburetor 100 on the connecting tube. The plunger is mechanically displaceable by accelerator control. Intake air, filtered in the air filter member 400, is introduced into the carburetor 100. The intake air is mixed with the fuel contained in the fuel reservoir to form a desired air-fuel mixture corresponding to the fuel requirement of the Internal Combustion (IC) engine at a lower speed and a higher speed of operation.

Figure 2 illustrates a perspective view of the intake manifold 200 in accordance with the present disclosure. The intake manifold 200 cooperates with the carburetor 100 through mounting arrangements 103. The intake manifold 200 includes an inlet 106 and an outlet 206, illustrated in Figure 3, fluidly communicating the air-fuel mixture via a long duct 201 and a short duct 202. The inlet 106 and the outlet 206 are selectively opened and closed corresponding to the engine speed and the desired torque by a flap valve 213, shown in Figure 3. The intake manifold 200 further includes a pneumatic actuator 104, particularly illustrated in Figure 4, for displacing the flap valve 213 between a first position and a second position to selectively block flow of the air-fuel mixture through the long duct 201 and the short duct 202, of the intake manifold 200 shown in Figure 3, respectively.
The displacement of the plunger of the carburetor 100 enables regulating the opening of the inlet 106 between a fully closed condition, an intermediate condition and a wide-open condition. The carburetor 100 enables supplying a desired air-fuel mixture to the intake manifold 200.
In the closed condition of the plunger "P" of the carburetor, the opening of the inlet 106 is closed to flow of air-fuel mixture. In the intermediate condition of the plunger "P", the opening of the inlet 106, of the intake manifold 200 shown in Figure 2, is partially open to enable flow of air-fuel mixture there-through. In the wide-open condition of the plunger "P", the opening of the inlet 106 is fully open to enable flow of air-fuel mixture there-through.
The air-fuel mixture enters the intake manifold 200, illustrated in Figure 3, through the inlet 106 from the carburetor 100. The long duct 201 and the short duct 202 are connected to each other or merge with each other at a junction 203, more specifically, the short duct 202 and the long duct 201 merge along merging points to form the junction 203 that configures fluid communication between the long duct 201 and the short duct 202. The junction 203 is configured downstream of the inlet 106 and the junction 203 is disposed away from the inlet 106. The long duct 201 defines a flow path which is substantially longer than that of the short duct 202. The long duct 201 and the short duct 202 enable conveying the air-fuel mixture from the inlet 106 to the outlet 206 depending on the requirement of the IC engine. When the IC engine

operates at a lower speed, the air-fuel mixture is conveyed from the inlet 106 to the outlet 206 via the long duct 201. On the other hand, when the engine operates at a higher speed, the air-fuel mixture is conveyed from the inlet 106 to the outlet 206 via the short duct 202.The outlet port 206 communicates the air-fuel mixture to the intake port of the cylinder head 300 and hence supplies the required air-fuel mixture to the IC engine.
The long duct 201 and the short duct 202 of the intake manifold 200 shown in Figure 3, functions in a manner, such that, when the plunger is displaced to fully open the inlet 106, the air-fuel mixture flows through the short duct 202. Further, when the plunger "P" is displaced to the intermediate position so as to block the inlet 106 by 50% or more, the air-fuel mixture flows through the long duct 201. The junction 203 is profiled such that the flow of the air-fuel mixture through the long duct 201 and the short duct 202 define a pre-determined angle there-between. The junction 203 is defined such that the plane containing the junction 203 divides the inlet 106 into substantially equal halves. Further, the plane containing the junction 203 defines a pre-determined angle with a vertical plane, substantially perpendicular to the operating plane of the inlet 106.
The flap valve 213 is positioned such that the outlet of the air-fuel mixture from the long duct 201 or the short duct 202 is selectively restricted corresponding to the engine speed. The flap valve 213 is displaceable between the first position and the second position to block exit of the air fuel mixture through the short duct 202 and the long duct 201 respectively. The flap valve 213 prevents exit of the air-fuel mixture through the short duct 202 in the first position of the flap valve 213. The flap valve 213 prevents exit of air-fuel mixture through the long duct 201 in the second position of the flap valve 213.
The displacement of the flap valve 213 is enabled by operation of the pneumatic actuator 104, illustrated in Figure 4. The pneumatic actuator 104 cooperates with wall mounting provisions 207 of the intake manifold 200 through provisions 217 by a locking arrangement 218, shown in Figure 5. The mounting provisions 217 are constrained within the provisions 207 by a screw (not shown in Figure). The

pneumatic actuator 104 includes a pressure switch 205, a connecting rod 208 and a flap operating linkage 101.
The sectional view of the pressure switch 205 is particularly illustrated in Figure 6 and includes a chamber 105 which is partitioned by a diaphragm 105A into a first section 105B and a second section 105C. The diaphragm 105A includes a support surface 1051 for supporting the compression spring 105G. The first section 105B is provided with an opening 105D to enable communicating the first section 105B with the atmosphere. The second section 105C is in fluid communication with the internal environment of the intake manifold 200, particularly the outlet 206. shown in Figure 3, such that, the pressure within the second section 105C varies with the variation in pressure at the outlet 206 of the intake manifold 200. The second section 105C defines a nozzle 105H distal from the diaphragm 105A. The fluid communication of the second section 105C with the internal environment of the intake manifold 200 is facilitated by the communicating tube 209A. The communicating tube 209A cooperates with the nozzle 105H at one end and a provision 209, which communicates with the internal environment of the intake manifold 200, at the other end, as illustrated in Figure 2. The first section 105B and the second section 105C include a first resting surface 105E and a second resting surface 105F. During operation of the pressure switch 205, the diaphragm 105A is deformed and is caused to rest on either of the first resting surface 105E and the second resting surface 105F. A compression spring 105G is disposed within the second section 105C. The compression spring 105G enables biasing displacement of the diaphragm 105A. The connecting rod 208 cooperates with the diaphragm 105A at one end and the flap operating linkage 101 at the other end. The diaphragm 105A is deformed either towards the first section 105B or the second section 105C, corresponding to the change in pressure within the second section 105C with respect to the atmospheric pressure within the first section 105B. The connecting rod 208, cooperating with the diaphragm 105A, is linearly displaceable with the deformation of the diaphragm 105A.

The linear displacement of the connecting rod 208 is communicated to the flap operating linkage 101. The flap operating linkage 101 includes a flap supporting element 214, a pivot element 212, and a link 211. The link 211 cooperates with the connecting rod 208 via a coupler element 209. The coupler element 209 includes a pin 210 having a cylindrical lobe 216. The cylindrical lobe 216 slides along a slotted path defined within a guide 215, illustrates in Figure 5, configured on the intake manifold 200 such that the slotted path of the guide 215 is substantially parallel to the path of linear displacement defined by the connecting rod 208 during linear displacement thereof. The flap supporting element 214 supports the flap 213 of the flap valve within the intake manifold 200. The link 211 causes rotation of the flap supporting element 214 through the rotational motion of the pivot element 212 such that the flap 213 is displaced between the first position and the second position so as to selectively block flow of the air fuel mixture through the short duct 202 and the long duct 201 respectively. Thus, the link 211 enables translating the linear displacement of the connecting rod 208 to the angular displacement of the flap 213 through pivot element 212.
The air-fuel mixture entering the intake manifold 200 flows through the long duct 201 when the engine operates at lower engine speeds while when the engine operates at higher speeds, the air-fuel mixture is caused to flow through the short duct 202. The flow of the air-fuel mixture through the long duct 201 or the short duct 202 is achieved by the operation of the pneumatic actuator 104 which displaces the flap valve 213 between the first position and the second position. When the flap valve 213 is displaced from the first position and the second position, the air-fuel mixture is caused to flow through the long duct 201 and the short duct 202 respectively. The pressure within the second section 105C is variable corresponding to the pressure within the inlet manifold 200, specifically the pressure at the outlet 206. The pressure switch 205 operates with the change in pressure within the first section 105B as compared to the atmospheric pressure acting in the second section 105C. The pressure at the outlet 206 is less than the atmospheric pressure acting within the first section 105B, at startup of the engine or when the engine operates at a lower speed and the plunger "P" of the carburetor blocks the inlet 106 by 50% or more. The pressure at the

outlet 206 increases when the engine operates at a higher speed and the plunger "P" of the carburetor 100 is at the fully open condition.
Figure 7 illustrates the flap valve 213 in its first position and the flow of the air-fuel mixture when the engine operates at low engine speeds. The pressure at the outlet 206 when the engine operates at low speed the pressure at the outlet 206 is lower than the atmospheric pressure. The pressure at the outlet 206 is communicated through the communicating tube 209A to the second section 105C to actuate the operation of the pneumatic actuator 104. Since the pressure within the second section 105C is substantially lower than the atmospheric pressure acting within the first section 105B, the variation of pressure between the first section 105B and the second section 105C causes the diaphragm 105A to tend to be displaced towards the second resting surface 105F, thereby creating a compressive force to act on the compression spring 105G. However, the spring force of the compression spring 105G restricts the movement of the diaphragm 105A towards the second resting surface 105F until the atmospheric pressure overcomes the spring force of the compression spring 105G. The displacement of the diaphragm 105A causes the connecting rod 208 to linearly move towards the second resting surface 105F. This causes the link 211 to rotate the flap supporting element 214 thereby causing the flap valve 213 to be displaced to the first position so as to block passage of the air-fuel mixture through the short duct 202 while allowing the air-fuel mixture to flow to the outlet 206 through the long duct 201. The flow of the air-fuel mixture through the long duct 201 causes turbulence and develops high torque required at lower engine speeds.
Figure 8 illustrates the flap valve 213 in its second position and the flow of the air-fuel mixture when the engine operates at high speed. When the engine operates at high speed where the carburetor plunger "P" is opening the inlet 106 between 50% to fully open condition the pressure at the outlet 206 is nearly same as the atmospheric pressure. The pressure at the outlet 206 is communicated through the communicating tube 209A to the second section 105C so as to actuate the operation of the pneumatic actuator 104. The pressure within the second section 105C is substantially same as that of the atmospheric pressure acting within the first section 105B. The variation of pressure between the first section 105B and the second section 105C causes the

diaphragm 105A to be displaced towards the first section 105B. When the diaphragm 105A is pushed towards the first section 105B in the fully open condition of the plunger, the compression spring 105G is in its extended configuration. The spring force of the compression spring 105G helps in maintaining the diaphragm 105A in the deformed condition within the first section 105B. The displacement of the diaphragm 105A causes the connecting rod 208 to be linearly displaced towards the first resting surface 105E. This causes the link 211 to rotate the flap supporting element 214 and hence cause the flap valve 213 to be displaced to the second position so as to block passage of the air-fuel mixture through the long duct 201 while enabling the air-fuel mixture to flow to the outlet 206 through the short duct 202. The flow of the air-fuel mixture through the short duct 202 enables in supply of air-fuel mixture within a short time and hence -improves quicker boosting of charge into the combustion chamber. Thus, high torque is achieved at when the engine operates at higher speed. Thus, the intake manifold 200, as envisaged by the present disclosure, enables selectively directing the air-fuel mixture through the long duct 201 at partially open condition of the inlet 106 and through the short duct 202 at fully open condition of the inlet 106. This helps in achieving good spread of torque throughout the operating range of the IC engine.
TRAIL RESULTS
The intake manifold of the present disclosure mounted on an IC engine was tested for variation of the Torque in (Newton-meter) with respect to engine speed in revolution per minute (rpm). Figure 9 illustrates a typical graphical representation depicting the variation of the Torque in (Newton-meter) with respect to engine speed in revolution per minute (rpm) for the intake manifold of the present disclosure and conventional intake manifold.
In Figure 9, curves al and a2 graphically represents Torque in Newton-meter Vs Engine speed (rpm), as produced by an IC engine wherein an intake system with the intake manifold of the present disclosure is installed, when the throttle is in fully open condition and in partially open condition respectively. Again, curves bl and b2 in Figure 9 represent the curve of Torque in Newton-meter Vs Engine speed (rpm) as

produced by a conventional Intake system mounted on an IC engine operating in fully open condition and partially open condition respectively.
From Figure 9, it can be observed that in partially open condition of the throttle, the curve a2 illustrates significant improvement in torque of the IC engine as compared with b2. Again, in the fully open condition of the throttle, the curve al illustrates that the intake manifold of the present disclosure enables in generating torque which is substantially similar to that generated by conventional intake manifold as illustrated by the curve bl. Thus, the intake system of the present disclosure provides significant improvement in torque at partially open condition of the throttle without compromising with the performance of the IC engine a.t fully open condition of the throttle.
TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including but not limited to the realization of:
• an intake manifold that enables good spread of torque throughout the engine operating range;
• an intake manifold that is simple in construction;
• an intake manifold that is reliable;
• an intake manifold with minimal moving parts;
• an intake manifold facilitating improved combustion of fuel within an IC engine; and
• an intake manifold adaptable in compact space.
Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression "at least" or "at least one" Suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.

The numerical values given of various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher or lower than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the disclosure unless there is a statement in the specification to the contrary. Wherever a range of values is specified, a value up to 10% below and above the lowest and highest numerical value respectively, of the specified range, is included in the scope of the disclosure.
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'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.
The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

WE CLAIM:
1. An intake manifold for conveying air-fuel mixture from an inlet to an outlet, the inlet and the outlet being connected to the carburetor and the cylinder head of the engine respectively,, said manifold characterized by:
• a long duct fluidly communicating between the inlet and the outlet;
• a short duct fluidly communicating between the inlet and the outlet;
• a junction defined at fluid connection between said long duct and said short duct, said junction configured downstream of the inlet;
• a flap valve disposed at said junction, a flap of said valve adapted to be displaceable between a first position in which said flap defines a first flow-path of the air-fuel mixture wherein said air-fuel mixture passes through said long duct circumventing said flap when the engine operates at a lower speed, and a second position in which said flap defines a second flow-path of the air-fuel mixture wherein said air-fuel mixture passes through said short duct without passing through said long duct when the engine operates at a lower speed, said flap further adapted to disposed in an intermediate position between said first position and said second position to define a third flow-path of the air-fuel mixture wherein said air-fuel mixture partially flows through said long duct and the remaining air-fuel mixture flows through said short duct; and
• a pneumatic actuator adapted to regulate the movement of said flap of said valve between said first position, said second position and an intermediate position between said first position and said second position.
2. The manifold as claimed in claim 1, wherein said inlet is configured with a plunger that moves to regulate opening of the inlet and defining a completely closed configuration in which said the air fuel mixture is restricted from entry into said manifold and a completely open configuration of said inlet in which the air-fuel

mixture is directed to pass through said short duct, said plunger further adapted to be displaced to an intermediate position in which the inlet is blocked by 50% or more, and the air-fuel mixture is directed to flow through said long duct.
3. The manifold as claimed in claim 1, wherein said flap valve is adapted to prevent exit of air-fuel mixture through said short duct in said first position of said flap of said flap valve.
4. The manifold as claimed in claim 1, wherein said flap valve is adapted to prevent exit of air-fuel mixture through said long duct in said second position of said flap of said flap valve.
5. The manifold as claimed in claim 1, wherein said pneumatic actuator comprises:
• a chamber;
• a diaphragm partitioning said chamber into a first section and a second
section, said first section having an opening communicating with the
atmosphere, said second section being in fluid communication with the
internal environment of said manifold, such that, the pressure within said
manifold is communicated directly to said second section;
• a compression spring adapted to bias the displacement of said diaphragm;
• a connecting rod cooperating with said diaphragm at one end, said connecting rod adapted to reciprocate along with said diaphragm corresponding to the pressure difference between said first section and said second section; and
• a flap operating linkage adapted to translate the reciprocating movement of said connecting rod to angularly displace said flap valve between said first position and said second position.
6. The manifold as claimed in claim 4, wherein said second section is in fluid communication with the internal environment of said manifold via a
communicating tube.

7. The manifold as claimed in claim 4, wherein said diaphragm is a deformable diaphragm to amplify the reciprocating movement of said connecting rod.
8. The manifold as claimed in claim 4, wherein said flap operating linkage consists of:

• a flap supporting element adapted to support said flap valve, said flap supporting element adapted to rotate about an axis substantially perpendicular to said connecting rod; and
• a link adapted to displace said flap supporting element, said link adapted to cooperate with said connecting rod via a coupler element, said link being adapted to translate the linear movement of said connecting rod to the angular displacement of said flap valve.
9. The manifold as claimed in claim 1, wherein said flap of said flap valve is
adapted to be angularly displaceable between said first position and said second
position.