Abstract:
An air intake system for a two-stroke or four-stroke internal combustion engine that is tunable through the use of interchangeable velocity stacks.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of Provisional Patent Application Ser. No. 61/201,043 filed Dec. 5, 2008, which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     The present invention relates generally to an air intake system for a two-stroke or four-stroke internal combustion engine. More specifically, it relates to an air intake system that is tunable through the use of interchangeable velocity stacks. 
     BACKGROUND OF THE INVENTION 
     Many smaller two-stroke and four-stroke internal combustion engines typically use an air intake boot to connect the air box to the carburetor or the throttle body if it is a fuel injected engine (collectively herein the “carburetor/throttle body”). As is shown in  FIG. 1 , an intake boot  01  of the prior art has a first end opening  02  with a larger cross-section that connects to the air box (not shown) and a second end opening  03  with a smaller cross-section that connects to the carburetor/throttle body (not shown). The intake boot  01  allows air to flow from the air box to the carburetor/throttle body. 
     The power characteristics of an engine are dependent on the velocity and volume of the air leaving the second end opening  03  of the intake boot  01  and entering the carburetor/throttle body (the “air flow”). For example, a higher velocity air flow will, in general, result in higher torque. 
     The problem with the intake boots of the prior art is that they do not provide a simple means for easily adjusting the velocity or volume of the air flow. It requires a given intake boot to be replaced with another intake boot with a different configuration, which different configuration causes a higher or lower velocity air flow. 
     It is an object of the present invention to provide a tunable air intake system in which the velocity and volume of the air flow can be easily adjusted through the use of interchangeable velocity stacks. 
     SUMMARY 
     The present invention is an air intake system for a two-stroke or four-stroke internal combustion engine that is tunable through the use of interchangeable velocity stacks. It includes an intake boot with a larger opening at the end that connects to the air box and a smaller opening at the end that connects to the carburetor/throttle body. The smaller opening is disposed removably to connect easily to one end of each of multiple interchangeable velocity stacks. When so connected, the funnel-shaped end of a velocity stack extends into the intake boot. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention, as well as its advantages, may be better understood by reading the following detailed description of preferred embodiments and the following drawings in which: 
         FIG. 1  shows a perspective view of an air intake boot of the prior art; 
         FIG. 2  shows a diagram of air entering a velocity stack; 
         FIG. 3  is a graph of the change in engine performance with different length velocity stacks; 
         FIG. 4  shows a perspective view of a preferred embodiment of an air intake boot of the present invention; 
         FIG. 5  shows a perspective view of the preferred embodiment of  FIG. 4  and a series of interchangeable velocity stacks; 
         FIG. 6  shows a cross-section view of another preferred embodiment of an air intake boot and a series of interchangeable velocity stacks of the present invention; and 
         FIG. 7  shows a detailed cross-section view of an air intake boot, carburetor/throttle body interface of the preferred embodiment of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The present invention is a tunable air intake system comprising an air intake boot with interchangeable velocity stacks that extend into the air intake boot wherein the velocity stacks can be easily interchanged with simple tools. A velocity stack is a trumpet-shaped device that is added to the air entry of an engine&#39;s fuel system. As shown in  FIG. 2 , from the exterior, a velocity stack  5  is a generally cylindrical device (although the generally cylindrical shape may be altered to accommodate the architecture of a given air intake system) with one end  6  funnel-shaped. The other end  7  is connected to a carburetor/throttle body  8  such that air flows into the funnel-shaped end  6 , through the velocity stack  5 , the interior of which may be cylindrical or may include an obstruction and into the carburetor/throttle body  8 . It is designed to: 
     1. Allow smooth and even entry of air into the velocity stack with the air flow adhering to the walls of the velocity stack; 
     2. Modify the dynamic tuning range of the air intake system by functioning as a small reverse megaphone that can extend the duration of pulses within the tract; and 
     3. Alter the dynamic tuning speed by including extra length. A velocity stack may be customized in a number of ways, including changing its length and changing its interior configuration.  FIG. 3  is a graph of change in engine performance with different length velocity stacks. 
     As is shown in  FIG. 4 , a preferred embodiment of the present invention includes an air intake boot  11  that has a first end opening  12  of a larger cross-section that connects to an air box and a second end opening  13  that connects to a carburetor/throttle body. The air intake body is preferably injection molded out of thermoplastic urethane (“TPU”) or a material with similar characteristics known to those skilled in the art. The body  14  of the air intake boot  11  has significantly more volume than the body  04  of an air intake boot  01  of the prior art, as shown in  FIG. 1 . 
     As shown in  FIG. 5 , the second end opening  13  of the air intake boot  11  has a flange  16  around its exterior surface. The second end opening  13  is disposed removably to connect to each of multiple velocity stacks  21 ,  23 ,  25 . Each of the velocity stacks  21 ,  23 ,  25  has a first end  28 ,  29 ,  30 , respectively, and a second end  32 ,  33 ,  34 , respectively, that is funnel-shaped. Each of the velocity stacks  21 ,  23 ,  25  has a different configuration. The first interchangeable velocity stack  21  is long, the second velocity stack  23  is shorter, and the third velocity stack  25  has a custom design. A velocity stack can be custom designed to achieve various combinations of power characteristics based on the velocity and volume of the air flow through the stack. The velocity stacks are also preferably molded out of TPU or a material with similar characteristics known to those skilled in the art. 
     The first end  28 ,  29 ,  30  of each of the velocity stacks  21 ,  23 ,  25 , respectively, has means for removably connecting the velocity stack to the second end opening  13  of the air intake boot  11 . Velocity stack  21  is illustrative of the means for connecting each of the velocity stacks. The first end  28  of the velocity stack  21  has a lip  42  around its exterior surface such that when the first end  28  is inserted into the second end opening  13  of the air intake boot  11 , the second end  32  extends through the second end opening  13  and into the air intake boot  11  and the lip  42  slips over the flange  16  and is held in place by a hose clamp (not shown) or other holding means known to those skilled in the art. 
     The first end  28  of velocity stack  21 , which is again illustrative of all the velocity stacks has, in turn, means for removably connecting to a carburetor/throttle body through the use of a ring  61  made of TPU or a material with similar characteristics known to those skilled in the art. A first side  62  of ring  61  engages the first end  28  of the velocity stack  21  and a second side  63  of the ring engages the carburetor/throttle body. The first side  62  and the second side  63  of the ring are held in place by hose clamps (not shown) or other holding means known to those skilled in the art. 
     In operation, the ring  61  can easily be disengaged with simple tools from the carburetor/throttle body and first end  28  of the velocity stack  21 . The lip  42  of velocity stack  21  can also easily be disengaged with simple tools from the rim  16  of the air intake boot so that the velocity stack  21  can be removed. A different velocity stack, for example velocity stack  23  or  25 , can then be substituted with simple tools, as described above, for the removed velocity stack  21 . The velocity stack to be substituted can be chosen to increase or decrease the velocity and volume of the air flow to the carburetor/throttle body, thereby tuning the engine&#39;s power characteristics to better suit the terrain or the rider&#39;s skill level. 
       FIG. 6  is a cross-section view of another embodiment of the present invention. Air intake boot  50  is shown removably connected to different velocity stacks. It is removably connected to short velocity stack  51 , mid-length velocity stack  52  and long velocity stack  53 . 
       FIG. 7  is a cross-section view of the velocity stack, carburetor/throttle body interface of this embodiment. Velocity stack  61  has a first end  62  and a second end  63  that is funnel-shaped. The first end  61  has a means for removably connecting the velocity stack  61  to an opening  64  in an air intake boot  65 . 
     The first end  62  of the velocity stack  61  has a flange  66  around its exterior surface. When the second end  63  of the velocity stack  61  is inserted through the opening  64  and into the air intake boot  65 , the flange  66  fits into an indentation  67  around the interior surface of the opening  64  in the air intake boot  65 . 
     The first end  62  of the velocity stack  61  also includes means for removably connecting the velocity stack  61  to a carburetor/throttle body. As shown in  FIG. 6 , the first end  62  of the velocity stack  61  has an indentation  70  around its interior surface such that a flange  71  around the exterior surface of a carburetor/throttle body extension  72  fits into the indentation  70  when the carburetor/throttle body extension  72  is inserted into the first end  62  of the velocity stack  61 . 
     While the principles of the invention have been described herein, it is to be understood by those skilled in the art that this description is made only by way of example and not as a limitation as to the scope of the invention. Other embodiments are contemplated within the scope of the present invention in addition to the exemplary embodiments shown and described herein. Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present invention.