Abstract:
An invention is provided for an internal combustion engine having a trunnion twin firing cylinder put in tandem for application of 4-6-8 cylinders as needed, including three moving parts, cylinder, piston rod, and crank that fires two pistons during up stroke while having a wet sump, cylinders are perpendicular to the crank and are enclosed at the bottom allowing four strokes every revolution with double firing pistons. The pistons do not require a wrist pin, and the pistons and rod assembly are one piece, pushing straight on the crank throw, eliminating piston side thrust, and reducing conical wear to rings with blow by. A conventional four cylinder engine at 1000 rpm fires 4,000 times in one minute. The trunnion twin firing cylinder engine with four pistons fires 8,000 times in one minute.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part of U.S. patent application having Ser. No. 12/055,989, filed on Mar. 26, 2008, entitled “Internal Combustion Engine Twin Power Unit Having An Oscillating Cylinder,” by inventor Joseph E. Springer, which claims the benefit of U.S. Provisional Patent Application having Ser. No. 61/016,454, filed on Dec. 22, 2007, entitled “Internal Combustion Engine Twin Power Unit Having an Oscillating Cylinder,” by inventor Joseph E. Springer, both of which are hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates generally to internal combustion engines, and more particularly to a twin firing oscillating cylinder engine having three moving parts: cylinder, piston-rod, and crank assembly for each tandem. 
         [0004]    2. Description of the Related Art 
         [0005]    To derive power, conventional internal combustion engines ignite a compressed air-fuel mixture in a combustion chamber. The ignition of the compressed air-fuel mixture generates force against a piston, which is linked to a crankshaft in a manner such that the motion of the piston is converted into rotational motion of a drive shaft. More particularly, in operation air and fuel is provided to a combustion cylinder and compressed by the piston. Once compressed, the air-fuel mixture is ignited powering the piston and the crankshaft. The exhaust is then expelled from the cylinder. 
         [0006]    Internal combustion engines generally can be either two-stroke or four-stroke engines. In general, two-stroke engines complete the power cycle during a single reciprocation of the piston, that is, one revolution of the crankshaft. Four-stroke engines generally require two reciprocations of the piston, or two revolutions of the crankshaft. Two-stroke engines offer certain advantages over four-stroke engines because the former produces power strokes twice as often as compared to the four-stroke engine. This permits two-stroke engines to be smaller in size and lighter in weight than four-stroke engines with a comparable power output. Two-stroke engines are also less expensive to manufacture and build because they require fewer parts that are subject to wear, breakdown and replacement. 
         [0007]    Conventional two-stroke engines, however, are generally not as efficient as four-stroke engines because two-stroke engines do not effectively remove all of the exhaust gases from the combustion chamber before the next power producing cycle. For example,  FIG. 1  is an illustration showing a prior art two-stroke engine  100 . The prior art two-stroke engine  100  includes an enclosed crankcase  102  below a cylinder  104  housing a piston  106 . The piston  106  is connected to a crankshaft  108  via a crank throw  110  and connecting rod  112 . To allow the piston  106  to travel up and down within cylinder  104 , the piston  106  is connected to the connecting rod  112  via a wrist pin  114 . As illustrated in  FIG. 1 , in the prior art two-stroke engine  100 , both the intake port  116  and the exhaust port  118  are open at the same time to enable the new air-fuel mixture to flow into the combustion chamber and to allow the escape of the exhaust gases. The concurrent opening of the intake port  116  and exhaust port  118  allows the fresh air-fuel mixture to purge the exhaust gases out of the combustion chamber through the exhaust port  118 . This is disadvantageous because some of the fresh air-fuel mixture escapes through the exhaust port  118  reducing engine efficiency by failing to utilize all of the fresh air-fuel mixture during the combination process. In addition, some of the exhaust gases mix with the incoming fresh air-fuel mixture which further reduces engine efficiency because noncombustible gases remain in the combustion chamber during the subsequent power cycle. 
         [0008]    Conventional internal combustion engines, including the prior art two-stoke engine  100  illustrated in  FIG. 1 , also lose power and efficiency because the reciprocating piston  106  is attached to the crankshaft  108  by the connecting rod  112  and the wrist pin  114  to translate linear reciprocating motion of the piston  106  into rotational movement of the crankshaft  108 . The use of the connecting rod  112  and wrist pin  114  results in uneven and excessive wear to the piston  106  and cylinder wall because lateral forces are transmitted through the connecting rod  112  in directions other than through the centerline of the piston  106 . In a typical engine, the cylinders are held stationary in the engine block and the pistons  106  are connected to the rotating crankshaft  108  by the connecting rod  112  which pivots about the wrist pin  114 . When the piston  106  is in any position other than the top dead center or bottom dead center of the cylinder  104 , the force acting through the centerline of the piston  106  is not aligned with the axis of rotation of the crankshaft  108 . Transverse or lateral force vectors, which cause uneven wear of the piston  106 , are created because the force is not acting directly upon the crankshaft  108 . 
         [0009]    In view of the foregoing, there is a need for an internal combustion engine that does not lose power due to non-alignment of the axis of rotation of the crankshaft and the connecting rod. In addition, the internal combustion engine should prevent wasteful air-fuel mixture escaping the system prior to combustion. 
       SUMMARY OF THE INVENTION 
       [0010]    Broadly speaking, the present invention addresses these needs by providing an oscillating cylinder twin power unit for an internal combustion engine that can be coupled together in tandem to form engines of varying sizes. Broadly speaking, embodiments of the present invention utilize parallel oscillating cylinders coupled to a rod assembly, which powers a crankshaft without requiring a wrist pin. In addition, a trunnion mount allows the twin power unit to oscillate back and forth across a small arc while tracking the rotational movement of the point of contact between the base on the rod assembly and the crankshaft. The crankshaft is formed by coupling together a plurality of power units via crank coupler assemblies. 
         [0011]    For example, in one embodiment a tandem internal combustion engine is disclosed. The tandem internal combustion engine includes a first and second power unit having an enclosed intake cylinder, an enclosed exhaust cylinder and two pistons each disposed within an enclosed cylinder. Each piston compresses air beneath the piston before the compressed air is transferred to the intake cylinder. The power units further each include a main journal attached to a crank coupler. The tandem internal combustion engine also includes a crank coupler assembly in physical communication with the crank couplers of the power units. For example, the crank couplers can have splined shafts and the crank coupler assembly can include a plurality of hardened pins positioned to fit splines of the splined shafts of the crank couplers. To provide additional flexibility each power unit can include a crank assembly comprising two crank halves coupled together via a bolt, with each crank half being attached to a main journal. In this aspect, each crank half further includes a crank throw portion. A sleeve surrounds the crank throw portion of each crank half of a crank assembly, and can include a plurality of keyway pins is disposed within the sleeve, and wherein one keyway pin is attached to the sleeve. To provide fuel savings, the first power unit can be separated from the second power unit when the tandem internal combustion engine is at idle. 
         [0012]    An additional tandem internal combustion engine is disclosed in further embodiment. Similar to above, tandem internal combustion engine includes first and second power units each having an enclosed intake cylinder, an enclosed exhaust cylinder and two pistons each disposed within an enclosed cylinder. Each piston compresses air beneath the piston before the compressed air is transferred to the intake cylinder. In addition, each power unit further including a main journal attached to a crank coupler and a crank coupler assembly in physical communication with the crank coupler. A coupling means, such as a belt or chain, is also included that couples the crank coupler assembly of the first power unit to the crank coupler assembly of the second power unit. To control the movement of the pistons, each power unit includes a plurality of cylinder control arms, each including a guide rail portion capable of guiding the movement of the pistons of the power unit during operation. For example, the movement of the pistons of each power unit cam be guided utilizing a rolling means that rolls along the guide rails. Each piston of each power unit can include an internal piston cooling means, such as a tube disposed within each piston that provides oil to an inside of the piston. 
         [0013]    In a further embodiment, an additional tandem internal combustion engine disclosed. As above, tandem internal combustion engine includes a first and second power unit having an enclosed intake cylinder, an enclosed exhaust cylinder and two pistons each disposed within an enclosed cylinder. Each piston compresses air beneath the piston before the compressed air is transferred to the intake cylinder. The power units further each include a main journal attached to a crank coupler. In addition, a coupling means is included that is in physical communication with the crank coupler of the first power unit and the crank coupler of the second power unit. For example, the coupling means can be a crank coupler assembly having a plurality of hardened pins disposed to fit splines of the crank couplers. Optionally, each power unit can be capable of being moved relative to the pistons such that a space between a top of the pistons and a top of the cylinders can be varied, thus providing variable compression. Further, each power unit can also include a hot spark plug and a cold spark plug, wherein the hot spark plug has more electrode area exposed than the cold spark plug. In this case, the hot spark plug can be used during idle and the cold spark plug is used during normal running. Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The invention, together with further advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which: 
           [0015]      FIG. 1  is an illustration showing a prior art two-stroke engine; 
           [0016]      FIG. 2A  is a diagram showing an oscillating cylinder twin power unit for an internal combustion engine, in accordance with an embodiment of the present invention; 
           [0017]      FIG. 2B  is a diagram showing an additional embodiment of an oscillating cylinder twin power unit illustrating cylinder control arms for use in guiding the pistons, in accordance with an embodiment of the present invention; 
           [0018]      FIG. 3A  is a side view of the twin power unit showing the exhaust cylinder, in accordance with an embodiment of the present invention; 
           [0019]      FIG. 3B  is a top view of a power unit having trunnion mounted fuel injection, in accordance with an embodiment of the present invention; 
           [0020]      FIG. 4  is a flowchart showing a method of operation for the oscillating cylinder twin power unit, in accordance with an embodiment of the present invention; 
           [0021]      FIG. 5A  illustrates a twin power unit during the beginning of a power cycle, in accordance with an embodiment of the present invention; 
           [0022]      FIG. 5B  illustrates a twin power unit at the beginning of a purge cycle, in accordance with an embodiment of the present invention; 
           [0023]      FIG. 5C  is a diagram illustrating a twin power unit at the end of a purge cycle, in accordance with an embodiment of the present invention; 
           [0024]      FIG. 5D  is a diagram showing a twin power unit during a charge cycle, in accordance with an embodiment of the present invention; 
           [0025]      FIG. 6  is a diagram showing an oscillating cylinder twin power unit for an internal combustion engine utilizing an exhaust valve and rocker assembly for purging combustion exhaust gases, in accordance with an embodiment of the present invention; 
           [0026]      FIG. 7A  is schematic diagram illustrating a crank assembly comprising two crank halves, in accordance with an embodiment of the present invention; 
           [0027]      FIG. 7B  is schematic diagram illustrating a crank throw journal sleeve and supporting keyway pins, in accordance with an embodiment of the present invention; 
           [0028]      FIG. 8A  is a schematic diagram showing a front view of crank coupler assembly, in accordance with an embodiment of the present invention; 
           [0029]      FIG. 8B  is a diagram showing splined crank coupler portion from two power units prior to being attached together via the crank coupler assembly, in accordance with an embodiment of the present invention; 
           [0030]      FIG. 9A  is a diagram showing a side view of an exemplary four-cylinder tandem engine, in accordance with an embodiment of the present invention; 
           [0031]      FIG. 9B  is a diagram showing a side view of an exemplary eight-cylinder tandem engine, in accordance with an embodiment of the present invention; 
           [0032]      FIG. 10A  is a diagram showing a top view of an exemplary four-cylinder inline tandem engine, in accordance with an embodiment of the present invention; 
           [0033]      FIG. 10B  is a diagram showing a top view of an exemplary six-cylinder inline tandem engine, in accordance with an embodiment of the present invention; 
           [0034]      FIG. 11A  is a diagram showing a side view of an exemplary decoupling four-cylinder tandem engine, in accordance with an embodiment of the present invention; 
           [0035]      FIG. 11B  is a diagram showing a side view of the exemplary decoupling four-cylinder tandem engine after decoupling, in accordance with an embodiment of the present invention; and 
           [0036]      FIG. 12  is a diagram showing an exemplary variable compression power unit having cylinder compression variance capability, in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0037]    An invention is disclosed for providing a twin power unit having an oscillating cylinders for an internal combustion engine. Broadly speaking, embodiments of the present invention utilize parallel oscillating cylinders coupled to a rod assembly, which powers a crankshaft without requiring a wrist pin. In addition, a trunnion mount allows the twin power unit to oscillate back and forth across a small arc while tracking the rotational movement of the point of contact between the base on the rod assembly and the crankshaft. Hence, the trunnion mount allows the twin power unit to oscillate such that the centerline of the pistons is at all times aligned with the crank throw of the crankshaft to eliminate lateral force vectors. Since the rod assembly directly connects the pistons to the crankshaft, there is no need for a wrist pin and connecting rod. Moreover, in one embodiment, a unique enclosed cylinder design is utilized to allow an intake air charge to be compressed beneath the pistons and later blasted into the cylinders above the pistons to purge combustion exhaust gases from the cylinders. As will be appreciated after a careful reading of the present disclosure, the twin power units described below can be utilized alone, or with multiple twin power units connected to the crankshaft. 
         [0038]    In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some or all of these specific details. In other instances, well known process steps have not been described in detail in order not to unnecessarily obscure the present invention. 
         [0039]      FIG. 1  was described in terms of the prior art.  FIG. 2A  is a diagram showing an oscillating cylinder twin power unit  200  for an internal combustion engine, in accordance with an embodiment of the present invention. The exemplary twin power unit  200  of  FIG. 2A  includes an intake cylinder  202  and exhaust cylinder  204 , each enclosing a piston sleeve  206 . Located in the intake cylinder  202  is an intake piston  208 , and disposed in the exhaust cylinder  204  is an exhaust piston  210 . An exhaust piston skirt  226  is attached to the exhaust piston  210  to seal the exhaust port during the charge and power cycles as will be described in greater detail subsequently. In the embodiment of  FIG. 2A , a fuel injector  212  is situated above the intake cylinder  202  and a spark plug  214  is located above the exhaust cylinder  204 , both of which being disposed in the cylinder head base  216 . Fixed below the pistons  208  and  210  is a rod assembly  218 , which includes a rod base bearing mount  220  connected to two tubular rod assemblies  222 , and a crank assembly  224 . Also illustrated in  FIG. 2A  are an exhaust port  228  connected to the exhaust cylinder  204  and an intake port  230  connected to the intake cylinder  202 . The intake port  230  also is in fluid communication with an intake charge passage  232  that connects the bottom portions of the intake cylinder  202  and the exhaust cylinder  204 . In addition, an air-fuel crossover passage  234  connects the top portions of the intake cylinder  202  and the exhaust cylinder  204 . As will be described in greater detail subsequently, the air-fuel crossover passage  234  allows an air-fuel mixture introduced in the intake cylinder  202  to be transferred to the exhaust cylinder  204 , and further allows an ignition in any cylinder to cause combustion of the air-fuel mixture in both cylinders. 
         [0040]    Embodiments of the present invention provide twin power pistons (i.e., the intake piston  202  and exhaust piston  204 ) that fire simultaneously to drive a crankshaft via a one piece rod assembly  218 , that rigidly fixes the intake piston and exhaust piston in a fixed spatial relation to each other. As will be described in greater detail below, the trunnion mounted cylinders allow the twin power unit  200  to rotate with the one piece rod assembly  218  allowing power transference without the need for a wrist pin. Moreover, the use of fully enclosed cylinders allows an intake charge without the need of an enclosed crankcase, which leads to oil mixing with the intake charge resulting in heavy emissions concerns. 
         [0041]    In operation, the twin power unit functions utilizing three cycles: 1) charge cycle, 2) power cycle, and 3) purge cycle. During the charge cycle both the intake piston  208  and the exhaust piston  210  rise within the corresponding cylinders  202  and  204 , compressing the air above the cylinders into the top portions of the cylinders  202  and  204 . As the pistons  208  and  210  rise, the fuel injector  212  is timed to deliver fuel to the intake cylinder  202  creating an air-fuel mixture. Because the simultaneous compression currently occurring within the top portions of the cylinders  202  and  204 , a swirling effect is created mixing the fuel with the compressed air, creating an air-fuel mixture that also flows into the top portion of the exhaust cylinder  204  via the air-fuel crossover passage  234 . 
         [0042]    In addition, as the intake piston  208  and exhaust piston  210  rise, the pistons move to reveal the intake charge passage  232 . The rising movement of the intake piston  208  and exhaust piston  210  draws in an air intake charge from the intake port  230  and through the intake charge passage  232  into the bottom portions of the intake cylinder  202  and exhaust cylinder  204  beneath the pistons  208  and  210 . Both the intake cylinder  202  and the exhaust cylinder  204  are fully enclosed, thus preventing the intake air from escaping. In addition, as will be described in greater detail subsequently, during the charge cycle the exhaust port  228  is covered by the exhaust piston skirt  226 , preventing the intake air charge from escaping via the exhaust port  228 . 
         [0043]    The power cycle begins once the pistons reach the top of the cylinders at 12 o&#39;clock and full compression is achieved. The spark plug  214  ignites the compressed air-fuel mixture powering the pistons  208 / 210  and driving the pistons  208 / 210  and rod assembly  218  toward the crankshaft. During full compression, the compressed air-fuel mixture is present in the top portions of both the intake cylinder  202  and the exhaust cylinder  204 , and also in air-fuel crossover passage  234 . Hence, the spark plug  214  ignites the air-fuel mixture in the exhaust cylinder  202 , which ignites the air-fuel mixture in the air-fuel crossover passage  234 , which ignites the air-fuel mixture in the intake cylinder  202 . As a result, both the exhaust piston  210  and the intake piston  208  are powered during the power cycle via the spark plug  214 . As the pistons  208  and  210  travel downward within the cylinders, the pistons  208  and  210  begin to drive the air intake charge currently stored beneath the pistons back into the intake port  230  via the intake charge passage  232 , as best depicted in  FIG. 3A . 
         [0044]      FIG. 3A  is a side view of the twin power unit  200  showing the exhaust cylinder  204 , in accordance with an embodiment of the present invention. The purge cycle begins as the pistons  208  and  210  travel downward and the exhaust piston  210  begins to clear the exhaust port  228 , when the crankshaft reaches about 3:30 and the twin power unit  200  rotates about the trunnion mount  304 . As noted above, the downward motion of the pistons  208  and  210  drives the intake air present in both cylinders below the pistons  208  and  210  back into the intake port  230  via the intake charge passage  232 . However, a one-way reed valve  300  present in the intake port  230  prevents the intake air from escaping out of the intake port  230 . As a result, the downward motion of the pistons  208  and  210  compresses the intake air in the bottom portion of the cylinders  202  and  204  and portion of intake port  230  on the piston side of the reed valve  300 . 
         [0045]    Once the exhaust piston  210  begins to clear the exhaust port  228 , the combustion exhaust gases from the power cycle begin to escape the exhaust cylinder  204  via the exhaust port  228  into the exhaust pipe  302 . As the pistons  208  and  210  continue to travel downward, the intake piston  208  begins to reveal the intake charge passage  232 . Once the top of the intake piston  208  drops below the top of the intake charge passage  232 , the intake charge air compressed beneath the pistons  208  and  210 , and in the portion of intake port  230  on the piston side of the reed valve  300 , is blasted into the intake cylinder  202  above the intake piston  208 . 
         [0046]    The rapid intake charge air blast purges the combustion exhaust gases from the intake cylinder  202 , through the air-fuel crossover passage  234 , through the exhaust cylinder  204 , and out the exhaust port  228 . As will be appreciated by those skilled in the art after a careful reading of the present disclosure, the rapid intake charge air blast also purges the combustion exhaust gases from the air-fuel crossover passage  234  and the exhaust cylinder  204 . 
         [0047]    As the intake piston  208  and exhaust piston  210  begin to travel back upward, the intake charge air, forced via the upward motion of the pistons  208  and  210  further expels the combustion exhaust gases from the cylinders  202 / 204  and air-fuel crossover passage  234  out the exhaust port  228 . In addition, another charge cycle begins with the fuel injector  212  delivering fuel to the intake cylinder  202 , and the pistons  208 / 210  rising to reveal the intake charge passage  232 , and thereby drawing in another air intake charge into the bottom portions of the intake cylinder  202  and exhaust cylinder  204  beneath the pistons  208  and  210 . 
         [0048]    To provide cooling for the pistons  202 / 204 , embodiments of the present invention utilize interior piston rod bolt tubes inside each piston to provide oil based piston cooling. For example, in  FIG. 3A  the exhaust piston  210  is illustrated having an interior piston rod bolt tube  350  disposed within the piston rod  218  of the exhaust piston  210 . Oil to cool the piston is provided under pressure from the journal. The oil then travels up the interior piston rod bolt tube  350  to the top of the piston  210  interior, and then down the inside of the piston rod  218 . The oil is allowed to exit the piston rod  218  via oil exit passageways  352  connecting the piston rod interior and exterior. 
         [0049]      FIG. 2B  is a diagram showing an additional embodiment of an oscillating cylinder twin power unit  200 ′ illustrating cylinder control arms for use in guiding the pistons, in accordance with an embodiment of the present invention. The exemplary twin power unit  200 ′ of  FIG. 2B  includes an intake cylinder  202  and an exhaust cylinder  204 , each enclosing a piston sleeve  206  and connected via an air-fuel crossover passage  234 . Located in the intake cylinder  202  is an intake piston  208 , and disposed in the exhaust cylinder  204  is an exhaust piston  210 . A fuel injector  212  is situated above the intake cylinder  202 . A hot spark plug  240  is located above the exhaust cylinder  204  and a cold spark plug  242  is located above the air-fuel crossover passage  234 . Fixed below the pistons  208  and  210  is a rod assembly, which includes a rod base bearing mount and tubular rod assemblies  222 . 
         [0050]      FIG. 2B  illustrates how the pistons  208 / 210  and rod assembly is guided up and down parallel to a central plane of the twin power unit  200 ′ via cylinder control arms  250   a / 250   b  and racking rollers  252   a / 252   b . In one embodiment, each cylinder control arm  250   a / 250   b  is attached to one side of the power unit. For example, in  FIG. 2B  cylinder control arm  250   b  is attached to the exhaust cylinder side of the twin power unit  200 ′ and cylinder control arm  250   a  is attached to the intake cylinder side of the twin power unit  200 ′. Each racking roller  252   a / 252   b  can be attached to a side of the rod assembly. In one embodiment, each racking roller  252   a / 252   b  can be movably coupled to a crank throw portion  708  of the crank assembly on each side of the rod assembly. For example, in  FIG. 2B  racking roller  252   a  is attached to one side of the rod assembly (toward the viewer in  FIG. 2B ) and racking roller  252   b  is attached to the opposite side of the rod assembly (away from the viewer and obscured from view by racking roller  252   a  in  FIG. 2B ). 
         [0051]    In one embodiment, each cylinder control arm  250   a / 250   b  includes a guide rail  254  fixed such that a racking roller  252   a / 252   b  can roll along the guide rail  254  as the rod assembly moves up and down in relation to the cylinders. Hence, in  FIG. 2B  cylinder control arm  250   a  is situated such that the guide rail  254  portion of the cylinder control arm  250   a  is disposed such that the racking roller  252   a  (attached to the viewable side of the rod assembly in  FIG. 2B ) can roll against guide rail  254  of cylinder control arm  250   a . Similarly, cylinder control arm  250   b  is situated such that the guide rail  254  portion of the cylinder control arm  250   b  is disposed such that the racking roller  252   b  (attached to the non-viewable side of the rod assembly in  FIG. 2B ) can roll against the guide rail  254  of cylinder control arm  250   b.    
         [0052]      FIG. 2B  also illustrates a spark plug arraignment having a hot spark plug  240  and a cold spark plug  242 . As is well known, a spark plug operates to force electricity to arc across a gap, to ignite compressed gases during operation of the power unit. To force a high voltage to travel to the electrode of the spark plug, the spark plug includes an insulated passageway, which is also designed to withstand the extreme heat and pressure present inside the cylinders during operation. In general, spark plugs use a ceramic insert to isolate the high voltage at the electrode, thus ensuring that the spark happens at the tip of the electrode and not anywhere else on the plug. In addition, ceramic generally does not conduct heat well, and as a result functions to protect the spark plug from too much heat during operation. 
         [0053]    As mentioned above, the power unit  200 ′ of  FIG. 2B  includes both a hot spark plug  240  and a cold spark plug  242 . The hot spark plug  240  includes a ceramic insert that has a smaller contact area with the metal part of the plug, thus reducing the heat transfer from the ceramic and making the hot spark plug  240  run hotter and thus burn away more deposits from fuel. When all the fuel in the cylinders is not burned during a burn, the spark plugs have a tendency to carbon up. In the past, the plugs were removed and cleaned with a wire brush to get the carbon off that builds up on the plug. However, the hot plug  240  cleans itself, as described above. But hot plugs do not work well at high speed because at high speed the spark may not be able to jump the gap of the hot spark plug  240 , and the hot spark plug  240  has a tendency to get too hot at high speed. Thus, during idle, the hot spark plug  240  is used. During normal running, the cold spark plug  242  is used. 
         [0054]      FIG. 3B  is a top view of a power unit  200 ″ having trunnion mounted fuel injection, in accordance with an embodiment of the present invention. As above, the power unit  200 ″ includes an intake cylinder  202 , an exhaust cylinder  204 , an intake port  230 , an intake charge passage  232 , and an exhaust port  228 . However, the power unit  200 ″ includes a fuel injector  212  situated within the intake port  230  so as to release fuel into the intake charge passage  232 . 
         [0055]    In this manner, when air is forced from beneath the pistons into the top of the cylinders  202 / 204 , as described above, fuel is injected into the air dramatically increasing the swirl effect and air-fuel mixing. In addition, by situating the fuel injector  212  with the intake port, less movement is required of the fuel injector when the engine is running since the fuel injector  212  can remain relatively steady within the trunnion mount. As mentioned above, the trunnion mounted cylinders of the embodiments of the present invention allow the twin power unit  200  to rotate with the one piece rod assembly  218  allowing power transference without the need for a wrist pin using a guide system as illustrated next with reference to  FIG. 4 . 
         [0056]      FIG. 4  is a flowchart showing a method  400  of operation for the oscillating cylinder twin power unit  200 , in accordance with an embodiment of the present invention. In an initial operation  402 , engine preparation operations can be performed. Engine preparation operations can include, for example, determining the number of twin power units to include in the engine, calculating proper timing for the twin power units according to size and performance needs, and other engine preparation operations that will be apparent to those skilled in the art after a careful reading of the present disclosure. 
         [0057]    In operation  404 , intake charge air is drawn in below the pistons and the intake charge air present above the pistons is compressed.  FIG. 5A  is a diagram showing a twin power unit  200  during a charge cycle, in accordance with an embodiment of the present invention.  FIG. 5A  illustrates the pistons  208 / 210  located in the middle of the cylinders  202 / 204  as they rise, when the rod base bearing mount of the rod assembly  218  is located at about 9:00 with respect to the crankshaft  500 . As the pistons  208 / 210  begin to travel back upward, the intake charge air, forced via the upward motion of the pistons  208 / 210  further expels the combustion exhaust gases from the cylinders  202 / 204  before being compressed as the exhaust piston  210  covers the exhaust port  228 . As the pistons  208 / 210  continue to rise, the fuel injector  212  delivers fuel to the intake cylinder  202  creating an air-fuel mixture. Because the simultaneous compression currently occurring within the top portions of the cylinders  202 / 204 , a swirling effect is created mixing the fuel with the compressed air, creating an air-fuel mixture that also flows into the top portion of the exhaust cylinder  204  via the air-fuel crossover passage  234 . 
         [0058]    In addition, the intake piston  208  and exhaust piston  210  rise to reveal the intake charge passage  232 . The rising movement of the pistons  208 / 210  draws in an air intake charge from the intake port  230 , through the intake charge passage  232  and into the bottom portions of the cylinders  202 / 204  beneath the pistons  208 / 210 . As discussed above, both the intake cylinder  202  and the exhaust cylinder  204  are fully enclosed, preventing the intake air from escaping. In addition, during operation  404  the exhaust piston skirt  226  covers the exhaust port  228 , thereby preventing the intake air charge from escaping via the exhaust port  228 . 
         [0059]    Turing back to  FIG. 4 , the air-fuel mixture present in the top portions of the intake cylinder and exhaust cylinder above the pistons is ignited utilizing a spark plug, in operation  406 .  FIG. 5B  illustrates a twin power unit  200  during the beginning of a power cycle, in accordance with an embodiment of the present invention. Once the pistons  208 / 210  reach the top of the cylinders  202 / 204  at 12 o&#39;clock with respect to the crankshaft indicated at  500 , the spark plug  214  ignites the compressed air-fuel mixture powering the pistons  208 / 210 , driving the pistons  208 / 210  and rod assembly  218  toward the crankshaft  500 . In operation  406 , the compressed air-fuel mixture is present in the top portions of both cylinders  202 / 204 , and in air-fuel crossover passage  234 . Hence, spark plug  214  ignites the air-fuel mixture present in the exhaust cylinder  204 , air-fuel crossover passage  234 , and intake cylinder  202 , resulting in both the exhaust piston  210  and the intake piston  208  being powered during the power cycle via the spark plug  214 . 
         [0060]    Referring back to  FIG. 4 , the combustion exhaust gasses are expelled from the exhaust cylinder as the exhaust pistons clears the top portion of the exhaust port and the intake charge air is compressed beneath the pistons, in operation  408 .  FIG. 5C  illustrates a twin power unit  200  at the beginning of a purge cycle, in accordance with an embodiment of the present invention. The purge cycle begins as the pistons  208 / 210  travel downward and the exhaust piston  210  begins to clear the exhaust port  228 . At this point, as illustrated in  FIG. 5C , the rod base bearing mount of the rod assembly  218  is located at about 3:00 with respect to the crankshaft  500 .  FIG. 5C  also illustrates the twin power unit&#39;s  200  rotation about the trunnion mount  304 , allowing the pistons  208 / 210  and rod assembly  218  to follow the crankshaft  500  as it turns, without requiring a wrist pin. 
         [0061]    During operation  408 , the downward motion of the pistons  208 / 210  also drives the intake air present in both cylinders  202 / 204  below the pistons  208 / 210  back into the intake port  230  via the intake charge passage  232 . However, the one-way reed valve present in the intake port  230  prevents the intake air from escaping out of the intake port  230 . As a result, the downward motion of the pistons  208 / 210  compresses the intake air in the bottom portion of the cylinders  202 / 204  and portion of intake port  230  on the piston side of the reed valve. 
         [0062]    In operation  410 , the compressed intake air is blasted into the intake cylinder via the intake charge passage.  FIG. 5D  is a diagram illustrating a twin power unit  200  at the end of a purge cycle, in accordance with an embodiment of the present invention.  FIG. 5D  illustrates the pistons  208 / 210  located at the bottom of the cylinders  202 / 204 , when the rod base bearing mount of the rod assembly  218  is located at about 6:00 with respect to the crankshaft  500 . As the pistons  208 / 210  continue to travel downward, the intake piston  208  reveals the intake charge passage  232 . The intake charge passage  232  is configured such that the intake piston  208  clears the top area of the intake charge passage  232  before the exhaust piston  210  during downward motion of the pistons  208 / 210 . Once the top of the intake piston  208  drops below the top of the intake charge passage  232 , the intake charge air compressed beneath the pistons  208 / 210 , and in the portion of intake port  230  on the piston side of the reed valve  300 , is blasted into the intake cylinder  202  above the intake piston  208 . The rapid intake charge air blast purges the combustion exhaust gases from the intake cylinder  202 , through the air-fuel crossover passage  234 , through the exhaust cylinder  204 , and out the exhaust port  228 . The rapid intake charge air blast also purges the combustion exhaust gases from the air-fuel crossover passage  234  and the exhaust cylinder  204 . 
         [0063]    Referring back to  FIG. 4 , post process operations are performed in operation  412 . Post process operations can include, for example, continuing with further power cycles, purge cycles, and charge cycles, and other post process operations that will be apparent to those skilled in the art after a careful reading of the present disclosure. As will be appreciated, embodiments of the present invention advantageously allow power to be applied to crankshaft without the need of a wrist pin via the trunnion mount which allows the twin power unit to oscillate. In addition, the intake charge air compression and purge allows the efficient expulsion of combustion exhaust gases without the need of an external system. Moreover, the location of the exhaust port allows the exhaust piston and exhaust piston skirt to cover the exhaust port preventing any wasteful loss of air-fuel mixture. In addition, to utilizing compressed intake charge air beneath the pistons during the purge cycle, embodiments of the present invention can further utilize uncompressed intake air combined with an exhaust valve to provide combustion exhaust gas purging, as illustrated next with reference to  FIG. 6 . 
         [0064]      FIG. 6  is a diagram showing an oscillating cylinder twin power unit  200 ″ for an internal combustion engine utilizing an exhaust valve  600  and rocker assembly  602  for purging combustion exhaust gases, in accordance with an embodiment of the present invention. The exemplary twin power unit  200 ″ of  FIG. 6  includes an intake cylinder  202  and exhaust cylinder  204 , each enclosing a piston sleeve  206  and connected via an air-fuel crossover passage  234 . Located in the intake cylinder  202  is an intake piston  208 , and disposed in the exhaust cylinder  204  is an exhaust piston  210 . A fuel injector  212  is situated above the intake cylinder  202  and a spark plug  214  is located above and off center of the exhaust cylinder  204 . Fixed below the pistons  208  and  210  is a rod assembly  218 , which includes a rod base bearing mount  220 . An exhaust port  228  out of the exhaust cylinder  204  and an intake port  230  providing air to the intake cylinder  202  also are included. In addition, an exhaust valve  600  is located above the exhaust cylinder  204  and is utilized to control the flow of combustion exhaust gas through the exhaust valve port  608 . The exhaust valve  600  is moveably attached to a rocker assembly  602 , which is further coupled to a rocker roller  604 . The rocker roller  604  rest on a ramp cam  606  and moves along the ramp cam  606  during operation, as will be described subsequently. 
         [0065]    Similar to the embodiment of  FIG. 2A , oscillating cylinder twin power unit  200 ″ of  FIG. 6  functions utilizing a power cycle, purge cycle, and charge cycle. The power cycle begins when the intake piston  208  and the exhaust piston  210  reach the top of the cylinders  202 / 204  and full compression is achieved. This occurs when the rod assembly  218  is at approximately 12 o&#39;clock with respect to the crankshaft. The spark plug ignites the compressed air-fuel mixture powering the both pistons  208 / 210  and driving the pistons  208 / 210  and rod assembly  218  toward the crankshaft. As mentioned previously, during full compression, the compressed air-fuel mixture is present in the top portions of both the intake cylinder  202  and the exhaust cylinder  204 , and also in air-fuel crossover passage  234 . Hence, the spark plug  214  ignites the air-fuel mixture in the exhaust cylinder  202 , which ignites the air-fuel mixture in the air-fuel crossover passage  234 , which ignites the air-fuel mixture in the intake cylinder  202 . As a result, both the exhaust piston  210  and the intake piston  208  are powered during the power cycle via the spark plug  214 . 
         [0066]    The purge cycle begins as the pistons  208  and  210  travel downward within the cylinders  202 / 204  and the twin power unit  200 ′ begins to pivot about the trunnion mount  304  allowing the rod assembly  218  and pistons  208 / 210  to follow the rotation of the crankshaft via the crank journal. As the twin power unit  200 ″ pivots about the trunnion mount  304 , the rocker roller  604  begins to roll up the ramp cam  606 . The ramp cam  606  is mounted outside the twin power unit  200 ″ and remains in a fixed position as the twin power unit  200 ″ pivots. The rocker roller  604  is coupled to the rocker assembly  602 , which is attached to the twin power unit  200 ″. Hence, as the twin power unit  200 ′ pivots, the rocking motion of the twin power unit  200 ′ causes the rocker roller  604  to roll back and forth along the ramp cam  606 . As the rocker roller  604  rolls up the ramp cam  606 , the attached rocker assembly  602  causes the exhaust valve  600  to open. Then, as the rocker roller  604  rolls back down the ramp cam  606 , caused by the twin power unit  200 ′ pivoting in the opposite direction, the attached rocker assembly  602  allows the exhaust valve  600  to close. 
         [0067]    In this manner, when the rod assembly  218  is located at about 3:00 with respect to the crankshaft, and the pistons  208 / 210  have traversed approximately half the distance to their bottom most position, the rocker roller  604  is positioned on the ramp cam  606  such that the rocker assembly  602  causes the exhaust valve  600  to open. The opening of the exhaust valve  600  allows the combustion exhaust gases in the upper portion of the cylinders  202 / 204  to escape the cylinders  202 / 204 . In addition, as the pistons  208 / 210  continue travel downward within the cylinders  202 / 204 , the exhaust the exhaust piston  210  begins to clear the exhaust port  228  when the rod assembly  218  reaches about 4:00 with respect to the crankshaft, allowing additional combustion exhaust gases to escape. 
         [0068]    The charge cycle begins as the pistons travel further downward and the intake piston  208  begins to clear the intake port  230 . At this point, a blower blast intake charge air into the intake cylinder  202  above the intake piston  208 . The intake blast air helps purge the remaining combustion exhaust gases present in both the intake cylinder  202  and the exhaust cylinder  204 . A bellows charges intake air through the intake port  230 , up the intake cylinder  202 , through the air-fuel crossover passage  234 , and out the exhaust cylinder  204  through the exhaust port  228  and the past the open exhaust valve port  608 . As can be appreciated, the twin power unit  200 ″ of  FIG. 6  uses slightly overlapping cycles, in that the purge cycle and charge cycle overlap to some extent. This continues as the pistons  208 / 210  reach their bottom most positions within the cylinders  202 / 204 . The charge cycle and purge cycle continue as the pistons rise until the exhaust piston  210  covers the exhaust port  228  and the intake piston  208  covers the intake port  230 . This occurs approximately when the rod assembly  218  reaches about 8:00 o&#39;clock with respect to the crankshaft. At this time the rocker roller  604  rolls back down the ramp cam  606  causing the rocker assembly  602  to allow the exhaust valve  600  to close the exhaust valve port  608 . 
         [0069]    Compression starts when the rod assembly  218  reaches about 9:00 o&#39;clock with respect to the crankshaft and the fuel injector  212  injects fuel into the intake cylinder  202 . The intake charge air coupled with the compression from the rising pistons  2058 / 210  causes the fuel to efficiently mix with the compressed intake air charge creating an air-fuel mixture. In addition, part of the air-fuel mixture in the intake cylinder  202  flows into the air-fuel crossover passage  234  and into the exhaust cylinder  204 , which at this point has all exhaust ports closed. Once the pistons  208 / 210  reach their top most positions within the cylinders  202 / 204 , another power cycle begins with the spark plug  214  igniting the air-fuel mixture present in both cylinders  202 / 204  and the air-fuel crossover passage  234 . 
         [0070]    As those skilled in the art will appreciate after a careful reading of the present disclosure, embodiments of the present invention provide power on each revolution of the crankshaft. Moreover, the trunnion mount allows the twin power unit to oscillate back and forth across a small arc while tracking the rotational movement of the point of contact between the base on the rod assembly and the crankshaft. Hence, trunnion mount allows the twin power unit to oscillate such that the centerline of the pistons is at all times aligned with the crank throw of the crankshaft to eliminate lateral force vectors. The rigid fixed-length rod assembly connecting the pistons to the crankshaft causes the cylinders to oscillate while the pistons rotate semi-elliptically in their motion to turn the crankshaft. Since the rod assembly directly connects the pistons to the crankshaft, there is no need for a wrist pin and connecting rod. Furthermore, the below piston compressed intake air charge and reed valve design of the embodiment of  FIG. 2  allows significant charging and purging of the cylinders without requiring outside assistance. 
         [0071]      FIG. 7A  is schematic diagram illustrating a crank assembly  700  comprising two crank halves  702   a  and  702   b , in accordance with an embodiment of the present invention. More specifically the crank assembly  700  includes crank halves  702   a  and  702   b , each including a main journal portion  704  and a splined crank coupler  706 . Although  FIG. 7A  illustrates a crank assembly  700  wherein each crank half  702   a / 702   b  includes a splined crank coupler  706 , it should be borne in mind that either crank half  702   a / 702   b  could include a main journal portion  704  without a splined crank coupler  706 , depending on the position of the particular power unit within a tandem engine. Each crank half  702   a / 702   b  further includes a crank throw portion  708 . Surrounding the crank throw portions  708  of each crank half  702   a / 702   b  is a crank throw journal sleeve  710 , which includes a locking keyway pin  712  positioned to hold the crank throw journal sleeve  710  in place. A bolt  714  holds the crank halves  702   a / 702   b  together. 
         [0072]    The crank assembly  700  of the embodiments of the present invention can advantageously be separated by removing the bolt  714  holding the crank halves  702   a / 702   b  together. To reassemble the crank assembly  700  the crank throw portions  708  of each crank half  702   a / 702   b  are positioned together and held in place using the crank throw journal sleeve  710 . The bolt  714  can then be reinserted to bolt the crank halves  702   a / 702   b  together. As illustrated in  FIG. 7A , the two crank throw portions  708  and crank throw journal sleeve  710  portions for a crank throw journal around which is positioned the racking rollers  252   a  and  252   b , which guide the pistons along the guide rails of the cylinder control arms. 
         [0073]      FIG. 7B  is schematic diagram illustrating a crank throw journal sleeve  710  and supporting keyway pins  716 , in accordance with an embodiment of the present invention. When set in position around the crank throw portions  708  of the crank halves  702   a / 702   b , the keyway pins  716  help to keep the crank throw journal aligned during operation. In addition, as mentioned above, the locking keyway pin  712  holds the crank throw journal sleeve  710  in place. More specifically, the locking keyway pin  712  includes a rounded end that locks into a hole in the crank throw journal sleeve  710  and prevents the crank throw journal sleeve  710  from turning as the crank rotates during operation. The crank couplers  706  are utilized to connect two power units together using a crank coupler assembly to form a tandem engine, as described next with reference to  FIGS. 8A and 8B . 
         [0074]      FIG. 8A  is a schematic diagram showing a front view of crank coupler assembly  800 , in accordance with an embodiment of the present invention. In one embodiment, the crank coupler assembly  800  includes an outer drive portion  802  and a center divider  804  that holds a plurality of hardened pins  806  in position. In use, the hardened pins  806  are positioned to fit along the splines of the crank coupler portions of two power units, while the center divider  804  functions to assist in alignment. 
         [0075]      FIG. 8B  is a diagram showing splined crank coupler portion  706  from two power units  200   a  and  200   b  prior to being attached together via the crank coupler assembly  800 , in accordance with an embodiment of the present invention. As illustrated in  FIG. 8B , the crank coupler assembly  800  joins together power units by sliding onto the crank coupler portion  706  of each power unit. In doing so, the hardened pins  806  of the crank coupler assembly  800  fit into the slots  750  of each splined crank coupler portion  706 . Once connected, the outer drive portion  802  of the crank coupler assembly  800  allows the crank coupler assembly  800  to be used as either a belt or chain drive, in which case the crank coupler assembly  800  can function as a sprocket. 
         [0076]    Referring back to  FIG. 8A , the number of hardened pins  806  included in a crank coupler assembly can be related to the number of cylinders that are to be included in a tandem engine to help align each power unit&#39;s rotational crank throw journal position correctly with the other power units. For example, when used with a six-cylinder tandem engine, six hardened pins  806  can be included in each crank coupler assembly  800  situated to align the crank throw journal of each power unit 120° degrees from adjacent power unit crank throw journals. Similarly, when used with a four-cylinder tandem engine, four hardened pins  806  can be included in each crank coupler assembly  800  situated to align the crank throw journal of each power unit 180° from the adjacent power unit crank throw journal. In this manner, crank coupler assemblies  800  can be utilized to form tandem engines, as described next with reference to  FIGS. 9A-10B . 
         [0077]      FIG. 9A  is a diagram showing a side view of an exemplary four-cylinder tandem engine  900   a , in accordance with an embodiment of the present invention. The four-cylinder tandem engine  900   a  of  FIG. 9A  includes two power units  200   a  and  200   b  disposed on a base  902  and coupled together via a crank coupler assembly  800 . The four-cylinder tandem engine  900   a  of  FIG. 9A  further includes a fly wheel and clutch assembly  904 . As described above, the crank coupler assembly  800  couples together power units  200   a  and  200   b  via the splined crank coupler section on each crank half. Specifically, the splined crank coupler section of each crank half slides into the crank coupler assembly  800 , coupling the two power units  200   a  and  200   b  together to form a four-cylinder tandem engine  900   a . The crank coupler assembly  800  couples the crank halves of the two power units  200   a  and  200   b  together to form a “crank shaft.” In this manner, any number of power units can be coupled together to form tandem engines of various sizes, such as an eight-cylinder tandem engine as illustrated in  FIG. 9B . 
         [0078]      FIG. 9B  is a diagram showing a side view of an exemplary eight-cylinder tandem engine  900   b , in accordance with an embodiment of the present invention. The eight-cylinder tandem engine  900   b  includes eight power units  200   a - 200   d  disposed on a base  902  and coupled together via a plurality of crank coupler assemblies  800 . As above, the eight-cylinder tandem engine  900   b  includes a fly wheel and clutch assembly  904 . Similar to  FIG. 9A , each crank coupler assembly  800  in  FIG. 9B  couples together two power units via the splined crank coupler section on each crank half, thus forming a “crank shaft” driving by the power units  200   a - 200   d.    
         [0079]    In one embodiment, the transmission can include a bell housing such that a tandem engine as described above can be joined to the transmission utilizing a crank coupler assembly  800  in a manner similar to coupling together two power units. In this embodiment, each transmission bell housing can include a fly wheel and clutch assembly that  904  includes a splined crank coupler section capable of being coupled to a power unit via a crank coupler assembly  800 . Moreover, as mentioned previously, the outer drive portion  802  of the crank coupler assembly  800  allows the crank coupler assembly  800  to be used as a belt or chain drive, allowing inline tandem engines as illustrated in  FIGS. 10A and 10B . 
         [0080]      FIG. 10A  is a diagram showing a top view of an exemplary four-cylinder inline tandem engine  900   c , in accordance with an embodiment of the present invention. The four-cylinder inline tandem engine  900   c  of  FIG. 10A  includes two power units  200   a  and  200   b  disposed side by side on a base  902  and coupled together via a belt  1000  and two crank coupler assemblies  800 . As above, each crank coupler assembly  800  is attached to a splined crank coupler section of the operable crank half of each power unit  200   a  and  200   b . In addition, a belt  1000  is positioned around each crank coupler assembly  800 , coupling the two power units  200   a  and  200   b  together. A further belt  1002  is positioned around an additional crank coupler assembly  800  on power unit  200   b  to couple power unit  200   b  to a fly wheel and clutch assembly (not shown). Although  FIG. 10A  has been described in terms of belt usage, it should be borne in mind that other coupling means can be utilized to couple the power units, such as a chain. Similar to above, using belts  1000  and crank coupler assemblies as illustrated in  FIG. 10A , any number of power units can be coupled together to form inline tandem engines of various sizes, such as a six-cylinder tandem engine as illustrated in  FIG. 10B . 
         [0081]      FIG. 10B  is a diagram showing a top view of an exemplary six-cylinder inline tandem engine  900   d , in accordance with an embodiment of the present invention. The six-cylinder inline tandem engine  900   d  includes three power units  200   a - 200   c  disposed side by side on a base  902  and coupled together via belts  1000  and crank coupler assemblies  800 . As above, each crank coupler assembly  800  is attached to a splined crank coupler section of the operable crank half of each power unit  200   a - 200   c . In addition, belts  1000  are positioned around each crank coupler assembly  800 , coupling the three power units  200   a - 200   c  together. A further belt  1002  is positioned around an additional crank coupler assembly  800  on power unit  200   b  to couple power unit  200   b  to a fly wheel and clutch assembly (not shown). As mentioned above, it should be borne in mind that other coupling means can be utilized to couple the power units, such as chains. 
         [0082]      FIG. 11A  is a diagram showing a side view of an exemplary decoupling four-cylinder tandem engine  900   e , in accordance with an embodiment of the present invention. The decoupling four-cylinder tandem engine  900   e  of  FIG. 11A  includes two power units  200   a  and  200   b  each disposed on separate decoupling bases  1100   a  and  1100   b . During idle and at low starting speeds the two power units  200   a  and  200   b  are coupled together via a crank coupler assembly  800 , similar to the four-cylinder tandem engine  900   a  of  FIG. 9A . However, as the vehicle increases in speed and no longer requires the torque provided by power unit  200   b , the decoupling four-cylinder tandem engine  900   e  has the ability to save fuel by decoupling power unit  200   b , as illustrated in  FIG. 11B . 
         [0083]      FIG. 11B  is a diagram showing a side view of the exemplary decoupling four-cylinder tandem engine  900   e  after decoupling, in accordance with an embodiment of the present invention. As mentioned above, once the additional torque provided by power unit  200   b  is no longer needed, the decoupling four-cylinder tandem engine  900   e  separates. More specifically, the base  1100   b  upon which rests power unit  200   b  moves away from the base  1100   a  upon which rests power unit  200   a . As a result, the crank coupler assembly  800  slides off the crank coupler  706  of power unit  200   a , thus separating power unit  200   a  from power unit  200   b . Once separated, power unit  200   a  can operate separately to power the vehicle as a two-cylinder engine, while power unit  200   b  can be turned off in order to save fuel. Later, during idle, the power units  200   a  and  200   b  can be coupled together again by moving base  1100   b  back toward base  1100   a . This action results in the crank coupler assembly  800  sliding back onto the crank coupler  706  of power unit  200   a , thus reconnecting the power units  200   a  and  200   b  to function as a complete four-cylinder engine again. Similar to above, any number of power units can be coupled together to form decoupling tandem engines of various sizes, such as an eight-cylinder tandem engine that decouples between the second and third power units to operate as a four-cylinder engine when decoupled. 
         [0084]      FIG. 12  is a diagram showing an exemplary variable compression power unit  1200  having cylinder compression variance capability, in accordance with an embodiment of the present invention. The variable compression power unit  1200  is a power unit similar to those described above with reference to  FIG. 2A-5D  and includes, for example, an intake port  230  disposed within a trunnion mount  304 . In addition, the variable compression power unit  1200  includes elements that enable the cylinder compression to be adjusted to enhance engine performance. For example, the exemplary variable compression power unit  1200  of  FIG. 12  includes a compression selection handle  1202  connected to a compression selector ring  1204 , which is positioned around the trunnion mount  304 . The selector ring  1204  also is connected to the engine case place  1208 . 
         [0085]    As can be seen in  FIG. 12 , the trunnion mount  304  is situated off-center from the center of the compression selector ring  1204 . That is, the center of the trunnion mount  304  is offset from the center of the compression selector ring  1204 . For example, in  FIG. 12  the center of the trunnion mount  304  is offset to the right from the center of the compression selector ring  1204  when the compression selector handle  1202  is disposed to the right of center. In this manner, when the compression selector handle  1202  is moved to left of center, the trunnion mount  304  travels slightly toward the top of the power unit  1200 . The movement of the trunnion mount  304  causes the power unit cylinders to move in the same direction because, as noted above, the power unit cylinders are connected to the trunnion mount  304 . However, the pistons are not connected to the trunnion mount. 
         [0086]    As a result, when the compression selector handle  1202  is moved to left of center causing the trunnion mount  304  and the power unit cylinders move slightly upward, more space is provided between the top of the pistons and the top of the cylinders during compression. Conversely, when the compression selector handle  1202  is moved to right of center causing the trunnion mount  304  and the power unit cylinders move slightly downward, less space is provided between the top of the pistons and the top of the cylinders during compression. 
         [0087]    In one embodiment, a worm drive shaft  1206  is provided to mechanically move the compression selector handle  1202  from right of center to left of center and vice versa. In this embodiment, teeth are included on the compression cylinder handle  1202  as illustrated in  FIG. 12 , and disposed between the external threads of the worm drive shaft  1206 . During operation, the worm drive shaft  1206  is rotated in a first direction to cause the compression selector handle  1202  to move from right of center to left of center. The worm drive shaft  1206  can be rotated in the opposite direction to cause the compression selector handle  1202  to move from left of center to right of center. 
         [0088]    For example, during normal running of the power unit  1200 , the worm drive shaft  1206  is used to move the compression selector handle  1202  to left of center, thus allowing more space between the top of the cylinders and the top of the pistons. During idle, additional compression can be achieved by using the worm drive shaft  1206  to move the compression selector handle  1202  to right of center, thus reducing the space between the top of the cylinders and the top of the pistons and increasing compression. 
         [0089]    Contacts can be included to allow the compression selector handle  1202  to signal when particular plugs or injectors should be used. For example, the exemplary variable compression power unit  1200  includes a hot plug selector contact  1210   a , cold plug selector contact  1210   b , and an injector selector contact  1210   c . During operation, when the compression selector handle  1202  is positioned to right of center, the hot plug selector contact  1210   a  is contacted and the hot spark plug is used for spark. Similarly, when the compression selector handle  1202  is positioned to left of center, the cold plug selector contact  1210   b  is contacted and the cold spark plug is used for spark. In addition, based on the position of the compression selector handle  1202 , injector performance can be controlled. Hence, power from the engine can come from fuel and/or compression. In addition, a tandem engine can include a leveling device that increases compression when the vehicle travels up hill, thus burning more fuel and providing more power. Similarly, the compression also can be increased when traveling down a long grade. 
         [0090]    Although the foregoing invention has been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications may be practiced within the scope of the appended claims. Accordingly, the present embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalents of the appended claims.