document: RELATED APPLICATIONS 
         [0001]    The application is a continuation application of prior U.S. application Ser. No. 12/568,034, filed on Sep. 28, 2009, and which claims the benefit of: (1) U.S. Provisional Application No. 61/173,355, which was filed on Apr. 28, 2009, (2) U.S. Provisional Application No. 61/166,260, which was filed on Apr. 3, 2009, and (3) U.S. Provisional Application No. 61/100,295, which was filed on Sep. 26, 2008. Each of these disclosures are herein incorporated by reference in their entirety. 
       
      
       BACKGROUND 
         [0002]    Internal combustion engines contain multiple cylinders. Exhaust gas is generated when a fuel and air mixture is ignited and expanded within a cylinder to drive a piston. The exhaust gas is typically vented from the cylinders through an exhaust stroke to the atmosphere. The exhausted gas typically has a very high temperature when leaving the cylinders. In some proposed systems, the exhaust gas is delivered to a second cylinder for further expansion. 
           [0003]    Some internal combustion engines have injected water into the same cylinder performing combustion with fuel and air intake. 
           [0004]    There has also been a proposal for a combined engine that has a combustion cylinder mounted upstream of an expansion cylinder. The expansion cylinder receives hot exhaust gas from the combustion cylinder, and also receives a source of water that is expanded into steam by the hot exhaust gas to create further drive for a common crankshaft. 
           [0005]    While this proposed system has good potential, there are many improvements that would make the system more practical. 
         SUMMARY 
         [0006]    In features of this invention, downstream expansion cylinders are associated with a combustion cylinder to provide an overall surface area and volumetric displacement of expansion cylinders sufficient to lower the temperature of fluids associated with the combined engine to such an extent that a radiator can be eliminated in an associated vehicle, or other system. 
           [0007]    In a separate feature, a catalytic material is placed on surfaces which will “see” the hot exhaust gases such that catalytic conversion of impurities in the gases can be achieved within the engine itself. 
           [0008]    In yet another feature, water is recovered from a system having both a water injection expansion cylinder, and a combustion cylinder, and the recovered water is re-used for the expansion. 
           [0009]    In yet another feature, gearing is provided between an expansion cylinder and a combustion cylinder such that the output of the combined engine is optimized, and the two cylinders do not drive the crankshaft in a one-to-one fashion. 
       
      
       
         BRIEF DESCRIPTION OF THE DRAWINGS 
           [0010]      FIG. 1  schematically shows a first embodiment engine. 
             [0011]      FIG. 2  is a flowchart of a basic system incorporating this invention. 
             [0012]      FIG. 3  shows a second embodiment system. 
             [0013]      FIG. 4  shows another potential embodiment. 
             [0014]      FIG. 5  shows yet another embodiment. 
             [0015]      FIG. 6  shows yet another embodiment. 
             [0016]      FIG. 7  shows yet another embodiment. 
             [0017]      FIG. 8  graphically shows the input versus output for exemplary systems. 
             [0018]      FIG. 9  shows a water cooling system incorporated into this invention. 
             [0019]      FIG. 10  shows another embodiment of the water cooling system. 
             [0020]      FIG. 11  shows a water recovery system. 
             [0021]      FIG. 12  shows a catalytic conversion system. 
         
      
      
       DETAILED DESCRIPTION 
         [0022]    An engine  20  is illustrated in  FIG. 1 , and incorporates combustion cylinders  32  and  34 , which are mounted adjacent to an expansion cylinder  33 . Each of the cylinders include pistons  50 , which are driven to drive a common crankshaft  52 . Although the cylinders are shown in side-by-side relationship, in practice, they will be inline such that the common crankshaft  52  is driven by each of the pistons  50 . Of course, other configurations can be used. 
           [0023]    The cylinders  32  and  34  are combustion cylinders and are shown having spark plugs  44 . However, other combustion cylinders which do not require spark plugs would also benefit from the teachings of this application. 
           [0024]    As shown, intake valves  40  control the flow of air and fuel into the cylinders  32 ,  34 , in some engine types, such as Diesel, the fuel may be directly injected into the cylinders. The combined air and fuel is compressed, ignited, and exhausted through exhaust valves  42  into an associated exhaust line  46 . The cylinders  32  and  34  may be four-stroke cylinders, and will operate as known, at least as described to this point. 
           [0025]    Inlet valves  48  on the expansion cylinder  33  alternately operate in sync with the alternating operation of valves  42  and receive the hot, high pressure exhaust from the exhaust lines  46 . The gases at least partially drive the larger displacement piston  50  associated with the expansion cylinder  33  in a two-stroke fashion. As known, the cylinders  32  and  34  will be out of phase by 360°. Cylinder  33  has a final exhaust valve not shown. 
           [0026]    A water injection system  70  takes water from a source of water  71  and injects it into the engine at any one of several possible locations. As shown, the water may be injected through line  72  into the exhaust line  46 . Water may be injected through line  74  to the top of the cylinder of the expansion cylinder  33 . The water may be injected as shown at  76  into the top of cylinders  32 ,  34 . If injected into the cylinders  32  and  34 , it is preferred that the water be injected late in an exhaust cycle. 
           [0027]    The water injection and metering can be performed in much the same way as high pressure fuel injection is commonly performed in a diesel engine, for example. The injection of water is estimated to be at a rate of 1 to 2 times the rate of fuel consumption for a gasoline engine. The water can be injected into the expansion cylinder  33  head at the time exhaust gases are being communicated to the expansion cylinder  33 . Owing to a finite thermal absorption and vaporization delay for the heat of the ignition to vaporize the injected water, it may be beneficial in some cases to move the injection of the water forward in the process, into the exhaust passage  46 , or into one of the cylinders as described above at  76 . In the case of injecting the water into one of the combustion cylinders  32  or  34 , this should occur at a mature point of the power-stroke, 160 degrees-175 degrees, past top dead center, for example. 
           [0028]    Valves V are shown for controlling the flow of the injection of the water, and may be controlled by an overall engine control, in a manner that would be apparent to a worker of skill in this art. 
           [0029]    While cam shafts are shown for controlling the operation of the several cylinder valves, other means of valve timing, such as electronic valve controls may be utilized. 
           [0030]    Fuel and air fed combustion cylinders  32  and  34  may fire nominally at 0 degrees and 360 degrees of rotation respectively. The cylinders  32 ,  34  alternate intake and power strokes while the expansion cylinder  33  executes an exhaust stroke. During the exhaust stroke, gases exit the expansion cylinder through a valve, not shown. Each cylinder  32 ,  34  contributes torque to a crankshaft  52  through the power-stroke. The combustion cylinders  32 ,  34  alternate compression and exhaust strokes while the second cylinder  33  is executing a power stroke. In the power stroke, the piston  50  in the expansion cylinder is driven by expansion of the steam and exhaust gas. The expansion cylinder  33  expands the exhausted gas of the cylinder  32  beginning nominally at  180  degrees of rotation and then, after completing an exhaust stroke, the cylinder  33  alternately further expands the emission from the cylinder  34  beginning nominally at 540 degrees of rotation, in a two-stroke fashion. 
           [0031]    In one example, displacement of the expansion cylinder  33  is four times that of the cylinders  32  or  34  (the displacements of the cylinder  32  and cylinder  34  may be nominally the same). Accordingly, the second cylinder  33  contributes significant positive torque to the crankshaft  52 . 
           [0032]    Oil pans  60  associated with the combustion cylinders  32  and  34  are shown. The sump  62  of the expansion cylinder may be sealed from the oil pans  60 , and their combustion cylinders  32  and  34 , such that water can collect, as will be described below. 
           [0033]      FIG. 2  is a flowchart which briefly describes the above-described system. First, an exhaust gas is produced in a combustion cylinder. This exhaust gas is expanded along with water via a water injection process. The expanded gas creates a pressure front which drives the expansion cylinder piston. The expanded gas is substantially cooled before discharge. Thermal transfer between cylinders maintains the working temperature of the first cylinder. 
           [0034]      FIG. 3  shows a top down view of an embodiment  100  with combustion cylinders  132  associated with an expansion cylinder  133 . An exhaust passage  146  connects cylinders  132  to cylinder  133 . Additional downstream expansion cylinders  102  are provided, to provide a multi-stage cascade. As shown, the exhaust  104  from the expansion cylinder  133  delivers expanded exhaust gas into the cylinders  102 . 
           [0035]    In general, the use of the several expansion cylinders provides that the total surface area of expansion cylinders is sufficiently large that all, or the great majority, of the generated heat and energy can be recaptured prior to being exhausted to atmosphere. In this manner, the invention may allow the elimination of the radiator. 
           [0036]    The pistons of the outer expansion cylinders  102  can have the same rotational phase as the four-stroke cylinders  132 , respectively, and could be 180 degrees out of phase with the central two-stroke expansion cylinder  133 . In this example, the need for ever larger displacement through a cascade is provided by having the combined displacement of the outer cylinders  102  be substantially greater than the displacement of the central cylinder  133 , while the interior configuration may operate as previously described. 
           [0037]    The example outer cylinders  102 , may have bores that are larger than the central cylinder  133  by a factor of √{square root over (2)}, causing a combined displacement four times larger than the first cascade in the central cylinder  133 . 
           [0038]    In one example, two outer cylinders  102  receive the exhausted gas. In other examples, cascading continues from cylinder  133  to a single downstream cylinder. The direction and number of cylinders receiving the exhaust is not limited. It is desirable that each downstream, or cascaded, cylinder has larger displacement than the cylinder providing exhaust gases. 
           [0039]    Water injection can occur through a water injection line  108  which is shown injecting water into the first stage expansion cylinder at  107 , and the second stage expansion cylinders  102  at  106 . As will be described below, the several stage cascading as disclosed in the  FIG. 3  embodiment allows the exhaust gas and water to be lowered to a very low temperature, and for a great majority of the potential energy generated by the combustion process to be captured as useful energy, rather than lost as wasted energy. 
           [0040]    As seen in  FIG. 4 , four-stroke combustion cylinder  202  drives a crankshaft  280 , and a two-stroke expansion cylinder  204  that is powered by exhaust and water as described above, drives a shaft  279 . An intermediate two-to-one gear reduction  206  may be a planetary transmission. The gear reduction  206  may be any type of coaxial gear reduction. One example would be a complex planetary gearing system, including more than one planetary gear set to eventually provide a 2:1 reduction, however, other gear reductions can be utilized. 
           [0041]    The crankshafts of the two cylinders  202 ,  204  are mechanically synchronized in this embodiment through gear reduction  206 , such that the 360 degree operation of cylinder  204  is effectively expanded to 720 degrees to match the operation of four-stroke cylinder  202 . The example arrangement has the heavier reciprocating mass of the two-stroke, secondary power-stroke expansion cylinder  204  now reciprocating at half speed of the lighter, but faster, fuel and air fed four-stroke cylinder  202 . The example arrangement has appreciable opportunity for additional thermal-to-mechanical energy extraction through a single cascade. 
           [0042]    As shown in  FIG. 5 , an alternative system may use a dual gearing  208  and  210  that achieves the two-to-one gear reduction from the expansion cylinder crankshaft  212  to the crankshaft  214 . This may allow the larger displacement requirement of expansion cylinder  204  to be achieved by a longer stroke or a combination of a larger bore and a larger stroke. 
           [0043]    The  FIG. 4  or  5  arrangements can be used in combined multiple groupings. Also, water injection would preferably be used with these embodiments. 
           [0044]    Referring to  FIG. 6 , two two-stroke secondary power-stroke expansion cylinders  502  can be coupled to one four-stroke combustion cylinder  504  in various different formations. In such formations, the four-stroke cylinder  504  supplies the exhausted gas required for secondary expansion alternately to the two two-stroke secondary power-stroke expansion cylinders  502 . In general, the expansion cylinders  502  are driven such that they operate at one-fourth the speed of the piston for the combustion cylinder  504 , and are out of phase with each other. A gear reduction  581  is shown schematically connecting their crank portions  580 . Typically, the three crank portions will be non-coaxial, although this is not a limitation on this portion of the inventive concepts. 
           [0045]    For each two-stroke expansion cylinder  502 , there are four quarter-exhaust strokes and four quarter-power strokes for each one thousand fourteen hundred forty degree cycle, or two four-stroke cycles. The first two-stroke cylinder  502  is offset from the second two-stroke cylinder  502 , such that when one is in an exhaust stroke, the other is in a power stroke. This allows the four-stroke  504  to feed one two-stroke at a time. 
           [0046]    Again, a water supply source  535  may inject water through a line  537  into an exhaust line  19  connecting the single combustion cylinder  504  to each of the expansion cylinders  502 . Of course, as with the earlier embodiments, any number of other locations for water injection may also be utilized. 
           [0047]    Again, an oil pan  583  may be maintained separate from water sumps  579 . 
           [0048]    An embodiment  700  is illustrated in  FIG. 7 . Combustion cylinders  706  generate hot exhaust gas which is passed downstream to a first expansion cylinders  704 , and then to second expansion cylinders  702 . Each expansion cylinder  704  and  702  has a progressively greater displacement and effective surface area compared to the combustion chambers  706 . As shown, gearing  714  drives gear  712  to achieve a first gear reduction, and gear  712  drives a second gear  713 . The gear reduction between gears  714  and  712  is selected such that there is a 2:1 step-down. Gears  712  and  713  provide a 1:1 drive arrangement. 
           [0049]    The operation of the system may generally be as described above. Again, water injection is shown schematically through a source  710  into the expansion cylinder  702  and  704 . Again, water pans  703  may be maintained separate from oil pan  701 . However, here oil pan  701  services both combustion cylinders  706  and hot first expansion cylinders  704  while only the second, and final in this example, expansion cylinders  703  are cool enough to be serviced by water pans  703 . 
           [0050]    In other examples, N-two-stroke expansion cylinders can be coupled to M positioned four-stroke cylinders to create multiple cascades. Here, N and M are arbitrary numbers greater than or equal to 1. 
           [0051]    In a similar example, one four-stroke cylinder could feed N-number of two-stroke, secondary-power-stroke expansion cylinders, where N is an arbitrary but generally even number. This creates an adaptable system configuration where the engine wastes little to no heat and the final exhaust temperature is brought to an exceptionally low value. Therefore, the only system energy exit is through the performance of mechanical work. This may allow the elimination of the radiator for an associated vehicle. 
           [0052]    High-temperature, water-lubricated polymeric materials may be used in critical places within the construction of the second cascade, such as the outer cylinders  702 . For example, the second cascade can have a dense, Teflon-like coating on the interior of the cylinder wall. The type of coating is not limited here. The connecting rod bearings similarly may use dense Teflon for bearing material, although similarly, not limited. The second cascade may be intentionally driven beyond the condensation point, such that water lubrication is available, as water condensation is captured within the engine for re-use. The heat loss by the final exhaust can be managed in this manner down to a negligible level. 
           [0053]      FIG. 8  shows a schematic summary of the overall operation of the several above disclosed embodiments. Air and fuel is brought into the system and combusted. Thermal insulation is preferably provided about the engine such that there is minimal heat loss to the environment from the engine. The energy output in a typical engine includes mechanical work, such as driving a crankshaft. The inventive systems are designed to maximize this output. 
           [0054]    The prior art systems typically lose heat to a radiator. The inventive systems attempt to minimize any heat to a radiator, and in fact to eliminate any need for a radiator, as will be explained below. 
           [0055]    Prior systems lose heat to the exhaust. The inventive systems aim to reduce the temperature of the exhaust to such an extent that there will be little or no heat loss at this location. The same is true with heat loss to convection. 
           [0056]      FIG. 9  shows an embodiment  900  of a water cooling system which may be maintained as a closed circuit, and separate from the water injection. In the water cooling system  900 , cascade or expansion cylinders  902  are adjacent to a combustion cylinder  904 . A water jacket  906  surrounds each of the cylinders. As can be appreciated, fuel, air and water injection lines, consistent with the above-described embodiments, would also extend through the water jacket in actual embodiments. A return line  908  returns water from the water jacket  906  through a flow control valve  910 , and to a water pump  912  which recirculates the water. The pump  912  is arranged such that it pulls the water from the vicinity of the combustion cylinder  904 , over the expansion cylinders  902 . The heat which is captured in the water by cooling a combustion cylinder  904  is partially captured to heat the expansion cylinders  902 . An optional heat exchanger  951  may be included which utilizes remaining heat in the return line  908  to heat water in the water injection line  950  heading for the expansion cylinders. However, this heat exchanger is optional, and need not be utilized. 
           [0057]    The main requirement for the cooling water jacket to cool the combustion cylinders, and then heat the expansion cylinders, is that the temperature of the cascade or expansion cylinders needs to be lower than the working temperature of the liquid coolant. This requirement can be facilitated by increasing the operating pressure, and therefore temperature, of the liquid coolant system. A temperature sensor  914  can be set such that it will send a signal to a control  916  to allow higher temperatures if such are desirable. While water may be used as the cooling fluid, any number of other coolants may be utilized. 
           [0058]    The temperature sensor  914  may provide information back to the control  916  which controls the water valve  910  to ensure adequate water supply to maintain the temperatures as desired. 
           [0059]    In addition, the control  916  may be an ignition control input which can control the timing of the ignition for the combustion cylinder  904 . In a standard engine, it would not be desirable to slow ignition timing based upon undue temperatures in the system, as this will simply reduce the overall produced useful energy. However, given that the present invention captures a much greater percentage of the useful energy, slowing of ignition timing can be utilized while still capturing sufficient power through the subsequent cascades. Thus, the control  916  may be programmed with an algorithm that will identify an undesirably high temperature at the temperature sensor  914 , and slow ignition timing. In this manner, the overall system can be more likely to capture a greater percentage of the useful energy created by combustion. 
           [0060]    In general, the control  916  can modulate the ignition timing to achieve tight control over the temperature of the combustion cylinder. A sensed over-temperature condition can be rectified by retarding the ignition timing by one to twenty-five degrees of crank rotation, for example. The exact amount may depend on the size and abruptness of the overall temperature condition. This will transfer some of the heat load to the expansion cylinders, where it can contribute to useful work. This retardation of ignition timing will also reduce the peak temperature and pressure for the benefit of reduction of pollutant generation. 
           [0061]      FIG. 10  shows another embodiment  920  wherein the expansion cylinders  902  are positioned to be separated by a thin wall  922  from the combustion cylinder  904 . All of the cylinders may be formed in a single block  921 . This embodiment may be a passive transfer system that does not include a pump. The liquid jacket  919  surrounding the block  921  may be a sealed container containing any vapor or liquid fluid having good heat transfer properties. 
           [0062]    Any number of other ways of transferring heat from the combustion chambers to the expansion chambers may be incorporated into this invention. 
           [0063]    With either of the  FIGS. 9 and 10  embodiments, the very hot combustion cylinder  904  transfers heat energy to the cascade cylinders  902 . The cascade cylinders  902  benefit from this additional heat, as it increases the temperature of the injected water environment to produce additional steam, and allows the recapture of this heat energy. 
           [0064]    By capturing and transferring the heat in this manner, the system is able to reduce the exhaust gas and water from the most downstream cascade cylinder to such an extent that no radiator may be necessary. 
           [0065]      FIG. 11  shows a water recovery system  930 . When utilized in a system, and in particular in a mobile vehicle system, the source of water to be injected must be contained within a tank  936  associated with the vehicle. The system  930  has a cylinder  932  provided with a piston  933  driven to expand from exhaust and water expansion, as are found in any of the embodiments described above. An exhaust  938  of this system passes through a water scrubber or water trap  940  which returns water through a line  941 , and passes exhaust gases downstream through a line  943 . More than one phase of water scrubbing may be provided. Eventually, the exhaust gas may reach a muffler  942 . Muffler  942  may be provided with yet another scrubber  944  which passes the final exhaust gas through line  945  to atmosphere, and returns water through yet another water return line  941  to an overall water return line  952 . Scrubber  944  may be included within the muffler housing or attached downstream. 
           [0066]    The piston  933  is provided with piston seals  948  which may provide a loose seal with an internal surface  950  of the expansion cylinder  932 . The amount of “clearance” is exaggerated in this Figure to show the fact of the clearance. The crankcase  946  for the expansion cylinder may be separated from oil such that the expansion cylinder components are lubricated only by this water. The water-containing crankcase may be similar to the case  62  in  FIG. 1 ,  579  in  FIG. 6 ,  703  in  FIG. 7  or any other arrangement. The use of the loose fit will ensure that a good deal of steam which has been expanded to the point of condensation in the cylinder  932  will fall to the crankcase  946 , and be returned through water return line  952  to the water tank  936 . A pump  937  may drive the water to the injection line  934  back into the cylinder  932 . 
           [0067]    The recovery of the water from the crankcase  946  may be only necessary on the most downstream expansion cylinder, however, it can optionally be utilized on more expansion cylinders than simply the most downstream. A water scrubber  939  is shown on the line leading from the crankcase  946 , and may remove an exhaust gas  929 , similar to the above-described embodiment. 
           [0068]    The water scrubbers may be known water traps, and in particular may be chilled or cold water traps of known design. Further, the crankcase drain line can be combined into the exhaust line  938  such that a single set of water scrubbers may be utilized to achieve the above-described features. 
           [0069]    By having this detailed water recovery system, the present invention ensures that the source of water will be largely recycled, and that an unduly large water tank will not be necessary. 
           [0070]    Across the embodiments, expansion cylinders may be provided in sufficient numbers, such that the final exhaust may be brought to a low temperature, say below 500° F., and in a preferred embodiment, at or below 212° F. When surrounded with high levels of an external insulation, this low temperature exhaust becomes almost entirely the sole source of thermal efficiency loss in steady-state operation. The frictional “loss” of internal moving components also becomes captured within the system so as to be either converted as part of the useful mechanical output or to otherwise be a component of this modest final exhaust emission. These engines may achieve steady-state thermal-to-mechanical efficiencies that are in the range of 94-96%. 
           [0071]    Steady-state operation may be characterized by the following rough thermal budget. In a current engine, say a radiator would account for 25% of the thermal budget, while in the described examples accounting for essentially 0%. In a current engine, conduction/convection might account for 25% of the thermal budget whereas in the described examples accounting could be approximately 1-2% of the thermal budget. In a current engine, exhaust may account for 25% of the thermal budget whereas in the described examples may account for approximately 2-3% of the thermal budget. Further, in a current engine, mechanical extraction may account for 25% of the thermal budget where as in the described examples might account for approximately 95% of the thermal budget. 
           [0072]    It is believed that there could be back pressure due to the injection of the exhaust gas that could complicate the breathing induction of the combustion cylinders. By injecting water into a cascade cylinder head space after the exhaust gas communication is complete (as an example at the 50% cut-off point for a 2:1 crank synchronization; at the 25% cut-off point for a 4:1 crank synchronization, there will be less back pressure for the exhaust cycle to work into. As another example, should there be a 8:1 speed reduction on the cranks, the above can occur at the 12.5% cut-off point. This will improve the breathing of the combustion cylinder to improve power density, while still allowing the establishment of a steam vaporization pressure front. 
           [0073]    Other ways of addressing this breathing concern can be utilized. As an example, the combustion four-stroke cylinder can be RAM charged or super-charged. The combustion cylinder can be of a particularly long stroke, as in a diesel cycle. The combustion cylinder can employ at Atkinson cycle, resulting in a very low cylinder pressure by the end of its power-stroke. The displacement ratio of the expansion cylinder to the combustion cylinder can be designed to be higher than described above. The combustion cylinder can be replaced with a split-cycle pair of cylinders, as has been proposed by Scuderi Motors. Water can be injected into the cascade cylinder head space after the exhaust communication is complete, as described above. Any of these methods of simplifying the breathing/back pressure issue can be utilized. 
           [0074]    Referring to  FIG. 12 , in one example, components have their surface materials chosen so as to catalyze certain desirable reactions for the benefit of reduced exhaust emissions. A surface within a cylinder assembly could include an inner lining  611  made of a particular surface material designed to have the same catalyzation effect as a catalytic converter. In one embodiment, the cylinder is an expansion cylinder, and more preferably, plural expansion cylinders such as are described above. The surface materials may include but are not limited to: platinum, palladium, rhodium, cerium, iron, and manganese. This example takes advantage of both the enhanced residence time as well as the enhanced surface area, as both increase with an increase in cascaded cylinders, to catalyze reactions that are presently catalyzed in a separate external catalytic converter subsequently eliminating or reducing the need for the converter. As shown in  FIG. 12 , a first cylinder  604  is associated with a downstream cylinder  606 , which is larger. Pistons  608  move within the cylinders  604  and  606 . Cylinder head  619  receives valves  617 . An exhaust connection  610  connects the two. The lining material  611  can be formed on any, or all, of the interior of the cylinders, the pistons, and the cylinder heads, the valves and in the exhaust passage  610 . The catalytic materials can be used on any surface, e.g., fluid flow paths, etc., that will “see” the hot exhaust gas. 
           [0075]    In another example, different surface materials for internal environments become required as the final exhaust emission is likely to be much cooler than presently-in-use four-stroke engines, and possibly much lower than desirable for best catalytic reaction kinetics. 
           [0076]    Generally, surfaces exposed to the hot gaseous fluid flow may have thermal insulation on the outside of the arrangement, or hot interior-surfaces and structural components may be made of thermally low conductive material. Another alternative would be to maximize heat loss prevention and use a low conductive material that is additionally thermally insulated on the outside. For example, the piston tops have substantial surface area exposed to hot gases, while their bottoms are exposed to crankcase oil. The heat-of-combustion to the displacement volume above the piston top may be confined for thermal-to-mechanical extraction and to avoid heating the crankcase oil. Therefore piston tops made of, for example, a thermally dead ceramic, or ones with a lightweight, crankcase-compatible insulation on the underside, or both, may be used. Another example would be pistons made of normal material, clad bonded with a thermally dead ceramic top surface. Similar concepts could be applied to the valves and valve tops, the hot gaseous-exposed interior-surface of the cylinder-head, the intake passages and exhaust passages from one cylinder to the next in the several above embodiments. This creates a continuous expansion motor with heat energy preserved through all the hot gaseous fluid flow and confined to mechanical energy extraction by the various, and now cascaded, power strokes. 
           [0077]    Ultimately, water vapor condensation concerns may limit the minimum desirable final exhaust temperature, but only after a far greater thermal-to-mechanical extraction has been accomplished relative to currently-in-use internal combustions engines. Distilled water may be sufficient for the disclosed purpose, but tap water, or, tap water with a de-calcification/de-crystallization agent alone may also be sufficient. Further, the fuel can carry de-calcification/de-crystallization capability. 
           [0078]    Many operating environments will be cold enough to freeze the water, causing a potential problem. However, this is likely manageable using, for example, flexible storage containers that can accommodate freeze expansion or similar technology. The final exhaust can also be used to melt the stored water over the longer operational term and a small high temperature thermal extraction channel from the  4 -stroke cylinders can be used to melt water initially for the near term start-up. One other possibility is an electric melt device which is most cost-effective for initial, temporary use. 
           [0079]    The combustion cylinder can be made up of, but not limited to, one or more of the following types of fuel and air cylinders including aspirated, fuel injected, carbureted, turbo-charged, super-charged, ram-charged, or any combination of these. The fuel can include, but is not limited to, the use of fuels including gasoline, diesel, propane, natural gas, alcohol, hydrogen, kerosene, or any other fuel known in the art. 
           [0080]    In another example, the combustion cylinders may include an Otto four-stroke cylinder, Atkinson four-stroke cylinder, Diesel four-stroke cylinder, or any other known four-stroke cylinder. 
           [0081]    While the expansion cylinders have generally been described as two-stroke cylinders, the invention would extend to four-stroke cylinder assemblies. 
           [0082]    Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.
summary: Downstream expansion cylinders are associated with a combustion cylinder such that an overall surface area and displacement volume of the expansion cylinder is sufficient to lower the temperature of fluids associated with the combined engine to such an extent that a radiator can be eliminated in an associated vehicle, or other system. In a separate feature, a catalytic material is placed on surfaces which will “see” the hot exhaust gases such that catalytic conversion of impurities in the gases can be achieved within the engine itself. In yet another feature, water is recovered from a system having both a water injection expansion cylinder, and a combustion cylinder, and the recovered water is re-used for the expansion. In yet another feature, gearing is provided between the expansion cylinder and a combustion cylinder such that the output of the combined engine is optimized, and the two cylinders do not drive the crankshafts in a one-to-one fashion. In another feature the combustion cylinder&#39;s ignition timing is delayed (retarded) to manage thermal control of said combustion cylinder between it and a subsequent expansion cylinder or cylinders.