Abstract:
Exhaust emissions are reduced, fuel consumption is improved for internal-combustion engines, and the number of cold starts reduced by storing heat energy from the operation of the engine in a heat-storage reservoir filled with a change-of-state heat-storage material. Absorbed heat energy is released back to the engine&#39;s intake manifold to maintain elevated engine temperature between uses and starting up of the engine.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of applications Ser. Nos. 190,932 now U.S. Pat. No. 4,393,817 and 190,933, now abandoned both filed Sept. 25, 1980, which are, respectively, a division and a continuation of Ser. No. 657,747 filed Feb. 13, 1976, now abandoned, which was a continuation-in-part of application Ser. No. 613,867, filed Sept. 16, 1975, now abandoned, which was a continuation-in-part of application Ser. No. 356,589 filed May 3, 1973, now abandoned, which was a continuation-in-part of application Ser. No. 227,440, filed Feb. 18, 1972, now abandoned. Application Ser. No. 227,440 is not relied on under 35 U.S.C. §120 because it does not disclose the invention claimed in the present application. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to internal-combustion engines, specifically to method and apparatus for improving the fuel efficiency of automobile engines and reducing their emissions during &#34;cold start&#34;. 
     Under typical &#34;cold start&#34; conditions, an internal-combustion engine requires a rich fuel-air mixture. The carburetor chokes off some of the air being fed to the intake manifold in order to achieve this. When such a rich mixture is being used, the fuel consumption of the engine is dramatically increased, also raising the level of exhaust emissions. As the engine warms, the carburetor gradually leans out the fuel-air mixture until the engine reaches its normal operating or cycle temperature, at which time fuel efficiency is maximized and exhaust emissions are minimized, assuming normal load conditions. In summary, when an automobile is first started in the morning, or is re-started during the day after having not been used for a period of time, the engine will use up more fuel and at the same time produce increased exhaust emissions. 
     The typical driver of an automobile will use the vehicle for a number of short trips during the day. Usually, enough time elapses between these trips for the motor to cool down significantly from operating temperature. Therefore, most automobiles are operated most of the time during their least efficient period, namely during &#34;cold start&#34;, when the engine temperature is being raised to operating temperature. Estimates made by the Environmental Protection Agency indicate that more than 30 percent of the United States&#39; total fuel consumption occurs during the &#34;cold start&#34; period. 
     &#34;Cold start&#34; time may be decreased and engine efficiency increased by maintaining an elevated engine temperature, particularly at the intake manifold, between such uses. The closer that temperature is to normal operating temperature, the more efficient the engine will be. 
     Heretofore, the &#34;cold start&#34; problem in the automobile industry has been made worse by the quick loss of heat from internal combustion engines between uses. Various devices have been proposed for maintaining engine warmth during extremely cold weather, but these devices were not addressed to the problem of engine cooling between relatively consecutive uses. For example, the U.S. Pat. No. 1,338,750 to Schranck and Kunkel employs a heat exchanger on the exhaust pipe of an internal-combustion engine. The heat exchanger contains a block of soapstone which absorbs heat and transfers it to a water cavity connected to the cooling system of the engine, all for the purpose of keeping the engine coolant from freezing in cold weather. The warmed coolant flows by gravity feed. Electrically operated warming is also disclosed. The system is designed to be detachable so that it need not be used in the summer. The Schranck and Kunkel system does not address the &#34;cold start&#34; problems solved by the present invention. 
     The U.S. patent to Snelling (U.S. Pat. No. 3,114,360) shows a remotely located heat-storage reservoir filled with a fusible salt which is used to store heat from an external source, such as a blow torch. The melted salt or fused material transfers heat to a fluid which evaporates and is then pumped to some portion of the engine which requires additional heat due to its own heat loss, for example, the carburetor casing. The vaporized fluid gives up its heat, condenses, and returns to the remote reservoir. One embodiment suggest the use of heat from an exhaust pipe heat exchanger or from electrical means. This device does not, however, store heat directly from and return it to the engine part needing it, such as the intake manifold, nor is any part continuously heated and ready for instant starting. 
     Boehmfeld (U.S. Pat. No. 3,498,539) and Prebil (U.S. Pat. No. 3,853,270) both show heat-preserving tanks for maintaining a warmed volume of coolant fluid to be supplied to the cooling system when the engine is started. Neither of these shows direct absorption from, nor warming of the engine parts which can improve &#34;cold start&#34; and reduce pollution, namely the intake manifold and the carburetor. 
     It is therefore desirable to enable the storage of heat energy produced by an internal-combustion engine during operation, for use in maintaining the engine, particularly its intake manifold and carburetor, at an elevated temperature for a substantial period of time between uses. 
     An object of the invention is the storage of waste heat from an internal-combustion engine and subsequent release of that heat back to the engine, keeping it warm after shut-down. 
     Another object of the invention is to provide a method of improving fuel efficiency and reducing the emission of pollutants in an automobile during cold starting. 
     Yet another object of the invention is to provide a method and apparatus for directly increasing the cold-starting temperature of an internal-combustion engine, without use of additional energy for providing such additional heat. 
     Still another object of the invention is to provide a heat storage reservoir for heat exchange with the intake manifold of an internal-combustion engine, whereby waste heat from the intake manifold is stored during engine operation and is released to the manifold when the engine is shut down. 
     A further object of the invention is to provide an exothermic reaction chamber in heat exchange relationship with the intake manifold and carburetor of an internal-combustion engine. 
     A still further object of the invention is to provide apparatus for storing the exhaust manifold heat of an internal-combustion engine and to redistribute that heat to warm the intake manifold and carburetor of the engine after it has been shut down. 
     Another object of the invention is the provision of a heat-storage bladder which can be placed atop the intake manifold, carburetor, and air filter assembly of an internal-combustion engine for storing heat energy therefrom. 
     Yet another object of the invention is to provide an improved intake manifold for an internal-combustion engine having a unitary heat-storage chamber or chambers for maintaining elevated manifold temperature after engine shut-down. 
     Yet another object of the invention is the use of heat energy stored in a change-of-state material to maintain an elevated shut-down temperature for an internal-combustion engine. 
     These and other objects, advantages and features of my invention will become apparent from the following detailed description of preferred embodiments taken with the accompanying drawings. 
     SUMMARY OF THE INVENTION 
     The invention provides a method and apparatus for improving combustion and exhaust emissions in an internal-combustion engine having an intake manifold, an air filter assembly, a carburetor or fuel injection system, and an exhaust manifold. The apparatus includes a heat-storage reservoir in heat-exchange relationship with the intake manifold and a heat-storage medium disposed in the heat-storage reservoir. Engine heat from operation of the engine is transferred from the intake manifold to the heat-storage medium by indirect heat exchange through the reservoir. When the engine is shut down, and begins to cool, the stored heat is transferred back to the intake manifold from the heat-storage medium in the reservoir, thereby maintaining an elevated intake manifold temperature for start-up. The preferred heat-storage medium is a change-of-state material having a melting point below the normal operating temperature of the engine. 
     The reservoir may be a bladder adapted to fit over the top of the engine, covering all but the inlet of the air filter assembly and extending over the outer portions of the intake manifold. In another type of bladder configuration, a dual-chambered bladder is employed, wherein a lower chamber is filled with change-of-state heat-storage material. This lower chamber is in heat-exchange contact with the air filter assembly and the intake manifold. An upper bladder chamber covers the lower chamber and is filled with either water or with a change-of-state heat-storage material. 
     Another form of reservoir is an additional chamber constructed as a unit with the intake manifold, wherein the chamber is filled with heat-storage material for direct heat exchange with the intake manifold. 
     A separate chamber may be constructed atop the intake manifold and surrounding the carburetor, but below the air filter assembly. This also may be filled with a change-of-state heat-storage material. In another embodiment, a similar chamber is constructed having two sections. The lower chamber is filled with a first substance which is itself saturated with a second substance that reacts exothermically when mixed with the first substance. The two sections are connected at two points: by a check valve permitting flow of the second substance&#39;s vapor to the upper section, and by a controllable valve centrally disposed between the two chambers. In this embodiment, when the engine temperature has risen to normal operating temperature, the second substance vaporizes and passes through the check valve; it is separated from the first substance by being kept in the upper section. When the engine has cooled down and is to be restarted, the controllable valve is opened, enabling the now-cooled and condensed second substance to mix with the first substance to cause an exothermic reaction, thereby providing warmth to the intake manifold of the engine. 
     Another embodiment of the invention provides heat-storage bags which have an aluminized reflective top surface and insulating cover, a flexible casing, and a lower surface which permits heat exchange. The bags are filled with a change-of-state heat-storage material. These bags are adapted to be laid on top of the intake manifold for heat exchange with it. 
     In another embodiment, a heat exchanger is placed in contact with the exhaust manifold of the engine. A heating coil containing a heat-storage material is run from the heat exchanger up to and around the inside of a bladder-type reservoir and from there back to the heat exchanger. By employing this apparatus, the elevated temperature of the exhaust manifold is used to transfer heat to the heat-storage material inside the heating coil. This heat-storage material preferably has a vaporization point lower than the operating temperature of the exhaust manifold. A control valve, a thermostat, and an expansion chamber may also be used here to relieve pressure and to control the heating coil. 
     Preferred change-of-state heat-storage materials include paraffins such as pentacosane, tritiacontane, and camphene, and certain magnesium salts, namely, magnesium nitrate hexahydrate and an eutectic mixture thereof with magnesium chloride hexahydrate. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     FIG. 1 is a graph, plotting temperature versus heat quantity for a typical change-of-state heat-storage material, and also showing the relative operating temperatures of an internal-combustion engine. 
     FIG. 2 is a front perspective view of an internal-combustion engine, partially broken away to illustrate a heat-storage reservoir embodying the principles of the invention. 
     FIG. 3 is a top perspective view of a heat-storage bag embodying the principles of the invention, partially broken away to illustrate internal construction. 
     FIG. 4 is a perspective view of a typical intake manifold, showing the heat-storage bags of the invention installed for operation. 
     FIG. 5 is a perspective view of a modified heat-storage intake manifold of the invention, partially broken away to illustrate the heat storage medium in the unitary chamber. 
     FIG. 6 is a view in vertical section of the modified heat-storage intake manifold of the invention, taken along the line 6--6 in FIG. 5. 
     FIG. 7 is a view in section of the modified heat-storage intake manifold of the invention, taken along line 7--7 in FIG. 5, illustrating the manner in which the heat-storage chamber surrounds the operating portion of the manifold. 
     FIG. 8 is a front perspective view of an internal-combustion engine with a portion of the fan removed, illustrating a bladder-type, dual compartment heat-storage reservoir of the invention, which is shown partially broken away to illustrate internal construction. 
     FIG. 9 is a front perspective view of an internal-combustion engine with part of the fan removed, illustrating a bladder-type heat-storage reservoir with an exhaust manifold heating coil disposed in the bladder; the bladder is partially broken away to illustrate internal construction. 
     FIG. 10 is a diagrammatic illustration of a bladder-type heat-storage reservoir having heat-storage material in direct communication with an exhaust manifold heat-exchanger. 
     FIG. 11 is a front perspective view of an internal-combustion engine embodying the principles of the invention, shown with a dual compartment heat-storage reservoir for exothermic reaction. 
     FIG. 12 is a diagrammatic illustration of a dual compartment exothermic reaction heat-storage reservoir embodying the principles of the invention, shown in cross section along line 12--12 in FIG. 11. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the method of the present invention, the heat from an internal combustion engine, particularly its intake manifold, is absorbed in a heat-storage medium disposed adjacent to the intake manifold in heat-exchange relationship with it. The waste heat from the intake manifold of an operating engine and from the engine block at engine shut-down (hot soak), which is otherwise unused, is stored in the heat-storage medium. Then, when the engine is shut down and begins to cool, the heat-storage medium releases stored heat energy back to the intake manifold, thereby maintaining it at an increased temperature and improving the engine&#39;s overall efficiency. It has also been discovered that even after the &#34;cold start&#34; period, engine efficiency will be improved by increasing and making more uniform the intake manifold operating temperature during normal use, but this improvement is less pronounced than that achieved during cold start. 
     While any substance with a capacity for holding heat may be used, a preferred type of material for the heat-storage medium is a change-of-state material. The heat energy absorbed during phase change is employed to enhance the temperature-maintaining effect of the invention and to help rapid reheating when restarting the engine. The operating temperature range of the engine imposes limits within which the heat storage material must undergo complete phase change or chemical change in order to achieve maximum heat recovery. In addition to the temperature range limits, the heat-storage material should preferably have a high heat of fusion or exothermic heat of reaction, high specific heat, and also a high heat of vaporization if the medium is chosen to extend into the vapor phase. Table I is a list of compounds which are preferred for use as the heat-storage medium of the invention. The substances in Table I are selected principally for their melting point ranges and their latent heats of transformation. 
     
                       TABLE I______________________________________Melting Points and Heat of Fusion of Some Heat-Storage Materials               C.°/F.°                         Cal/Gm               Melting   Heat ofSubstance           Point     Fusion______________________________________Paraffins Eicosane           36.4/97.5 52 Pentacosane        53.3/127.9                         54 Tritiacontane      71.1/159.9                         54Naphthalene         80./176   36Camphene            51./123.8 57Elaidic Acid        544./111  52p-Toluidine         44.5/112  40Phenol              42./108   29Nickel Nitrate      57./134   36Phosphoric Acid     42./108   26Sodium Thiosulfate  48./119   23Calcium Chloride    30./86    41Calcium Nitrate     43./109   34Manganese Nitrate   36./96    28Phosphorus          44./112   150Rubidium            38./100.44                         520Magnesium Chloride  117./243  40Magnesium Nitrate   90./194   38Glaubers Salt       32./90    57Sulfur Trioxide     50./122   76Sodium Phosphate    35./94    67White Vitriol - (Zinc Sulfate)               39./102Magnesium nitrate hexahydrate               87./190   39Eutectic mixture of magnesium               57./135   32nitrate hexahydrate andmagnesium chloride hexahydrate______________________________________ 
    
     Normally, an engine will operate in the range between slightly below 100° C. and ambient temperature. During the immediate shut-down or &#34;hot-soak&#34;, engine temperatures may elevate to even higher than the boiling point of water. 
     FIG. 1 shows an idealized relationship between the heat-storage medium and normal engine operational temperatures. There it is seen that some of the heat which was wasted during engine operation and in the immediate shut-down period can be absorbed by the heat-storage medium. The resulting absorption of heat energy will, as illustrated, afford significant increases of heat energy during phase change. This process of heat absorption is reversible and exhibits the same characteristic changes of heat energy when the heat-storage medium is allowed to cool. Therefore, a significant quantity of heat energy which is absorbed during phase change may be returned to the intake manifold upon solidification of the heat-storage medium. 
     As illustrated in FIG. 1, a change-of-state heat-absorbing material will be a solid when below a particular temperature (indicated along the line between points A and B). Once the temperature reaches the melting point of the material (point B), it changes to a liquid and experiences an increase of heat energy without temperature increase during the melting process (as indicated between points B and C). As the engine temperature rises again, and after all the heat storage material has turned to liquid, the liquid temperature also rises (shown between points C and D). Another marked increase of heat energy occurs at the vapor point, and heat energy continues to be absorbed until the liquid has turned entirely to vapor (illustrated between points D and E). Once all of the liquid has vaporized, the vapor temperature increases with a proportional rise in heat energy as more heat is absorbed by the system. The present invention employs these marked absorptions of heat energy during phase change to store energy which is then given back to the engine when the process is reversed and engine temperature lowers. For example, the heat energy given off upon solidification equals the energy absorbed on melting. 
     The container-type heat-storage reservoir of FIG. 2 
     FIG. 2 illustrates a typical internal-combustion engine 20 having a fan 21, an engine block 22, an oil pan 23, an air filter assembly 24, an intake manifold 25, a carburetor 26, valve covers 27, and an exhaust manifold 28. The air filter assembly 24 has an intake port 29. The engine has a heat-storage reservoir 30 disposed below the air filter assembly 24, surrounding the carburetor 26 and on top of the intake manifold 25, in direct heat-exchange relationship with it. The heat-storage reservoir 30 occupies otherwise unused engine space and does not interfere with the normal engine operation. The reservoir 30 is filled with a heat-storage medium 31 which may be water or, preferably, one of the change-of-state heat-storage materials of Table I. 
     Engine heat is transferred from the intake manifold 25, the engine block 22, and the valve covers 27, to the reservoir 30, where it is stored in the heat-storage medium 31, which eventually melts. After engine shut-down, as the engine 20 cools to temperatures below that of the melted heat-storage medium 31, the system tends to equilibrate by the transfer of heat from the storage medium 31 back to the intake manifold 25 and carburetor 26, keeping them warm as the medium 31 solidifies. 
     The heat-storage bags of FIG. 3 
     FIG. 3 shows a heat-storage bag 35 of the invention. The bag 35 is filled with a heat-storage material 31, preferably a change-of-state material such as those shown in Table I. A flexible casing 36 is employed, and the top of the bag 35 has an insulating cover 37 with an aluminized reflective surface 38. The bottom 39 of the bag is adapted for heat exchange. The heat-storage bag of the invention may be placed atop the intake manifold 25 of an internal combustion engine as illustrated in FIG. 4. In that manner, direct heat exchange between the heat-storage bag 35 and the intake manifold 25 may be achieved. A single form-fit heat-storage bag may be used, or a plurality of smaller heat-storage bags may be placed together atop the intake manifold 25. Heat storage and release is accomplished by the same mechanism as in the embodiment of FIG. 2. 
     The modified intake manifold of FIGS. 5-7 
     Alternatively, as illustrated in FIG. 5, the internal-combustion engine 20 may be provided with an intake manifold 40 which is unitary with surrounding chambers 41 holding a heat-storage medium 31. As shown in FIGS. 6 and 7, the unitary reservoir 41 surround the manifold passages 42 through which the fuel-air mixture travels, thereby giving the greatest possible area of surface contact for direct heat exchange with the intake manifold 40. The reservoirs 41 are preferably filled with a change-of-state heat-storage material, which absorbs heat directly from the manifold 40 and transfers it directly back to the manifold as the engine 20 cools. A fill plug 48 is provided for adding heat-storage material to the chambers 41. It is preferred to leave a space 44 for expansion of the heat-storage material. 
     The dual chamber bladder of FIG. 8 
     As illustrated in FIG. 8 a bladder-type reservoir 45 may be employed for holding heat-storage material. The bladder 45 has a lower chamber 46 and an upper chamber 47. The lower chamber 46 is adapted to fit over the top of the engine 20, covering all but the intake port 29 of the air filter assembly 24 and extending over the sides of the valve covers 27. The intake manifold 25 is also covered, as shown at the front of the engine 26. A change-of-state heat-storage material 31 is disposed in the lower chamber 46. The upper chamber 47 may be filled with water or with an additional change-of-state heat-storage medium 31&#39;. The upper chamber 47 extends over the lower chamber 46 and is, preferably, substantially even with its perimeter, acting as an insulating cover and as an additional heat storage unit. Each chamber 46, 47 is provided with a fill cap 49 for adding heat storage materials 31. 
     Care should be taken that the opening to the air inlet port 29 for the air filter assembly 24 is not blocked or covered over. 
     The bladder 45 must be made of material which is resistant to temperatures greater than those which an engine 20 may be expected to reach. The bladder 45 may be made of a flexible hose-like material or of an inflexible plastic. It may have a point of attachment to the wing nut atop the filter 24 above the engine 20 and may be placed over the top of the engine 28, so that the reservoir 45 radiates heat down to the engine 20 as it cools. 
     The exhaust manifold heat exchanger embodiment of FIGS. 9 and 10 
     As illustrated in FIG. 9, a heat exchanger 50 may be placed on the exhaust manifold 28 of an engine. The heat exchanger 50 is connected to a heat coil 51 which passes through a bladder-type heat-storage reservoir 52, preferably around its perimeter. The reservoir 52 is fitted with a heat-storage medium 31, such as water or preferably a change-of-state material. An expansion chamber 53 and a thermostat/control valve 55 are connected to the heat coil 51. The heat coil is filled with a second heat-storage medium 56, preferably a change-of-state material which extends into the vapor phase at normal exhaust manifold 28 operating temperatures. The second medium 56 transfers extra heat to the heat-storage material 31 in the bladder 52, besides that which it absorbs from the engine 20. The bladder 52 could be replaced by a heat-storage reservoir 30 such as that of the embodiment shown in FIG. 2. 
     The elevated operating temperature of the exhaust manifold 28 is transferred through the heat exchanger 50 to the second heat-storage material 56, causing it to vaporize. The vapor rises through the heat coil 51 when the valve 55 is open, through the reservoir 52 or 30 to transfer heat to the heat storage material 31, after which the second heat-storage material 56 condenses and returns by gravity feed to the heat exchanger 50 to repeat the cycle. The expansion chamber 53 absorbs the increased pressure of the second heat-storage material when it turns to vapor. The heat stored in the reservoir 52 is transferred to the intake manifold 25 and the carburetor 26 as the engine cools after operation. 
     FIG. 10 diagrammatically illustrates another embodiment of the invention, in which exhaust manifold heat is conserved in a bladder-type heat-storage reservoir 57. A conduit 58 connects the heat storage material 31 inside the reservoir 57 to a heat exchanger 59 on the exhaust manifold. The conduit 58 is disposed to withdraw heat-storage material from the periphery of the reservoir 57, and transfer it to the heat exchanger 59, where it absorbs heat from the exhaust manifold and becomes either extremely hot liquid or vapor, depending on the type of material used, and finally returns the heated material to the reservoir near its center. In this manner, both gravity and convention work to circulate the material 31. 
     The exothermic reaction reservoir of FIGS. 11 and 12 
     As illustrated in FIGS. 11 and 12, a reservoir 60 may be installed around the carburetor 26, between the air filter assembly 24 and the intake manifold 25 of an internal-combustion engine 20. The reservoir 60 has an upper chamber 61 and a lower chamber 62, which are connected at the front by a check valve 63 permitting only upward flow, and in the middle by a controllable valve 64. 
     During assembly the lower chamber 62 is first partially filled with a first substance 65, such as aluminum nitrate, which is then saturated with a second substance 66, such as water (as water of crystallization), which reacts exothermically when mixed with the first substance 65, until an optimum ratio between the two substances is reached. Preferred materials for the first and second reversable exothermically-reacting substances 65 and 66 are described in Table II, along with their corresponding heats of reaction and reaction temperatures. 
     
                       TABLE II______________________________________Reversable Exothermic Reacting Substanceswith Water of Crystallization                    Exothermic                    Heat                    of Reaction                               ReactionSubstance   Formula      gm cal/gm  Temp______________________________________Aluminum nitrate       Al(NO.sub.3).sub.3.9H.sub.2 O                    -897.34    73.° C.Aluminum sulfate       Al.sub.2 (SO.sub.4).sub.3.18H.sub.2 O                    -2118.5    86.5° C.Bromine hydrate       Br.sub.2.10H.sub.2 O                    -700.       6.8° C.Calcium Nitrate       Ca(NO.sub.3).sub.2.4H.sub.2 O                    -509.37    42.7° C.Ferric nitrate       Fe(NO.sub.3).sub.2.6H.sub.2 O                    -784.4     60.5° C.Ferrous Sulfate       FeSO.sub.4.7H.sub.2 O                    -718.7     64.° C.(copperas)Lithium bromide       LiBr.3H.sub.2 O                    -301.9     44.° C.Lithium iodide       LiI.3H.sub.2 O                    -285.02    73.° C.Magnesium nitrate       Mg(NO.sub.3).sub.2.6H.sub.2 O                    -624.36    95.° C.Magnesium sulfate       MgSO.sub.4.7H.sub.2 O                    -808.7     70.° C.Potassium fluoride       KF.2H.sub.2 O                    -277.0     41.° C.Sodium tetra borate       NaB.sub.4 O.sub.7.10H.sub.2 O                    -1497.2    75.° C.Sodium sulfide       Na.sub.2 S.9H.sub.2 O                    -736.7     50.° C.______________________________________ 
    
     When the engine 20 is for the first time started and reaches operating temperature, the saturated first substance 65 (i.e. already saturated with the second substance 66) is heated to the point where the second substance 66 (e.g. water) is driven from it as a vapor that migrates to the upper chamber 61 by way of the check valve 63. The second substance 66 is retained in the upper chamber 61 until the next time when the engine 20 is started. As the engine cools between uses, the second substance 66 liquifies; so it is ready to be mixed again with the first substance 65. The controllable valve 64 is opened upon engine start, and the two substances mix, react, and give off heat which warms the carburetor 26 and the intake manifold 25 to improve engine efficiency, even though the engine may have cooled down between uses. The vaporization and separation steps are then repeated as the engine comes up to operating temperature, so the system is ready for the next use. 
     Alternatively, a control (not shown) may be provided for selectively opening said controllable valve 64 by a very small amount, for automatically introducing a small flow of said second substance 66 into said first substance 65 and thereby generating heat to keep the engine warm between relatively closely timed uses. In this embodiment, the valve 64 automatically opens fully upon engine start-up, resetting the control and the controllable valve 64 for normal operation. 
     The preferred embodiments described herein are intended to be purely illustrative, and not limiting of the scope of the invention. For example, although the drawings illustrate a V-type engine, the present invention is applicable to any form of internal combustion engine such as a rotary engine, a fuel-injected engine, or an engine having no top air filter assembly. Other embodiments and variations will be apparent to those skilled in the art and may be made without departing from the essence and scope of the invention as defined in the following claims.