a single cylinder and head structure of a typical internal combustion engine is illustrated in fig1 with the individual steam boiler for that cylinder installed . as illustrated , the structure is for an air cooled engine , but the system is equally adaptable to liquid cooled engines . a cylinder head 10 is mounted on the upper end of a cylinder 12 , the head having a combustion chamber 14 with a spark plug 16 and an intake valve 18 . the exhaust valve 18 is actuated by a push rod 20 through a rocker arm 22 in a conventional manner , the rocker arm being enclosed by a rocker cover 24 . a boiler pack 26 is installed between the cylinder 12 and head 10 , which are milled out as necessary to receive the boiler pack . many existing engines have sufficient material in their basic structure to accommodate the boiler pack , which is very thin and compact . the boiler pack , shown in detail in fig2 and 5 , is a hollow ring member having an inner cylindrical wall 28 and a concentric outer wall 30 , joined at their lower edges by a bottom wall 32 . the lower portion of inner wall 28 has an inset circumferential channel 34 to receive an o - ring , as later described . the upper edge of inner wall 28 has a radially inwardly projecting flange 36 . the upper edge of outer wall 30 has a similar inwardly projecting flange 38 , spaced above and parallel to flange 36 . fixed between flanges 36 and 38 is a circumferential superheat ring 40 . between the inner and outer walls 28 and 30 are vertically spaced baffle rings 42 and 44 , dividing the space between the walls into a lower or first annular chamber 46 , a second annular chamber 48 and an upper or distributing chamber 50 . the chambers could be filled with a porous thermally conductive material 51 which would improve heat transfer and reduce the actual volume of fluid in the chambers . outer wall 30 has a water inlet connection 52 and , at the point of inlet , the lower baffle ring 42 has an upwardly looped portion 54 over the inlet , to direct incoming water into the first chamber 46 . diametrically opposite the looped portion 54 , the baffle ring 42 has a gap 56 , indicated in fig3 and 4 , to allow the water to pass into the second chamber 48 . above the looped portion 54 , the upper baffle ring 44 has a gap 58 through which the water passes to the distributing chamber . the water thus passes twice around the boiler ring before entering the distributing chamber . it should be noted that additional baffle rings could be used to form additional chambers and increase the number of passes , depending on the amount of heat transfer required . the superheat ring 40 has a plurality of upper and lower ports 60 and 62 , respectively , in the form of thin flat slots forming channels between the ring and the enclosing flanges 38 and 36 . ports 60 and 62 are circumferentially spaced in vertically opposed pairs , the ports of each pair being inclined in opposite directions to the radius of the ring , to direct the steam into the cylinder with a swirling action . at the intersection of each pair of ports is a transfer hole 64 through the ring , as in fig5 . superheat ring 40 also has a peripheral blade portion 65 projecting outwardly into distributing chamber 50 , to split the flow the the ports 60 and 62 . lower flange 36 has an inner ring portion 66 extending beyond upper flange 38 and projecting into the upper periphery of cylinder 12 . ring portion 66 has a plurality of circumferentially spaced holes 68 therein adjacent the inner edge to increase the effective heat transfer of the ring portion . the outer edge of the combustion chamber 14 has a downwardly protruding lip 70 , formed when the head is milled out for the boiler pack . lip 70 is closely spaced above ring portion 66 , forming a circumferential , inwardly opening injection slot 72 . by installing the boiler pack within the engine structure , almost the entire surface area of the ring member is in thermally conducting contact with the engine . water from a suitable source is supplied through a pump 74 and a supply line 76 to inlet connection 52 . in series in the supply line 76 are a control valve 78 and a check valve 80 , the latter preventing blow back from pressure in the cylinder . as illustrated , control valve 78 is normally closed and is opened by a solenoid 82 in time with the engine cycle . installed in the rocker cover 24 is a magnetically actuated switch 84 , such as a readily available mercury diaphragm switch , which is ridigly mounted in any suitable manner . a magnet 86 is attached to the rocker arm 22 on a support 88 , so that each time the intake valve 18 opens , the magnet approaches and actuates switch 84 , as indicated in the broken line position in fig1 . switch 84 is connected through solenoid 82 to a battery 90 , to open control valve 78 of the cylinder which is in the compression cycle , each time the switch 84 is actuated by movement of the rocker arm . it should be noted that a mechanical connection between rocker arm 22 and control valve 78 could be used in place of the electrical system shown . to prevent flooding of the engine by excess water when speed is reduced , or during low speed running , the solenoid 82 is also controlled by a second magnetic shut off switch 92 in series with switch 84 . shut off switch 92 is held closed by a holding magnet 94 on the plunger 96 of a vacuum actuator 98 . the plunger is biased by a spring 100 to keep holding magnet 94 in close proximity to switch 92 . actuator 98 is connected to the vacuum advance , or to an intake source of vacuum on the engine . when engine speed is reduced the vacuum pull increases and the actuator 98 retracts plunger 96 and magnet 94 allowing switch 92 to open and de - energize solenoid 82 . this closes valve 78 and shuts off the water supply to the boiler pack . when the engine speed picks up , vacuum is reduced and actuator 98 releases plunger 96 , so that magnet 94 can close switch 92 . control valve 78 is then again responsive to control by switch 84 . pump 74 is driven by a motor 102 which is controlled by a temperature responsive speed control 104 , the basic arrangement being well known . a thermal sensor 106 is installed around the boiler pack 26 and is protected by a baffle 108 and insulation material 110 from cooling air flow around the engine , which could cause incorrect temperature readings . the sensor 106 thus detects cylinder temperature and the speed control 104 adjusts the water flow rate accordingly to maintain proper heat balance . in a multi - cylinder engine , the speed control could respond to an average of all the sensors , or to the highest temperature cylinder , depending on the particular engine installation . the boiler pack is sealed to the cylinder 12 by an o - ring 112 seated in channel 34 , and is sealed to head 10 by a further o - ring 112 held between a channel 114 in the head and a shallow groove 116 in upper flange 38 . the o - rings are of conventional high temperature resistant type , such as copper covered asbestos . as indicated in fig3 the water passes around chamber 46 , through gap 56 , back around chamber 48 and through gap 58 to the distributing chamber 50 . the water will normally be converted to steam at this stage and will pass through ports 60 and 62 of the superheat ring 40 , to be injected into the cylinder through injection slot 72 and holes 68 . if any liquid remains at the superheat ring it will be momentarily trapped in transfer holes 64 and converted to steam . ring portion 66 , which extends into the cylinder and is subjected to the heat of combustion , becomes very hot and acts as a final liquid vaporizer . heat from ring portion 66 is also conducted to the superheat ring 40 for maximum heating effect . in normal operation only superheated steam would be injected into the cylinder , the final heating stages being used to accommodate temporary imbalance which may occur during substantial and abrupt speed changes in the engine . the basic fuel / air mixture drawn into the cylinder need not be critically lean , as in some engines set for lean burn to reduce exhaust pollution . the primary ignition takes place unimpeded and , as the flame front spreads outwardly , the superheated steam mixes with and cools the hot gases . injection of the steam in a swirling action through the inclined ports of the superheat ring ensures good mixing . the steam adds to the volume of gases in the cylinder and effectively increases the compression ratio , but the cooling effect inhibits detonation . this allows the use of fuel of a lower octane rating than would normally be used with such a compression ratio . it should be noted that the water could include additives such as alcohol , or the like , according to the particular engine and performance characteristics . in addition to the cooling action in the combustion chamber , the engine is further cooled by the extraction of heat to convert the water to steam . at starting , when the engine is cold and no steam is being generated , the compression ratio is very low and low octane fuel is satisfactory . as the engine heats up , the steam is injected and the compression ratio rises , but the cooling effect of the steam prevents detonation at the higher compression ratio . the reduced combustion temperature in the cylinder reduces production of hydrocarbons and oxides of nitrogen , which normally increase as combustion temperature rises . the thermal efficiency of the engine can be further improved by treating the exhaust , as indicated in the energy flow diagram in fig6 . heat output of the engine 120 is partially recycled to heat the water in the boilers 122 , the excess heat being carried off by cooling air in cooling the heads and cylinders , crankcase and oil . the exhaust is fed through a desuperheater 124 , in which the steam rich exhaust is cooled by atomized water injection . the steam is condensed in a condenser 126 , the water droplets are separated by a centrifugal separator and condensate is returned to the water supply tank 130 . this type of water cooling of exhaust gases and the associated apparatus are well known . the resultant exhaust products are below the temperature of the boiling point of water and have a very low content of pollutants . an engine installed in a vehicle and fitted with the steam system , as shown and described , has been tested under various driving conditions . it has been found that fuel consumption was decreased and that engine operating temperature was reduced from normal . pollutant content of the exhaust was also greatly reduced .