an internal combustion engine in which a compact ring type boiler pack is installed around each cylinder under the cylinder head . water is pumped through each boiler at a rate proportional to the cylinder temperature , to maintain a proper cooling and steam injection balance , the generated steam being injected peripherally into the cylinder in pulses , timed by a valve which is controlled by movement of the inlet valve actuating mechanism of the particular cylinder . the boiler has multiple stages to ensure complete conversion of the water to steam , the peripheral steam injection providing internal cooling of the cylinder walls without interfering with normal combustion . the steam system is adaptable to existing internal combustion engines and results in reduced fuel consumption , very low pollutant emissions in the exhaust and a very efficient thermal cycle .