this is due to the combined effects of partial vacuum agitation through bubbling action or surface fanning and heating of both the mixture itself as well as of the fractional mixing air being delivered into the vaporizer chamber effective vaporization of the water and all fuel components is readily achieved under these conditions this together with continued heating of the resultant vapors and mixing air inflowing upwardly and out of the vaporizer assures optimum conditioning for delivery of the heated vaporous mixing air into the combustion chambers of the engine exhaust pollutants from an engine operating with this invention are minimized due to the resultant completeness of combustion and apparently also due to the effects of water present in the form of superheated steam during the combustion cycle in a typical case the vaporizer may be operated in the range of 1000 u00b0 f more or less in any case the heat exchanger design should be such as to subject the fuel components to vapor producing temperatures under sustained operation temperatures typically in the range above about 450 u00b0 f for most grades of gasoline if desired a thermostatic exhaust flow control not shown may be employed to maintain vaporizer temperature in the range of about 1000 u00b0 f or at any other selected operating temperature using well known methods while not shown conventional vacuum advance systems to control spark timing may also be retained in engines using this invention as may be step function throttle infeed ducting controls to increase engine draw in times of heavy acceleration demands if desired an automatic choke mounted and operated in a conventional manner in the leaning air duct 22b may also be used typically with a water vapor injection.