An ignition transformer for use with a spark ignition system for an internal combustion engine, said transformer comprising: a central core that defines a first end and a second end; a primary coil wound about the central core, wherein the primary coil is configured to vary magnetic energy into the central core in response to a primary current applied to the primary coil; a secondary coil wound about the central core, wherein the secondary coil is configured to generate a secondary voltage in response to changes in the magnetic energy in the central core; and a magnetic return that defines a return-path configured to couple magnetic energy from the first end to the second end, characterised in that the magnetic return material comprises iron particles and includes: - injection moldable polymers filled with 30 to 60% by volume of said iron particles, said material having a relative permeability in the range of 10 to 100 or, - more densified compression molded iron particles, said material having a relative permeability in the range of 500 to 1500 so that, the transformer has a non-linear or curved secondary-current versus time-response characteristic configured to decay initially to the fifty-percent (50%) value of an initial secondary current when ten percent (10%) to twenty-five percent (25%) of a burn-time interval has passed, the injection moldable polymers filled with the 30 to 60% by volume of said iron particles configured for delaying the the occurrence of the fifty-percent (50%) value of the initial secondary current and, the more densified compression molded iron particles configured to cause the fifty-percent (50%) value of the initial secondary current to occur earlier. a central core that defines a first end and a second end; a primary coil wound about the central core, wherein the primary coil is configured to vary magnetic energy into the central core in response to a primary current applied to the primary coil; a secondary coil wound about the central core, wherein the secondary coil is configured to generate a secondary voltage in response to changes in the magnetic energy in the central core; and a magnetic return that defines a return-path configured to couple magnetic energy from the first end to the second end, characterised in that the magnetic return material comprises iron particles and includes: - injection moldable polymers filled with 30 to 60% by volume of said iron particles, said material having a relative permeability in the range of 10 to 100 or, - more densified compression molded iron particles, said material having a relative permeability in the range of 500 to 1500 so that, - injection moldable polymers filled with 30 to 60% by volume of said iron particles, said material having a relative permeability in the range of 10 to 100 or, - more densified compression molded iron particles, said material having a relative permeability in the range of 500 to 1500 so that, the transformer has a non-linear or curved secondary-current versus time-response characteristic configured to decay initially to the fifty-percent (50%) value of an initial secondary current when ten percent (10%) to twenty-five percent (25%) of a burn-time interval has passed, the injection moldable polymers filled with the 30 to 60% by volume of said iron particles configured for delaying the the occurrence of the fifty-percent (50%) value of the initial secondary current and, the more densified compression molded iron particles configured to cause the fifty-percent (50%) value of the initial secondary current to occur earlier.