Injection system for two-stroke engines

A controlled ignition two-stroke endothermic engine, comprising at least one cylinder whose interior slidingly houses a piston, wherein the at least one cylinder is connected to a head on its upper side so as to define a combustion chamber, the head comprising at least one spark plug, wherein the at least one cylinder is connected to a pump-crankcase on its lower side, wherein the pump-crankcase is in communication with the at least one cylinder at least via a central transfer port, wherein the at least one cylinder is in direct communication with the external world via an exhaust duct and an intake duct, wherein the intake duct is crossed by the central transfer port, wherein further the intake duct houses on its top side an upper fuel injector and houses on its bottom side a lower fuel injector, wherein the lower fuel injector is oriented so that fuel sprayed from it reaches the inside of the at least one cylinder after first having crossed the intake duct and subsequently running the upper part of the central transfer port which connects the intake duct with said cylinder, wherein air pressure of air introduced into the at least one cylinder from the intake duct does not exceed the pressure of the external world.