Abstract: Method and apparatus for increasing the efficiency and the performance of normally aspirated internal combustion engines. A combustion air intake housing including a fuel injector for introducing an atomized spray of highly volatile, preferably non-petroleum based, combustible fuel in a region of convergence of a plurality of convergent, progressively operated intake ports formed in the air intake housing. The highly volatile combustible fuel rapidly and significantly cools the intake (combustion) air, thereby densifying the air. Thus, the cooled air contains, per unit volume, a greater quantity of combustible matter to be introduced into the engine combustion chamber(s) which consequently increases the explosive combustion charge within the chamber(s) upon ignition of the charge, thereby enhancing engine efficiency and performance.