Internal-combustion engines in which a combustible mixture is ignited in the working cylinder at the beginning of the working stroke, as in the ordinary operation of internal-combustion engine, after which and at some time before the end of the working stroke an additional quantity of compressed air or equivalent non-combustible gas is supplied to the working cylinder and mingles with the burned gases therein, the piston being impelled through the remaining portion of its working stroke by the combined action of the burned gases and the air supplied thereto.
