An intake-manifold system for an internal-combustion engine, including: - a heat exchanger, for cooling the air at inlet to the engine with a coolant; wherein said heat exchanger has a body having: - an inlet and an outlet for the coolant, and - opposite ends for the inlet and the outlet of a flow of air to be supplied to the engine - an intake manifold, defining a tubular portion in communication with the air-inlet end of the body of the heat exchanger, for supplying a flow of air to said air-inlet end of the body of the heat exchanger; and - an outlet manifold, having a hollow body with a mouth in communication with the air-outlet end of the body of the heat exchanger and including, on a downstream side thereof, with reference to the direction of the flow of air, a plurality of branches that are to supply air to respective cylinders of the engine, said system being characterized in that: - the heat exchanger has a body made of a single piece obtained with additive-manufacturing technology and includes a complex of labyrinths of passages (20, 21) for the air and the coolant; and - the body of the heat exchanger is made of a single piece also with the body of said intake manifold, said labyrinths of passages (20, 21) for the air and the coolant having a portion that extends into a part of said intake manifold upstream, with reference to the direction of the flow of air, of a theoretical plane at the inlet end of the heat exchanger, so that the volume occupied by the intake manifold is in part also used to increase inside it the volume occupied by the labyrinths of passages for both the air and the coolant, so as to increase the heat exchange, wherein also said outlet manifold has a body made of a single piece with the body of said heat exchanger, and wherein within the outlet manifold or upstream thereof, but downstream of the aforesaid heat exchanger, a further heat exchanger is provided that operates with a different coolant, or with the same fluid but at a different thermal level, consisting of a body made of a single piece with said outlet manifold, with the main heat exchanger, and with the intake manifold. - a heat exchanger, for cooling the air at inlet to the engine with a coolant; wherein said heat exchanger has a body having: - an inlet and an outlet for the coolant, and - opposite ends for the inlet and the outlet of a flow of air to be supplied to the engine - an intake manifold, defining a tubular portion in communication with the air-inlet end of the body of the heat exchanger, for supplying a flow of air to said air-inlet end of the body of the heat exchanger; and - an outlet manifold, having a hollow body with a mouth in communication with the air-outlet end of the body of the heat exchanger and including, on a downstream side thereof, with reference to the direction of the flow of air, a plurality of branches that are to supply air to respective cylinders of the engine, - an inlet and an outlet for the coolant, and - opposite ends for the inlet and the outlet of a flow of air to be supplied to the engine - an intake manifold, defining a tubular portion in communication with the air-inlet end of the body of the heat exchanger, for supplying a flow of air to said air-inlet end of the body of the heat exchanger; and - an outlet manifold, having a hollow body with a mouth in communication with the air-outlet end of the body of the heat exchanger and including, on a downstream side thereof, with reference to the direction of the flow of air, a plurality of branches that are to supply air to respective cylinders of the engine, said system being characterized in that: - the heat exchanger has a body made of a single piece obtained with additive-manufacturing technology and includes a complex of labyrinths of passages (20, 21) for the air and the coolant; and - the body of the heat exchanger is made of a single piece also with the body of said intake manifold, said labyrinths of passages (20, 21) for the air and the coolant having a portion that extends into a part of said intake manifold upstream, with reference to the direction of the flow of air, of a theoretical plane at the inlet end of the heat exchanger, - the heat exchanger has a body made of a single piece obtained with additive-manufacturing technology and includes a complex of labyrinths of passages (20, 21) for the air and the coolant; and - the body of the heat exchanger is made of a single piece also with the body of said intake manifold, said labyrinths of passages (20, 21) for the air and the coolant having a portion that extends into a part of said intake manifold upstream, with reference to the direction of the flow of air, of a theoretical plane at the inlet end of the heat exchanger, so that the volume occupied by the intake manifold is in part also used to increase inside it the volume occupied by the labyrinths of passages for both the air and the coolant, so as to increase the heat exchange, wherein also said outlet manifold has a body made of a single piece with the body of said heat exchanger, and wherein within the outlet manifold or upstream thereof, but downstream of the aforesaid heat exchanger, a further heat exchanger is provided that operates with a different coolant, or with the same fluid but at a different thermal level, consisting of a body made of a single piece with said outlet manifold, with the main heat exchanger, and with the intake manifold.