Translate the following sentences into Chinese. 1 . Engine is the power source of the automobile. Power is produced by the linear motion of a piston in a cylinder. 2 . The fuel system works according to the requirements of the engine as it provides an air-fuel mixture which must be in proportion to the speed and load placed on the engine. 3 . The valve gear provides timely admission of the fresh charge into the cylinders and exhaust of spent gases from them. 4. In order to make the aluminum stronger and less likely to warp, certain materials are added to the metal or a steel liner placed in the block.