1.Automobile Mechanics；1.1Engine Classification and Overall Mechanics

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The automobile engines can be classified according to: 1.numbers of cylinders; 2.arrangement of cylinders; 3.arrangement of valves; 3.type of cooling; 5.number of cycles (two or four); 6.type of fuel burned; 7.type of ignition.

The engine is the source of power that makes the wheels go around and the car move. The automobile engine is an internal-combustion engine because the fuel (gasoline) is burned inside it. The burning of gasoline inside the engine produces high pressure in the engine combustion chamber['tʃeimbə]. the high pressure['preʃə] forces piston to move, the movement is carried by connecting rods to the engine crankshaft. The crankshaft is thus made to rotate; the rotary motion is carried through the power train to the car wheels so that they rotate and the car moves.

The engine requires a fuel system to supply it with a mixture of air and fuel. The fuel system does this by pumping liquid gasoline from a tank into the carburetor [,kɑ:bju'retə, 'kɑ:-, a mixing device that mixes the gasoline with air. The mixture is delivered to the engine where it is burned.

The engine also needs a cooling system, the combustion of the air-fuel mixture in the engine creates a very high temperature. The cooling system takes teat away from the engine by circulating a liquid coolant (water mixed with antifreeze) between the engine and a radiator ['reidieitə. The coolant gets hot as it goes through the engine. It cools off as it goes through the radiator. Thus, the coolant continually takes heat away from the engine where it could damage, and delivers it to the radiator. Air passing through the radiator takes heat away from the radiator.

The engine also includes a lubricating system. The purpose of the lubricating system is to supply all moving parts inside the engine with lubricating oil; the oil keeps moving parts from wearing excessively.

The engine requires a fourth system, the ignition system. The ignition system provides high-voltage electric sparks that ignite, or set fire to, the charges of air-fuel mixture in the engine combustion chambers.

The fifth is starting system and its purpose is to change the electrical current into the mechanical energy to push the crank-shaft around. By means of this, the engine can be started.

These five systems are discussed briefly in following sections.