Engine

AUTOMOTIVE MECHANICS

                                                            Engines

    Automotive engines are called internal-combustion (IC) engines because the fuel that runs them is burned internally, or inside the engines. There are two types, reciprocating and rotary.

Reciprocating means moving up and down or back and forth. Almost all automotive engines are of the reciprocating type. In these engines, pistons move up and down, or reciprocate, in cylinders. This type of engines called a piston engine.

    Rotary engines have rotors that spin, or rotate, The only such engine now used in automobiles is the wankel engine. It is described in a following chapter.

    There are two kinds of piston engine spark-ignition and compression-ignition (diesel). The differences between the two are

• The type of fuel used
• The way the fuel gets into the engine cylinders
• The way the fuel ignited            

    The spark-ignition engine uses a highly volatile fuel which turns to vapor easily, such as gasoline or gasohol. The fuel is mixed with air before it enters the engine cylinders. The fuel turns into a vapor and mixes with the air to from a combustible  air-fuel mixture. This mixture then enters the cylinders and is compressed. Next an electric spark produced by the ignition system sets fire to, or ignites, the compressed air fuel mixture.

     In the compression-ignition, or diesel, engine, the fuel is mixed with the air after the air enters the engine cylinder. Air alone is taken into the cylinders of the diesel engine. The air is then compressed as the piston moves up. The air is compressed so much that its temperature goes up to 1000 F (538 C) or higher. Then the diesel engine fuel a light oil is injected (sprayed) into the engine cylinders. The hot air, or heat of compression, ignites the fuel. This is wey the diesel engine is called a compression ignition engine.