【正文】 also pipes, passages and drillings in various parts。 (9) Engine’s electronic control system. These are the systems for petrol engines. Diesel engines have similar systems except for the fuel and ignition systems. Some parts of the systems are built into the engine, some parts are attached to the engine and other parts are located on the body panels in the engine partment. Starting system The starter is used to rotate the engine during starting. It consists of an electric motor and a drive. The drive has a small pinion that meshes with the ring gear on the flywheel during starting. The battery supplies the electrical energy to operate the starter and rotate the engine until it fires and runs on its own. Fuel system These are four basic types of fuel systems: carburetor systems for petrol engines, fuel injection systems for petrol engines, gas fuel systems ( LPG or NGV ), and diesel injection systems. All these systems operate in different ways, but they all have somewhere to store fuel ( a fuel tank or a cylinder ) and a way of supplying the engine with the fuel. They also have a way of supplying air and fuel mixed in the correct proportion so that it can be effectively burn in the bustion chambers. Ignition system Petrol engines and engines operating on gas require an ignition system. This is needed to provide the sparks that fire the charges in the bustion chambers. For this reason, petrol engines are sometimes referred to as sparkignition engines. This distinguishes them from them diesel engines that do not need a spark because they use pression ignition. Combustion in a diesel occurs when the fuel is sprayed into the bustion chamber. The air in the cylinder is at high temperature from being pressedhigh enough to ignite the fuel 22 that is sprayed from the injector. Cooling system A considerable amount of heat is produced in an engine by the burning airfuel mixture. Some of the heat is used to do useful work, some is transferred to other parts of the engine and some is carried away with exhaust gases. However, there is still enough heat to cause damage unless it is removed. This is still the function of the cooling system, which removes about onethird of the heat that is produced. The cooling system does not just remove heat。 (7) Exhaust system。 (5) Lubricating system。 (3) Ignition system。 it acts as the heart of a person, which provides the power that the cars need to run on the road. All the automotive engines today are the Internal Combustion Engines ( ICEs ) because the fuel is burnt inside their cylinders and the energy is provided. ICEs are those heat engines that burn their fuel inside the engine cylinder. In ICEs, the chemical energy stored in their fuel converted into heat energy during the burning part of their operation. The heat energy is converted into mechanical energy by the expansion of gases against the piston attached to crankshaft that can rotate. The engines that burn petrol are known as petrol engine. Other types of ICEs burn heavier oils, of these types the diesel engine has e into the widest use. Diesel and petrol engines have the same mechanical parts, except that diesel ponents are generally stronger and heavier. Both engines are internal bustion engines, but they have different fuel system and use different fuels. With a diesel, only air enters the cylinder during the intake stroke. A petrol engine takes in an airfuel mixture. Following are some general parisons between diesel and petrol engines: In a diesel, the fuel is injected into the cylinder as a fine spray near the top of the pression stroke. With a petrol engine, the fuel is injected into the exha ust ports at the start of the induction stroke. Ignition in a diesel is by the high temperature from the highly pressed air. A petrol engine needs a spark for ignition. Diesel engines generally operate at lower engine rpm than petrol engines. Diesel engines use distillate for fuel, which is less volatile than petrol. The design of diesel engines makes them noisier than petrol engines and they have a unique diesel knock. Small diesel engines, as well as petrol engines, are used in passenger cars and light mercial vehicles. Larger diesel engines are used in all heavy mercial vehicles, earthmoving equipment, and farm machinery. １ . Engine Configurations The term engine configuration refers to the way that the cylinders of an engine are arranged. The cylinders can be inline, or at an angle ( Vtype ). Within these three basic arrangements, there are a number of variations. Inline engine With inline engines, the cylinders are arranged in a straight line, one behind the other. Most inline engines have their cylinders vertical, but some are slanted. That is, the engine is tilted at an angle to reduce the overall height. These engines are sometimes referred to as slanted engines. Some inline engines have their cylinders horizontal, so that the engine is more or less on its side. This reduces the overall height of the engine. This arrangement is 19 used mainly in larger mercial vehicles with the engine mounted under part of the cab. The mechanical arrangement of a fourcylinder inline for a passenger car is shown in . The cutaway view in enables the various parts to be identified. Horizontally opposed engine This arrangement has its cylinders arranged in two flat blanks with the crankshaft between them. The engine shown has a short rigid crankshaft with five bearings. A horizontally opposed engine has even firing impulses and good balance. Movement of a piston in direction is opposed by movement of a piston in the opposite direction. Horizontally opposed engines, with their flat design, give the engine a low height and also help to keep the center of gravity of the vehicle low. A low center of gravity gives the vehicle st