To study and prepare report on the constructional details working principles and operation of the following
Automotive Engine Systems And Sub Systems
Labeled diagram, construction details, working principle and operation of the engine systems and sub systems
Methods of cooling
Various methods used for cooling of automobile engines are
Air cooling
The basic principle involved in this method is to have current of air flowing continuously over the heated metalsurface from where the heat is to be removed. The heat dissipated depends upon following factors;
Water cooling
In water cooling sstem, the cooling medium used is water. In this, the engine cylinders are surrounded by water jackets through which the cooling water flows. Heat flows from the cylinder walls into water which goes to the radiator where it loses its heat to the air. Usually some antifreeze is added to the cooling water, due to which it is often referred to as coolant. Both these terms have been used in this chapter, often mean unless the context requires otherwise.
Water cooling systems are of two types;
The various systems adopted for the lubrication of automobile engine are 1 Petroil system
Petroil system
This is used generally for small two stroke engines, e.g. in majority of scooter and motor cycle engines. It is the simplest of all types of engine lubrication systems. Certain amount of the lubricating oil is mixed with the petrol itself, the usual ratio being 2% to 3% of oil. If it is less, 31 there is danger of oil starvation or insufficient lubrication causing damage to the engine; if however, it is more, there will be excessive carbon deposits in the cylinder head and the engine will also give dark smoke. When the petrol mixture enters the crankcase, due to high temperatures there, the petrol component vaporizes leaving a thin film of lubricating oil on the crankcase, cylinder walls, crankshaft and bearings. The main requirements of lubricating oil for two stroke engine are that it should readily mix with petrol and burn without leaving much residue.
Splash system
This was employed for the engines of early motor cycles. It is one of the cheapest methods of engine lubrication. A scoop is made in the lowest part of the connecting rod and the oil is stored in the oil trough (fig.) it being pumped there from the crankcase oil sump. When the engine runs the scoop causes the oil to splash on 35 the cylinder walls each time it passes through its BDC position. This affects the lubrication of engine walls, gudgeon pin, main crankshaft bearings, big end bearings etc.
Pressure system
This system is used almost universally in modern car engines. The splash system though cheaper, is not suitable for automobile engines because of the absence of positive lubrication. In the pressure system (fig ) an oil pump takes the oil from the wet sump through a strainer and delivers it through a filter to the main oil gallery at a pressure of 200 to 400 kPa. The oil pressure is controlled by means of a pressure relief valve, situated in at a pressure of 200 to 400 kPa. The oil pressure is controlled by means of a pressure relief valve, situated in the filter unit or the pump housing.
Dry sump system
This system is employed in some racing car engines for situations where the vehicle has to be operated at very steep angles, for example, sports cars, jeeps etc. if ordinary pressure system of lubrication is used in such cases, the situations may arise when there is no oil at the place where oil pump is installed. To avoid such instances, dry sump system is used (fig )wherein two pumps, instead of one, are used. The scavenge pump A is installed in the crankcase portion which is the lowest. It pumps oil to a separate reservoir B, from where the pressure pump C pumps the oil through filter D, due to the cylinder bearings; a full pressure system of lubrication is employed. The oil pressure is maintained at 400-50 kPa for the main and big end bearings while about 5100 kpa pressure is used for timing gears and cam shaft bearings etc.
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