The main engine that is installed on most cars is the 2108. Therefore, the book further describes the structure of this engine and gives its features (if they exist) units and parts of engines 21081 and 21083.
The 2108 engine is a four-stroke, carburetor, four-cylinder engine with an in-line vertical arrangement of cylinders and an overhead camshaft. The engine is specially designed for transverse placement on a front-wheel drive vehicle. Therefore, it is maximally compressed in length and its layout and main dimensions are chosen so that it, together with the gearbox, can be placed transversely between the mudguards of the front wheels.
When developing the engine, special attention was paid to reducing its weight and improving fuel efficiency, as well as meeting environmental protection requirements - reducing the toxicity of exhaust gases. Good weight indicators (92 kg for engine 2108 and 95 kg for 21083) was achieved through rational engine layout and the use of new design solutions: installation of an original oil pump with direct drive from the crankshaft, compact valve drive, etc.
The solution to the complex problem - improving efficiency and simultaneously achieving maximum engine power - was achieved through many measures. Here we have the improvement of the combustion chamber shape with a high (9.9) compression ratio, and the selection of valve timing, camshaft profile, and finding a new design of carburetor and ignition devices with the most advantageous adjustments.
Complete with gearbox (figure 8) and clutch (located in the crankcase 3) engine 4 forms a single rigid unit - the power unit. This design solution simplifies the conveyor assembly process of the car, since the power unit can be assembled separately and then installed as an assembly on the car.
Figure 8. Power unit (the arrows show the clamps for slinging the power unit):
1 - gearbox; 2 - starter; 3 - clutch housing; 4 - engine; 5 - generator; 6 - air filter; 7 - oil filler cap; 8 - fuel pump; 9 - ignition distributor sensor; 10 - thermostat.
All engine components that require maintenance during vehicle operation are located in an easily accessible area: on top or on the left side of the engine, which is the front side due to its transverse position on the vehicle. On the left are the spark plugs, generator 5, starter 2 and oil level indicator dipstick. On top are the air filter 6 and ignition distributor sensor 9. Fuel pump 8 is also installed on top, but on the right side of the engine (rear, if you look in the direction of the car's movement). This location of the fuel pump reduces the risk of fires in the event of an accident due to damage to the fuel lines.
The engine cylinders are combined with the upper part of the crankcase and are a single casting - cylinder block 3 (figure 9). This arrangement ensures the strength, rigidity and compactness of the structure, and reduces the weight of the engine. The cylinder block is covered from below by a stamped steel sump 1 of the crankcase, which also serves as a container for oil. Between the sump and the cylinder block there is a gasket made of a cork-rubber mixture.
Figure 9. Longitudinal section of the engine:
1 - crankcase; 2 - oil pump; 3 - cylinder block; 4 - camshaft drive belt; 5 - cylinder head; 6 - cylinder head cover; 7 - camshaft; 8 - fuel pump; 9 - ignition distributor sensor; 10 - piston; 11 - connecting rod; 12 - flywheel; 13 - crankshaft; 14 - main bearing cap.
A common aluminum head 5 for four cylinders is installed on top of the cylinder block, in which the combustion chambers, valve mechanism and gas channels are located. Between the head and the cylinder block there is a sealing metal-asbestos gasket. Each cylinder has one intake and one exhaust valve, which are driven by a camshaft installed on the cylinder head. The upper location of the camshaft allows to reduce the weight of reciprocating moving parts and thus ensure high reliability of the valve timing mechanism at high engine crankshaft speed.
The camshaft 7 is driven from the crankshaft by a special toothed belt with an eccentric roller tensioner. The advantages of such a drive are the simplicity of the design, lower weight compared to other types of transmissions and reduced engine noise. The belt drive is covered at the front with a plastic cover and at the back with a steel cover.
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Crankshaft 13 cast iron five-bearing. Such a shaft is cheaper than forged and more durable in operation. Five supports provide its high rigidity. It bends less and creates better conditions for the operation of bearings. Large diameters of the shaft journals (51 mm - main and 48 mm - connecting rod) reduce the load on the bearings, due to which the wear of the journals and bearing liners is reduced, and the durability of the crankshaft increases. The ends of the crankshaft are sealed with self-tightening rubber seals.
Pistons 10 are cast aluminum, have two compression rings and one oil scraper. The piston pin is pressed into the upper head of the connecting rod and can rotate freely in the piston bosses. Connecting rods 11 are forged steel.
Engine lubrication system - combined (under pressure and splashing). The main and connecting rod bearings of the crankshaft, and the camshaft supports are lubricated under pressure. A distinctive feature of the lubrication system is the original oil pump with internal gears. The pump is driven directly from the crankshaft, on the front end of which the pump drive gear is installed. Oil filter 2 (figure 10) with a filter element made of special cardboard, full-flow, i.e. all the oil used to lubricate the engine passes through the filter. The oil used to lubricate the engine has a complex of additives that give the oil high lubricating properties, resistance to oxidation, and allow it to operate in a wide range of temperatures.
Fig. 10. Cross-section of the engine:
1 - cylinder block; 2 - oil filter; 3 coolant pump; 4 exhaust manifold; 5 - inlet manifold; 6 - carburetor; 7 - air filter; 8 - crankcase ventilation system pipeline; 9 - cylinder head; 10 generator; 11 - oil pump receiver.
The cooling system is a liquid, closed type, filled with a special cooling liquid that has anti-corrosion and anti-foaming additives and freezes only at low temperatures. A thermostat with a solid filler maintains a constant thermal mode of the engine. To reduce weight, the radiator has plastic tanks and an aluminum core. Air is blown through the radiator by a four-bladed plastic fan with an electric drive. The system operates at a higher thermal mode than that of previous engines. The start and full opening temperatures of the main thermostat valve are 87 and 102°C, respectively. Coolant pump 3 is a centrifugal type, located directly in the cylinder block and rotates with the same belt drive as the camshaft.
The fuel system includes an air filter, fuel pump, fuel tank and carburetor. Air filter 7 is dry type, with a thermostat and a replaceable filter element made of special cardboard, which has a preliminary cleaner made of nylon wool.
The fuel pump is diaphragm-type, with a mesh filter and a manual fuel pumping lever. To increase the reliability of fuel supply, the fuel system is equipped with a drain for excess fuel from the carburetor back into the fuel tank. Additionally, the fuel system has a fine filter and a gasoline vapor separator that prevents vapors from escaping into the atmosphere.
Carburetor 6 — a new design of the emulsion type, two-chamber, with a falling flow and sequential opening of the throttle valves. It has a balanced float chamber, a system for sucking crankcase gases behind the throttle valve, a power mode economizer with a pneumatic drive, a diaphragm accelerator pump, an electronically controlled forced idle economizer that takes into account the crankshaft speed, a starting device with a pneumatic drive. The throttle and air valves of the carburetor are driven by a cable.
The ignition system is electronic, contactless, high energy. It provides reliable spark formation at any crankshaft speed.
The engine as a whole has high reliability and durability. The use of a thin-walled cast iron cylinder block, a five-bearing crankshaft with developed journals, steel-aluminum thin-walled crankshaft bearing liners ensures at least 125 thousand km of vehicle mileage before major repairs.