Renault 19 engines differ not only in volume, power and principle of operation, but also in the principle of operation of valves. So, the camshaft in the C-engine is located slightly to the side in the engine housing. In F-engines, on the other hand, the valves are actuated by a camshaft, which is located in the cylinder head. The 16-valve engine has 2 camshafts in the cylinder head. While 1.4-, 1.7- and 1.8-liter engines, as well as diesel, require periodic valve clearance adjustment, the 16-valve engine does without this operation, since the valves are actuated by hydraulic tappets. If you look at the pictures of the engines posted later in our guide, you will see that the engines are very different also in the cylinder head cover. Here is a table with the characteristics of the engines that are described in this section:
Engine | 1.4 l | 1.7 l | 1.7 L F3N-N | 1.8 l |
Volume (cm3) Power (kW) System injection | C3J 1390 43 single point injection | F3N-L 1721 54 single point injection | 1721 66/69 Multi-point injection (4 injection points) | F3P 1794 65 single point injection |
Engine | 1.8 l | 1.8 liter 16 valve engine | 1.9 L diesel | 1.9 L turbocharged diesel (TD) |
Volume (cm3) Power (kW) System injection | F3P 1794 81 Multi-point injection (4 injection points) | F7P 1764 99 Multi-point injection (4 injection points) | F8Q 1870 47 Diesel injection system | F8Q 1870 66 Diesel injection system |
* Combinations of letters and numbers mean the following in that order:
- 1st letter: C = gray cast iron engine case with side camshaft; F = Engine housing with dry gray cast iron cylinder liners.
- 2nd digit: 3 = valve arrangement and power system; 6 and 7 = types of combustion chamber and type of fuel system.
- 3rd letter: F = 1126-1200 cm3; J = 1351-1425 cm3; N = 1651-1750 cm3; P = 1751-1850 cm3; Q = 1851-1950 cm3.
The principle of operation of a diesel engine
For those who want to brush up on their knowledge, we summarize the principle of diesel operation.
In a diesel engine, like a gasoline engine, the pistons move up and down in the cylinders. However, when moving down - the intake stroke - they suck in only clean air through the filter. When the piston moves up, the intake air is compressed much more than in a gasoline engine. For example, on a diesel Renault 19, the air taken in this way is reduced to 1/23.5 of the original volume. Due to this intense compression, the air is very hot. Something similar happens, for example, in a bicycle pump when you inflate a tire. Atomized diesel fuel is then injected into the hot air, and the fuel droplets ignite due to the high air temperature; so sometimes called diesel «self-igniting». It does not require a spark plug to ignite the working mixture. The ignition timing of a diesel engine is controlled by a high pressure fuel pump (injection pump), which at the right time through nozzles ejects the required amount of diesel fuel into hot compressed air. The pressure from fuel combustion, as in a gasoline engine, causes the piston to move downward; while doing useful work. The crankshaft turns and the piston moves up again, while the combustion products are removed from the cylinder. The piston and cylinder are now ready for the intake stroke and power stroke again.
Composite working chamber
Since, unlike a gasoline engine, the fuel droplets injected into the combustion chamber burn explosively in a diesel engine, its operation could be very noisy and, in addition, the engine bearings would experience severe overloads. «Soft» combustion of fuel in a diesel engine of a passenger car is achieved through the use of a composite working chamber. In this case, the combustion of fuel occurs in a separate «compartment» cylinder heads. The pressure arising from combustion is uniformly transmitted through the channel connecting the vortex combustion chamber with the over-piston space of the diesel engine to the piston.
1 - nozzle; 2 - glow plug; 3 - vortex chamber; 4 - channel for connecting the vortex combustion chamber with the over-piston space of the diesel engine; 5 - pistons.
Vortex chamber
Of all the possible options for a composite working chamber, Renault designers chose «vortex chamber mixing». The vortex chamber located in the cylinder head is located relatively far from the combustion chamber due to the mentioned channel for connecting the vortex combustion chamber to the diesel engine above-piston space. When the piston goes up during compression, the air in the cylinder is compressed in the vortex chamber. There, due to the shape of the chamber, a swirl of air occurs. The fuel injected at this moment through the nozzle mixes well with air, turns into steam and burns out. Combustion occurs mainly in the swirl chamber and only then spreads to the combustion chamber of the cylinder. At the same time, the vortex chamber becomes very hot and during engine operation it becomes red-hot, in the full sense of the word. However, this effect plays a positive role, since due to this, fuel particles entering the vortex chamber are better evaporated.
Other diesel engine manufacturers often use a so-called prechamber instead of a swirl chamber, for example in Mercedes-Benz passenger cars. The prechamber is much more effectively protected from the combustion chamber, which ensures quieter engine operation, especially at low revs. The use of a swirl chamber results, however, in a lower fuel consumption at a speed of more than 5000 rpm.
22.12.2022 21:58
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