Elements of the ignition system located around the ignition module
1 - ignition distributor cover with electrical wires and ignition distributor rotor; 2 - contact connection to the winding of the pulse sensor; 3 - pin connection for plus «+», mass «–» and tachometer; 4 - high voltage wire from the ignition coil; 5 - ignition coil; 6 - ignition module; 7 - pulse sensor; 8 - electromagnetic sensor of the speed of rotation of the engine flywheel.
Distributor
The electronic components ensure that the ever-revitalizing sparks of ignition on the Renault 19 petrol engines are generated, resulting in amazing ignition timing accuracy throughout the life of the engine. However, for the distribution of spark discharges for each cylinder, as before, the good old rotating rotor in the ignition distributor housing is responsible.
Spark discharge
In order for a spark plug to spark in the combustion chamber, a voltage of at least 30,000 V is required between the spark plug electrodes. Since the battery only delivers 12 V, it means that its voltage must be increased significantly.
In the future, we will talk about a spark discharge with a duration not of tenths or even hundredths, but of thousandths of a second. Therefore, even a minimally late or too early discharge can lead to a malfunction of the ignition function and thus to a deterioration in engine performance.
Top dead center and ignition timing
The spark discharge must occur at the right time. Combustion occurs most efficiently if the working mixture ignites at the moment when it is compressed in a tight space. Such a moment on a four-stroke internal combustion engine occurs at the end of the compression stroke by the piston (2 beat) and before moving down (stroke stroke 3).
Before the direction of movement of the piston changes, it is stationary for a fraction of a second at the highest point of its movement. This point is called «top dead center» (TDC).
Early ignition: The ideal ignition point is the point at which the piston starts to move down. The compression is at its highest and the piston is ready to move down from the energy of the combustion of the fuel. But it would be a mistake to set the ignition timing exactly at TDC. Since the working mixture needs a certain time (about 1/3000 of a second) for ignition and development of full pressure from combustion. Thus, ignition should occur a little earlier - this is called «early ignition». Therefore, the signal for the occurrence of a spark discharge is transmitted even during the piston lift, however, the combustion pressure begins to act only after passing the TDC.
As the engine speed increases, the spark must jump earlier and earlier, since it always takes the same time to ignite the working mixture. Thus, combustion must take place exactly at a certain time, namely, when the piston starts moving down again. The rate of combustion of the working mixture also depends on its composition. When the gas pedal is not fully pressed (partial load) the working mixture in the combustion chambers ignites worse; so it burns out more slowly. In this case, the ignition must also be earlier.
Late ignition: in other situations, on the contrary, the ignition timing should be set later. In this case, ignition occurs only when the piston has already passed TDC. It is carried out almost during the exhaust stroke, which improves the composition of the exhaust gases, however, this reduces engine power. Therefore, late ignition can be considered normal if the engine is running without load (e.g. when rolling from a hill without depressing the gas pedal).
Electronic ignition
Ignition is on all modifications of Renault 19 an integral part of engine management. What seemed complicated is, in fact, quite simple: the ignition is controlled by the same control device as the injection. This has the advantage that both systems can optimally tune in to each other. In addition, the same sensors can be used for carburetion and ignition timing.
In IEZ digital ignition system (Integrated Electronic Ignition) only the rotating ignition distributor remained mechanically working.
Thus a spark is born
- The basic principle of ignition is that the current from the battery passes through the primary winding of the ignition coil.
- This winding consists of several turns of thick wire. When an electric current is applied around the iron rod in the ignition coil, a strong magnetic field is generated to ignite the working mixture.
- When the piston in the cylinder approaches the point that converts the ignition of the withdrawn and compressed working mixture, namely the moment of ignition, the supply of electric current to the ignition coil is interrupted. This occurs at the command of the control device in the ignition module.
- When the electric current is turned off, the magnetic field in the ignition coil disappears. In this case, the following happens: in the secondary winding, consisting of a large number of turns of a thin wire, a high-voltage current pulse of several thousand volts occurs.
- This voltage is applied through the ignition distributor to the spark plug that (in the order of ignition strokes) just should work. The working mixture ignites, the engine cranks further. The electrical circuit closes and the cycle repeats.