Improving the operation of the ignition system of VAZ vehicles with a carburetor engine. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Automobile. Ignition

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Many articles have been published in the press on the topic of improving various ignition systems. One of the reasons for such a large number of publications is the not very good work of the regular ignition system, including the "people's car" VAZ of the first models. If you fill such a car with high-quality gasoline, carefully adjust the carburetor and clean the candles, then the ignition system works normally. But these conditions are not always met, for example, low-quality gasoline often comes across. As a result, there are problems with starting the engine, especially in winter. It is proposed to improve the operation of the ignition system of a VAZ car without significantly complicating it.

Usually, the effectiveness of the ignition system is judged by the reliability of starting the engine at low temperatures. The ignition system also affects other vehicle characteristics, such as fuel consumption and carbon monoxide content in exhaust gases. But this influence is not very strong, it is not easy to quantify and measure it. So, to determine the amount of carbon monoxide in exhaust gases, you need a special device. It is not an easy task to accurately measure the kilometer fuel consumption, as it depends on many factors.

The effectiveness of the ignition system can be judged by the appearance of the spark discharge and by the maximum distance between the spark gap electrodes, at which a spark still occurs. Knowing the maximum distance between the electrodes and the dielectric strength

air, you can calculate the amplitude of the alternating voltage on the secondary winding of the ignition coil. A good system should provide a spark with a length of 8 ... 10 mm. The value of 7 mm, which is given in some sources, is insufficient in practice. This conclusion is also confirmed by calculations, while it must be taken into account that the electric strength of air is approximately proportional to pressure.

The reliability of the ignition of the air-fuel mixture depends not only on the presence of a spark discharge, but also on its energy. Visually, the energy of a spark discharge can be estimated from the thickness and color of its streamer - a visible channel of ionized gas through which the discharge propagates. If the blue streamer is thin, the discharge is weak. If it is thick, the discharge is strong enough. The highest energy discharge has a thick blue streamer surrounded by a reddish glow zone with an uneven border (the so-called "furry spark"). It is this discharge that the ignition system must provide for a reliable engine start in winter. But such a result is not always possible to obtain.

Many car enthusiasts believe that a good spark must be blue without a reddish tint. But this opinion is not supported by practice or experiments. And the experiment can be put next. If in the thyristor ignition system the capacitance of the storage capacitor is gradually increased from 1 μF to 10 μF, then the spark power increases, and a light red shell appears at the blue streamer.

Fig. 1

The figure shows a diagram of a modified ignition system that provides a reliable start of a cold engine. According to a similar scheme, the ignition system was assembled on Moskvich cars. It contains: ignition coil B115V, designed for a voltage of 7.8 V; additional resistor R1, which is a spiral of soft steel wire in a ceramic insulator; additional capacitor C1 and two relays K1, K2. When the engine is started by a starter, a voltage of +12 V is supplied through the closed contacts of the ignition switch to the resistor and to the winding of the traction relay. Relay windings K1 and K2 are connected in parallel with the traction winding. Relay K1 is activated and closes resistor R1.1 with its contacts K1. In this case, the starter turns the engine crankshaft, and the +12 V voltage is applied directly to the ignition coil. As a result, during start-up, an increased voltage is supplied to the spark plugs, providing a sufficiently powerful spark. Relay K2 also works by connecting an additional capacitor C2.1 to the breaker with its contacts K2. As a result, sparking between the contacts of the interrupter is reduced and the power of the spark discharge in the spark plugs is further increased.

During starter operation, the battery voltage is less than 12 V (its value depends on the state of the battery), so the ignition coil, which is switched on directly, does not experience large electrical overloads at this time. After starting the engine, the relay windings are de-energized, and +12 V is applied to the ignition coil through resistor R1, which lowers the voltage on it to the required value.

Relays K1 and K2 are standard automotive relays. Instead of two relays, one can be used if it has two groups of closing contacts. Additional resistor R1 - with a resistance of 1,5.1,8 ohms from any car. The author used an additional resistor supplied with the B115V ignition coil. It is also possible to rewind the spiral of an existing resistor to the required resistance.

The ignition coil can be made with a tap from the middle of the primary winding. Then, when the starter is turned on, a voltage of +12 V must be applied to the middle terminal of the primary winding, and after the starter is turned off, to the entire primary winding. Relay K1 in this case should be used with changeover contacts. Connect the switching contact to terminal "15" of the ignition switch, normally closed to the output of the full winding of the coil, and normally open to the outlet from the middle. The problem here is that the industry does not produce center tapped ignition coils. Therefore, such a coil will have to be made independently from a conventional factory ignition coil, designed for a voltage of 12 V.

The improved ignition system has been operating flawlessly for about 5 years.

Author: A. Sergeev

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