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The ignition coil is not easy. As a rule, it is one, but many cylinders.

Mikhail KOLODOCHKIN

It is necessary for the coil to cooperate with the high-voltage distributor - alone it does not serve all the candles. The dispenser feels its significance and allows itself to be capricious - then its slider will break through, then the ember in the lid will freeze. For all that, he refuses to work in the mud, but is panicky afraid of wet cleaning. And if the owner decides to install a powerful ignition system, the spark discharge can simply turn off the road from the coil to the candle, finding a shorter path to the "mass".

To get rid of the scandalous colleague, the coil acquired a second high-voltage output (Fig. 1). But the two-pin works exactly the same as its predecessor. Note that at the same time not two discharges arise, but one! Two synchronous sparks in different cylinders are actually the same discharge, the current of which flows through the spark gap of the candles connected in series. In this case, only one of the mentioned sparks is useful - to understand this, we turn to Fig. 2.

The conclusions of the left circuit ignition coil connected to the candles of the first and fourth cylinders. When the current of the primary winding of the coil is opened, breakdown of the spark gaps of both cylinders will occur, however, the energy of the spark discharge released in this case will be distributed between them differently. Its value is directly proportional to the pressure in the cylinder, so the first cylinder has a great advantage over the fourth, directly connected to the atmosphere. As a result, ignition of the working mixture will occur in the first cylinder, and in the fourth, energy will be uselessly dissipated, comparable in magnitude to the losses in the spark gaps of the decomposed distributor. After one cycle, the picture will change - the discharge in the fourth cylinder will coincide with the end of the compression cycle, and in the first it will work idle. The second coil similarly commands the second and third cylinders.

In order to ensure the response of the ignition coils, it is enough to alternately connect their primary windings to a low-voltage power source - a similar method of distributing spark discharges is called non-contact or static. This is how double-output coils work on the Oka or on the Volga with the 406th motor, as well as on the Samaras and Muscovites equipped with microprocessor ignition systems.

Externally, the two-pin coil is more like a line transformer from a TV than its cylindrical predecessor. This is due to structural reasons - it is difficult to arrange two high-voltage leads in an oil-filled metal case, ensuring proper leak tightness. The current coils are dry, flooded with polymer compounds.

It is quite easy to buy a two-pin coil today - we managed to get five different copies (photo 1–5). Generally speaking, all of them must be able to cooperate with different "electronics" - from dual-channel switches of type 42.3734 to complex injection and ignition control systems of the type MIKAS or AVTRON. On the "half" of the engine in the "Oka" "pair" of the coil is an ordinary switch type 3620.3734.

The electrical parameters of the coils are shown in the table.

Since the parameters of coils No. 2–4 practically coincide, they are interchangeable in terms of their output characteristics. In comparison with them, coil No. 5 has a lower value of the inductance of the primary winding, and therefore the energy stored for sparking is also lower. Accordingly, the characteristics of a spark discharge are worse. However, all five coils during testing at the stand provided uninterrupted sparking required by the standard and demonstrated short-term operation on a spark gap with a gap of 12 mm. Nevertheless, we recommend readers first of all reels No. 2 and 3, and in their absence - No. 1 and 4. It is better to bypass coil No. 5.

Fig. 1. One-and two-output ignition coils: almost identical, but completely different … The beginning and end of each of the windings are conventionally marked with the symbols H and K. In the two-output coil there is no contact between the primary and secondary windings, while the secondary winding consists of several sections and is located on top of the primary.

Fig. 2. This is how two two-pin ignition coils work in a four-stroke four-cylinder engine. The moments of “useful” sparking are conventionally marked in red, and the “idle” discharges in blue.

1. Coil 29.3705 - "grandmother" of domestic two-output coils.

Manufacturer - JSC "MZATE". Once intended for the first "microprocessor eights." It has long been discontinued, but is still on sale. If replacement is necessary, you can apply 3012.3705 or 3022.3705, and it is better to replace both coils at once.

2. Coil 3012.3705.

Manufacturer - JSC "MZATE". Designed for VAZ and GAZ, can replace the "old woman" 29.3705.

3. Coil 3022.3705.

Manufacturer - JSC "MZATE". It differs from 3012.3705 by the presence of fastening brackets intended for installation on AZLK-21412 vehicles as part of a microprocessor ignition system.

4. Coil KZ-1.

Manufacturer - NPO Lightning (Ufa). It is delivered to KamAZ for a complete set of cars "Oka". Compared with the previous ones, it was done pretty badly: a roofing iron bandage, a casting compound is heterogeneous and contains bubble inclusions, etc. It is unlikely that the parameters of such products can be stable.