Contact ignition systems, device, principle of operation

Where is it used?

Past and present owners of VAZ “classics”, who understand the design of such cars, are well aware of the weak points and operating principles of the contact-type ignition circuit.

Its peculiarity lies in the distribution of voltage to the combustion chambers of the engine through contact connections (hence the name).

Modern cars are equipped with more modern (electronic) ignition, which is controlled by a microprocessor.

The main systems operating on the contact principle include:

• KS3 (KSZ) - the most common type of circuit, the structure of which contains a distributor, a coil and a breaker.

• KTS3 (HKZ-2, JFU4, HKZk) - ignition system with a contact sensor and preliminary energy storage.
• KTC3 (TSZi) is another type of system that operates on the contact principle. It contains a transistor and contacts, as well as an inductive energy storage device.

Contactless sensor: who is it and how is it useful?

In fact, the contactless ignition system, the operating principle of which we are considering today, is not structurally very different from its predecessors.

The operating algorithm remained the same, but it completely lost any mechanical contacts in the low-voltage part. To understand how everything works, let's take a look at the design of the contactless system. It consists of the following elements:

• battery and generator;
• egnition lock;
• pulse sensor;
• transistor switch;
• ignition coil;
• distributor;
• ignition timing regulators;
• candles.

As you may have noticed, many of these elements are already familiar to us. Fundamentally new in the list of components of the contactless ignition system is the pulse sensor, which replaced the breaker present both in the classic contact circuit and in its more advanced transistor version.

Using a special element, it monitors the engine crankshaft speed. Such an element can be a Hall sensor (the most common option), which generates electrical pulses depending on changes in the magnetic field, an optical sensor, or an inductive one.

The impulses created by it, generated precisely at those moments when it is necessary to create a spark in the candle, enter the commutator.

If you have read previous articles, then remember that the basis of the switch is a transistor - an electronic device that can control large currents using small ones.

It is this that is affected by the same electrical impulses from the sensor, and it, in turn, controls the operation of the ignition coil, which converts the low voltage of the on-board network into a much higher one, necessary for the formation of a spark (about 30,000 Volts).

By the way, the pulse sensor is combined into one housing with a distributor and together they form a single device, which is called a sensor-distributor.

General operating principle

The presence of a contact ignition system in a car means that the ignition of the fuel in the cylinders is carried out upon the appearance of a spark from the spark plug.

In this case, the spark itself occurs when a high voltage pulse arrives from the ignition coil.

The key function is performed by the ignition coil, which, according to its operating principle, resembles a transformer.

It consists of two windings (primary and secondary) wound on a metal core.

First, voltage is applied to the primary winding, after which a current is created in the coil.

As soon as a short-term break in the primary circuit occurs, the magnetic field is leveled, but a high voltage (about 25,000 Volts) appears in the secondary winding.

At this moment, a voltage of 300 Volts is also present on the primary winding.

The reason for its appearance is self-induction currents. It is because of the appearance of this current that the breaker contacts burn and spark.

From the above we can conclude that the secondary voltage directly depends on the following aspects:

• Magnetic field;
• The intensity level of the current drop in the primary winding.

To increase the secondary voltage and reduce the risk of burning the contact group, a capacitor is included in the circuit (installed in parallel). Even with a slight opening, the capacitor is charged.

A schematic diagram of the contact ignition system is shown below.

The capacitance discharge occurs through the primary winding, through the formation of a reverse voltage pulse current. Thanks to this feature, the magnetic field disappears and the secondary voltage increases.

The optimal capacitor capacity for a contact ignition system is 0.17-0.35 µF. For example, domestically produced Zhiguli cars have a capacitor with a capacitance of 0.2-0.25 μF (at a frequency of 50 to 1000 Hz).

If the vehicle's ignition system operates without failure, the secondary voltage should constantly increase. It depends on two main parameters - the size of the gap between the spark plug electrodes, as well as the pressure in the cylinders of the machine.

For a contact ignition system, this parameter (secondary voltage) should be at the level of 8-12 Volts.

In order for the system to operate without failures, at the moment of interruption the mentioned indicator increases to 16-25 kV. The presence of such a reserve allows you to avoid adverse consequences from certain fluctuations in the ignition system.

The problems mentioned above include adjustments to the composition of the combustible mixture or changes in the distance between the spark plug electrodes.

For example, a decrease in the oxygen level in the fuel-combustible mixture leads to an increase in voltage to 20 kV.

Despite a number of measures taken, the creators of the contact ignition system were unable to completely avoid burning the contact group. The optimal way to reduce this effect is to strictly maintain the gap at a minimum level (0.3-0.4 mm).

As an example, we can cite domestic VAZ cars, in which the gap in the breaker is 0.35-0.45 mm, which corresponds to an angle of 52-58 degrees (provided that the contact group is in a closed state).

If this angle changes, the voltage in the secondary winding is also adjusted. As a result, sparks appear not only on the contacts, but also on the sliders. For this reason, the quality of the spark decreases and the engine loses power.

The reliability of the contact ignition system, which depends on a number of factors, deserves special attention:

• Shape, energy and time of spark appearance;
• The number of sparks in a certain area;
• Secondary voltage (one of the most important characteristics). The larger this parameter, the less dependent the system is on the composition of the combustible mixture and the level of cleanliness of the electrodes.

Distributor diagnostics

Many older vehicle ignition systems had a distributor installed, and it was often the cause of engine malfunctions. In contact breakers-distributors, the elements of the contact group often burn out, and for this reason the motor may be difficult to start or may not start at all. In non-contact distributors, the Hall sensor may fail, but this is not a typical “disease” of distributors - sensors do not break so often.

The most common distributor malfunctions:

• burnout of the resistor on the slider;
• the appearance of cracks and burnout in the distributor cover;
• breakage of the Hall sensor wiring (this is often noted in VAZ 2108-09, GAZ 31029-3110 distributors with a ZMZ 402 engine);
• wear of the shaft bearings.

The distributor cap on Russian cars is very inexpensive, can be changed within a few minutes, and therefore it is better to always have such a part in stock. The easiest way to check the cover is to replace it - if the motor starts working properly, it’s all about it.

Device

It is no secret that the contact ignition system consists of many different elements:

• battery;
• Mechanical breaker and distributor. The first gives a low voltage current, and the second - a high voltage;
• Lock, coil and spark plugs;
• There are two types of ignition timing regulators - centrifugal and vacuum;
• High voltage wires.

Let's look at the main elements in detail:

• A breaker is a unit that provides short-term separation of the current chain in the low voltage winding. At the moment of rupture, a high voltage is formed in the secondary circuit.
• Capacitor - a part whose purpose is to prevent burning of contacts in the breaker circuit. The container is installed parallel to the contact group, which allows the product to absorb a larger amount of energy. An additional function of the capacitor is to increase the voltage on the secondary winding.

• Distributor - an element of the contact ignition system, which ensures the distribution of voltage potential to each of the cylinder spark plugs. Structurally, the device consists of a cover and a rotor. There are contacts in the upper part, and the potential from the coil is directed to the central contact, and through the side contacts to the spark plugs.

• Ignition coil - a device that converts voltage (from low to high). The part is located in the engine compartment, as are most of the elements of the contact ignition system. Structurally, the product has two windings. One is low voltage and the other is high voltage.

• Distributor - is a device in which a breaker and a distributor are located together, operating from the engine crankshaft.

• Centrifugal regulator is a unit that provides a change in the ignition timing. This parameter represents the crankshaft rotation angle at which voltage is applied to the spark plugs. To ensure complete combustion of the combustible mixture, the angle in question is set ahead of time.

Structurally, the regulator is a pair of weights that act on a plate with breaker cams placed on it. It is worth noting here that the plate moves freely, but the advance angle is set due to the position of the motor distributor.

• Vacuum type regulator - a device that provides a change in the advance angle against the background of adjusting the level of load on the engine (changes when you press the gas pedal). The regulator is combined with the cavity of the throttle assembly and adjusts the angle taking into account the level of vacuum.

• Spark plugs are standard ignition elements that convert energy into a spark necessary to ignite the fuel mixture in the engine cylinders. At the moment the impulse is transmitted to the spark plugs, a spark is formed, igniting the combustible mixture.
• High-voltage wires (armored wires) - an unchanged element of the contact ignition system, with the help of which high voltage is transmitted along the path “coil - distributor - spark plugs”. Structurally, the product is a flexible conductor of large cross-section with one copper core and multilayer insulation.

History of the spark

At the dawn of the automobile industry, the ignition system of internal combustion engines was a real headache for engineers.

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Various methods of igniting fuel were invented, and at times they could hardly be called simple and safe. For example, one of the fathers of the industry, Gottlieb Daimler, used a glow tube in his first engines, which had to be heated red-hot with a blowtorch before starting work.

The first prototypes of modern electrical systems appeared at the end of the 19th century.

The so-called magneto, a small generator that produces the necessary voltage to form a spark, enjoyed quite a lot of success among them. The well-known Robert Bosch is considered its inventor.

In fact, the magneto became the progenitor of all spark methods of igniting the mixture, and the contact ignition system that we are talking about today is no exception.

Of course, it is much more advanced than those first devices, but today, in the world of electronics and innovation, it is gradually becoming history.

Mainly, its carriers now are domestic cars - VAZ “classics” and the like. What is she like?

Operating principle

To fully service the contact ignition system, it is important to understand its operating principle, as well as the features of the interaction of various elements.

While the circuit breaker is closed, current flows only through the primary winding.

As soon as the circuit is disconnected using the interrupting device, a high voltage is generated in the second winding.

At the same moment, the created impulse is sent through wires to the distributor cover, and then to the spark plugs. In this case, the distribution is carried out at a certain advance angle.

The revolutions of the crankshaft and camshaft are in complete interaction. This means that as the speed of the first increases, the speed of the second also increases.

Here a centrifugal-type regulator comes into operation, the weights of which diverge and move the movable plate with cams.

A little earlier, the breaker chain is disconnected, and the advance angle increases.

If the crankshaft speed decreases, the reverse process occurs - a decrease in the advance angle.

The operation diagram is shown below.

Selection of BSZ

When purchasing a new BSZ, you should pay attention to the presence of the components of the entire kit. The factory kit should contain:

1. Distributor (main distributor). The code for engines 1.5 and 1.6 is 38.37061. For 1.3 engines, the number will be 38.3706–01, because the height of the 1.3 engine block is lower and the distributor shaft is shorter.
2. Switch number 36.3734 or 3620.3734.
3. High voltage coil (reel). Marking 27.3705
4. Thin wires with connectors.

In appearance, the BSZ kit for the VAZ 2121 NIVA is very similar. But it’s better not to install this kit on a VAZ 2107 or a VAZ 2106, because the characteristics of the “six” and “seven” are very different from the “Niva”. Distributor brands for Niva: 3810.3706 or 38.3706–10.

The best manufacturer of electronic ignition systems for old VAZ cars is. The production capacity base is located in the city of Stary Oskol. According to reviews from car owners of classic BSZ SOATE models, this is an excellent option.

Contact-transistor ignition system

In order to optimize the circuit, the developers added a transistor switch to the design, which is installed in the primary winding. It is controlled using breaker contacts.

The circuit diagram is shown below.

The peculiarity of the system is that the use of an additional device made it possible to reduce the current in the circuit and extend the life of the contact group of the breaker (it began to burn less).

The contact-transistor circuit, thanks to minor changes, has received better characteristics when compared with the classic ignition option. Due to the use of a transistor, a new node was added to the system - a switch.

The advantage of the transistor in this circuit is that even a small current directed to the control (to the base) is enough to control a larger current.

As already noted, the new contact-transistor type system has slight differences from the previous version of the system. Its peculiarity lies in the special characteristics that the standard contact circuit cannot boast of.

The main difference is that the chopper interacts directly with the transistor, rather than with the bobbin. Otherwise, the operation of the contact-transit system is similar.

As soon as the current in the primary winding is interrupted, a high voltage pulse occurs in the second circuit.

If you do not pay attention to the design features and principles of connecting the switch, you can highlight one main advantage - the ability to increase the primary current thanks to the use of a transistor.

At the same time, it is possible to solve a number of problems:

• Increase the gap between the spark plug electrodes;
• Raise secondary voltage;
• Eliminate problems with starting at low temperatures;
• Optimize the spark formation process;
• Increase engine speed and power.

Another feature of the contact-transistor circuit is the need to use a coil with a separate primary and secondary winding.

The considered changes to the circuit made it possible to reduce the load on the contact group of the breaker and reduce the current passing through it. As a result, contacts last longer and system reliability increases.

Despite the considered advantages, one cannot fail to note a number of disadvantages of the contact-transistor system, which are associated with the operation of the breaker.

Thus, a spark is formed in the circuit at the moment when the current in the “bobbin” is interrupted. The current that enters the transistor is of sufficient magnitude to affect the operation of the part.

In addition, a decrease in current at the breaker contact group negatively affects certain system characteristics.

Tuning on carburetor modifications of the VAZ 2107

All old textbooks on servicing classic Zhiguli models describe a method for setting the moment of spark formation using a light bulb, although experienced motorists can easily do without it. You will understand why this happens as you read this material, but for beginners it will be useful to familiarize yourself with the old proven technique.

To correctly set the ignition of the “seven”, you need to ensure that the following conditions are met simultaneously:

• the notch on the crankshaft pulley is opposite the long mark on the timing cover;
• in this case, the round mark marked on the camshaft chain drive gear coincides with the boss on its body;
• the piston of the 4th cylinder has completed the compression stroke and is at top dead center;
• the contacts inside the distributor are open;
• The movable contact of the slider faces the fixed contact on the distributor cover, where the wire from the spark plug of the 4th cylinder is connected.

The diagram shows what happens in the cylinders when the marks are aligned

The light bulb is used to control the ignition timing, for which it must be connected with one wire to the “K” contact of the high-voltage coil, and with the second to the vehicle ground. You should know that at the same moment the piston of the first cylinder is also in the TDC position, only there the air-fuel mixture is not compressed, but exhaust gases are released after its combustion. This is why ignorant car enthusiasts often confuse the first cylinder with the fourth when installing the ignition.

Layout of marks on the timing cover

When the above actions occur simultaneously, a spark discharge occurs on the electrodes of the spark plug of the 4th cylinder, as evidenced by the flash of the connected light bulb. To achieve these conditions and set the ignition correctly, follow the instructions:

1. Turn the crankshaft with a 36 mm wrench, aligning the notch on the pulley with the long notch on the timing cover.
2. If at this moment the engine valve cover is removed, then it is better to navigate by the mark on the camshaft gear, placing it opposite the housing boss.
3. Take the ignition distributor, remove the cover and turn its shaft to place the slider opposite the wire leading to cylinder No. 4 (there are cylinder number markings on the cover). Insert the distributor into the engine hole, holding the slider and housing in this position, and then secure it with a 13 mm wrench nut.
4. Connect the light bulb wires and turn on the ignition by turning the key. Loosen the nut securing the distributor and slowly turn it by the housing until the lamp flashes, indicating the moment of sparking. Reattach the distributor.
5. Turn off the ignition and make sure that the contacts inside the distributor are currently open. Take a 0.35 mm feeler gauge and check the gap between them, if necessary, adjust it by loosening the fastening screws with a screwdriver.

The marks must be aligned by turning the crankshaft with a wrench

The ignition is considered to be set correctly if, after installing the distributor cap and connecting the wires, you manage to start the engine, and then you need to adjust the timing. The non-contact system is installed in the same way, with the exception of checking the gap in the contact group due to its absence.

The mark on the camshaft gear is aligned with the boss on the body

Important point. In most cases, the ignition is set without removing the valve cover, which is why the position of the mark on the gear is not visible. You have done everything according to the instructions, but the engine does not start. This means that a spark is supplied to the 4th cylinder during the exhaust stroke, and compression at this moment occurs in the first cylinder. The problem can be solved simply:

• remove the distributor cover;
• unscrew the nut securing it;
• pull the distributor out of the socket, turn the slider exactly 180° and insert the element back;
• Press the distributor skirt with the nut and install the cover.

conclusions

All systems used to ignite a fuel mixture are good in certain areas of mechanical engineering. Everyone is not without their shortcomings. It is not always necessary to create a complex and highly reliable system; sometimes it is much cheaper to use simple and cheaper ones. There is no need to install an expensive ignition system on a car that is much lower in cost than others in its class. Such actions can only increase its cost, but the quality, unfortunately, will remain the same. Why change anything if the ignition system has shown only the best results in many tests?