Control block
It is located on the right in the drainage channel and receives information from the following parts via a multi-pin plug:
- From the Hall sensor in the ignition distributor about the engine speed.
- From the lambda probe in the front exhaust pipe about the oxygen content in the exhaust gases.
- From the throttle position potentiometer and the amount of incoming air.
- From the temperature sensor at the inlet of the injection system about the temperature of the incoming air.
- From the temperature sensor on the coolant pipe in front of the cylinder head about the coolant temperature.
From all these signals, the control unit calculates the duration of the opening of the injector controlled by the electromagnet, and with it the amount of injected fuel. In this case, the control unit accesses the engine characteristics memory block, in which data on possible engine states are stored. It also contains information about the required quantities of fuel - of course, in the form of electrical signals. With the Monomotronic system, the control unit stores the amount of fuel and ignition timing corresponding to a given operating state.
Central injection system
More parts of the central injection system are assembled in one housing. Not only does it look like a carburetor, but it also has a throttle body that is moved by the pedal "gas". Incoming air passes through the body and here fuel is added to it using an injector in the same way as in a carburetor.
Injector
It opens with an electromagnet. Thus, fuel can flow or not, according to the signal from the control unit. In order for the fuel to be atomized in the best possible way, the injector has beveled outlets through which the fuel is injected onto the conical surface of the outlet and forms a swirl there.
Air temperature sensor
It is located on the side of the injector housing and measures the temperature of the air entering the injection system.
Pressure regulator
It provides a constant fuel pressure at the injector of 1 bar. To do this, it diverts more or less fuel back to the fuel tank. The fuel supply is kept constant.
Throttle positioner
A small bevel gear motor moves the push rod closer to or further from the throttle stop. As a result, the throttle valve may open more or less. This allows you to keep the idle speed constant under various loads. There is a switch in front of the throttle positioner pushrod that tells the control unit to release the pedal "gas".
Throttle Potentiometer
It informs the control unit about the movements of the throttle and its position. Thus, for example, the control unit "learns" about hard pressing on the pedal "gas". A potentiometer is nothing more than a variable resistance.
Schematic representation of the injection system and its parts
1 injection system
2 Air temperature sensor
3 Throttle positioner
4 Throttle valve potentiometer
5 Heating element of the intake pipe heating system
6 Bloch control
7 starter ignition switch
8 Battery
9 Transistor ignition switch
10 Lambda probe
11 Coolant temperature sensor
12 Ignition distributor
13 Electric fuel pump
Function of the injection system
The fuel pump delivers pressurized fuel to a pressure regulator which maintains a constant pressure at the injector (1 bar).
The control unit receives information about the operation of the engine in the form of pulses from the ignition system and the resistance value of the throttle potentiometer (throttle position). From this, the control unit draws a conclusion about the magnitude of the engine load and mixes (by injector) the required amount of fuel with incoming air. With this mixing, it is important that the ratio of fuel and air is correct (1=1) for optimum performance of the catalyst. This ratio is corrected according to the signal from the lambda probe.
The injector can only open and close, but not meter the amount, so the amount of fuel delivered during one injection changes. This happens as follows: with each pulse from the ignition system, the injector produces one injection. If a little fuel is required, the injector opens at this pulse for a very short time - less than one thousandth of a second.
Injector (2) with connected plug (1) removed from the nest (3) injection systems. Side view of the injector» strainer fuel filter
If the engine needs more fuel (cold or full load), the injection takes longer. This is repeated with each ignition pulse.
Cold engine
The control unit receives information about the engine temperature from the coolant temperature sensor. The colder the engine, the longer the injection time to create a richer mixture. In this mode, the lambda signal is not taken into account, since an optimum mixture for the operation of the catalyst cannot be created.
Idling
A switch on the throttle positioner informs the control unit of this operating mode. The throttle positioner controls the idle speed.
At the same time, the switch disables the operation of the two-way valve. Thus, the vacuum is no longer supplied to the distributor to regulate the ignition timing. When the vacuum control of the ignition timing is turned off, the ignition timing is slightly shifted to the side "Later", which improves the composition of exhaust gases.
Movement with acceleration
sudden supply "gas" The control unit recognizes, thanks to the signal from the potentiometer, as the start of acceleration, as a result of which the mixture is immediately enriched.
Full load
At full "gas" or more specifically, at 72.5°throttle position, the control unit provides the rich mixture required for full load operation. Thus, the proportion is shifted in the direction of increasing fuel. The potentiometer informs about the position of the throttle valve. In this mode, the lambda signal is ignored.
Coasting
When descending a mountain with the pedal released "gas" fuel is saved because its supply is stopped. The control unit recognizes this mode by releasing the pedal "gas" (throttle shaft switch) and high engine speed.
Engine speed limitation
If the maximum speed is exceeded to protect the engine from overload, the control unit interrupts the fuel supply. Speed limitation on vehicles with a catalytic converter cannot be carried out by switching on the ignition, since unburned fuel will enter the catalytic converter. Doing so may cause it to reach dangerous temperatures and be damaged.
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