Motronic fuel injection system. Free Technical Library article

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Motronic fuel injection system

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Encyclopedia of radio electronics and electrical engineering / Automobile. Electronic fuel injection

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The "Motronic" fuel injection system is a combined system with multiport injection, i.e. Each cylinder has a separate injector. Each of the main injectors is controlled individually by an electronic control unit. In addition, an additional starting injector is installed on the intake manifold, controlled by a signal from a thermal relay. The injection system may include an el-mechanical fuel pump, a fuel fine filter, a fuel distributor battery, a fuel pressure regulator in the system, a fuel damper, an electronic control unit (ECU), an idle speed controller, injectors, a starting injector, an air mass meter, crankshaft angle control elements, thermal relay, engine coolant temperature sensor, TDC sensor, throttle position control elements, ignition elements and control relays.

The injection system functions (see Fig. 1) as follows: the fuel pump (2) through the fine fuel filter (3) supplies fuel under pressure to the fuel distributor (4) and then to the injectors (11 and 12). At the end of the fuel distributor there is a fuel pressure regulator in the system (6), which ensures the optimal fuel pressure, including the dependence on the vacuum in the engine intake tract. When the required fuel pressure in the system at a particular moment is exceeded, the pressure regulator returns excess fuel back to the fuel tank through the fuel damper (5).

Due to the constant pressure and recirculation of fuel in the system, the possibility of the formation of fuel vapors is excluded. Injectors (11) mounted on the intake manifold in close proximity to the intake valves ensure good mixture formation. They are controlled by the ECU according to a special program. The longer the injector is open, the richer the fuel mixture becomes. The opening time of the ECU injectors is calculated depending on the output signals of the sensors. This takes into account the temperature of the engine, the amount of intake air and its temperature, throttle position, engine speed. In addition, feedback via the lambda probe (18) can be included in the control system. If there is an oxygen content sensor in the exhaust gases (lambda probe), the ECU regulates mixture formation taking into account the signals from this sensor. The ECU stops supplying fuel to the engine cylinders if the crankshaft speed limit is reached and in forced idle mode.

The number of revolutions of the crankshaft is controlled by the TDC sensor (23), and the angular position of the crankshaft by the corresponding sensor (24). The ECU controls the engine temperature by the signals of the coolant temperature sensor (20), the amount of air by the signal of the intake air flow meter (16), and its temperature by the temperature sensor (17). The position of the throttle valve is controlled by the signals of the throttle angle sensor (potentiometer) and the switch of its extreme position (15). When starting a cold engine, the signal from the thermal relay (19) turns on the additional nozzle (12), due to which the mixture is enriched, which is necessary for starting the engine. Due to the regulator of additional air supply (21), the required crankshaft speed on the engine is maintained. Based on the signals from the TDC sensor and the crankshaft angle sensor, the ECU controls the ignition timing.

Structural diagram of the fuel injection system "Motronic"

Fig. 1

1. Fuel tank
2. Fuel pump
3. Fuel filter
4. Fuel accumulator
5. Fuel damper
6. Fuel pressure regulator
7. Electric control unit
8. Ignition coil
9. Ignition distributor
10. Spark plug
11. Injector
12. Starting nozzle
13. Mixture control
14. Throttle valve
15. Throttle sensors
16. Air flow meter
17. Air temperature sensor
18. Lambda probe (O2)
19. Thermal relay
20. Coolant temperature sensor
21. Regulator XX
22. Adjustment screw XX
23. TDC sensor
24. Crankshaft position sensor
25. Battery
26. Egnition lock
27. Control relay
28. Fuel pump relay

Publication: cxem.net

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