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Pic. 41. Distributed fuel injection system: 1. Air supply pipe; 2. Air filter housing; 3. Air filter cover; 4. Fuel frame; 5. Nozzle; 6. Fuel drain tube; 7. Fuel supply pipe; 8. Pressure regulator; 9. Filter element; 10. Mass air flow sensor; 11. Electric fuel pump with fuel level sensor; 12. Inlet hose (connects to throttle body); 13. Fuel drain line; 14. Fuel supply line; 15. Hose for supplying crankcase gases from the cylinder head cover; 16. Fuel tank; 17. Wiring harness for injectors; 18. Coolant temperature sensor; 19. Throttle pipe; 20. Fuel filter; 21. Throttle cable; 22. Crankcase suction hose at idle; 23. Throttle position sensor; 24. Idling regulator; 25. Vacuum supply hose to pressure regulator; 26. Receiver; 27. Plug of the union for accession of the manometer; 28. Crankshaft position sensor; 29. Pressure regulator valve; 30. Pressure regulator diaphragm; 31. Support bracket; 32. Inlet pipe; 33. Support bracket; 34. Hose for draining liquid from the throttle pipe; 35. Fluid supply hose for heating the throttle pipe; 36. Hose for suction of gasoline vapors from the adsorber (installed in a feedback injection system); 37. Inlet valve; A. Air suction to the throttle pipe; B. Draining fuel into the fuel tank; C. Fuel supply from the fuel rail.
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Pic. 42. Wiring diagram of the distributed fuel injection system: 1. Crankshaft position sensor; 2. Diagnostic block. 3 Idling regulator; 4. Electronic control unit (ECU); 5. Knock sensor; 6. Block for connecting the air conditioner; 7. CO-potentiometer; 8. Ignition module; 9. Spark plugs; 10. Nozzles; 11. Electric fuel pump with fuel level sensor; 12. Safety fuse for protection of the electric fuel coca, its relay and injectors; 13. Relay for turning on the electric fuel pump; 14. Fuse protecting the speed and mass air flow sensors; 15. Ignition relay; 16. ECU protection fuse and ignition module; 17. Mass air flow sensor. 18. Board with a control lamp "CHECK ENGINE"; 19. Block connecting to the instrument panel wiring harness; 20. The electric motor of the fan of the engine cooling system; 21. Mounting block; 22. Speed sensor; 23. Coolant temperature sensor; 24. Throttle position sensor; K9. Relay for turning on the electric fan; A. To the battery terminal; B. To the ignition switch (to the conclusion "15/1"); C. To the tachometer; D. To trip computer.
Device
On VAZ 21093 and VAZ-21099 vehicles, engines with a distributed fuel injection system can be installed, i.e. fuel is injected by four injectors (one injector per cylinder) in the intake pipe, on the intake valves. Here, the fuel evaporates, mixes with air and enters the engine cylinders in the form of a combustible mixture. The fuel injection system reduces the toxicity of exhaust gases while improving the driving performance of the car. There are two systems of distributed injection: with and without feedback.
The feedback system is mainly used on export vehicles. She has a catalytic converter and an oxygen sensor installed in the intake system, which provides feedback. The sensor monitors the oxygen concentration in the exhaust gases, and the electronic control unit, using its signals, maintains the air / fuel ratio that ensures the most efficient operation of the converter. Use only unleaded gasoline as fuel. Use of leaded gasoline will damage the catalytic converter, oxygen sensor and system failure.
In the injection system without feedback, a converter and an oxygen sensor are not installed, and a CO potentiometer is used to adjust the concentration of CO in the exhaust gases. This system also does not use a gasoline vapor recovery system. On fig. 41 and 42 show the device of this particular system, since it will be mainly used on cars sold in Russia. And the text below describes the nodes of both systems and gives the features of the system with feedback
The converter is installed in the exhaust system in front of the additional muffler. It contains two oxidation catalysts (chemical reaction accelerator) and one recovery. Oxidation catalysts (platinum and palladium) contribute to the conversion of hydrocarbons into water vapor, and carbon monoxide into carbon dioxide. Recovery Catalyst (radium) promotes the conversion of nitrogen oxides into harmless nitrogen.
Due to the fact that the catalytic converter requires oxygen to neutralize hydrocarbons and carbon monoxide, and at the same time it must take oxygen to neutralize oxides of nitrogen, it is necessary to maintain a very strict air/fuel mixture balance (approximately 14.7:1), entering the engine. This function is performed by the electronic control unit.
Electronic control unit (ECU), located under the instrument panel on the left side of the body, is the control center of the fuel injection system. This is a dedicated computer. It continuously processes information from various sensors and manages systems that affect exhaust emissions and vehicle performance.
The ECU also performs a diagnostic function for the fuel injection system. It can recognize malfunctions in the system, warning the driver about them through a warning lamp "CHECK ENGINE". In addition, it stores diagnostic codes indicating fault areas to assist technicians in carrying out repairs.
The air filter is installed in the front of the engine compartment on rubber clips. The filter element 9 is made of paper, with a large area of the filtering surface. When replacing the filter element, it must be installed so that the corrugations are parallel to the center line of the vehicle.
Throttle pipe 19 is fixed on the receiver. It doses the amount of air entering the intake pipe. The intake of air into the engine is controlled by a throttle valve connected to the accelerator pedal drive.
The composition of the throttle pipe includes a throttle position sensor 23 and an idle speed controller 24. In the flow part of the throttle pipe (in front of and behind the throttle) there are vacuum extraction holes necessary for the operation of the gasoline vapor recovery system. If the latter system is not used, then the adsorber purge fitting is plugged with a rubber plug.
The idle speed controller 24 controls the idle speed of the crankshaft by controlling the amount of air supplied to bypass the closed throttle. It consists of a two-pole stepper motor and a cone valve connected to it. The valve extends or retracts according to the signals from the ECU.
The throttle position sensor 23 is mounted on the throttle body 1 and is connected to the throttle valve axis. The sensor is a potentiometer, one end of which is supplied with a supply voltage of 5 V, and the other end is connected to "weight". From the third output of the potentiometer (from the slider) is the output signal to the ECU.
The fuel supply system includes an electric fuel pump 11, a fuel filter 20, fuel lines and an injector rail 4, complete with injectors 5 and a fuel pressure regulator 8.
The electric fuel pump 11 is a two-stage rotary type, installed in the fuel tank. Fuel from the pump through the fine fuel filter 20 is supplied to the fuel rail at a pressure of more than 284 kPa. The electric fuel pump is switched on using the auxiliary relay 13 (see fig. 42). The fuel filter with a paper filter element is installed under the body floor behind the fuel tank.
Ramp 4 injectors is a hollow bar with injectors and a fuel pressure regulator installed on it. The frame of the injectors is fixed with two bolts on the inlet pipe 32. On the right side on the injector rail there is a fitting for controlling the fuel pressure, closed with a screw plug 27.
Nozzle 5 is a solenoid valve. When a voltage pulse arrives at it from the ECU, the valve opens, and fuel is injected through the sprayer with a finely sprayed jet under pressure into the intake pipe to the intake valve.
After the electrical impulse is stopped, the spring-loaded injector valve shuts off the fuel supply. The nozzles are fixed on the ramp with spring clips. The upper and lower ends of the nozzles are sealed with rubber sealing rings.
The fuel pressure regulator 8 consists of a valve 29 with a diaphragm 30. Spring-loaded to the seat in the regulator housing. The purpose of the regulator is to maintain a constant pressure differential between air pressure in the intake pipe and fuel pressure in the raihp the engine running, the regulator maintains the pressure in the injector rail within 284-325 kPa.
The regulator diaphragm is acted upon by fuel pressure on one side and fuel pressure on the other (underpressure) in the intake pipe. When the pressure in the intake pipe decreases (throttle valve closes) The regulator valve opens at a lower fuel pressure, allowing excess fuel to flow through the return line back to the tank. The fuel pressure in the rail drops. When the pressure in the intake pipe increases (when opening the throttle) the regulator valve opens already at a higher fuel pressure in the rail rises.
Coolant temperature sensor 18 is a thermistor (resistor whose resistance changes with temperature). The sensor is wrapped in the coolant outlet on the cylinder head. At low temperatures, the sensor has a high resistance (100 kOhm at -40°C), and at high temperature - low (177 Ohm at 100°C).
The oxygen concentration sensor is used in the feedback injection system and is installed on the downpipe of the mufflers. The oxygen contained in the exhaust gases reacts with the oxygen sensor, creating a potential difference at the output of the sensor. It varies from approximately 0.1 V (high oxygen content - lean mixture) up to 0.9V (little oxygen - rich mixture). A heating element is built into the sensor to increase its efficiency.
The mass air flow sensor 10 is located between the air filter and the intake pipe hose 12. It is hot-wire type. The sensor uses three sensing elements. One of the elements determines the ambient air temperature, and the other two are heated to a pre-set temperature that is higher than the ambient air temperature. During engine operation, the passing air cools the heated elements. The mass air flow is determined by measuring the electrical power required to maintain a given temperature rise of the heated elements over the ambient air temperature. Frequency sensor signal. High air flow causes a high frequency signal, and low air flow causes a low frequency signal.
Vehicle speed sensor 22 (pic. 42) mounted on the gearbox between the speedometer drive and the tip of the flexible shaft of the speedometer drive. The principle of operation of the sensor is based on the Hall effect. The sensor outputs rectangular voltage pulses to the computer with a frequency proportional to the speed of rotation of the drive wheels.
CO potentiometer 7 (pic. 42) installed in the engine compartment on the wall of the air intake box and is a variable resistor. It sends a signal to the ECU, which is used to adjust the air-fuel mixture in order to obtain a normalized level of carbon monoxide concentration (SO) in exhaust gases at idle. The CO potentiometer is like the mixture screw in carburetors. Adjustment of the CO content using a CO potentiometer is only carried out at a service station using a gas analyzer.
The crankshaft position sensor 28 is of the inductive type, mounted on the oil pump cover opposite the drive disk on the generator drive pulley. The driving disk is a gear wheel with 58 equidistant (6°) depressions. To create a synchronization pulse, two teeth are missing. As the crankshaft rotates, the teeth change the sensor's magnetic field, inducing AC voltage pulses.
Ignition system
Ignition system does not use traditional distributor and ignition coil Module 8 is used here (pic. 42) ignition system consisting of two ignition coils and high energy control electronics. The ignition system has no moving parts and therefore requires no maintenance. It also has no adjustments (including ignition timing), because the ignition is controlled by the ECU.
The ignition system uses a spark distribution method called the spark distribution method "idle spark". The engine cylinders are combined in pairs 1-4 and 2-3 and the neoplasm occurs simultaneously in two cylinders: in the cylinder in which the compression stroke ends (working spark), and in the cylinder in which the exhaust stroke occurs (idle spark). Due to the constant direction of the current in the windings of the ignition coils, the sparking current in one candle always flows from the central electrode to the side, and in the second - from the side to the central one. Candles are used type A17DVRM or AC.R43XLS with a gap between the electrodes of 1.0-1.13 mm.
The ignition in the system is controlled by the ECU. The crankshaft position sensor provides the ECU with a reference signal, on the basis of which the ECU calculates the firing sequence of the coils in the ignition module. To accurately control the ignition, the ECU uses the following information:
- crankshaft speed;
- engine load (mass air flow);
- coolant temperature;
- crankshaft position.
The gasoline vapor recovery system is used in the feedback injection system. The system uses the method of trapping vapors with a carbon adsorber installed in the engine compartment. When the engine is not running, gasoline vapors from the fuel tank are fed into the adsorber, where they are absorbed by activated carbon. When the engine is running, the adsorber is purged with air, and the vapors are sucked off to the throttle pipe, and then into the inlet pipe for combustion during the working process.
The ECU controls the purge of the canister, including a solenoid valve located on the canister cover. When voltage is applied to the valve, it opens, releasing vapors into the intake pipe. The valve is controlled by pulse-width modulation. The valve turns on and off at a frequency of 16 times per second (16 Hz). The higher the air flow, the longer the duration of the valve activation pulses.
The ECU turns on the canister purge valve when all of the following conditions are met:
- coolant temperature above 75°C;
- fuel management system operates in closed loop mode (with feedback);
- vehicle speed exceeds 10 km/h. After the valve is turned on, the speed criterion changes. The valve will turn off only when the speed drops to 7 km / h;
- throttle opening exceeds 4%. This factor does not matter further if it does not exceed 99%. When the throttle is fully opened, the ECU turns off the canister purge valve.
The electric fan 20 of the cooling system is turned on and off by the computer depending on the engine temperature, engine speed, air conditioning (if it is on the car) and other factors. The electric fan is switched on using the auxiliary relay K9. located in the mounting block 21. When the engine is running, the electric fan turns on if the coolant temperature exceeds 104°C or a request is given to turn on the air conditioner. The electric fan turns on after the coolant temperature drops below 101°C, after the air conditioner is turned off or the engine is stopped.
Operation of the injection system
The amount of fuel supplied by the injectors is regulated by an electrical pulse signal from the electronic control unit (ECU). The ECU monitors data on the state of the engine, calculates the need for fuel and determines the required duration of fuel supply by injectors (pulse duration), to increase the amount of fuel supplied, the pulse duration is increased, and to reduce the fuel supply, it is shortened.
The ECU has the ability to evaluate the results of its calculations and commands, as well as remember the experience of recent work and act in accordance with it. "self-learning" The ECU is a continuous process that continues throughout the life of the vehicle.
Fuel is supplied by one of two different methods: synchronous, i.e. at a certain position of the crankshaft, or asynchronous, i.e. independently or without synchronization by the rotation of the crankshaft. Synchronous fuel injection is the predominantly used method. Asynchronous fuel injection is used mainly in the engine start mode.
The nozzles are switched on in pairs and in turn: first the nozzles of the 1st and 4th cylinders, and after 180°of rotation of the crankshaft - the nozzles of the 2nd and 3rd cylinders, etc. Thus, each injector is activated once per revolution of the crankshaft, i.e. twice per full engine cycle.
Regardless of the injection method, the fuel supply is determined by the state of the engine, i.e. its mode of operation. These modes are provided by the ECU and are described below.
Initial fuel injection. When the crankshaft of the engine starts to scroll with the starter, the first pulse from the crankshaft position sensor causes a pulse from the ECU to turn on all the injectors at once. This serves to speed up the engine start.
Initial fuel injection occurs each time the engine is started. The duration of the injection pulse depends on the temperature. On a cold engine, the injection pulse increases to increase the amount of fuel, and on a warm engine, the pulse duration decreases. After the initial injection, the ECU switches to the appropriate injector control mode.
Engine start mode. When the ignition is turned on, the ECU turns on the relay for the electric fuel pump, and it creates pressure in the fuel supply line to the fuel rail. The ECU checks the signal from the coolant temperature sensor and determines the correct air/fuel ratio for starting.
After the crankshaft begins to rotate, the ECU will operate in starting mode until the speed exceeds 500 rpm or purge mode occurs "flooded" engine.
Engine purge mode. If the engine "filled with fuel" (those. fuel wet spark plugs), it can be started by fully opening the throttle while cranking the crankshaft. In this case, the ECU does not supply injection pulses to the injectors, and the engine must "be cleansed". The ECU maintains this mode as long as the engine speed is below 500 rpm, and the throttle position sensor indicates that it is almost fully open (over 75%).
If the throttle is held almost wide open when attempting a normal start "not flooded" engine, the engine may not start, because. at wide open throttle, injection pulses are not applied to the injector.
Fuel management operating mode. After starting the engine (when the rpm is over 500 rpm) The ECU controls the fuel supply system in operating mode. In this mode, the ECU calculates the pulse duration for the injectors based on signals from the crankshaft position sensor (speed information), mass air flow sensor, coolant temperature sensor and throttle position sensor.
The calculated injection pulse width may give an air/fuel ratio other than 14.7:1. An example is when the engine is cold, as this requires a rich mixture to ensure good driving performance.
Operating mode for injection system with feedback. In this system, the ECU first calculates the pulse width to the injectors based on signals from the same sensors as in the open-loop injection system. The difference is that in the feedback system, the ECU still uses the signal from the oxygen sensor to correct and fine-tune the calculated pulse to accurately maintain the air/fuel ratio at 14.6...14.7:1. This allows the catalytic converter to operate at maximum efficiency.
Enrichment mode when accelerating. The ECU monitors sudden changes in throttle position (by sensor, throttle position) and behind the signal of the mass air flow sensor and provides the supply of an additional amount of fuel by increasing the duration of the injection pulse. Acceleration rich mode is only used for transient fuel control (when moving the throttle).
Power enrichment mode. The ECU monitors the throttle position sensor signal and engine speed to determine when the driver needs maximum engine power. A rich fuel mixture is required to achieve maximum power, and the ECU changes the air/fuel ratio to approximately 12:1. In a feedback injection system in this mode, the signal from the oxygen concentration sensor is ignored, because. it will indicate the enrichment of the mixture.
Braking lean mode. When braking a car with a closed throttle, emissions of toxic components into the atmosphere can increase. To prevent this, the electronic control unit monitors the decrease in the throttle opening angle and the signal from the mass air flow sensor and reduces the amount of fuel supplied in a timely manner by reducing the injection pulse.
Fuel cut-off mode during engine braking. When braking with the engine in gear and clutch engaged, the ECU may completely shut off the fuel injection pulses for short periods of time. Turning off and on the fuel supply in this mode occurs when certain conditions are met for the coolant temperature, crankshaft speed, vehicle speed and throttle opening angle.
Supply voltage compensation. If the supply voltage drops, the ignition system may produce a weak spark, and mechanical movement "discoveries" injectors may take longer. The ECU compensates for this by increasing the energy storage time in the ignition coils and the duration of the injection pulse.
Accordingly, with increasing battery voltage (or voltage in the vehicle's on-board network) The ECU reduces the energy storage time in the ignition coils and the duration of the injection.
Fuel cut off mode. When the ignition is off, the nozzle does not supply fuel, which excludes the self-ignition of the mixture when the engine is overheated. In addition, fuel injection pulses are not given if the ECU does not receive reference pulses from the crankshaft position sensor, i.e. this means the engine is not running.
The fuel cut-off also occurs when the maximum permissible engine speed of 6510 rpm is exceeded to protect the engine from twisting.