Audi A4, S4
since 2000 release
Repair and operation of the car
Audi A4, S4
+ Governing bodies and methods of safe operation
+ Current leaving and service
+ Cooling systems, heating and air conditioner
- Power supply systems, release and decrease in toxicity of the fulfilled gases
+ Power supply systems of petrol and diesel engines
- System of injection of fuel of the petrol engine
General information and security measures
Functioning of a control system and injection of the petrol engine
General check of system of injection of the petrol engine
Check and adjustment of number of turns of the single course / moment of ignition/concentration WITH
+ System of injection of fuel of the diesel engine
+ Systems of release and decrease in toxicity of the fulfilled gases. Turbocompressor
+ Systems of electric equipment of the engine
+ Manual box of gear shifting
+ Automatic transmission
+ Coupling, power shafts and differential
+ Brake system
+ Suspension bracket and steering
+ Onboard electric equipment
Functioning of a control system and injection of the petrol engine
Motronic control system elements in a compartment of engines of 1.8 l (AVJ, BFB)
Fuel distributive highway and injectors. Engine of 1.8 l of AVJ/BFB
Control system elements in a compartment of V6 engines
Control system elements in a compartment of engines of the S4 model
Fuel is sucked in from a fuel tank by the electric fuel pump and moves via the fuel filter to the fuel distributive highway. The regulator of pressure provides maintenance of pressure in fuel system, equal 3.5, 4.0 or 6.0 atm., depending on the engine.
Through the electrooperated injectors fuel pulsewise is injected into the inlet pipeline located just before inlet valves of the engine. The control unit of the engine makes consecutive management of injectors according to an ignition order, regulates time of injection and, thereby, amount of injectable fuel.
The air necessary for formation of fuel mix is sucked in by the engine via the air filter and arrives through a butterfly valve and the inlet pipeline to inlet valves. The amount of the soaked-up air is regulated by a butterfly valve which moves the step electric motor operated by the engine control unit. At turbocharged engines the soaked-up air compresses the turbocompressor set in motion by exhaust gases of system of release. Then compressed air is cooled in a cooler of the forced air and comes to the engine for formation of fuel mix.
The volume of the soaked-up air is defined by the measuring instrument of amount of air. The measuring instrument is located in the channel of the soaked-up air. In the case of the measuring instrument the thin, electrically warmed touch plate cooled by the passing stream of the soaked-up air is located. The electric current heating a plate is regulated by a control system so that to maintain constant plate temperature. If, for example, the amount of the soaked-up air increases, temperature of the heated plate starts decreasing. Thus the size of electric current at once increases to keep temperature of a plate invariable. Fluctuations of electric current of a plate indicate to the control unit of the engine its condition of loading that allows to define amount of injectable fuel correctly.
The control unit defines optimum time of ignition, the moment of injection and amount of injectable fuel. Thus there is a coordination of operation of the control unit with other systems of the car, for example, to management of a transmission or anticreeping system.
Information from other sensors and the operating tension arriving to executive bodies ensures optimum functioning of the engine in any situation. If some sensors fail, the control unit switches in the mode of the emergency program to exclude possible damage of the engine and to provide the further movement of the car. In this case the engine works unevenly and at increase in gas has tendency to a stop.
Sensors and executive mechanisms of system of injection
The sensor of provision of a cranked shaft will be screwed in the block of cylinders at a flywheel. He transfers to the control unit information on number of turns of the engine and position VMT of the piston of the first cylinder.
The sensor of provision of a camshaft is located in an end face of a cover of a head of cylinders. He together with the sensor of provision of a cranked shaft transfers to the control unit information on VMT of the piston of the first cylinder. It serves for synchronization of the moment of ignition and sequence of ignition.
The potentiometer of a butterfly valve is located in the executive mechanism of a butterfly valve and gives the control unit information on the current coal of provision of a butterfly valve. The second potentiometer gives the control unit information on basic value and forms a spare signal at failure of a potentiometer of a butterfly valve.
The sensor of a pedal of an accelerator is located the region of an arrangement of feet of the driver directly on a pedal axis. He gives the control unit information on the provision of a pedal. For reliability reasons from the sensor of a pedal the duplicating signal, just as from a potentiometer of a butterfly valve arrives.
Sensors of temperature of cooling liquid it is located in the thermostat case. It represents the resistor with negative temperature coefficient which resistance decreases with growth of temperature.
The sensor of temperature of the soaked-up air also represents the NTC resistor.
The system of ventilation of a fuel tank consists of an adsorber and the electromagnetic valve. In an adsorber fuel couples which are formed as a result of fuel heating accumulate. During the operation of the engine of couple are sucked away from an adsorber and move in engine combustion chambers.
Lambda probes (oxygen sensors) measure the content of oxygen in the fulfilled gases before and after the catalytic converter and transmit the corresponding signals to the control unit of the engine. One lambda probe another is located before, and after the catalytic converter.
The sensor of a detonation will be screwed sideways in the block of cylinders. It interferes with emergence of dangerous shock combustion of fuel mix. Thanks to it the moment of ignition can keep on detonation border that provides effective use of energy of combustion of fuel and by that reduces fuel consumption.
The switched inlet pipeline (the engine of 2.0 l of ALT)
The necessary characteristic of power and torque is reached by means of the two-level switched inlet pipeline. Thus switching of the pipeline with short on the long happens in the range of turns of 2.000 - 3.700 in the min. The switching roller dividing certain inlet canals by means of elastic sealing rings and sealing levels opens the soaking-up path. Switching between provisions of a torque and power happens electric air (depending on loading, number of turns and temperature) (address to illustrations below).
Instead of the ordinary drive of gas on a pedal of gas there is a sensor of provision of a pedal (an illustration lower) which transfers to the control unit of the engine information on the provision of a pedal. On the basis of the received information the control unit via the electric motor operates the provision of a butterfly valve.
In the case of the sensor of situation there are two contact potentiometers which are fixed on the general to a shaft. At each change of provision of a pedal resistance of potentiometers and tension transferred to the control unit of the engine changes.
At failure of any sensor the lamp of malfunction of the drive of gas lights up and in memory of malfunctions of the control unit damage is registered. If both sensors fail, the engine works with the raised number of turns and does not react to a gas pedal any more.
The block of the drive of a butterfly valve (address to an illustration below) turns on in the structure the electric motor, two potentiometers and system of cogwheels with a returnable spring. It regulates the provision of a butterfly valve. A problem of the control unit is stabilization of turns of idling, irrespective of connection of additional consumers, such as, of the power steering or the compressor of the conditioner.
The potentiometer of a butterfly valve is at a shaft of a butterfly valve and transfers to the control unit the current information on coal of position of the gate. The second potentiometer transfers to the control unit information on basic value and provides a spare signal at failure of a potentiometer.