Audi 80/Avant (B4)
since 1991-1995 of release
Repair and car operation
+ Technical specification
+ System of production of the fulfilled gases
+ cooling System
+ Fuel tank and fuel pump
+ Air filter and airintaking channels
- Injection system
+ System of injection of Mono-Motronic
+ System of injection of Digifant
+ System of injection of KE-III-Jetronic
- Systems of injection of MPI and MPFI
Malfunctions and independent diagnostics
Check of separate elements
Removal of elements
Hummock drive of "gas"
Check of a mode of idling and analysis of exhaust gases
List of malfunctions
+ Transmission and transmission
+ Suspension bracket and steering
+ Brake system
+ Anti-blocking system of brakes
+ Wheels and tires
+ Body electrosystem
+ ignition System
+ Signalling devices
+ Devices and auxiliary devices
+ Heating and ventilation
+ body Elements
+ Search of malfunctions
Systems of injection of MPI and MPFI
Cхема in detail shows ignition and injection system on a MPFI system example with the pressure sensor in an inlet collector. On the left side sensors and the sensors influencing behavior of the control unit are located. On the right components of systems of ignition and injection to which the control unit sends the teams are presented.
Cистема of injection of MPI/MPFI with т.з. supply of fuel
Electronics helps to constrain a few "appetites" of the engine even the most powerful Audi 80 version. However, at more than probable fuel consumption over 12 l on 100 km not always it is possible to be quite convinced that this good intention is carried out. But nevertheless follows that high engine capacity justifies this extra charge for high high-speed qualities of the car.
The 2,8-liter engine is supplied with injection system with MPI designation. Behind this reduction the English words Multi Point Injection – in Russian «multipoint injection» disappear. (The distinctive sign of system of injection of MPI is a flowmeter of air in an air inlet sleeve behind on the right in a motor compartment).
For the best understanding of the general functioning of this system of injection it is necessary to get acquainted with separate problems of components at first.
Between arriving (from various sensors) the control unit is information and vpryskny nozzles. He allows the engine, depending on operating conditions of loading and temperature, to receive precisely certain amount of fuel. For achievement of it the control unit varies duration of opening of nozzles with an electromagnetic drive. As pressure in system of supply of fuel constantly remains almost invariable, the amount of injected fuel can be regulated only by means of change of duration of injection. From where the control unit receives information according to which he establishes this duration of injection? For it various sensors answer:
Vprysknye of a nozzle
In an inlet collector of each cylinder of the engine is on one vpryskny nozzle. They deliver to the corresponding cylinder amount of fuel necessary at present and at the same time provide thin dispersion of gasoline.
It is intended for uniform supply by fuel of all vpryskny nozzles. Besides, the distributor of fuel operates and as the fuel store, thereby preventing pressure differences. The U-shaped form of the pipe, allowing a fuel supply to all six nozzles is very interesting.
Regulator of pressure of supply of fuel
It is located behind on the right on the distributor of fuel and should – according to the name – to support constant level of pressure in the fuel distributor. It is carried out by means of more or less strong outflow of fuel back in a fuel tank on the drain highway. If on the drain highway more fuel leaves, pressure decreases; if it is less – pressure raises.
Fuel pump and relay
In more detail about the electromagnetic fuel pump, the relay of the fuel pump and other MPI/MPFI relays you learn the Fuel tank and the fuel pump in head.
On a way of a stream of soaked-up air there is a wire which is warmed up electricly. Depending on the let-in quantity the air stream changes that leads to more or less strong cooling of the mentioned wire. Change of temperature leads to change of electric resistance of a wire which is measured by the control unit.
The pressure sensor in an inlet collector
The pressure sensor in an inlet collector is in the MPFI control unit. Connection between an inlet collector and the sensor represents a thin hose. Pressure in an inlet collector is for the control unit information front view for calculation of loading of the engine. It influences duration of injection and the ignition moment.
Sensor of temperature of inlet air
The sensor of temperature of inlet air is screwed in in the inlet channel of the third cylinder (behind on the right). In addition to the pressure sensor in an inlet collector it is for the control unit an inofrmatsiya source for calculation of load of the engine. At high temperature of inlet air (that is equivalent low density of air) it is necessary to reduce, for example, duration of injection and to shift the ignition moment aside "later" a little.
Case of throttle knot
Where the stream of soaked-up air gets to an inlet collector of the engine, in one case there are two butterfly valves. Smaller from a zaslonok it is connected by means of a hummock drive to an accelerator pedal. It doses out a stream of inlet air in the engine before situation by a loading half. By further pressing an accelerator pedal the lever of draft opens the second, big zaslonka until in the provision of full loading there are no completely open both zaslonka.
Butterfly valve potentiometer
The potentiometer of a butterfly valve is put in action by the butterfly valve roller. The potentiometer defines the provision of a butterfly valve at present time and hands over to the control unit this information in the form of electric resistance. The control unit needs this information on loading, for example, for regulation of frequency of rotation in a mode of idling, a choice of the characteristic of ignition and calculation of duration of injection.
Valve of stabilization of frequency of idling
As it is already clear according to the name, this valve constantly provides constant frequency of rotation of a shaft of the engine in an idling mode – all the same, whether the engine is cold or heated-up, are included or not powerful consumers of the electric power such as the conditioner.