Audi 80/Avant (B4)

since 1991-1995 release

Repair and operation of the car

Audi 80/Avant
+ Technical specification
+ Engines
+ System of production of the fulfilled gases
+ Cooling system
+ Fuel tank and fuel pump
+ Air filter and airintaking channels
- System of injection
   + System of injection of Mono-Motronic
   - System of injection of Digifant
      Operating procedure
      Malfunctions and independent diagnostics
      Independent repair
      Visual check
      Check of separate elements
      Removal of vpryskny nozzles
      Check of the mode of idling and analysis of exhaust gases
      List of malfunctions
   + System of injection of KE-III-Jetronic
   + Systems of injection of MPI and MPFI
+ Coupling
+ Transmission and transmission
+ Suspension bracket and steering
+ Brake system
+ Anti-blocking system of brakes
+ Wheels and tires
+ Body electrical system
+ System of ignition
+ Lighting
+ Signalling devices
+ Devices and auxiliary devices
+ Heating and ventilation
+ body Elements
+ Search of malfunctions
+ Specifications

Operating procedure

Cold start: the valve of stabilization of idling allows to let in an air quantity in addition to the air arriving in the regular way. At the same time the control unit receives from the sensor of temperature of cooling liquid information "the cold engine". On the basis of all these data the control unit counts long opening of vpryskny nozzles for preparation of richer mix. Besides, for a short time the control unit activates the starting valve for receipt of an additional portion of fuel.

Phase of warming up of the engine: the sensor of temperature of cooling liquid reports the increasing temperature of cooling liquid further to the control unit. That in turn makes the order about closing of the valve of stabilization of idling, fuel supply duration nozzles decreases to the usual.

Idling: from messages of a potentiometer of a butterfly valve and potentiometer on an air flowmeter the control unit distinguishes when the engine works in the idling mode. If rotation frequency in the mode of idling falls, the control unit changes the ignition moment; at the same time the idling stabilization valve thanks to what the amount of injectable fuel increases opens the air channel.

Normal operation does not demand any special adaptations. Duration of opening of vpryskny nozzles is defined by the provision of a butterfly valve and valvate lock in an air flowmeter.

Acceleration: fast opening of a butterfly valve distinguishes a monitor according to messages of a potentiometer of a butterfly valve as acceleration. Injection respectively duration for a short time increases.

Lambda regulation: continuous change of the enriched or grown poor mix is necessary for catalytic converter for excellent job. At present time the lambda probe (it is located in catalytic converter) retells the matter of residual oxygen to the control unit which gives to fractions of a second to vpryskny nozzles the order on shorter or more long time of injection and, thereby, amount of fuel.

Interruption in supply of fuel in the mode of compulsory idling: information on removal of a foot from an accelerator pedal again gets through a potentiometer of a butterfly valve to the control unit. If at the same time the sensor of temperature of cooling liquid reports that the engine reached the working temperature, and the Hall sensor in the distributor reports that the frequency of rotation of the engine makes more than 1500 rpm, the control unit does not give the order on opening of vpryskny nozzles.

Full loading: for development of full capacity at completely squeezed out accelerator pedal the engine needs more fuel. On the basis of the message "full gas" from a potentiometer of a butterfly valve in combination with completely open valvate lock the control unit distinguishes a condition of "full loading" and increases duration of injection of nozzles, and the signal a lambda probe thus is ignored.

Restriction of frequency of rotation: for protection against excess of the most admissible frequency of rotation of a shaft of the engine the control unit disconnects vpryskny nozzles if the sensor of the Hall reports about the frequency of rotation of 6400 - 6500 rpm.

Work at state of emergency: if the signal from one of suppliers of information does not come absolutely or the senseless indicator, system of injection of Digifant has and in these conditions is not beaten out from the normal course of work. The control unit chooses the so-called spare indicator which is already written down in memory. It, of course, cannot consider many service conditions, but the car after all remains under way. The driver can distinguish lack of a signal from the sensor on the insufficient power or bad starting properties.