Audi 80/Avant (B4)

since 1991-1995 of release

Repair and car operation

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
- Injection system
   + 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 a 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 electrosystem
+ ignition System
+ Lighting
+ Signalling devices
+ Devices and auxiliary devices
+ Heating and ventilation
+ body Elements
+ Search of malfunctions
+ Specifications

System of injection of Digifant

On this illustration the system of injection of Digifant with its components is schematically presented. White shooters show a way of air, supply by fuel is presented by red color.

1–fuel tank;
2–fuel filter;
3–pressure regulator;
4–fuel distributor;

6–inlet collector;
7–air flowmeter;
8–valve of stabilization of idling;
9–fuel pump.

Multipoint injection

The injection system in which each cylinder has own vpryskny nozzle better is suitable for probably more exact distribution of a mix of fuel/air, than that in which injection is carried out by only one central nozzle. Therefore the engine in capacity of 85 Kw is supplied with the multipoint (distributed) system of injection. It is a question of elektronno operated system with the programmed characteristic of injection, with operated system of ignition, with the moment of ignition regulated on a detonation, with the integrated stabilization of frequency of rotation in a mode of idling and with fuel interruption of supply in a mode of compulsory idling.

To whom the name of this system of injection is reminded by the word "Elefant" (elephant), that is at all near from truth. Engineers-electronics engineers of Volkswagen and Audi took this name from «a white elephant» (weiber Elefant) – among programmers so call Jacks of all trades. New word-formation – Digitaler Elefant.

Basic elements

Control unit

The control unit receives via the multicontact tip the following types of information from:

  • Starter from the plug 50 – about the beginning and the completion of process of start.
  • Butterfly valve potentiometer – about the current provision of a butterfly valve.
  • The Hall sensor in the ignition distributor – about frequency of rotation of the engine.
  • Lambda probe in catalytic converter – about the content of residual oxygen in the fulfilled gases.
  • Potentiometer in an air flowmeter – about position of the retaining valve (amount of the let-in air).
  • The sensor of temperature of inlet air in an air flowmeter.
  • The sensor of temperature of cooling liquid in a branch pipe of system of cooling.
  • The sensor of detonation combustion on the block of cylinders for "detonation" combustion, see also head ignition System.

On the basis of information on frequency of rotation and loading the control unit counts duration of opening of electromagnetic vpryskny nozzles and by that injected amount of fuel. For this purpose at the disposal of the control unit there are characteristics of injection and in addition the ignition characteristic. These characteristics represent collection of data for every possible situations at operation of the engine and the corresponding amounts of fuel, and also the ignition moments. These indicators the control unit can change after receipt of so-called adjustment signals (for example temperatures of inlet air and cooling liquid).

Butterfly valve

Two butterfly valves are in a branch pipe in an inlet collector. Smaller from these a zaslonok it is connected by a cable of a drive of "gas" with a pedal in salon. It doses out a stream of inlet air in the engine. If the pedal of an accelerator is squeezed out more strongly, draft opens the second, big zaslonka, in the provision of full "gas" both zaslonka are open.

Butterfly valve potentiometer

The potentiometer of a butterfly valve covers the provision of a butterfly valve at present from "idling" (the butterfly valve is closed) to «full loading» (the butterfly valve is completely open). On the basis of its information idling stabilization, fuel interruption of supply in a mode of compulsory idling or enrichment of gas mixture at complete opening of a butterfly valve is activated.

Pressure regulator

It is located in front of the distributor of fuel and regulates pressure of supply of fuel to vpryskny nozzles. For this purpose he receives information on a depression condition in an inlet collector. At the closed butterfly valve and high depression it keeps lower pressure in an idling mode. At decrease in depression at bigger loading of the engine the regulator of pressure increases pressure of supply of fuel. The fuel pump submits fuel with more high working pressure, but thanks to a regulator of pressure of plums of gasoline back in a fuel tank respectively increases or, if necessary, decreases.


At each turn of a cranked shaft they inject gasoline in the vpryskny suited in front of the inlet valve of the corresponding cylinder – duration of this process defines the control unit. The corresponding cylinder receives one portion for emergency, and the second at the open inlet valve directly in the combustion chamber.

The sensor of temperature of arriving air

It is located sideways in a flowmeter of air and thus can precisely define temperature of arriving air. The temperature of inlet air gets to the control unit in the form of a resistance indicator. This indicator is necessary for an optimum dosage of fuel.

The sensor of temperature of cooling liquid

The temperature of cooling liquid is necessary for management of many functions of injection: enrichment of a starting mix, poststarting enrichment (on all range of temperatures), enrichment at acceleration and shutdown of supply of fuel in a mode of compulsory idling (movement nakaty). Information on temperature of cooling liquid arrives in the control unit also in the form of a resistance indicator. The control unit counts necessary duration of injection which at the engine warmed up to working temperature is in a range between two and eight milliseconds. This indicator can increase to 70 % if the temperature of cooling liquid reaches – 25°С.

Air flowmeter

The air necessary for combustion arriving from the air filter, more or less (depending on the let-in quantity) wrings out aside a klapanny lock in an air flowmeter, thus the valve of attenuation connected with a klapanny lock, prevents fluctuations of a klapanny lock. The potentiometer sends to the control unit depending on the provision of a klapanny lock a signal in the form of tension: a high voltage at complete opening and a large amount of air, small tension at small opening.

Starting fuel valve

This vpryskny nozzle with an electromagnetic drive injects in vpryskny a collector additional amount of fuel during 1 — 4 with depending on engine temperature at start. Duration of injection defines the control unit of system of injection of Digifant.

Valve of stabilization of idling

In a warming up phase, at complete turn of the amplifier of the steering mechanism, at the working conditioner or at the included step of an automatic transmission this valve releases the additional air channel, bypassing thereby a butterfly valve.

The strengthened air exchange in the direction of an inlet collector at the same time leads to strengthened supply of fuel. So the raised friction in the engine in a cold condition or higher load of the engine, caused by the pump of the amplifier of a wheel spending energy, the conditioner compressor, and also an automatic transmission is counterbalanced.

The valve of stabilization of frequency of rotation of a shaft of the engine in a mode of idling is used and in a mode of compulsory idling. He allows to arrive to amount of air necessary for movement at the closed butterfly valve.