Audi A4

since 1994 of release

Repair and car operation

A4 Audi
+ Running gear
+ Regular servicing
+ Engines
+ Turbo-supercharging
+ exhaust System
+ cooling System
+ Fuel tank and fuel pump
+ Air filter and absorption channels
- Injection system
   + System of injection of Motronic
   - System of injection of MPI and MPFI
      Additional functions
      Knots of system of injection
      Adjustment with the help a lambda probe
      Violations in work and self-diagnostics
      Visual control
      Check of knots
      Dismantle of separate details
      Butterfly valve cable
      Inlet collector
      Idling adjustment
      Check of exhaust gases
      The help at malfunctions
+ Coupling
+ Transmission and main transfer
+ Suspension bracket of wheels and steering
+ Brakes
+ Wheels and tires
+ Electrotechnical equipment
+ ignition System
+ Lighting
+ Alarm equipment
+ Tools and devices
+ Heating and ventilation
+ body Details
+ Salon
Search of malfunctions
Technical characteristics


The coordinated work of separate details

When the engine works, pistons rising and falling in cylinders soak up air. If you completely wring out a gas pedal, the engine soaks up the maximum quantity of air as in this case both butterfly valves are completely open. It is necessary for a neat job of the engine, that with soaked-up air fuel in an exact proportion mixed up. For definition of a proportion of air and gasoline in a working mix in MPI the mass of soaked-up air is used. In MPFI in comparative size information on pressure serves in an inlet collector and temperature.

Now the control unit can submit the correct signals for opening and closing of valves of injection. Long opening is provided for big amount of fuel, short time — at need for a small amount of fuel.


For start of the cold engine more saturated is necessary, i.e. the working mix rich with fuel as the set of droplets of fuel settles on walls in the field of absorption for their way to chambers of combustion and does not participate any more in combustion process. Therefore the share of fuel in a fuel and air mix should be raised.

During management of start of the cold engine duration of injection by valves increases. Such factors as the temperature of cooling liquid and frequency of rotation of the engine, influence duration of injection. After a certain number of turns of the engine the amount of the fuel necessary for start of the cold engine, slowly decreases and starts to correspond to the standard.

Heated-up engine

After start some time the enriched working mix as still certain amount of fuel is condensed in the field of absorption is necessary to the engine. For this purpose there is «a poststarting increase». Depending on temperature some time moves more fuel. The control unit receives the necessary information on engine temperature from the sensor of temperature of cooling liquid.

Engine oil, quite viscous at the cold engine, causes the raised internal friction in the car. The increased effort to hold engine turns is necessary. Already mentioned valve of stabilization of idling is intended for ensuring giving of this increased quantity of a working mix.


At the closed butterfly valve through roundabout the channel round a butterfly valve is carried out a small amount of air. This air is fixed by a measuring instrument of a stream of air, or a pressure sensor and consequently in a working mix for idling it is supplemented with necessary amount of fuel. As a whole the working mix idling contains more gasoline, than at usual operation in order that the engine worked exactly and trouble-free in ignition.

The amount of the air, passing the roundabout channel (and, therefore, number of turns of the engine idling), is defined by the valve of stabilization of idling.

Partial loading

At partial loading the engine receives standard amount of fuel. Thus value is given to fuel consumption minimization.


If the gas pedal is suddenly wrung out, the enrichment of a fuel and air mix necessary for acceleration when the gain soaked up / oh amounts/masses of air in a second exceeds a certain size is caused. As the potentiometer of a butterfly valve gives a signal about acceleration. At the cold engine accelerations need bigger amount of fuel. Therefore the control unit estimates each impulse of a measuring instrument of a stream of fresh air or a sensor of pressure and a butterfly valve potentiometer as a signal about acceleration and increases supply of fuel.

Full loading

The potentiometer of a butterfly valve shows to the control unit that the driver completely wrung out a gas pedal. To develop the maximum capacity, the engine receives now more enriched working mix (enrichment of a working mix at full loading).

Mode of compulsory idling

At movement downhill with the released pedal of gas it is not necessary to submit fuel to the engine. The car itself slides at the expense of weight or dispersal. On high turns of the engine and the provision of a butterfly valve (from its potentiometer) the control unit learns, when there is a mode of compulsory idling, and can «save fuel».

Restriction of number of turns

The system of injection compares frequency of rotation of the engine at present to the maximum number of turns in 6500 rpm and at their excess simply closes «the crane with fuel».