Audi A4

since 1994 release

Repair and operation of the car

A4 Audi
+ Running gear
+ Regular servicing
+ Engines
- Turbo-supercharging
   Draft switching off valve
   Check of adjustment of pressure of pressurization
   The help at malfunctions
   The turbocompressor is faulty?
   Radiator of nadduvochny air
+ System of an exhaust
+ Cooling system
+ Fuel tank and fuel pump
+ Air filter and channels of absorption
+ System of injection
+ Coupling
+ Transmission and main transfer
+ Suspension bracket of wheels and steering
+ Brakes
+ Wheels and tires
+ Electrotechnical equipment
+ System of ignition
+ Lighting
+ Alarm equipment
+ Tools and devices
+ Heating and ventilation
+ body Details
+ Salon
Search of malfunctions
Technical characteristics


Generally the turbocompressor consists of two bladed wheels located on one shaft. By means of one of them exhaust gases of the engine are removed, depending on the frequency of rotation of the engine it brings a shaft into more or less fast rotation. The related second bladed wheel, certainly, rotates together with it and soaks up air in combustion chambers, but now under pressure.

At bigger intake of air also supply of gasoline for providing the correct composition of working mix increases.

At the left in a motive compartment of the turbo engine with a power of 110 kW you see a radiator of nadduvochny air (1) and a thick air hose (2) from a turbocompressor to a radiator of nadduvochny air.

Turbocompressor model in a section

1 – a bladed wheel on the party of an exit of exhaust gases;
2 – turbo-supercharging shaft;

3 – a bladed wheel on the party of absorption;
4 – vacuum box of the regulator of a turbo-supercharging.

Adjustment of pressure of pressurization

The chosen constructive data of a turbocompressor possess pleasant property to give nadduvochny air to cylinders even at rather low turns of the engine. From this it follows that at high turns too large amount of air can be represented. Pressure in system of pressurization could rise to such level which would be harmful to durability of the engine.

Not to allow it is business of the regulator of pressure of pressurization. By opening of the valve it provides passing only to part of exhaust gases through a bladed wheel of the supercharger. As a result of it pressurization power decreases, and pressure cannot exceed the maximum size.

Rigid adjustment in this case is inadmissible as in some road situations that is necessary more, there is less than air. Therefore the Motronic control unit has impact on adjustment of pressure of pressurization. The electric air valve, "the electromagnetic valve of restriction of pressure of pressurization", by means of a vacuum box operates the bypass channel of pressurization (the valve of adjustment of pressure of pressurization). When bypass the channel opens, pressure of pressurization goes down.

Height sensor (an installation site is connected to the Motronic control unit: the electronic block in a motive compartment). Thanks to it adjustment of pressure of pressurization is able to level change of density of air at trips in the mountain district.

More rarefied air at the same offer of power ( i.e. at the same amount of injectable fuel) would cause glut of fuel and air mix. It is not allowed at the expense of a raising of pressure of pressurization and, therefore, the strengthened air supply.

Therefore the engine capacity and composition of exhaust gases at the turbo engine remain constants under any traffic conditions.