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
+ Coupling
+ Transmission and transmission
+ Suspension bracket and steering
+ Brake system
+ Anti-blocking system of brakes
+ Wheels and tires
+ Body electrical system
- System of ignition
   Various systems of ignition
   Principle of work of ignition
   Executive body
   System "brain"
   Impulses for the control unit
   Regulation on a detonation
   Security measures during the work with system of ignition
   Repair of system of ignition
   Diagnostics of system of ignition
   Ignition distributor
   Sensor of detonation combustion
   Elements of high voltage
   Replacement of spark plugs
   Spark plugs
   Check of the moment of ignition
+ Lighting
+ Signaling devices
+ Devices and auxiliary devices
+ Heating and ventilation
+ Body elements
+ Search of malfunctions
+ Specifications





Impulses for the control unit

The open distributor of ignition (on the example of the 4-cylinder engine):

1 – Hall's sensor;
2 – zamykatel;
3 – connecting plug of the sensor of Hall.


Hall's sensor is located at the 6-cylinder engine far behind behind the left head of the block of cylinders:

1 – case of the sensor of Hall;
2 – connecting plug.

Hall's sensor

The inclusion mentioned in the last section and switching off of current to the coil of ignition is provided (passing also through the control unit and the electronic switchboard – about it below) with the sensor of Hall which is located at models with 4-and 5-cylinder engines in the ignition distributor, and at models with 6-cylinder engines behind at the left head of the block of cylinders.

Its name has nothing in common with big halls, etc., and is connected with a name of an opener of effect of Hall used during the operation of this sensor.

Hall's sensor is located below in the case of the distributor and consists of the following elements: a zamykatel (trigger) with 4, 5 or 6 dredging (depending on number of cylinders), a permanent magnet and actually integrated circuit of Hall located opposite to it. Everything together functions approximately as the photorelay, but here instead of light magnetic waves work.

It will become completely evident if we imagine an automatic door of the elevator. If you get up in an aperture and will interrupt a ray of light, the door of the elevator remains open. As soon as you departed and opened to light the road, the door mechanism receives the order on closing.

Let's return to system of ignition: if in magnetic field there is a plate of a zamykatel, then Hall's sensor passes current to the control unit. If the plate leaves a gap between the integrated circuit of Hall and a permanent magnet, then food to the control unit does not arrive. It is also the impulses operating ignition.

 Hint: dredging in a zamykatel of the distributor is located in such a way that the impulse of a high-tension current, for example, at the 4-cylinder engine, gets to the control unit for 60 ° to VMT. During this time the control unit counts the optimum moment of ignition on the basis of information on engine speed (by means of the sequence of impulses of a high-tension current) and loads of the engine (by means of indicators of resistance of a flowmeter of air, a potentiometer of a butterfly valve or the sensor of pressure in an inlet collector).

Sensor of speed of the engine and sensor of the moment of ignition

Models with 6-cylinder engines

In addition to Hall's sensor 6-cylinder engines are equipped with the sensor of number of turns/frequency of rotation of the engine and the sensor of the moment of ignition. Both are so-called inductive sensors.

The sensor of frequency of rotation works as follows: in the sensor there are a coil and a magnet. They are supplemented by gear inflows on a flywheel behind on a bent shaft. Every time when under the sensor there passes the tooth, magnetic field of a permanent magnet changes, and in the coil tension is created. This small signal is enough for processing in the control unit of systems of injection MPI/MPFI. Thus information on the speed of a bent shaft arrives.

To record the exact provision of a bent shaft, on one certain place of a flywheel the steel pin was established. If it passes under the sensor, there is tension peak which the control unit uses for definition of situation.








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