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

Regulation on a detonation

Except engines of 66 kW

The detonation combustion arising if the moment of ignition was too far moved towards "an ignition advancing", harms the engine. The overheat, damage of bearings and pistons are a consequence of it.

But the engine works with the maximum power if "early ignition" is established as much as possible that is if the engine works at a detonation side. This border of a detonation is caused by many factors (quality of fuel, adjournment on walls of combustion chambers, etc.) so it cannot be recorded precisely. Therefore usually the bigger "interval of safety" is necessary for regulation of ignition. Or "sentry" who defines whether detonation combustion – regulation on a detonation takes place.

The principle of action of regulation on a detonation

Combustion in cylinders is controlled by the so-called sensor of detonation combustion which is located at models with 4-and 5-cylinder engines at the left on the block of cylinders. Models with 6-cylinder engines are supplied with two sensors on the right and at the left above on the block of cylinders. The sensor of detonation combustion "feels" if at combustion in the cylinder there are uneven fluctuations instead of usual uniform. He transfers this information further to the control unit.

There is a following: with receipt of a signal "the detonating combustion at the last ignition" the following cylinders with normal combustion receive a spark still at the ignition moment calculated earlier. But at that cylinder in which the detonation was installed the moment of ignition is displaced approximately on 3 °. And it occurs, it is necessary to notice, only at this only cylinder. All others work as before.

If detonation combustion in the specified cylinder still remains, then at the following working step the moment of ignition is displaced for 3 °. It is already possible to regulate to at most 15 ° (calculated from the standard moment of ignition).

If in the corresponding cylinder now combustion proceeds normally, then after a while the ignition moment moves in the direction of "early ignition" again. Adjustment happens on 0,5 °, the break during many working steps before there is a repeated adjustment for 0,5 ° in the direction of "early ignition" follows then.

This process continues until initially planned moment of ignition is reached or so far the sensor will not report about detonation combustion again.

Sensor of detonation combustion

He "listens" whether he is not present in detonations: the sensor of detonation combustion (shooter) at the 85 kW 4-cylinder engine (at the left) and at the 5-cylinder engine is located on the left side of the engine. Models with the 6-cylinder engine (on the right) have two sensors of detonation combustion: on one on the right and at the left above under a final collector. Important: the fixing bolt of the sensor of detonation combustion has to be tightened precisely by the moment of 20 N • m, otherwise the sensor does not work.

The piece of a pyezokeramika, material with which we are familiar on lighters is inserted into this sensor (gives a spark). Mechanical forces (stretching, compression) influencing a pyezokeramika are transformed by it to voltage. Uneven fluctuations – arising because of detonation combustion – are enough for activation of a sensor. Important: the moment of an inhaling of the sensor of detonation combustion has to make precisely 20 N • m.