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
+ Coupling
+ Transmission and main transfer
+ Suspension bracket of wheels and steering
+ Brakes
+ Wheels and tires
+ Electrotechnical equipment
- Ignition system
   That provides ignition
   When there is an ignition of a fuel and air mix?
   Different systems of ignition
   So there is an ignition spark
   Executive body
   System brain
   The signals arriving in the control unit
   Detonation adjustment
   Be careful in the address with ignition
   Works on ignition system
   Search of malfunctions in ignition
   Ignition distributor
   Knot of a high voltage
   Replacement of spark plugs
   Right choice of spark plugs
   Check of the moment of ignition
+ Lighting
+ Alarm equipment
+ Tools and devices
+ Heating and ventilation
+ body Details
+ Salon
Search of malfunctions
Technical characteristics





When there is an ignition of a fuel and air mix?

Drawing illustrates concept «Top dead point» and «Bottom a dead point». The space between them is working volume of the cylinder. On the contrary, between the highest position of the piston (2) and bottom edge of a head of the block of cylinders (1) the combustion chamber is shown.


Basic element of system of ignition of the four-cylinder engine with working volume of 1,6 l is the separate coil of ignition (1) and the terminal cascade (3) with the socket (2). Distribution of tension of ignition on cylinders here carries out the ignition distributor.


Package of coils of ignition of the six-cylinder engine with the removed cover of the engine (static distribution of ignition). Figures on sockets of a high voltage explain, to what cylinder there is a wire.


In the engine of 1,8 l in capacity of 92 kW the ignition coil on the cylinder 3 serves also the cylinder 1, and the ignition coil on the cylinder 4 – also the cylinder 2. Above on coils of ignition the terminal cascade is established.


Ignition of a turbodvigatel of 1,8 l in capacity of 110 kW: each cylinder has an own coil of ignition (1–4).

The spark should slip in the combustion chamber at the right time. Combustion of a fuel and air mix occurs most effectively while it is compressed to the most minimum volume. This maximum compression is reached during that instant when the piston at end of a course of compression wants to pass from progress to return movement of a working step. Before the piston passes to movement in the opposite direction, a share of an instant it is in the highest point of a trajectory of the movement. This point is called «the top dead point» by (VMT).

So, the ideal moment of ignition is that moment when the piston only begins the return movement. The compression maximum, and the piston can be wrung out with force to the engine block.

Despite it, would be wrong to establish the moment of ignition precisely in the top dead point. As the fuel and air mix needs certain time (about 1/3000 c) before its ignition and development of a total pressure of combustion. Therefore the moment of ignition is established for earlier term. We speak about «an ignition advancing». Therefore the starting shot for a spark sounds even during piston movement up, and pressure of combustion develops right after VMT.

Top dead point and ignition advancing

With increase in number of turns of the engine the spark of ignition should slip everything earlier since – as it was already told – the fuel and air mix always needs the same time for ignition. Combustion process precisely in due time namely when the piston again only starts to move back is only this way carried out. Combustion of a fuel and air mix depends also on its structure. At slightly wrung out pedal of gas (at «partial loading») the mix in chambers of combustion possesses the lowered ability to ignition therefore it burns down more slowly and for this reason ignition too should work with a big advancing.

Ignition installation with delay

In other situations it is necessary to shift the ignition moment in the delays direction. Ignition occurs when the piston passed for a long time the top dead point. I.e. ignition is carried out almost on an exhaust step that improves composition of exhaust gases, but worsens engine capacity. Therefore, late ignition can be correct when the engine works without loading in a mode of a kacheniye of the car (for example, downhill without gas).