Audi 80/Avant (B4)

since 1991-1995 of release

Repair and car operation

Except engines of 66 kW

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

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

Principle of action of regulation on a detonation

Combustion in cylinders is supervised 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 non-uniform fluctuations instead of the usual uniform. It transfers this information further to the control unit.

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

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

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

This process proceeds until initially planned moment of ignition or while the sensor again will not report about detonation combustion will be reached.

Sensor of detonation combustion

The slice is inserted into this sensor пьезокерамики, a material with which we are familiar on lighters (gives out a spark). Mechanical forces (stretching, compression), influencing on пьезокерамику, are transformed by it to electric tension. – arising because of detonation combustion – it is enough non-uniform fluctuations for sensor activation. Important: the moment of an inhaling of the sensor of detonation combustion should make precisely 20 N • m.