15.5. Engine electric equipment
The control system of detonation combustion of fuel of models with a turbo-supercharging
Too early ignition and operation of the engine on fuel with low octane number are the reasons of detonation combustion of fuel. The detonation occurs when the speed of distribution of a flame in the combustion chamber approaches sound speed, generally closer to the end of combustion process, residual gases are strongly compressed and have high temperature. The detonation is characterized by very high pulse pressure which leads to an engine overheat, damage of the piston, a head of the block of cylinders and inserts of bearings of a bent shaft.
Nevertheless during the operation of the engine with the maximum load the moment of ignition has to be displaced to the earliest without crossing of the border of detonation combustion of fuel.
Fig. 15.49. Elements of the control system of detonation combustion of fuel of cars 1986 and 1987 of years of release: 1 – ignition coil; 2 – ignition distributor; 3 – control unit;
4 – diagnostic socket; 5 – detonation sensor; 6 – control unit of ignition
The control system of detonation combustion of fuel consists of the sensor of a detonation, the control unit of a corner of an advancing of ignition and the EGI control unit (fig. 15.49). The sensor of a detonation reacts to the high-frequency fluctuations of the block of cylinders arising at a detonation and transforms them to the electric signals arriving on the control unit. This information then is compared to the signals received during combustion of fuel without detonation. At emergence of a detonation the moment of ignition is displaced towards delay on 6 °.
With a frequency of rotation of a bent shaft of the mines-1 engine 1650-4500 or under conditions when pressure in an inlet collector is lower atmospheric, the control unit of the engine gives a signal which provides ignition moment shift of earlier aside on the control unit of ignition.
The procedure for test given below extends only to models 1986 and 1987 of years of release as at service of cars of later releases the special equipment therefore it is necessary to address on service station is required.
Check of the sensor of a detonation
Carefully concern the probe of the voltmeter of a conclusion "1U" on the control unit. Idling tension shown by the voltmeter has to be equal to zero. If the indication differs, check a wire from the control unit to the control unit of an ignition advancing corner (contact of "G").
Check installation of a corner of an advancing of ignition idling, then disconnect the diagnostic socket from the control unit. Slightly knock with the hammer on a wall of a receiver and check whether the ignition moment aside later is displaced. If the moment of ignition is displaced to later, connect the socket and again knock on a receiver wall. Make sure that ignition is not displaced to later that demonstrates normal operation of the control unit of ignition. Otherwise the control unit is faulty and it needs to be replaced.
If at the first test the moment of ignition is not displaced to later, disconnect the diagnostic socket, connect obviously serviceable sensor of a detonation to the socket and connect it to "weight". Slightly knock on the sensor and check ignition moment shift to later ignition. If ignition is displaced to later, the working sensor is faulty. Otherwise check wires from the sensor to the control unit. If wires as it should be, replace the control unit of ignition.
Replacement of elements
For replacement of the sensor of a detonation disconnect the socket and turn out the sensor from the block of cylinders. Installation is carried out to the sequences, the return to removal.
For replacement of the control unit of ignition disconnect a wire from the negative plug of the rechargeable battery. Disconnect the socket from the block, turn off two nuts and remove the block. Installation is carried out to the sequences, the return to removal.