Distributor Ignition (DI) System EZ 116 K
Design and function
Distributor ignition (DI) system EZ 116 K
The DI system can be divided into five sub-systems.
^ The sensor system sends information to the control system required to achieve optimum control of the ignition.
^ The control system ensures that optimum ignition timing and ignition voltage are obtained for each ignition.
^ The high tension system produces and distributes high tension voltage.
^ The on-board diagnostic (OBD) system has three test functions to facilitate fault tracing. The OBD system works commonly for the fuel system, the TC control system and the DI system.
^ The EGR system reduces the emission of nitrogen oxides.
Sensor system
Coolant Temperature Sensor:
Engine coolant temperature (ECT) sensor
The DI system uses the same ECT sensor as the MFI system. The ECT sensor has two NTC resistors, one for each system.
Throttle position (TP) switch
The ignition system uses the same TP switch as the fuel system. However, the DI system only uses the idle switch.
RPM sensor
The RPM sensor provides the control module with information about engine speed and crankshaft position (CKP) and is the most Important of the sensor signals. Without it the control module cannot give a signal to the power stage/ignition coil and the engine cannot be started.
When the holes in the flywheel pass the sensor a magnetic field is modified producing a sine wave signal. As there are no holes In two places on the flywheel the control unit can read its position in relation to tdc. By measuring the time between two voltage peaks the control module can compute engine speed.
Knock sensor (KS)
The KS consists of a piezoelectric crystal sensitive to the vibrations in the engine block caused by engine knock.
Control system
Ignition timing control
The DI control module computes ignition timing twice per revolution, once per ignition. It bases the basic ignition timing on engine speed and the load signal from the MFI control module.
Under certain conditions the control module then adjusts the basic ignition timing to provide for optimum combustion and operation.
- When the car is being started ignition timing is only dependent on engine speed and engine temperature.
- When the engine is idling ignition timing is only dependent on engine speed.
- At temperatures below 55°C (131°F) ignition is retarded as a function of temperature.
- At temperatures below 60°C (140°F) no account is taken of the KS signal.
- If the engine is over-revving the control module uses the power stage to provide a spark only to every other spark plug so that engine power is reduced.
Ignition voltage control
The control module controls the ignition voltage so that it is independent of battery voltage and engine speed. At low voltage the control module sends a signal to the power stage to start charging earlier thereby extending charging time.
Emergency program
The control module has a reversible limp-home mode. This means that If a signal returns to a reasonable value after It has been faulty, the control module will utilize this value again rather than remaining in limp-home mode.
- If there is no signal from the KS the ignition is retarded approx. 10°.
- If there is no load signal from MFI, ignition timing is calculated for full load except when the TP switch indicates that the engine is idling.
- If there is no engine temperature signal, ignition timing is based on the engine being warm.
- If there is no TP signal, the control module takes account of load when the engine is idling.
Load information
The DI system receives information about load from the MFI control module. When load is high and fuel/air consumption high, the ignition is retarded. If engine load changes rapidly the ignition is retarded significantly on all cylinders to prevent knocking.
Knock control
If one of the cylinders begins to knock the ignition is retarded for that cylinder until the knocking ceases. When the knocking stops the ignition is advanced by degrees. The rate of advance is dependent on engine speed. This rate is faster at low engine speeds and slower at high speeds.
Adaptive knock control
If the engine is under heavy load for a long period the ignition will often be retarded by the knock control. To prevent knocking this will cause the control module to retard the ignition by 10 on all cylinders for as long as the engine is under abnormal load.
High-tension system
The high-tension system consists of the power stage, ignition coil, distributor and spark plugs.
The power stage closes, breaking the power through the ignition coil primary coil. When the primary coil current is interrupted a high-tension voltage of 30-35 kV is generated in the secondary coil.
This high-tension voltage is transmitted to the distributor.
The distributor then distributes this voltage to the spark plugs via the ignition leads.
Exhaust Gas Recirculation (EGR) system
In certain markets cars are equipped with an EGR system which reduces emissions of nitrogen oxides (NOx) in the exhaust gases. The EGR system recycles some of the exhaust gases into the combustion chamber at high engine loads. This reduces combustion temperature, resulting in a reduction in NOx.
The EGR valve
The EGR valve controls the flow of gases from the exhaust manifold to the Intake manifold. This valve is controlled by a vacuum in the vacuum hose from the vacuum regulator.
The EGR vacuum controller
The EGR vacuum controller controls the vacuum to the EGR valve from the output at the base of the controller (yellow hose). The vacuum from the intake manifold is fed into the upper section of the vacuum controller (white hose). The EGR vacuum controller stabilizes the vacuum in the Intake manifold and converts the electrical signal from the control module into a modulated vacuum signal to control the EGR valve.
Temperature sensor, EGR
The temperature sensor measures the temperature of the recirculated exhaust gases. The control module can monitor the operation of the EGR system by monitoring temperature variations.
There are two types of temperature sensor, PTC sensors on earlier models and NTC sensors on 1992 models.
The resistance of the PTC sensor Increases with temperature.
The resistance of the NTC sensor decreases with increasing temperature.
The upper EGR pipe
The upper EGR pipe transports the recirculated exhaust gases from the EGR valve to the intake manifold.