DIS ignition system

The cars manufactured in the 90's and 00's can be equipped by double ignition system. These systems use an ignition coils with two secondary high-voltage leads. In most cases ignition coils are incorporated in one block. High-voltage leads connected with spark plugs using a spark plug wires.

In DIS ignition system two spark plugs fire simultaneously. Each DIS ignition coil serves two companion cylinders, working with gas distributor phase shift 360° by the crankshaft position. Companion cylinders are the cylinder pair whose piston position is the same. They will be on different strokes. For example, on a 4-cylinder engine, when cylinder №1 is on the compression stroke, cylinder №4 is on the exhaust stroke. To the spark plugs of this companion cylinders high-voltage current flows from two opposite leads of the secondary winding of DIS ignition coil, owing to the polarity of high-voltage pulses on the spark plugs of these cylinders are opposite. Because of the different polarity of high-voltage pulses in DIS ignition systems, connecting of high-voltage capacitive transducers in diagnostics should be in order of signal polarity. The spark on the cylinder on the exhaust stroke does not initiate combustion because there is no combustible mixture in that cylinder. This spark, then is wasted.

Primary voltage waveform diagnosis.

In order to diagnose DIS ignition system by the primary voltage waveform, it is necessary to check serially each of the DIS ignition coil. To diagnose DIS ignition coil by the primary voltage waveform, it is necessary to connect oscilloscope probe to the operating lead of the primary coil of DIS ignition coil. The oscilloscope probe must be connected to an analog input №5 of the USB Autoscope III. In the program "USB Oscilloscope" select "Control => Load user preset => Ignition => Ignition_Primary". Start the engine. A primary voltage waveform will be displayed.

The DIS ignition coils may be built as one unit or separate. The ignition control module (ICM) may be underneath the ignition coils, making primary connections for the purpose of obtaining waveforms very difficult/impossible.

Secondary voltage waveform diagnosis.

The order of connecting of high-voltage transducers:

disconnect all sockets from the USB Autoscope III;
connect power supply wiring of the ignition system adapter Ignition Adapter to the vehicle battery (red to positive, black to negative);
connect the ignition system adapter to the USB Autoscope III;
connect the red DIS capacitive probes to the input In+ of the ignition system adapter;
connect the green DIS capacitive probes to the input In- of the ignition system adapter;
start the engine;
connect the synchronization transducer Sync (black) to the input In Syncro of ignition system adapter and serially connect it to the everyone high-voltage wire of the ignition system, simultaneously observing LED color on ignition system adapter;
connect capacitive DIS transducers to the high-voltage wires correspondingly with the LED color, by one transducer to the one wire;
connect synchronization transducer Sync to the high-voltage wire of the first cylinder.

Connections of high-voltage transducers.

start the program "USB Oscilloscope";
in the program "USB Oscillocope", select "Control => Load user preset => Ignition => Ignition_Dis".

Normal operating parameters for a DIS (Waste Spark) ignition system are as follows:
   firing voltage, also known as break down voltage – on the average 10…15 kV;
   spark voltage – also known as burn voltage 1…2 kV;
   spark duration – also known as burn time ~1,5 ms.
For separate cylinders firing voltage can considerably change. The spark duration and spark voltage have constant values on the established working modes of the engine.

Typical DIS ignition system waveforms.

Wiring diagram of a typical DIS ignition system.
1. Attachment points for the capacitive DIS Cx probes.
2. Where to attach the synchronization transducer Sync.
3. Connection points of oscilloscope probes for obtaining primary waveforms.
4. Vehicle battery.
5. Ignition switch.
6. Ignition coils.
7. Crankshaft Position (CKP) sensor. It is a Variable Reluctance Sensor (VRS).
8. Camshaft Position (CMP) sensor. VRS-type.
9. Spark plugs.
10. The engine control module (ECM) or ignition control module (ICM).
11. Connection point for the CKP signal.
Note: Some CKP's are not referenced to ground, it may be necessary to use differential oscilloscope probe.
12. Connection point for the CMP signal. Same note as for CKP apply.

Secondary waveform from a DIS ignition system.
1. The transistor in the ICM turns on, primary current starts to flow and a magnetic field is being built up in the ignition coil.
2. The moment of transition of ICM to the current limit mode in primary winding (After achievement of a current equals about 8 А in a primary winding of the DIS ignition coil, the ignition control module starts to work in the current limit mode at this level).
3. Spark breakdown between electrodes of the spark plug and start of spark burning (The transistor turns off and a high voltage is induced).
4. The spark line.
5. The spark is extinguished. The beginning of the intermediate section with some damped oscillations.

Primary voltage waveform from a DIS ignition system.
1. The transistor in the ICM turns on, primary current starts to flow and a magnetic field is being built up in the ignition coil.
2. The moment of transition of ICM to the current limit mode in primary winding (After achievement of a current equal about 8 А in a primary winding of the DIS ignition coil, the ignition control module starts to work in the current limit mode at this level).
3. The transistor turns off and a high voltage is induced (Spark breakdown between electrodes of the spark plug and start of spark burning).
4. The spark line.
5. The spark is extinguished. The beginning of the intermediate section with some damped oscillations.

The waveform from the synchronization transducer.
1. Firing spark on the compression stroke.
2. Waste spark on the exhaust stroke.

Waveform from the CKP.

Waveform from the CMP.