DIS Ignition System

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 ignition diagnosis

In order to diagnose DIS ignition coil by the primary voltage waveform the measuring adapter must be connected to the operating lead of the primary coil of DIS ignition coil and connected to input 5 of USB Autoscope IV.

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.

To display the current waveform from the primary circuit, current transducer CTi M must be connected to input 4 of USB Autoscope IV and attached to the supply or control wire of the ignition coil. Select “Modes => Ignition => Ignition_Primary” in the USB Oscilloscope program. Start the engine. A primary ignition system waveform will be displayed.

Secondary voltage waveform diagnosis

When working with DIS ignition systems, the following connection order should be used:

  • the red probes from DIS Cx 6 set connects to the input “In+”, located on the front panel of the USB Autoscope IV;
  • the green probes from DIS Cx 6 set connect to the input “In-“;
  • the black synchronization probe connects to the input “In Synchro”;
  • start the engine;
  • attach the black synchronization probe to one of the plug wires. If the red polarity indicator flashes, attach one of the red probes to this plug wire, as close to the ignition coil as possible. If the green polarity indicator is flashing, attach one of the green probes as close to the ignition coil as possible;
  • repeat until all the plug wires have a red or green probe attached to them;
  • attach the black synchronization probe transducer to the plug wire for cylinder 1 (or the timing cylinder if different) as close as possible to the spark plug.
Connection of high voltage probes

Connection of high voltage probes

  • Start the program “USB Oscilloscope”;
  • in the program “USB Oscilloscope” select “Modes => Ignition => Ignition_Parade” or “Modes => Ignition => Ignition_Raster”.

So, program “USB Oscilloscope” starts to show “Parade” and parameters of ignition high voltage ignition pulses: firing voltage, time and voltage of spark fire for each cylinder individually.

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

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

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

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

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 CKP.

Waveform from the CMP.

Waveform from the CMP.