DIS primary ignition voltage (dual driver) and current

The purpose of this test is to monitor the driver voltages and the current draw during both driver events, making it possible to see whether both coils draw the same amount of current during the operation cycle.

Note: This helpfile refers to a 10:1 attenuator. If you are using a 20:1 attenuator please adjust the Probe settings for the relevant channel. These settings can be found under the Channel Options button, then: Probe > 20:1 Attenuator.

Figure 1

How to perform the test

First disconnect the wiring multiplug from the ignition coil. Reconnect the multiplug using suitable breakout leads as illustrated in Figure 1.

Channel A: Primary Voltage - Coil Driver A

1. Plug the 10:1 Attenuator into Channel A of the PicoScope.
2. Plug a BNC test lead into the attenuator.
3. Place a large black clip on the black test plug.
4. Place the black clip on the battery negative.
5. Plug the colored test plug into the socket on the breakout lead for the Primary Driver 1, as illustrated in Figure 1.

Channel B: Primary Voltage - Coil Driver B

1. Plug a second 10:1 Attenuator into Channel B of the PicoScope.
2. Plug a BNC test lead into the attenuator.
3. Piggyback the black test plug into the Channel A black test plug.
4. Plug the colored test plug into the socket on the breakout lead for the Primary Driver 2, as illustrated in Figure 1.

Channel C: Primary Current - Both Drivers

1. Plug the low-amp current clamp into Channel C of the PicoScope.
2. Select the 20 A range if available  and switch the current clamp on.
3. 'zero' the clamp before connecting it to the circuit.
4. Place the current clamp on the breakout lead wire that supplies the coil. Do not place it around the loom that also contains the negative (or negatives depending on the ignition system). The connection is illustrated in Figure 1.

Example waveform

Waveform notes

The waveform shows the driver voltages for both windings in the ignition coil. It also shows the current drawn during both driver events, allowing you to see if both coils are drawing the same amount of current during the operating cycle.

Technical information

Distributorless Ignition System (DIS)

DIS has major advantages over the distributor-based ignition system. These advantages include an absence of rotating high-voltage distribution components, and far lower levels of electromagnetic interference.

DIS is fitted only to vehicles that have an even number of cylinders, such as 2, 4, 6 or 8. This is because two cylinders are connected to one coil, which can send a spark to both cylinders at the same time. This system is commonly known as a wasted spark system. The two spark plugs are arranged so that one is fired on the power stroke of the engine and the other on the exhaust stroke of the opposing cylinder, offset by 360 degrees. After a complete rotation of the engine the two cylinders are now on the opposing strokes and the two spark plugs fire again but with opposite roles.

On a four-cylinder engine, there are two coils with individual drivers that tend to operate cylinders 1 and 4, and 2 and 3. This means there is a dual spark every 180 degrees, with one of those sparks wasted on an exhaust stroke of the opposing cylinder which is firing on the power stroke.

For further information, see the following topics:

• Primary ignition voltage
• Primary ignition current

AT395-1

Suitable accessories