The purpose of this test is to examine a positive fired secondary ignition waveform from a Multi-Coil-on-Plug ignition unit.
Uninsulated HT pickups are designed to clip around double-insulated HT leads only – they are not designed for direct connection to a hazardous live voltage.
To prevent injury or death, when connecting or disconnecting an HT pickup:
Many multi-coil ignition systems employ wasted spark coils, this means there will be both negative and positive fired spark plugs. If your waveform is missing or appears to be inverted you have two options;
The example waveform shows a typical picture from an engine fitted with electronic ignition. The waveform is from the coil-on-plug unit fitted on the Vectra Z22SE engine.
The operation of the coil-on-plug unit is essentially the same as any other ignition system.
The distributorless ignition systems are 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 that produces a spark in both cylinders at the same time. This 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 to before.
On a 4-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.
The only real difference between COP and other ignition systems is that each COP coil is mounted directly onto the spark plug, so the voltage goes directly to the plug electrodes without having to pass through a distributor or plug leads. This direct connection method delivers the strongest spark possible and improves the durability of the ignition system.
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