Bosch CP009 User Manual download pdf (Page 148)

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Page 65

DS2020

User’s Guide

ILL.4-30. Secondary Pattern - DLI Double Ended Coil

As shown in the illustration, DS2020

displays two waveforms. This is

because an ignition Coil of this type discharges both positive and negative

electricity simultaneously to two spark plugs.

For 4-cylinder engines, there are two ignition coils and each coil is connected

to two spark plugs. When one of the coils discharges positive electricity for

example to cylinder #1, it also discharges negative electricity to cylinder #4

simultaneously. When the other coil discharges positive electricity to cylinder #3,

it also discharges negative electricity to cylinder #2 simultaneously.

Therefore, there will be positive discharges in cylinder #1 and #4, and negative

discharges in cylinder #3 and #2 at the same time. Will this cause cylinder #1

and #4 to fire together? No. When one cylinder is in combustion stroke, the

other will be either in the exhaust, intake or compression stroke. Since the

mixture in the other cylinders is not dense enough to properly combust, it burns

but does not fully combust.

From the two cylinders that ignite together, the waveform of the valid electricity

discharge that creates combustion is called 'True Waveform', and the other that

ignites but does not fully combust is called 'Waste Waveform'.

The density of mixtures in the cylinders that are in the strokes other than

combustion stroke are below combustible level. The higher the resistance level,

the higher the voltage is required to bridge the ignition gap. This means that the

peak voltage of the TRUE waveform is higher than that of the WASTE waveform.

Between the two waveforms, TRUE waveform can be distinguished from the

WASTE form in this manner. In ILL. 43, the second waveform is TRUE.

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Bosch CP009 User Manual Page 148