12 13 ... Normal Oscillogram (M, S, W Engines Only)

1. Start Of Ignition Voltage Peak.
2. Level Of Ignition Voltage.
3. Level Of Combustion Voltage.
4. Period Of Combustion.
5. Combustion Curve Characteristics.
6. Start Of Decay Process.
7. Termination Oscillations.
Fig 1: Evaluation Of Normal Oscillogram Patterns (1 Of 5)
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Secondary voltage patterns, beside one another: Evaluation of ignition voltage peaks at idle speed (this example shows an engine with 4 cylinders). Note:   The display of ignition voltage spikes is approx. 20-25% lower than the real value. The uniformity of all cylinders to each other is more important than the height of ignition voltage peaks. Differences of 3000-4000 V are permitted. In event of greater differences, refer to FURTHER FAULT PATTERNS WITH EVALUATION .

Fig 2: Evaluation Of Normal Oscillogram Patterns (2 Of 5)

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Evaluation of ignition voltage peaks at increased speed of approx. 2000 RPM (this example shows an engine with 4 cylinders).

Fig 3: Evaluation Of Normal Oscillogram Patterns (3 Of 5)

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Secondary voltage diagrams, superimposed: Evaluation of combustion characteristics curve and decay characteristics at idle speed (this example shows a 4-cylinder engine).

Fig 4: Evaluation Of Normal Oscillogram Patterns (4 Of 5)

Courtesy of BMW OF NORTH AMERICA, INC.

Secondary voltage diagrams, consecutive: Note:   Only the major differences in the ignition voltage patterns are revealed by this method of comparison. The identified fault must be allocated to the relevant cylinder using the secondary voltage representation forms next to/on top of each other.

Fig 5: Evaluation Of Normal Oscillogram Patterns (5 Of 5)

Courtesy of BMW OF NORTH AMERICA, INC.