Engine Performance - Functional Description: Ignition: Notes

2011 BMW 335i 4D Sedan, AutomaticSECTION Notes

The engine features an inductive ignition system with static ignition distribution.

The ignition circuit consists of the following components:

  • Ignition coil with primary and secondary coil
  • Ignition output stage in the Digital Motor Electronics (DME) for controlling the current via the primary coil
  • Spark plug which is connected to the secondary coil.

Each spark plug is activated by a high voltage from a separate ignition coil (pencil ignition coil) that is inserted directly into the cylinder head cover and activates a separate ignition output stage in the Digital Motor Electronics (DME).

The ignition coils use the vehicle voltage to generate this high voltage that ignites the fuel-air mixture in the combustion chambers.

The point at which the ignition spark ignites the fuel-air mixture must be set so as to ensure optimum torque, low fuel consumption and minimum pollutant emissions. The essential variables are:

  • Engine speed
  • Engine torque
  • Air ratio value
  • Coolant temperature
  • Intake air temperature.

These values are recorded by sensors, processed by the Digital Engine Electronics (DME), digitalized and output as a signal for the ignition output stages.

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