Functioning of the parametric ignition system (BMW 3 Series E30)

In a parametric ignition system, the optimum ignition timing is determined depending on the current engine operating mode. The control parameters are engine speed, engine temperature, intake air temperature and engine load level (manifold vacuum, throttle position). The engine load level refers to the current engine load (for example, there is a difference in how the engine runs at 4000 rpm when the car is on an uphill or downhill slope).



The required field of ignition system control parameters was determined as a result of bench testing and refined in road tests, which allowed obtaining optimal values for fuel consumption, exhaust gas composition and road performance. The obtained values are stored in the memory of the electronic control unit.

While driving, the control unit receives information about the current engine speed, its temperature and load, and based on this data, the optimal ignition timing for the current conditions is generated (for example, 10° before top dead center or 0°).

Without information on the number of revolutions, degree of load, etc., deterioration in driving characteristics may occur, for example, a decrease in engine power. An increase in fuel consumption is also possible. There is no need to fear serious engine malfunctions if the defect is eliminated at the earliest opportunity.

The ignition distributor with a parametric ignition system has another task, namely, the distribution of ignition voltage to individual spark plugs. The distributor runner is driven directly from the camshaft. In this case, inertial weights, a vacuum membrane and an inductive sensor system are not required, since their functions are performed by the microprocessor in the control unit.