In the parametric ignition system, the optimal ignition moment is determined depending on the current engine operating mode. The control parameters are the engine speed, engine temperature, intake air temperature and engine load level (manifold vacuum, throttle position). Engine load level refers to the current engine load, for example, there is a difference in engine operation at 4000/min when the car is on an uphill or downhill slope.
Required field of ignition system control parameters (see fig. Y 1207) determined as a result of bench tests and refined in running tests so that the optimum values for fuel consumption, exhaust gas composition and running characteristics were obtained. 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, on the basis of which the optimal ignition timing for the current conditions is generated (for example, 10° before TDC or 0°).
Without information on the number of revolutions, degree of load, etc., deterioration in driving characteristics may occur, such as a decrease in engine power. Increased fuel consumption is also possible. Long-term engine failures should not be feared if the defect is corrected 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 a microprocessor in the control unit.
Models 520i, 525i produced since May 1990. (m50 engine)
The M50 engine has a more advanced DME system. The spark plugs are controlled without moving parts only by the control unit, there is no mechanical ignition distributor. The ignition voltage is induced in 6 ignition coils located directly above the spark plugs.