In the parametric ignition system, the optimal ignition timing is determined depending on the current engine operating mode. Control parameters are engine speed, engine temperature, intake air temperature and engine load (intake manifold vacuum, throttle position). The engine load degree refers to the current engine load, for example, there is a difference in engine operation at 4000 rpm when the vehicle is uphill or downhill.
Required field of ignition system control parameters (see fig. Y 1207) determined as a result of research on the stands and refined in sea trials so that as a result optimal values were obtained in terms of fuel consumption, exhaust gas composition and driving 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, on the basis of which the optimal ignition timing is generated for the current conditions (e.g. 10°BTDC or 0°).
In the absence of information about the number of revolutions, the degree of load, etc. deterioration in driving performance, such as a reduction in engine power, may occur. It is also possible to increase fuel consumption. Long-term engine failures are not to 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 the ignition voltage to the individual spark plugs. The distributor runner is driven directly from the camshaft. In this case, inertial weights, a vacuum membrane and a system of inductive sensors are not required, since their functions are performed by a microprocessor in the control unit.
Models 520i, 525i since May 1990 (M50 engine)
The M50 engine has a more advanced DME system. The spark plugs are controlled without moving parts only from the control unit, there is no mechanical ignition distributor. Ignition voltage is induced in 6 ignition coils located directly above the spark plugs.