Due to the dual air supply system on the 8-cylinder engine, an additional control facility for the two turbochargers with respect to each other, i.e. so-called air mass equalization, is necessary to ensure effective engine operation. Air mass equalization is implemented by a software function in the DDE, the equalization controller.
The two mass airflow sensors measure the volume of fresh air drawn in on both sides of the air guide system. The equalization controller attempts to keep the intake air mass on the left-hand and right-hand page the same. This ensures an equal load on the two turbochargers and protects them against overspeed.
The equalization controller achieves this by setting the pulse duty factors for the left and right charge-air pressure controllers in such a way that equal air masses are drawn in on both sides.
The following components influence air mass equalization:
The following points are monitored for the purpose of detecting faults in the air mass system:
As a response to the fault, the injection volume is reduced resulting in a considerable reduction in power output. The charge-air pressure control is deactivated and the turbocharger is operated with fixed pulse duty factors.
Effect of a defective turbocharger adjustment on one side:
In order to protect the turbochargers from further damage, both units are operated with relatively low pulse duty factors. If the adjustment of one turbocharger is blocked this means it can no longer respond correctly to activation with the low pulse duty factor (= low charge-air pressure and air throughput). This means that higher air mass will be measured on the side of the defective turbocharger.
Before replacing a turbocharger, the adjustment of both turbochargers must always be checked first.