Hi Igor, good question. The turbo-charger is always "engaged". It's driven by exhaust gas and it's turning whenever the engine is running. It does however need to be spinning fairly fast to provide an increase in manifold pressure(boost). The boost pressure increases with RPM. When you feel it start to "pull" it means the injection pump is providing fuel enrichment. Without fuel, all the boost in the world won't procuce any power. On your car, at the rear of the intake manifold, you'll find a clear plastic tube attached with a banjo fitting. The other end of this tube goes to the aneroid compensator on the injection pump. This lets the pump know the boost pressure so it can provide fuel enrichment. This tube is prone to clogging over time, and when it does there's a serious lack of power. The thing to remember about diesel engines is that the more fuel you add, the more power you make. The turbo-charger force feeds the air charge to the engine. The injection pump adds the fuel. By the way, the 617 turbodiesel may be the best powerplant MB has ever produced, in my opinion.