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  Electric Exhaust Gas Turbocharger

Isn't that tragic? The combustion engine has just made up for one of its last disadvantages, and its end is slowly coming into view. It has been particularly popular, especially as a direct-injection Diesel economical, especially for larger loads, and has now deposited the soot from its exhaust gases in the particle filter and the excess of nitrogen oxides by Twindosing.

Now they want to ban it because of its dubious properties in cold running, but we will return to that at the end of this chapter. First we celebrate its greatest triumph in this year, the elimination of the turbo lag. After all the announcements of a solution, almost no one believed in it anymore.

The problem is that once the speed of the central shaft for the turbine and compressor had been reduced, it could not be increased as quickly as one would have wished by stepping on the accelerator pedal. Sure, there are methods to reduce the speed as little as possible by means of a (thrust-)recirculation valve, but it was not possible to increase it actively.

Now it is realisable with the so far rather inconspicuous mild hybrid. 48 volts from a LiIo battery are sufficient to drive the shaft by an electric motor between the turbine and compressor as quickly as possible. to get it on the move. Why has this not been possible so far? Well, after all, the realisation comes from Mercedes AMG and Garrett, i.e. from racing, or more precisely from Formula 1. Finally the fairy tale of the many developments in motor racing for civil motor vehicle technology comes true for once.

Here the technology is in the so-called Motor Generator Unit-Heat, for a long time a problem and almost completely removed again. Why? Because the necessary rpms were probably too high even for an electric motor. With the construction described here this should be up to 170,000 rpm. In addition, it is simply too hot in the middle of the turbocharger.

In Formula 1 the problem was solved by extending the common shaft of turbine and compressor on one side to gain more distance. This would course problems in the crowded engine compartment even in the upper class. My question to an involved engineer according to the duration of development was answered: Two and a half years. I must say, he has been nearly right.

Now the electric motor widens the turbocharger only slightly by approx. 4 cm. Its warming is reduced by the connection to the cooling system. Amazing that 48 volts are sufficient for such a task. At last, a mild hybrid like this provides much more than start-stop and a barely noticeable starting of the engine in the lower speed range. Its activity will probably be felt much more strongly.

With petrol engines, you could save on enrichment at least in ECO mode.

You may have noticed the 'generator' in its name. Yes, it can also produce electricity driven by the turbine, perhaps more than the currently somewhat overestimated recuperation, because in many cases being active for a longer time. Because when sailing, recuperation is zero, but the power generation by a slowly braked charger is intact.

Of course, AMG has the litre output of petrol engines in mind. One is a kind of world champion anyway with 310 kW (421 hp) from two litres of engine displacement. Presumably they will still have the ability to put something on top of it, not only power but also and especially torque. We would like to have the same design in the normal Diesel engine. The turbocharger probably has somewhat lower torque anyway. temperatures and can actually not be that much effort.

At last the hybrid is getting an extra sense of purpose, because its image has been crumbling lately. As a plug-in they even want to deny it the state premium, unfortunately with some justification. And then this means that exhaust gas restrictions are imposed on the combustion engine that are really difficult to achieve. This would mean doing away with the cold-running phase. There would therefore have to be mandatory charging for plug-ins when the engine is cold and empty battery, only then they would be allowed to keep their state premium.

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