#Remove turbo lag with electric turbo from Mercedes

06 / April 2022
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Remove turbo lag with electric turbo from Mercedes

Seletron Performance

Garrett electric turbocharger from Mercedes


What is this about? What are electric turbochargers? How do they differ from electric centrifugal compressors? Let's answer these in order, but first a question, "Have you already read our previous article explaining what turbo-compounds are?" If you haven't, read it!


Electric turbochargers (in this case, we are talking about a Garrett model produced for Mercedes) are devices that incorporate an exhaust-gas turbine (with associated electronically-controlled waste-gate management), a central core (with associated lubrication and cooling system), a centrifugal compressor (with respective electronically controlled by-pass system), and a novel and unknown component on normal turbochargers: an electric motor powered by the 48V line that serves to eliminate turbo-lag.


What is turbo-lag in turbochargers?


Turbo lag is the term used to describe the delay required for the turbocharger to generate supercharging. Basically, the time that elapses from when the accelerator pedal is depressed and how much the turbo is able to accelerate until it generates pressure in its centrifugal compressor. Turbo-lag is not a numerical figure but a definition. The turbo response depends not only on the intrinsic characteristics of the turbo itself but also greatly on the engine-turbo coupling and the electronic management of the engine.


The same turbocharger could have a lag (delay) of 1 second on a large-displacement engine and a lag of 5 seconds on a smaller-displacement engine with different electronic management. Obviously, the mass of the turbocharger (inertia of the turbine, the shaft, the bearings, if any, and the compressor) greatly impacts the readiness of the complete system, as does the fluid dynamics of the scrolls and rotors. In any case, each turbocharger has a response lag that will be greater the bigger it is. Some technologies like VNT, two-stage turbocharging, twin-scroll, etc., have greatly improved this aspect. However, Mercedes and Garrett wanted to go another route, namely the electric turbocharger.


The system provides that under particular conditions, such as a demand for torque/power after a deceleration, a brush-less electric motor causes the rotors to accelerate before the exhaust gases energetically hit the system's turbine. This results in almost no time to go from the zero supercharged state to the maximum supercharged state. Naturally, all this results in a very quick turbo engine response. As soon as the exhaust gases supply energy to the turbine, the electric motor ceases to operate, turning the system into a normal turbocharger.


The electro-turbocompressor assembled in this way is very complex and has various connections to the engine and the control and lubrication system, namely the:

- exhaust gas inlet

- exhaust gas outlet

- atmospheric air inlet

- compressed air outlet

- lubricant inlet

- lubricant outlet

- refrigerant inlet

- refrigerant outlet

- waste-gate valve control connection

- by-pass valve control connection

- motor power supply line connection

- electric motor control unit connection


On the other hand, electric centrifugal compressors are simple compressors that employ an electric motor to rotate a centrifugal rotor at high speed to act as a compressor. They are systems (now rarely used) in some engines with two-stage turbocharging where an initial low pressure is generated by this electric compressor and then sent to the inlet of a regular exhaust gas turbocharger which generates the maximum boost for the engine.


Also, today, we hope to have satisfied some of your curiosity about special turbochargers. If you like these technical topics, we recommend that you also read the others found in this same section!


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