The ISG is part of a 48 volt system, which drives an electric water pump, an electric AC compressor, and an electric auxiliary compressor that Mercedes calls an eZV. This means there’s no belt-driven accessory drive, reducing overall engine length—a godsend for an inherently long engine like an inline-six.
The electric compressor is basically a 48-volt turbo that crams air into the cylinders when the engine is at low RPMS and the big exhaust-driven turbo isn’t cutting it. Mercedes says the eZV accelerates to 70,000 RPM within 0.3 seconds, and that, between it and the ISG, this inline-six should get off the line quickly with “no turbo lag.”