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This Is How Audi's Electric Supercharger Works To Eliminate Turbo Lag

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Audi’s newest SQ7 is powered by a 4.o-liter twin-turbocharged V8 diesel engine with a third compressor powered by a 7kw electric motor, running on a separate 48v system. Large turbochargers create more power by flowing more air, but they take longer to spool up. By adding in this electric supercharger, Audi is able to provide boost as soon as you step on the throttle. It’s a clever solution to an ages-old problem, but it’s not exactly the simplest system ever invented. Allow Jason Fenske of Engineering Explained, then, to explain the engineering behind it.

Using a few simplified cutaway graphics supplied by Audi, Jason jumps right into the heart of the issue, giving us a good idea of why the electric supercharger is needed, how it works, and why the separate 48 volt electrical system is needed to ensure it works correctly. This Audi TDI engine is incredibly complex, essentially acting as an electrically supercharged engine at low RPMs, switching to a single turbo setup at mid-range RPM once the turbo has spooled up, then a second turbocharger (and another set of exhaust valves) are activated at higher RPM for big power delivery. There are a lot of phase changes at play here, and Jason manages to explain it all in just over 6 minutes.