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

Illustration for article titled This Is How Audis Electric Supercharger Works To Eliminate Turbo Lag
Image: Audi

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.

Jalopnik contributor with a love for everything sketchy and eclectic.

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Spamfeller Loves Nazi Clicks

Designs like this are just offensive to me from an engineering perspective, period. It’s not smart. It’s not clever. It’s not innovative. But because it’s Audi? Of COURSE they built an unnecessarily complicated, fragile as hell, overwrought pile of unnecessary parts for absolutely no justifiable reason whatsoever.

SIMPLEST, they could have simply used a supercharger, which has no lag at all. Gasp! Logic! How dare I, right? Oh right, that’s not “fancy” enough for an Audi.

They could have mechanically twincharged it, which ALSO would eliminate lag. But oh no. Those plebians at Nissan did that with the Micra. Therefore it’s not complicated enough for Audi.

And it’s not like Honeywell makes variable geometry turbos specifically for large displacement diesel operation. (Yes, that is ALL THE SARCASM.) Even if they’re bullshitting the history. (First mass production VNT was the ‘89 CSX-VNT though it uses a Garrett unit.) No, no, that’s “90's” technology and therefore there must be something “better!”

There’s NO reason that any of this overly complicated, hideously expensive shit is necessary. It’s all stuff that could and has been accomplished by cheaper, old methods. But that’s not “sexy” enough, so Audi went and built one of the most unnecessarily complicated setups they could possibly come up with just so they could spout a bunch of marketing bullshit.