When the Audi SQ7 first came out, there was a lot of hubbub about its engine. Under the hood of the SQ7 lies a 4.0 liter V8 diesel with, what many people say, three turbochargers. Audi even claimed it to be a triple-turbocharged SUV. Which it sort of is but it’s more complicated than that. That’s because the Audi SQ7 features two traditional turbochargers and one electric one. That might sound a bit confusing and if it does, check out this video from Engineering Explained.
Now, in the video, EE’s Jason Fenske calls it an electric supercharger. That’s because it is. Actually, technically, it’s called an EPC (Electrically-Powered Compressor). That’s basically just an electric supercharger. However, Audi likes to call its superchargers turbochargers, hence why Audis with the old 3.0 liter supercharged V6 were badged “3.0T”. In fact, Audi claims that superchargers are just mechanical turbochargers. Which I guess is true. Semantics aside, the work that Audi has done making an electric “turbocharger” is incredibly impressive.
It starts off by using a 48-volt electrical subsystem to power the 7 kW EPC. Audi must use this 48-volt system because a the standard 12-volt battery simply isn’t enough to spin the EPC fast enough move enough air to make a difference on its own, never mind do that while running every other electronic system in the car. So Audi needed to add the second 48-volt system, which is very complicated.
Then, Audi worked on creating a sort of diverter valve allows the EPC to work at low engine revs and routes air around it at higher revs. This allows the EPC to create boost as soon as throttle is applied, thus eliminating turbo lag. Once the engine begins to rev up enough, though, the exhaust gasses create enough boost that it no longer needs the EPC so it shuts down and the SQ7 relies on its two traditional turbochargers.
While the EPC barely creates any power, it does help in create a more responsive engine and more instantaneous power. In total, the Audi SQ7’s “tri-turbocharged” 4.0 liter TDI V8 engine makes 435 hp and 664 lb-ft of torque. That allows it to hit 60 mph in 4.7 seconds. Which is rapid for a 5,200 lb SUV.
The Audi SQ7 TDI is one of our absolute favorite Audis on the market and really clever engineering like this is part of the reason why. It’s a brilliant machine and one that we should hope for more of from the industry as a whole. Now Audi just needs to sell it in the US.