An electric turbo system boosts efficiency between 15 and 20 percent, according to Audi.

Turbochargers, like acoustic guitars, use moving air to create magic. And electric turbochargers, like electric guitars, provide the ability to amp up that magic to amazing new levels.

Electric guitars make cool sounds, and do so with a lot more volume than acoustics. Electric turbochargers will make quantifiable gains in both efficiency and power, in addition to harder-to-quantify gains in drivability compared to conventional turbochargers.

An electric turbo system, which includes an energy recovery system to provide power for the electric turbo, boosts efficiency between 15 and 20 percent, according to Audi. It also effectively eliminates turbo lag, the time it takes for turbo boost to build power to levels requested by the driver's right foot. Audi says its electric turbo needs only a quarter of a second to reach full boost.

The company recently demonstrated electric turbo-equipped RS5 and A6 prototypes at an event, where Volkswagen Group technical head Ulrich Hackenberg told Autocar magazine that Audi will release an SQ7 equipped with electric turbocharger technology in 2016.

That would make the SQ7 the world's first production vehicle equipped with an electric turbo, and surely the first of many to come.
Audi Electric Turbo

Technically they are compound turbocharger/electric supercharger systems.

One quick clarification: turbos, by definition, use exhaust gas to power their compressors. So an electrically driven compressor would actually be a supercharger, not a turbocharger. However, because the electric compressors are used in tandem with turbos, they are commonly referred to as electric turbochargers. Technically they are compound turbocharger/electric supercharger systems.

There are good reasons why many of us could find ourselves driving such cars in the mid-distant future, mostly related to the benefits and shortcomings of traditional turbos. Industry powertrain gurus predict that the gasoline engine will follow the lead of the diesel, with normal aspiration being universally displaced by forced induction, along the lines of Ford's EcoBoost engine family.

Turbochargers, like acoustic guitars, use mechanical means to move air. Guitars' strings vibrate the hollow body, which moves the air inside to make sound. Turbos have a turbine in the engine's exhaust stream to spin a shaft connected to another turbine that compresses air coming into the engine so it makes more power.

Why haven't electric turbos appeared already? Power. Musicians can plug their guitar amps in to a wall outlet for power, but an electric turbocharger needs more power than a conventional 12-volt automotive electrical system can provide.

Audi Electric TurboAudi Electric turbo

Around the turn of the millennium, there was the expectation that cars would ditch 12-volt electrics for 42-volt systems to support the many new electronics and electric comfort devices such as seat heaters. That switch never occurred, but the know-how and hardware that had been developed for hybrid-electric cars is suitable for application to the electric turbocharger problem.

"We've been in pre-development for more than ten years," noted Steve McKinley, Honeywell Turbo Technology's vice president of engineering. "It was a matter of waiting for that electric infrastructure to develop on the vehicles."

Audi Electric Turbo Engine"You have to have a fair amount of power going into the supercharger," he said. "But when you have other parts of the vehicle being electrified," it becomes possible to use some of that power for the turbo.

Indeed, Audi says that the peak current to the electric turbo in the A6 and RS5 prototypes it demonstrated to the press is 7 kilowatts, about the equivalent of 4.5 hair dryers.

The 48-volt system used by Audi lowers the amperage needed to provide that to a manageable 145 amps, something that would be impossible using a conventional 12-volt system, which would need 583 amps.

The exact voltage depends on the needs of the specific vehicle. "Pick a number, whatever number you like," said McKinley. If the industry settles on a single standard it seems likely to help reduce costs. It is important to stay below 60 volts because that is the threshold at which electricity becomes lethal to people, and non-lethal electric power is much less expensive because it doesn't require the safeguards seen in high-voltage electrics such as employed in hybrid vehicles.

While the electric turbocharger stands to boost fuel efficiency, as sort of a mid-step between conventional engines and hybrid-electrics, early applications are likely to be in performance vehicles, because those are the models whose price can justify the added expense, McKinley observed.

These advanced sports models will surely enjoy improved efficiency as a bonus, but they will also have increased peak power. That's because the drive to eliminate turbo lag has led carmakers to install small, quick-accelerating turbos.

With an electric turbo installed to eliminate lag, the exhaust-driven turbo can be sized for maximum power at wide-open throttle, McKinley pointed out. "You will do things differently in terms of turbo sizing for the high-load, high-pressure situations," he said.

Audi Electric TurboAudi Electric Turbo

With an electric turbo installed to eliminate lag, the exhaust-driven turbo can be sized for maximum power at wide-open throttle.

Audi's prototype A6 is equipped with a 3.0-liter TDI diesel engine using a single conventional turbocharger plus the electric turbo to produce 326 horsepower and 479 pound-feet of torque. The RS5 has twin turbochargers, as well as the electric turbo, and produces 385 hp and 553 lb-ft, for 0-62 mph acceleration of about four seconds.

Today's production 3.0-liter TDI V6 engine produces 240 hp and 428 lb-ft of torque, accelerating the A6 to 60 mph in 5.5 seconds.

As shown by the Audis, these devices will be built as two separate turbines, connected by plumbing, at least at first. But ideally, the electric boost will be built into a single device that also uses exhaust gas energy, McKinley said.

But the heat associated with the engine's exhaust poses durability challenges to an electric motor. "At this point the benefits are not outweighing the risks of attaching it to the [turbo] shaft."

A possible solution could be a long shaft connecting the impeller and compressor sides of the turbocharger, so that the electric motor could safely live on the compressor side at some distance from the exhaust-driven impeller. Mercedes uses a split turbo design in its Formula One racecar this season, and perhaps not coincidentally, has demonstrated the most engine power.

Audi RS5 Electric Turbo

At least five years out before you see very mainstream adoption." – Steve McKinley

Connecting the electric motor to the turbo's spinning shaft also provides the potential to recapture energy from that exhaust stream by using the electric motor as a generator at part throttle.

"How that translates into vehicles, with small and light components, it might be difficult to propose something like that in a real production environment," McKinley concluded.

When could we see electric turbos in high-volume production cars, as Ford's EcoBoost engines are used currently? "At least five years out before you see very mainstream adoption," McKinley predicted.

That should give people plenty of time to prepare for the change, though it may not sound as dramatic as the arrival of electric guitars was.


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  • 52 Comments
      EVSUPERHERO
      • 4 Months Ago

      Since Cadillac installed the electric starter in 1912, electric components have been making gassers better.

      Ryan Schneider
      • 4 Months Ago

      Wonder what buzz-words manufacturers will come up with when this tech takes hold?

      Thunderblower, Electrocharger, Powerbomb, Lightning-poofer.

        Plunger 2x
        • 4 Months Ago
        @Ryan Schneider

        LOL ..sound like you should be smokin some sweet stankin' weed from a Lightining-poofer..

        JB
        • 4 Months Ago
        @Ryan Schneider

        Beaver-Ram-Air

      Lachmund
      • 4 Months Ago

      Why do you keep writing it is an electric turbo...?! It is an ELECTRIC COMPRESSOR/SUPERCHARGER! (as written in the descriptions on the technical drawings) A turbo(charger) is driven by exhaust gases which isn't the case with this system.

        Bobby D
        • 4 Months Ago
        @Lachmund

        it's electrically powered forced air induction.

        What are the morons who don't know the difference between and "engine" and a "motor" gonna do now with BOTH under the hood?  

        Hazdaz
        • 4 Months Ago
        @Lachmund

        Probably because people are familiar with turbos, so why confuse the issue.  


        Also, it sounds like these electrified turbos might only use the electric motor to spool up the turbo and still be driven by exhaust gas, so the use of the term still fits.  


        Even in the age of high speed internet, we still call them modems, even if they aren't modulating and demodulating analog signals.  A term is used, and its next-generation replacement still follows with the same name.

        Matt
        • 4 Months Ago
        @Lachmund

        Technically it's a gas turbine generator that happens to use its generated electricity to power a compressor. 

          pavsterrocks
          • 4 Months Ago
          @Matt

          I don't see a turbine generator in the diagram.   Power comes from elsewhere.  If their figures are correct, we are talking about roughly 6,000 Watts of power to run this sucker to full boost.  I bet you're going to need a hefty alternator + some super caps. 

          Matt
          • 4 Months Ago
          @Matt

          pavsterrocks, the "turbocharger" in the diagram is a gas turbine generator. It's like a regular turbo, except instead of driving a compressor, the turbine is driving a generator. 

        KaiserWilhelm
        • 4 Months Ago
        @Lachmund

        You are correct sir

        pete
        • 4 Months Ago
        @Lachmund

        I'd say a TURBO is defined as a compressor that generates it's charge indirectly from the motor through exhaust gas or alternator. A SUPERCHARGER generates charge directly from the motor. 

          scraejtp
          • 4 Months Ago
          @pete

          Why would you throw the alternator as a source in the definition of a turbocharger? A turbo is exhaust driven, typically directly, but I could concede indirectly would count as well.

        KaiserWilhelm
        • 4 Months Ago
        @Lachmund

        You are correct sir

        Jason
        • 4 Months Ago
        @Lachmund

        I think they reasonably explained why they refer to it as an electric turbo.

        JB
        • 4 Months Ago
        @Lachmund

        Splitting hairs.  

        Peter Middleton
        • 4 Months Ago
        @Lachmund

        cause then people are gonna ask what that is and then I have to explain it and they dont actually care

      Nicholas
      • 4 Months Ago

      Okay, but will it still make that cool whistling sound?

      2 wheeled menace
      • 4 Months Ago

      Have you noticed the thread yet..

      .. the more electric motors are added to gasoline engine technology, the more efficient the vehicle becomes..
       ;)

      scraejtp
      • 4 Months Ago *Edited*
      Apparently I'm mistaken and the post system may still have some syncing issues. Carry on.
      Buthter
      • 4 Months Ago

      "Audi says that the peak current to the electric turbo in the A6 and RS5 prototypes it demonstrated to the press is 7 kilowatts..." This made the electrical engineer in me cringe a little bit. Still, very cool concept. Can't wait for these systems to work their way into the broader market.

      Louis MacKenzie
      • 4 Months Ago

      German Leaf Blower > eBay Leaf Blower

        KaiserWilhelm
        • 4 Months Ago
        @Louis MacKenzie

        The germans don't make leaf blowers, they make tree blowers.

          cj
          • 4 Months Ago
          @KaiserWilhelm

          No no those are just seriously overengineered leaf blowers!

      Rotation
      • 4 Months Ago

      That looks absolutely terrible.

      It's a turbocharged car with an electric supercharger in parallel. In classic VAG fashion that seems like the most complicated way to accomplish this feat. The electricity doesn't really spin the turbo up, it just augments the boost until the turbo is ready to go.

      I feel the same way about this as about the twincharger VW. As I did about my 5V Audi engine. If you really have to go to such lengths to do it, maybe you shouldn't do it. Maybe you should find a better way.

      I think a turbocharger with electric boost on the main turbo shaft makes sense. More sense than this. I'll just keep waiting I guess.

      The worst part of all this is it's still using air-air intercooling. That's really on the way outs now. Air-water-air allows better packaging with less induction lag.

      I'm skeptical to say the least.

        Jason
        • 4 Months Ago
        @Rotation

        I hear your point. But VW is not alone in this approach. Wait...

      pavsterrocks
      • 4 Months Ago

      I have my doubts about this tech.  It's great on F1 cars an all, where they need a short burst of extra acceleration and have a bunch of stored-up power, but the story simply doesn't make sense in street cars.  At least normal street cars.  The only benefit of this system vs conventional turbocharging is quicker boost, although it still isn't lag-free - I've heard figures of 1 second from 0 to full boost.  But the added complexity is staggering - the power requirements come close to those of a hybrid drive-train, including a very beefy alternator/generator as well as some kind of an energy store.  

      Charles
      • 4 Months Ago

       

        Matt
        • 4 Months Ago
        @Charles

        I think you may want to brush up on turbos and back pressure because what you said made no sense. Everything beyond the exhaust ports on the head creates back pressure. For a turbo you don't want to eliminate the exhaust back pressure as that reduces exhaust velocity which leads to more turbo lag. That's why you'll see the primaries on turbo manifolds are smaller than the primaries on an N/A car with less power. Turbochargers are all about exhaust velocity, setting up your exhaust to maximize scavenging has no benefit, you have a turbo; you want boost. Just don't go so small on the manifold's primaries' diameters that you choke off the high end. Everything past the turbo (downpipe, cat, resonators, mufflers, etc)? That's where you want no back pressure, straight through 3" turbo back catless exhaust  hell, hook a Hoover up to it if you can.

      danfred311
      • 4 Months Ago

      ever increasing complexity to try to compensate for the fecality of the ICE

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