By on August 11, 2016

Audi eROT system

The search for better fuel economy takes engineers down weird paths, and the latest plan to wring out extra mileage is no different. It involves an unlikely part of the vehicle — the suspension.

Audi just announced a new suspension system that harvests wasted energy and turns it into electricity, capable of adding juice to a vehicle’s 48-volt electrical subsystem.

The automaker calls the system “eROT” after the electromechanical rotary dampers that capture kinetic energy and store it in a battery. Currently in the prototype phase, the system does away with conventional shock absorbers, replacing them with lever arms connected to a small gearbox and alternator.

“Every pothole, every bump, every curve induces kinetic energy in the car,” said Stefan Knirsch, Audi’s technical development boss, in a release. “Today’s dampers absorb this energy, which is lost in the form of heat. With the new electromechanical damper system in the 48-volt electrical system, we put this energy to use. It also presents us and our customers with entirely new possibilities for adjusting the suspension.”

The lever arm absorbs the motion of the wheel carrier, transferring the power to an electric motor through a set of gears. The motor converts that force into electricity, which is stored in the system’s 0.5 kilowatt-hour battery. That battery has an output of 13 kW, and can feed the vehicle’s generator, leading to a slight improvement in fuel economy.

During an average drive, the system is able to capture between 100 and 150 watts of energy, Audi claims. Rough roads mean greater energy capture, while smooth-as-glass highway jaunts might harness just a few watts.

The system’s benefits are many. Not only does it boost mileage, it would it allow drivers to adjust their ride comfort via the freely programmable dampers. Also, the lack of upright shock absorbers means more trunk space. Audi says the system’s appearance on future vehicles is “certainly plausible.”

The automaker plans to test a beefed-up version of the system in a mild hybrid vehicle next year, with the upgraded eROT expected to boost mileage by 0.7 l/100 km.

[Image: Audi AG]

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42 Comments on “Audi Develops Suspension that Generates Electricity, Boosts MPG...”


  • avatar
    bunkie

    MGB owners rejoice! The lever shock is returning!

  • avatar
    SCE to AUX

    “…expected to boost mileage by 0.7 l/100 km”

    Or roughly 10% on a 30 mpg car. Not bad, but it sounds awfully complex.

    Shouldn’t GM’s MagneRide be able to accomplish the same thing more elegantly?

    • 0 avatar
      Scoutdude

      No the MagneRide system works by putting electrical energy into the system and there is no way to get electrical energy back out of the system. The way it works is that the shock is filled with magnetically reactive fluid. Then by surrounding the fluid with an electrically generated magnetic field the viscosity of the fluid can be altered. No magnetic field and the fluid has low viscosity, a strong magnetic field causes high viscosity.

      • 0 avatar
        bunkie

        To further explain, the fluid is FerroFluid, a colloidal suspension of iron particles in a viscous fluid.

        Ferrofluid was developed for the HiFi industry. It is injected into the gap between the speaker’s voice coil and the magnetic pole assembly. Its sole function is to provide a thermal bridge between the voice coil and the pole piece allowing the heat from the delicate voice coil to be absorbed by the pole piece. The iron particles hold the fluid in the gap, preventing it from just flowing out.

        I once bought a liter of the stuff to solve a problem with blown tweeters at the speaker company I was running. It cost $800 in 1979 dollars. One night during a break-in, the thieves knocked it of the shelf and the bottle shattered leaving, perhaps, the most expensive puddle I’ve ever seen.

        • 0 avatar
          brn

          bunkie, $800/liter might be why I never see it used anymore. From what I understand, ferrofluid also has a tendency to thicken over time, impacting the performance. I say that as someone with 25 year old B&W speakers that work just fine with ferrofluid filled tweeters.

    • 0 avatar
      Sigivald

      I like the idea – if this is implemented properly – of “not having to replace shocks”.

      THAT’S the buried-lede win here, from my perspective.

    • 0 avatar
      mfennell

      There is no possible way this thing produces that kind of gain. 1 liter of gasoline contains about 8.9 kWh. At the higher range claimed (150w), it would take 41hrs of operation for this system to produce the amount of energy in 0.7L.

      EDIT: another way to look at it is through EVs. Roundly, an e-golf or Leaf take about 15,000 watts to sustain 60 mph. Another 150 watts is in the noise.

  • avatar
    cheezman88

    I love how these fuel efficiency regulations have forced automakers to come up with complex systems like this just to gain an extra couple of MPG’s. Over the life of the car i doubt it’d even save enough fuel to pay for this system. And if it breaks? Say goodbye to the money savings from the extra fuel efficiency.

    • 0 avatar
      Fred

      I doubt this gets you a couple mpg, maybe more like .1 mpg. Still the cost and complexity surely is going to make owning these cars with 100k miles a bit expensive. Or maybe the fix is to disconnect and remove the device. Which is what I did on my Silverado when the rear abs pump failed and was told it would cost $1500 for a new pump.

      • 0 avatar
        Scoutdude

        Well it looks like this completely replaces the shocks so disconnecting/removing it will have the same effect as driving with no shocks, ie a very uncontrolled ride.

        • 0 avatar
          Sigivald

          And – see above – if they do it right and it’s long-term reliable, it *saves you money and time on shock replacement*.

          I mean, we’re supposed to replace them every 50,000 miles, right?

          This not only suggests – in principle – saving that money, but it’d suggest that you never have “worn out shocks”, too…

      • 0 avatar
        jacob_coulter

        I agree, on one hand they are saying it generates 100 watts per trip, I’m guessing that means .1 kWh?
        No way that represents anything but a menial gain in fuel economy.

        Its almost like the difference in fuel economy on a hybrid if you have your headlights on vs off.

        I can’t wait to see how many of these systems hit a big puddle and fry, wiping out theoretical fuel economy gains of 50+ years of ownership.

        • 0 avatar
          stuki

          I think the idea is an average 100-150 watt trickle. About 1/5 hp at the alternator, perhaps 2/3 at the engine. Less in practical, budget constrained, real world applications, and for sane people with taller than Audi/Bmw tire sidewalls.

          The technology, if it can be done in a lightweight fashion, could make a more meaningful difference to the rapidly growing market of electric assist bicycles.

      • 0 avatar
        BatmanBrandon

        I think the days of cars lasting 10 years/100k miles may be coming to an end. Manufacturers have a vested stake in getting us back into the showroom; adding complex, costly systems that have a designated lifespan is one way to force the public at large into the next vehicle, all in the name of safety and efficiency. Kind of like how Tesla says your wrecked car has to be repaired at their certified facility who then tells you all damaged parts must be replaced to avoid future issues. My coworker had a Tesla shop in his area, he totaled about 50% of the claims he saw. The OEMs aren’t dumb, they’d rather sell you a new car than parts to do repairs, whether accident related or just wear and tear.

        • 0 avatar
          RHD

          Cars lasting just 100K miles ended somewhere around 1974.
          The only way any modern car should be ready for the crusher at 100K is if it gets totaled in a wreck, gets salted for ten straight winters, or never gets any scheduled maintenance.
          A new car should run well for at least 200K, if properly taken care of. (Notwhthstanding an automatic transmission falling apart due to poor design or lack of changing the fluid.)
          I have a neighbor with a Honda minivan with over 350K. My Volvo wagon is at 201K. There are Chrysler minivans on Craigslist with nearly 200K, and some well over that, and (apparently) still going strong.
          You are right about complex and expensive systems – they will doom a depreciated car when the circuit boards develop a crack or a brittle plastic part requires an entire assembly behind the dash to be replaced.

    • 0 avatar
      heavy handle

      This system is replacing shocks and springs, so it’s not necessarily more complex. Shocks don’t last forever either.

      • 0 avatar
        Scoutdude

        It is not replacing the springs, only the shocks. Motors, transmissions, wiring, controller and battery certainly are more complex and expensive than a piston with orifices in a cylinder filled with oil.

        • 0 avatar
          heavy handle

          I didn’t see springs in the illustration, but that doesn’t mean there aren’t any. You would need something to keep the car from drooping too much at rest, at the very least.

          The system is more complex than shocks, granted, but shocks eventually fail. They are a wear item.

          Also, this is replacing shocks in a high-end car, meaning that the competition has air bags, magnetic ride, and whatnot. It’s not replacing a $29.95 jobber special.

          • 0 avatar
            stuki

            If they could hold tolerances tight enough, you’d think they could implement the generator linearly, allowing for more of a drop-in replacement for regular shocks.

            Looking at the latest Raptor ads, Ford should be able to power a small city with generator shocks fitted to that thing…

  • avatar
    redav

    I’ve had this idea for a while. Shock absorbers are just devices for converting kinetic energy into heat, so why not convert the energy to electricity instead? If you have a system like magnetic ride control, the hardware is pretty much all there. The principle is identical to regenerative braking.

    • 0 avatar
      Scoutdude

      Magnetic ride control has none of the hardware to generate electricity, only hardware to consume it. Magnetic ride control works by using a magnetically reactive fluid that changes its viscosity based on the electronically generated magnetic field surrounding the fluid.

    • 0 avatar
      mfennell

      The problem is that they just don’t convert all that much energy to heat. Shocks on a street car barely get warm while brakes get to I-wish-I-didn’t-touch-that temps just driving around town despite considerably more mass and airflow around them.

      • 0 avatar
        redav

        The phenomenon of “getting hot” is an issue of both power and energy. Brakes are high power (fast transfer of energy) and high energy–but only when they are used. If you go for a long drive on an open road and don’t use your brakes, they won’t be hot–at all. On a normal street, shocks are low power and low energy. According to Audi, on a bumpy road they will get to 100 def F to 125 deg F.
        http://gtspirit.com/2014/06/28/audi-developing-power-generation-suspension-system/

        On that long drive on an open road, the suspension will recoup more energy than the brakes.

        This article incorrectly summarizes the Audi claim on power generation: “The recuperation output is 100 to 150 watts on average during testing on German roads – from 3 watts on a freshly paved freeway to 613 watts on a rough secondary road.”
        https://www.audi-mediacenter.com/en/press-releases/the-innovative-shock-absorber-system-from-audi-new-technology-saves-fuel-and-enhances-comfort-6551

        That’s enough to power interior lights or other light-duty electronics. This article calls it “energy,” but it should be “power” (energy = integral of power over time). Thus for a one hour drive on typical German roads, it will generate 0.1 kWh to 0.15 kWh. If that energy were used in a an EV, it would add around a half mi of range, so on a 200 mi range EV, it might add ~2 mi (1%) to the range.

  • avatar
    indi500fan

    I think this means that Audis running in Michigan will be getting 90mpg.

  • avatar
    RS

    Similar ideas have been patented for a while. Maybe the original patents have expired or they are licensing it…or found a way around it. Levant Power has done something very similar. Linear vs rotary may be the difference.

  • avatar
    jmo

    Automotive technology advances – B&B horrified. Film at 11.

  • avatar
    sportyaccordy

    I will wait another 10-15 years for the Japanese to capitalize on the Germans “real world beta-testing”.

    When I hear rotary damper I’m instantly reminded of the poor Suzuki TL1000 which was nearly ruined by that kind of damper. That was an easy 20+ years ago though and it relied on fluid rather than electrons, so I’m sure this will work a lot better.

    So many potential issues though. Reliability and cost are the biggies. Classic VWAG… big, grand, brilliant technical idea they are almost certain to bungle in execution.

    • 0 avatar
      manny_c44

      It won’t be bungled, I’m sure it will work just fine. But eventually it will have to be repaired and the costs may be eye-watering. That’s the VAG downside.

  • avatar
    JimC2

    They’re playing with the numbers.

    150W is about 1/5hp. An average gas engine will burn about 0.05-0.1 liters per hour to make that much power. (Or rather, it will burn about that much less gas each hour to make 24 4/5 hp than it would to make 25hp.)

    • 0 avatar
      redav

      The Audi site claims to reduce emissions 3 g CO2/km, and the current standard is 130 g CO2/km. Clearly, they aren’t claiming huge gains, but even that 3 g CO2/km number seems high.

  • avatar
    Bazza

    Just another thing to break, and with Audi it’s a virtual lock that it will.

  • avatar
    Brunsworks

    A pair or more of sufficiently horny consenting adults would never have to buy fuel again.

    Of course, they’d spend the savings on contraceptives, but what a way to go.

  • avatar
    Chocolatedeath

    IF Mazda did this you guys would hate it wouldnt you…LOL

  • avatar
    Big Al from Oz

    Having this vehicle on Australian roads would be the closest thing ever invented close to perpetual energy.

  • avatar
    Lou_BC

    This would be great on the Ford Raptor.

  • avatar
    shaker

    I like to say that “efficiency is its own reward”, but this tech is a bit over the top – what you want are improvements on the supply side of things – cheap renewable energy should be the focus.

    Now, if I were on Mars, and needed to get to an old spacecraft many kilometers away to make a miracle escape, I’d be very happy that the electric rover had these “shocks”.

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