By on March 1, 2010

The Wankel rotary engine returns to its native land at last. Since the NSU Ro 80 went out of production in 1977, Mazda has been the keeper of the flame. But Audi has announced that it will show an A1 e-tron concept at the Geneva show this week, and the pug-in will feature a single-rotor Wankel range extender (gen set). Rotaries and micro-turbines have often been suggested as the ultimate range extenders due to their compact size and low weight.

The “e-tron” will become a moniker for all electrified Audis, promises Audi chief Rupert Stalder to the German magazine Focus, “just like Quattro has become synonymous for four-wheel drive.”

Audi is claiming a 31 mile range in EV mode, before the rotary begins to spin juice. Rotaries are generally less efficient than piston engines, but the trade-off for weight and power density may make it worthwhile. According to Green Car Congress,  the A1 e-tron will only have an additional 124 miles running on its single rotor Wankel range extender.  Must be a mighty small fuel tank, or is the rotary really that thirsty?

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28 Comments on “Audi To Unveil A1 e-tron Concept With Wankel Range Extender...”


  • avatar
    TonyJZX

    i would think that if the rotary engine was designed for ONE rev range like the Volt, it could well be very very efficient?

  • avatar
    jmo

    Must be a mighty small fuel tank, or is the rotary really that thirsty?

    “In an interesting move, the A1 e-tron also features a range-extending engine–but not your typical small four-cylinder. Instead, it’s a rotary Wankel engine mated to an electrical generator with a charge rating of up to 15 kilowatts.”

    15kilowatts is equal to 20.11hp – I’d assume after going 124 miles the rotary/battery combo is no longer capable of providing adequate performance.

  • avatar
    beken

    I was wondering who was going to do it.

    In a discussion with a friend awhile back I had already asked by GM is using a 4 piston engine instead of a rotary or turbine engine to generate electricity for the Volt. For a steady state engine, a piston engine has got to be one of the most inefficient type of engine to use. Way too many moving parts to do so little. Didn’t GM used to have rights to use a rotary engine?

    • 0 avatar

      Efficiency of modern engines is pretty much determined by the combustion temperature. The number of parts does not figure in it. Now, parts affect the cost of the unit, but that’s a different kind of efficiency.

    • 0 avatar
      Quentin

      Pete – I think “more parts” is in reference to the whole back and forth motion of a piston engine. There is no need to have a flat torque profile for drivability in a series system like this. May as well make use of that momentum and go w/ something rotary like a wankel or turbine.

    • 0 avatar
      MadHungarian

      Does the ICE in the Volt in fact run at a steady RPM? If I am remembering correctly, it doesn’t. Probably it does not have as wide of a range of engine speeds as in an ordinary car, but I think it does rev up and down according to power needs when it is running. I have always heard that engines can be designed for max efficiency at a single speed. But I think the demand on the generator in range extending mode varies (by speed, hills, etc.). I suppose we could run the engine at a fairly high constant speed, putting the extra juice back into the batteries when it is not needed, then just switch back to the batteries when they have enough juice again. But would that generate more of the electricity using gasoline, thus reducing the overall efficiency of the system? I suspect this is a very complicated question.

  • avatar
    TonyJZX

    i think almost every company has rights to the wankel engine

    they’re just not exercising that right… and with the abysmal numbers put out by the Mazda RX8, who would blame them?

  • avatar
    AlexD

    Can a 6 plus footer actually sit in this thing, or do I have to saw the top of my skull off like in the A3?

    • 0 avatar
      Quentin

      Did you try lowering the seat? I’m 5’8″ and I can easily put 8″ of space between my head and the roof liner by cranking the seat down in my GTI (sister to the A3). Seriously, I can crank the seat so low that I cannot see over the dashboard.

    • 0 avatar
      AlexD

      Quentin, sit in an A3 and you’ll see what I mean. I suppose you could rip the front seat out and sit on the floor and get your 8 inches of head room.
      There is no comparison between the 2 cars – I can drive in my GTI wearing a mariachi hat.

      In any case I’d like to see another Audi A2 on the market – smaller footprint but with room for adults like the B200.

  • avatar
    davejay

    Pfft, wake me up when someone’s using a four-pack of small (R/C sized) turbines, where a single turbine provides enough power for sitting still with headlights and A/C running, and all four turbines provide enough power to keep the battery alive at 80MPH with all the accessories in use, with software bringing individual turbines on/offline as needed and rotating ‘em in and out so that the lifetime of all units is maximized.

    • 0 avatar
      grifonik

      I think car companies are reluctant to tackle turbines because of the special alloys required for high temps.

      I’d trade the extra turbines for a larger one with air flow pathway adjustment mechanism something like two stage turbos use (http://honeywellbooster.com/turbotalk/honeywell-dual-stage-turbo-technology/). And maybe a Rankine cycle secondary turbine for longer trips or sitting in traffic for long periods (no point in wasting all that heat energy if you can use it.

      While I’m dreaming this up, large bank of capacitors to produce huge power bursts. A powerful electric motor at every wheel with an independent traction control sensor.

      I guess the downside is a good mechanic will cost $200/hr.

      All this coming from a guy who all he wants on a car is powerful engine, good handling, and A/C.

    • 0 avatar
      chaparral66

      The efficiency of turbines goes down as the size of the turbine goes down, so 4 small turbines will use more fuel than one larger turbine. Also the larger turbine would weight less. Sure the one small turbine at full load would probably be more efficient than the larger turbine at partial load, you can use start-stop technology used in hybrids to make up the difference.

  • avatar

    Old Ro80 aficionados may revive the customary greetings when one Ro80 met the other on the road: Stick the hand out of the window. The number of raised fingers indicates the number of exchanged engines …

    • 0 avatar
      cwmoo740

      My uncle went through three before he finally gave that car up. Too bad he moved on to an RX-7 a couple of years later, and kept that through 4 engine rebuilds.

  • avatar
    th009

    One hopes that today’s engines would be somewhat more reliable …

    But even with multiple raised fingers, the Ro 80 was still a tour de force when it came out. Not just for the rotary, but also for Claus Luthe’s stunning design, which still looks fresh today, almost 35 years later. (Luthe went on to create other remarkable evergreen designs, including the original Audi 50 (later reborn as the original Polo) and the BMW E30 3-series.)

  • avatar

    The rotary is that thirsty. Design constraints force it to have a flat, almost two dimensional (well I’m exaggerating slightly there) combustion chamber, which loses heat and therefore energy like a sieve. A sphere would make the most heat-retaining combustion chamber, which a big part of the attraction of the hemi. There are other dimensions to the Wankel’s inefficiency, but that’s the biggest one.

    I’m skeptical about the plug-in thing. Someone from National Renewable Energy Lab once described the Volt to me as actually more of a conventional hybrid.

  • avatar
    PeriSoft

    Angry Audi is angry.

  • avatar
    Daanii2

    I want to see someone use a free-piston generator. Some guys in Australia have a Pempek prototype that gives 45 kilowatts in just 45 kilograms. Those are neat, with a permanent magnet on the piston and a coil of wire around the cylinder. The piston also has valves so it just goes back and forth, generating sine wave AC current.

  • avatar

    I would have bought an RX-8 if the Wankel weren’t so thirsty. It is a wonderful car to drive, and adults can actually sit in the back seat.

  • avatar
    criminalenterprise

    I’d like to see a true rotary engine in a modern car. An A1 enviromobile spewing frothed grease from every pore as a total loss lubrication system splattered the engine bay with 10w30 would be something to behold.

  • avatar
    Mike_H

    Why not a 2 cylinder ICE? Or perhaps a 2 cylinder, pressurized 2-stroke ICE?

  • avatar
    Boff

    As a confirmed rotorhead, I’m not sure what to think about this!

  • avatar
    Tricky Dicky

    Forget hybrid, I’d just love the sound of a car that was fitted with a helicopter style gas turbine. Then all I’d need is a Batman style outfit, a sidekick and a nemesis. If Bob Lutz goes into retirement, do you think he could play The Joker?!

  • avatar
    strangeo

    But back to Paul’s original question: “Must be a mighty small fuel tank, or is the rotary really that thirsty?”

    I own a 2009 RX-8, and got 28 mpg on a long highway drive. So while it is a little more thirsty than a comparable V-6, it’s not that bad. 124 miles from the engine for range extension??! Even allowing 20 mpg, that’s a 6 gallon tank. Really? Or did they actually place an engine in this car that gets only 6mpg? Something doesn’t add up here.

  • avatar
    saponetta

    apparently the concept uses a .25 litre rotary engine and the fuel capacity is 3 gallons. This comes out to around 41 mpg from the range extending motor. Apparently the range extending motor operates at a constant 5000rpm and the driver alone controls whether it is on or off.

  • avatar

    The Volt is indeed a conventional hybrid. We produce a single-rotor Wankel Range-Extender with 15 kw output since 2 years. Our system consumes less than 2 liters gasoline per hour at constant use.

  • avatar
    jmilner

    e-cardriver: we are interested in your single-rotor engine. please send email to contact@milnermotors.com. thanks!


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