By on May 6, 2012

This weekend, Audi’s R18 e-tron quattro hits the track at the World Endurance Championship (WEC) in Spa, Belgium. Not enough that the race car is powered by a V6 diesel engine. It also uses a flywheel as energy storage. Why should we care? Audi makes noises that this technology could soon show up in production cars.

Says just-auto:

“In the R18, a V6 diesel engine sends drive to the rear wheels, while for the front axle, the energy is electrically recuperated and fed into a flywheel. This can then be returned to the front wheels during acceleration. Of interest here is that Audi has chosen this technology over batteries. Why? According to Wolfgang Ullrich who heads up Audi’s Motorsport division, even the most advanced cells would have been too heavy.”

Ullrich says that this it not just tinkering with race toys:

“I can safely state that the things we’re testing with flywheel energy storage are of interest to our production colleagues too. The combination of different systems is an aspect that will have to be considered in various applications in the future.”

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21 Comments on “Audi: Vorprung Durch Flywheel?...”

  • avatar
    Austin Greene

    In the 1980s the National Research Council modified a 30 foot city transit bus to include a flywheel. The flywheel looked like a large lawn roller or a small steamroller and it was engaged when the brakes on the bus were activated. The flywheel would spin up to speed storing the kinetic energy and then when the accelerator was touched this kinetic energy was transferred back into forward motion. It seemed to be well suited to the work of an urban transit bus that spends most of its time stopping at, and pulling away from, bus stops. I have no idea what happened with technology – but it’s interesting to see that the idea has come back 30 years later.

  • avatar

    I’ve been doing a bit of reading on the history of electric and hybrid cars. EVs have always, and will probably always face a harsh reality, energy density. If, in 2012, with racing technology, which can do things that would not be financially practical for a production car, they can store more energy in kinetic form in a flywheel, at a greater energy/weight ratio than in chemical form in a battery, batteries still have a ways to go.

    One interesting little factoid is that while top speeds have gone up, EVs have had battery powered ranges of 40-100 miles since the early days, enough to be a practical town car but not enough for long road trips. I guess that battery chemists are running into some basic physical realities.

    • 0 avatar

      Somewhat false comparison. The model T was 1200 lbs. The Leaf weight 3500 lbs. If the range has remained the same, battery performance has apparently at least tripled, not to mention an EV hitting 70 mph would have been unthinkable back when. You were probably lucky if it could do 15 mph.

      So it’s an apples and oranges comparison.

      • 0 avatar

        Tripling or even 5x EV range improvement in a century is pretty poor. The goal today is to get the equivalent range of a tank of gas – say 300 miles in a 4000-lb minivan.

        The market won’t wait another 100 years for that breakthrough.

  • avatar

    My recollection is that the two big disadvantages of flywheels are dealing with gyroscopic effects and the disastrous consequences of flywheel failure (so much angular momentum). They’re also pretty heavy. Pesky physics.

    • 0 avatar

      Counter-rotating flywheels as one solution

      The second is that the casing has to be heavy, but he wheel itself not necessarily so. Since Ke = 1/2mv^2, you get more benefit by spinning something faster than spinning a heavier flywheel slower…

      Which brings us back to the failure aspect. Probably for the future, we are looknig at very exotic materials to withstand the strains, but then again, we are already looking at very exotic materials trying to get batteries to work harder.

  • avatar

    FYI. Audi diesel powered R-18 take unprecedented 1-2-3-4 sweep in second round of FIA WEC yesterday. I salute Audi for defying conventional wisdom race cars have to be powered by petrol.


    • 0 avatar

      I salute Audi for recognizing that the FIA LeMans rulebook was hopeless antiquated in allowing a five-liter engine size limit for diesels rather than the puny 3.5 liter limit for gasoline engines, and in allowing variable-geometry turbochargers and a much larger air restrictor for said engines.

      I salute the FIA for recognizing that diesel is a good thing for the sport publicity wise and for being very reluctant to change the rules enough to make gasoline LMPs competitive again.

      That is all.

      • 0 avatar

        Please don’t confuse R-15 TDI with R-18 TDI. Those are old FIA regulations. For 2012 races, Audi’s R-18 TDI has 3.7 L V6 and the engine is also much heavier than its petrol counterparts. In contrast to previous Audi Le Mans sports cars the R18 TDI is only fitted with a single turbocharger. The fuel tank capacity of diesel-engined LM P1 cars are further reduced by 5 litres due to insecurity from other petrol rivals.

        Also, 2 out of 4 winning R-18 are e-trons AKA TDI hybrids. Trust me, I know this is pretty surreal news for petrol heads worldwide.

        That is all.

      • 0 avatar

        3.7 liter, still with a turbo. Gasoline LMP1s are still limited to 3.4 liters atmo, 2 liters with a turbo, and still with smaller intake restrictors. It’ll be closer this year, but make no mistake: the rules still favor diesel. A near 100% displacement advantage sees to that.

        And let’s not forget the fact that minimum weights for LMPs have not returned to the pre-diesel days… where they were raised to accomodate the older TDi racecars. A big handicap for cars limited to running smaller motors.

      • 0 avatar

        I guess it must be drivers’ error causing Kronos’ petrol driven Aston Martin 6.0 L V12 to be slowed than 3.7L TDI R-18 @ last year’s 24 hours Le Mans. Why penalize TDI because of its superiority? Speaking about unfair advantage, all diesel LMP1’s fuel tank are limited to 60 liters when 2012 24 hours Le Mans start in June versus petrol LMP1 vehicles with 90 liters of fuel. Either the governing body favors petrol racers or oil burners are 1/3 more efficient ?

      • 0 avatar

        It’s always tricky when you have race cars in the same class operating under different rules and budgets. Audi does deserve credit both for developing the technology and for showcasing the modern state of diesel engines, but it doesn’t prove that diesel engines are superior for this purpose. Whether diesel would be competitive in a racing series with minimal powertrain and fuel regulations, I can’t say. The current state of performance cars indicates that diesel is still not competitive in the consumer market.

      • 0 avatar

        Indeed… and downsized GDI turbo engines look set to give diesels a run for their money. Still probably not as fuel efficient as the diesel option, but better power density and performance.


        “Why penalize TDI because of its superiority? Speaking about unfair advantage, all diesel LMP1′s fuel tank are limited to 60 liters when 2012 24 hours Le Mans start in June versus petrol LMP1 vehicles with 90 liters of fuel. Either the governing body favors petrol racers or oil burners are 1/3 more efficient ?”

        So we missed the fact that they have air intake restrictors that are larger, twice as much displacement allowed as turbocharged gasoline vehicles, that the lower weight limits for LMP1s were raised to accomodate TDs and hybrids and that they make more power everywhere? Just checking.

        The tank size adjustment was a means of encouraging closer racing AFTER it became apparent that they allowed for too much power and technology for the diesels under LMP1 rules… but I think that was wrong, too. They should simply limit both diesel and petrol to the same air restrictor and turbo sizes and let the diesel’s better economy pull them through, this would ensure closer lap times and better racing, rather than trying to artificially handicap the diesels through extra pit stops… that doesn’t work.

        Diesel does well on equal footing against petrol in endurance racing. BMW has consistently fielded strong turbodiesel entries at the 24 hour Nurburgring endurance. But for spec racing like LeMans and even touring cars, to point to the strength of diesel entries here as a sign of the strength of diesel in terms of performance is missing the point of spec racing… badly. That’s like saying a Chevrolet Cruze is a faster on-track weapon than a BMW 3-series on the basis of WTCC results.

        Pound for pound, a turbocharged gasoline engine will still outperform a turbocharged diesel engine, if they are given the same technologies… direct injection, variable geometry turbocharging, etcetera… the big difference is that the diesel will always use less fuel.

        While I certainly applaud Audi for the brilliant move of pioneering the use of diesel in such a high performance racing class, it’s worth bearing in mind that class rules for diesel are STILL catching up with the times. Those class rules and engine size restrictions were written back when diesels were barely making half the power of their gasoline counterparts, even with turbochargers (hence the initial 5 liter turbo versus 2 liter turbo rule… and why it’s still 3.7 to 2 in favor of diesel).

        Hybrids are another matter, entirely. While recovering brake energy is a good idea, there’s still the question whether the amount collected is worth the extra weight and complexity. But given the high lower weight limit, it still makes sense in LM P1. As opposed to F1, where the low weights meant that Red Bull Racing was dominant for two seasons even with what is arguably the worst hybrid “KERS” system on the grid.

  • avatar

    The bomb is also in the 918. Have to start somewhere!

  • avatar

    Here’s some great reading on flybrid systems for racing, F1 in particular. Lots of good pics for you closet engineers:

  • avatar

    Not sure I’d want something spinning lightweight and really fast, I’d prefer a bit heavier I think and a bit slower.

    I’ve seen this idea on engineering experiments and it seems to work fairly well. Not sure if it can be packaged well so that consumers will accept it. I guess that’s the real challenge. Also I’m sure there will be some noise associated with it, I hope they can tune it to a pleasing sound, it’s very easy for something like this to cause an annoying vibration and hum, especially after being used for 3-4 years.

  • avatar

    Batteries are heavy… why don’t we just spin them?
    Maybe too close to perpetual motion to even consider.

  • avatar

    I remember that after the last Arab oil embargo (circa 1979) there was a lot of interest in flywheel energy storage. Stuntmonkey is correct in that rotational speed trumps mass. I recall they were spinning these to over 100,000 rpm. They were composit wheels and were tested to failure with no breach of the containment device.

    There’s also interest in using flywheels for over night storage of energy generated by solar farms.

  • avatar

    Am I the only one that is missing the ‘s’ in VorSprung ?

    Otherwise a good article on a great automotive site.

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