Mazda Patents Spinning Dorito To Extend EV Range

OK, so a Wankel engine doesn’t really use a Dorito as its cylinders, but it sure looks like one. The company has announced it will offer a range extender rotary engine for the MX-30 electric “crossover” vehicle, but [CarBuzz] dug into the patent papers to find out that it has some interesting twists.

The MX-30 is an EV with a relatively small 35.5 kWh battery. Like a hybrid vehicle, the car includes a small internal combustion engine that can charge the battery. It does not, however, directly drive the wheels at any time. The Wankel has several improvements, including a secondary port that allows more air into the combustion chamber when the engine has to produce high power. But there’s a problem…

The secondary port is great when you are pushing hard, but at low speed, it produces inefficiency. To combat that, Mazda includes a valve to seal off the second port when it doesn’t make sense to open it. But that’s not the strange part. The strange part is that the engine also has its own electric assist motor that runs off the main battery.  That’s right. The battery you are charging provides some energy to operate the electric assist motor to help the engine that is charging the battery. If that makes your head spin like the Wankel’s rotor, you aren’t alone.

The assist motor can assist or retard the output shaft during the intake stroke. This can optimize the intake to the combustion chamber. Of course, this will cause odd movement in the engine’s output, but since it doesn’t drive the car, who cares? The battery isn’t going to mind if the output isn’t smooth.

The Wankel shows up in a lot of odd places. We’ve seen Wankel air compressors. Despite detractors, there have been many improvements in the design over the years.

44 thoughts on “Mazda Patents Spinning Dorito To Extend EV Range

  1. Awesome. I love dorito powered engines. They are so much fun. I know Mazda can’t produce a new cars like the RX7/8 but seeing it used again, even in a situation like this, just makes me smile.

    I really can’t wait for the first ammonia based cars though. I think that might be the future. We already use it in ships and it’s amazing. Hydrogen without the huge problems of storing it. Just create it when needed.

    1. Hmm…. not sure I’m excited about the prospect of ammonia leaks. Actually, ever since I had to rebuild an evap filter a couple of cars back I’ve been looking forward to owning a car that has nothing which might produce noxious fumes.

          1. Ammonia is very easy to synthesize.

            Personally I’ve never heard of the concept so I’m not going to say if it’s a good idea or not, just only that I know ammonia synthesis is an already established industry (for farming, fertilizer specifically), much more developed than most other synthetic fuels… If this is even possible

  2. Sorry, but I don’t understand.

    This kind of drive with no mechanical coupling has the advantage that the combustion engine can always run with its optimal RPM and load.

    So, partial load seems not to be a usecase.

      1. But then you’ve just built an ICE car that needlessly carries around a heavy battery. I think it makes much more sense to cycle the battery (within reasonable limits) and run the engine more efficiently.

        1. Yes, but it is one operational mode they have to think about. If the engine at its optimum load generates more power than is needed to drive the car AND charge the battery, eventually the battery will become full and the car will begin to run off of the energy from the generator and not the battery.

          This situation is most likely when the car is running long distance in the “range extended” mode, starting with a fully charged battery and taken over to cross the country on the highway, which means the engine must be able to operate extended periods of time at partial load.

        2. Needlessly cycling the battery is a big no-no with EVs with small battery capacities. It is more critical because a 20% loss in capacity is felt more if it’s 10 miles out of 50 than 100 miles out of 500.

      2. If you’re cycling your li-ion battery when it’s at 50% SOC and always charge/discharge +-10%, it will last 10s of 1000s of cycles before usable capacity drops below 80%

        The lower the charge voltage, the longer it will last.

  3. What’s not to love about the Wankel? Mixing fuel with oil on purpose, poor fuel economy, the company talking about it as though it’s a small engine with high output when it’s really more akin to an engine twice that displacement! So much good stuff! /s

    1. Mazda (and other Japanese manufacturers) seem to be trying really really hard not to build a proper BEV. Guess they want to hold on on their ICE investment for as long as possible.

      1. Well for a prolonged period their likely customers don’t want EV anyway – far to many folks very actively resistant to the very concept of loosing the ICE, so being the maker of fun sporty or practical cheap hybrids where the European brands are largely going all in on Electric is a way to stand out, and give you a near monopoly on that resistant to change section of the market.

        And at least for some years to come not everyone will be able to practically use a BEV as the real gain to those is being able to charge at home while you sleep – practically never have to hit a fuel stop, hydrogen fuel cell may suit those users that can’t do that, but the infrastructure for that doesn’t exist yet. That leaves efficent ICE hyrbid units as the way to go for some time to come.

        Also worth noting Japan is a very very odd place from what I can tell – old tech that everyone else would have abandoned at least a decade and you would think has no place in a high tech society stays common in Japan. I really can’t claim to have any great understanding of the culture to hazard a guess as to why, I just know it does often enough to be noticeable.

  4. To be honest, wankel should have substituted 2 temps engines in motorbikes and equipment not so much car engines.
    But then you look at rx7 and rx8 and your heart wanted to make those engines work properly.
    I always thought about getting a rx8 with a broken engine, and making it an ev, and refurbish (and maybe sell) the wankel. Would fulfill two dream projects an ev conversion and a wankel rebuild

    1. How much do you think you’ll get for an unrebuildable POS pile of scrap?

      The RX-8 is the worst possible choice for rotary engines. They’re that cheap for a reason.

      Wankels are possibly useful as airplane engines. Where frequent rebuilds at high cost are expected anyhow and light weight plus simplicity is a bigger bonus. They’ve been tried and have failed as street car engines, stick a fork in em.

      Automotive engineers have forgotten KISS, all of them, but Mazda appears to be insanely bad. All they need is a Jatco CVT and they’ll have it perfected.

      1. No kidding. Look at Infiniti’s variable compression engine. I own a G35x and its been a wonderful and reliable car (and the wife loves it and the brand now). But ive told her I think the current crop of Infiniti’s are a big no-go at the moment. Just looking at that insanely complex variable compression ratio engine makes me wallet shiver in fear.

        One of the things about BEVs that excite me are their potential for much lower maintenance costs and frequencies. We will see if thats the way it plays out, but the potential is there simply from a parts count standpoint.

    1. I’m very curious myself as I’ve wondered where the breakeven point is with modern technology. The average american consumer wants fast and powerful – so big engines that you don’t need 90% of the time.

      For example, the last couple s10’s I owned lost about 30% of their rated horsepower by the time it made it down the transmission and differential to the drivetrain, and nobody in their right mind would drive it at the “maximum torque” rpm’s – guaranteed to blow up in no time.

      So, with modern engine efficiencies and modern ac and brushless dc generators and motors, I find it hard NOT to believe that a system that is able to operate at actual NEEDED engine power for daily driving with a battery buffer system for acceleration and whatever the day brings would be more efficient in all senses.

      . . . of course i’m ignoring all the issues with li-ion batteries – I live in WNY and am not looking forward to the electric future for a lot of reasons – still a lot of infrastructure and technical issues to address.

    2. I can’t speak to this very specific implementation (Wankel engines I know I have nowhere near enough info on) but the Hybrid concept in general CAN be much more efficient – the torque curve and efficiency of an electric motor is very good across a wide range of speeds where ICE are generally really crap with only a very narrow window that is even approaching good – so the electric drive train with hybrid recharge can operate in the ideal efficiency window for the ICE and gain a great deal by it.

      Though in the real world you do it seems have to really know how to drive ’em for there to be huge efficiency gains. They do tend to be better than similarly modern and comparable cars even without the right driving style though, even if that isn’t besting vehicles from decades into the the last millennium – all the modern crash safety requirements have added so much weight despite improving ICE engines the MPG for economy focused cars hasn’t really been improving.

  5. Replace half the batteries with capacitors. Use the capacitor bank for a boost when accelerating and fast recovery when breaking.

    Personally I’m waiting for a manufacturer to bring back nuclear powered cars.

    1. That’s a stupid idea, if i ever heard one. By doing this, your sacrifising capacity (you need tons of capacitor volume to even hame remontly enough capacity).

      What if, i know, crazy idea, just use li-ion chemistry that is capable of very high currents. You’re losing way less capacity than replacing some of the volume with caps.

      There are lithium cells than can deliver in excess of 200C of current. That means 1000Amps with a 5Ah cell. A 50kWh pack could theoreticaly deliver 10MW of peak power. So yeah, lithium isn’t the bottleneck here, if you want serious power.

  6. so many people here, and a company, trying to reinvent the Prius.
    recently sold my ’05 with 250K to a friend for $3K and it still gets over 40mpg.
    never a major problem.
    hyrbids should have eased us into the EV transition so it would be a slower process.
    perhaps that would have happened if the prius happened to be a more stylish car.

    1. Yes, but, a diesel Focus will give you 65mpg. (250 miles, cruise control set to 75mph on a real trip, verified against a calibrated fuel pump. The same engine in a Ranger is 33mpg on the exact same trip.
      Which is the most evil? It’s not an easy question to answer. NOx v CO2. Kill people or kill the planet.

      1. Yep, can confirm. 1.5TDCi in newer FORDs can be very efficient on longer curises. 60MPG+ isn’t that uncommon, if you drive normally.

        Hell, i hit 75MPG doing 55 on a 2 litre rwd diesel pushing decent power.

        Diesel is an efficiency kind, too bad it’s emissions aren’t that great.

      2. Not that simple either – Diesel is denser per volume, containing more carbon – so it will often be more sooty nasty to breath stuff and no gain in CO2 output, as there was more carbon to burn in that gallon.

        Diesel Engines actually in production cars does have a tendency to better efficiency in the energy extraction over Petrol, though the gap seems to vary over the decades as new refinements in each become common. But that does mean it aught to produce some less CO2 per mile, but as with all these things it is so dependent on exactly which engine and how it is used – and it certainly isn’t a massive saving. Diesel was pushed as ‘a better fuel’ more to make use of the thicker components in the Crude directly – it was easier to simply separate and use all grades as they come out of the ground than crack the heavy stuff to the lighter more popular fuels.

  7. Hydraulic hybrids are a not much investigated technology. A small ICE runs at its optimal speed, driving a hydraulic pump to push fluid into a tank, compressing air in the tank. The compressed air pushes the hydraulic fluid out through a hydraulic motor that drives the wheels.

    For smooth operation a pair of tanks should be used so one is having fluid pumped in while the other is pushing fluid out.

    It’s a simple system that was originally built in the 1970’s. Dig through The Mother Earth News online archive for some articles. One guy in 1978 put a Bradley GT (the uglier first version) fiberglass body on a VW beetle chassis with his homebrew hydraulic drive and was able to get 40 MPG, and be able to cruise over 60 MPH, with bursts to higher speed for passing. That was with mostly off the shelf parts and the engine running all the time. IIRC it also used a single pressure tank. Dual tanks working alternately would have been better.

    Current technology could make it even more efficient with electronic fuel injection and a start/stop system on the engine so it can be off when there’s sufficient pressure in the tanks.

    The hydraulic pump and motor could be optimized for the application VS using off the shelf ones. The fluid piping, connections and valves could be made to minimize turbulence.

    1. There’s a reason this never cought on. Inefficiences in the system and low capacity of the air tanks would make this not viable in the modern world. Also 40mpg is shit nowadays.

      Batteries are the way foward.

  8. Mazda seems to be trying really hard not to make an BEV, that isn’t a pile of poo poo (in other words, a compliance car).

    Using an inherently inefficient engine design (lets face it, rotary even sprinkled with all the pixie dust still be poor in terms of BSFC) and using it with variable loads (why would you do that for a device that simply charges the battery).

    The only way this sorta system “make sense” is to use a simple, efficient engine design, tune it for a specific RPM (like 3000) and run it at that load constantly or when it’s needed (when battery loses certain SOC for example). By doing this, there’s no need for cam phasing or fancy intakes or anything like that.
    I’d argue, if we lived in a world where emissions don’t matter, a simple reed vavle 2 stroke engine using GDI would make a lot of sense.

    But at the end of the day; with the amount of space and weight this sorta system takes, you’re better off just using a bigger battery pack instead.

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