Could Range-Extended Cars Save The Rotary Engine? Mazda Says Yes

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Rotary engine

Rotary engine

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While the Wankel rotary engine, Mazda’s power plant of choice for many years, has a fantastic power to weight ratio, it isn’t exactly what you’d call a green engine. 

As a consequence, since the Mazda RX-8 ended its production in June this year, you won’t find a rotary engine powering any new Mazda on sale in the U.S. today.

That doesn’t mean the Wankel engine is dead, however.

Speaking at this week’s Moscow Motor Show, Mazda president and CEO Takashi Yamanouchi confirmed to Autocar that Mazda was preparing to give the rotary engine a new lease of life: in a range-extended electric car.

Back in June, we told you that the the Japanese automaker was considering combining a hydrogen-burning rotary engine with an electric drivetrain to produce a range-extended electric-hydrogen plug-in hybrid.

That might sound far-fetched, but Mazda has been leasing a rotary hydrogen hybrid to customers in Japan since 2009, the Mazda Premacy Hydrogen RE Hybrid. 

“We are still learning,” Takashi told Autocar. “The rotary has a very good dynamic performance, but if you accelerate and brake a lot there are efficiency disadvantages. The range extender overcomes that. We can keep it spinning at its most efficient 2000 rpm while also taking advantage of its size.”

Mazda Premacy Hydrogen RE Hybrid

Mazda Premacy Hydrogen RE Hybrid

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Rotary engines may have come full circle since hitting their peak in the early 1970s, but as Audi recently noted, building range-extended electric cars with rotary engines might not be cheap. 

Citing limited-run production costs and a predicted price tag just under $50,000 Audi cancelled its plans to produce the A1 e-tron, a range-extended, rotary-engined electric car initially unveiled at the 2010 Geneva Motor Show.

Unlike Mazda however, Audi has very limited experience with rotary engines. 

Mazda, by Takashi’s own admission, is still in love with the compact engine. 

“When I joined the company in 1967, it was the rotary engine that motivated my decision,” he admitted. “We continue to explore ways to improve the fuel efficiency and capabilities of the rotary engine so it can be the primary power source of a car again.”

Before you get too excited however, it’s worth noting that the likelihood of Mazda bringing a limited-run production extended range car to the U.S. is for now, unlikely. 


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Comments (27)
  1. It's good to see so much innovation in cleaner technologies, but you have to bear in mind that a range extender is not there to recharge the battery, it is there to provide drive power when the battery is exhausted. Will this efficent at 2000rpm engine be able to deliver enough power to keep you going at full speed on the motorway? Other range extended cars vary the revs to suit demand, will this rotary have to do the same? will it become less efficent if it does?

    Many people think range extenders just trickle charging the battery from a small engine, but this is not how range extenders need to work. The first battery powered drive should be just that pure EV, no fuel top-up, then we can convert the 85% of journeys that are short to 100%EV

  2. Mike there's no way this can be cleaner technology since the rotary is like a two stroke. It lubricates the rotor tips by injecting oil along with the fuel into the combustion chambers where its burned and exhausted into the atmosphere.It cannot lubricate the walls of the combustion chamber like a reciprocating engine(where the lubricant is kept seperate) as its physically impossible, therefore it becomes a total loss system consuming oil that has to be replenished periodically.

  3. No way?

    1. Fuel type

    2. Material science [regarding lubrication]


  4. Will have to wait and see. They haven't cleaned it up in fifty years or improved the fuel consumption.Mazda only perservered on performance grounds.
    I do like the engines having owned two in NSU RO80's but that was a different era.

  5. The Wankel has been cleaned in 50 years and the seal are no longer a problem. This is a 50 year old myth.

    Laser ignition and direct fuel injection will improve the Wankel for sure. Run it at its constant speed "sweet spot" and it has found its niche. The Wankel runs far more efficiently when at a constant speed.

    Then the knock-on effects of being one third of the weight and size. As a range extender the engine can be hidden under luggage compartments. They are super quiet and smooth. Longevity is guaranteed as the engine is only a part time engine as range extender.

    I can't wait for them to come along. All makers will have to adopt Wankels as range extenders.

  6. I wasn't making a claim this was cleaner, just saying looking for cleaner is good, my point was actually raising scepticism of their claim.

  7. @Mike. I'm confused. How does the range extender on cars like the Chevy Volt work if the gas motor is not connected to the wheels (either directly or via a transmission)?

  8. Al, I took this from an old GCR blog by John V., but hope it answers your question.

    After the battery pack is depleted, the Volt's 1.4-liter gasoline range extender switches on--not to power the wheels but to turn a generator that provides electricity to the 111-kW (149-hp) electric motor that actually turns the drive wheels.

    So the range extender doesn't drive the wheels, it turns a generator that powers the electric motors that then turn the wheels.

    That's always been my understanding, but please correct me if I'm wrong... Anyone...

  9. In reference to Mazda worshiping the rotary like a god, there is a good reason, ever been in a Rx-7? do you have any idea the power that one of these things can produce? I drive my 79 Rx-7 every day, I premix oil into the gas tank for better lubrication of the apex seals, I also have no emmisions system of any kind, when I let off the gas flames come out of my exhaust, it burns your eyes and throat to be behind it while running, F*** the environment, I kill trees when i drive by and laugh, I also enjoy my 10 MPG so that I can enjoy driving it like it was meant to be driven, like a sports car, screw all this efficiency crap. The Rotary is a performance engine, nothing else, Keep it that way.

  10. The baddest assed dune buggy I ever built had an R-13C twin turbo from a 93 RX-7. Bad to the bone, 11000rpm run like a striped assed gazelle and went up the dune like a friggin rocket was under your ass. 130mph+ dune runner

  11. robok2 your right, but it'll only give you 111kw at full revs, which is actually hard to achieve, I don't know what power its giving at 40mph cruise but it's much, much less. Only surplus and regen goes to the battery (subject to additional charging losses) if the battery tops up enough the extender cuts out totally.

  12. I agree. The propulsion system should be designed around what each energy source does best. The battery is best for supporting stopped, stop/go, moderate urban driving. The ICE is best for cruise.

    An engine/gen should be designed to sustain cruise speed at 95th%-ile highway speed (ex-Autobahn!) -- 75m/hr / 120km/hr. In a slippery 1500kg car this would be about 30kW. Intelligent nav in the car will "know" when the vehicle is entering an expressway environment and start the genset.

    In this sort of role the rotary could do well. But continued improvements in reciprocating engines, projecting >120kW/liter, will be tough to catch. Plus, genset mounting options obviate many perceived NVH advantages of rotaries.

  13. If the setup is truly a "range extender" then the idea is NOT for it to power the car at freeway speeds, but actually extend the range of the EV. "I'm going on a 400 mile trip" so start the extender and the battery still depletes slowly, but instead of running out after 100 miles, it is out at 400 miles.

  14. I recently visited the main Mazda factory in Hiroshima and from that visit one would surmise that all Mazda cars have a Rotary engine. All they talk about in the museum is their history with Rotary engines (in particular the spectacular Le Mans winning car).

    Rotary engines should have a bright future in the range extender world as they perform best at constant speed and represent a good power/weight density, hence their use in light aircraft, microlights.

    Lets hope Mazda can keep things interesting

  15. From what I understand, the advantage of the rotary engine is the fact that is is very compact, small and can produce a lot of HP at high RPM with fairly small displacement. But the downsides are that it lacks torque at low RPM and it sucks a lot of fuel to produce the actual power at high RPM. But the extra weight saving is a potential advantage as weight extender...

  16. so if the car only runs in "range extended" mode it could conceivably run several hours if driving at street speeds which would make it a huge benefit in certain situations but all for naught. i am not a fan of Hydrogen. we are simply too far away from viability right now. so make a research vehicle? oh ya, definitely!

  17. With emphasis on clean burning engines I fail to see how the rotary will make a comeback without a break through solution for lubricating the rotor tips. The rotary is like a two stroke since oil is injected into the combustion chambers,burned with the fuel and exhausted making it dirty. When it was invented almost five decades ago this was not a problem but is totally unacceptable in todays environment. This is a major flaw of the engine.

  18. Think it through and you will succeed in seeing how it can make the comeback. ;)


  19. Maybe "you" could tell "me" how. Yes with some miracle material that would withstand combustion temps,centrifugal forces and didn't need external lubricant while using a non polluting fuel. Ive owned two rotary's (NSU RO80's) and liked them but feel a micro turbine would be better suited as a generator drive unit in todays climate.
    Might as well use a micro turbine.

  20. As I said above... 1. Fuel type. Use of H2 alone is enough. That is a feature H2 and alcohol share over electricity -- they clean the environment.

    2. One word... fullerenes. I don't believe that is a miracle any more; they have replicated it.


  21. Hydrogen has to be produced or cracked and would only be as clean as the source used to produce it, plus it takes more energy to produce hydrogen than the amount of energy it provides,its highly explosive and difficult to store and handle.Its worse than battery electrics in freezing temps.
    Carbon nanotube usage is still opening doors but until a motor manufacturer (Mazda) explores its characteristics for automotive engine (Rotary) use we will never know.

  22. 1. The article stated H2.

    2. H2 source is the same for electricity. To shoot down H2 regarding source is to shoot down electricity/BEV's. ;)

    3. Your arguments are based on minimum 30 year-old data. H2 production/storage has gone beyond that. (Get up to speed)

    4. "...we will never know."??? Most new tech (fullerenes) is adopted by smaller companies first before larger companies come on board, such as the way Mazda solved seal issues with aftermarket companies producing/marketing them first. You may never know, but including *all* is a bit presumptuous. Staying informed is part of the battle. :)


  23. Yeah, just be sure to get back to all of us when your wonder fullerenes are into production at Mazda with a rotary engine. You love to lecture others about getting up to speed, but perhaps you can let us know when exactly the rotary engine itself will do the same? I mean, dead even to the company that worships it like a God, but hey, zealots always have faith, irrational as it may be in cases like this.

    And the small companies adopt most tech is nonsense in this case; Mazda is slowly dying and not even profitable and even other OEMs aren't interested in it. But in your ideal world, they'll show us all what a rotary engine can do. Which appears to be simply disappearing from production, even at Mazda.

  24. There are more comments in this thread
  25. In my opinion, just another stall tactic in releasing an EV where a car maker announces a pie in the sky concept so people think they are doing something.

  26. I wouldn't say extended range could save the rotary engine. Instead, continuously variable transmissions (CVT's), which are commonly associated to hybrid vehicles, could save the rotary engine. I hear rotary engines show a much better performance when operated at constant rpm's. And this is one of the advantages of CVT's among others: they allow you to shift an infinite number of gears at constant engine's rpm. As a result, CVT's allow you to operate an engine at peak performance, which currently happens at a specific rpm.

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