Mazda Rotary Engine To Return As Range Extender


A fitting application for the future.

Mazda’s first rotary engine was launched half a century ago and the Japanese manufacturer is currently developing its modern successor. The good news is we will probably see it in less than two years from now, but, unfortunately, it won’t also power a plug-in sports model. Instead, according to recent reports, the good old Wankel will be used as a range extender in an upcoming electric vehicle for the masses.

In theory, the rotary motor is the perfect choice for a range extender, as it has compact dimensions, high power output, and low vibrations during work. Speaking to Automotive News, Mitsuo Hitomi, global powertrain boss in Mazda, has confirmed that, most likely, the new Wankel engine will generate electricity for a production battery-powered car.

“I think that’s probably what it will be,” Hitomi revealed recently at a technology preview at the Japanese carmaker’s proving ground in western Japan.

Mazda Hazumi

The electric vehicle in question will be released in 2019 in two variants – one will be a pure EV, while the other one will use a range extender.

The former is seen as a perfect option for Europe, China, and Japan, where the relatively short range of current EVs will be enough for most of the customers. However, given the much longer daily drives in North America, a version of the model with a range extender is believed to be crucial for a market success in the United States.

To be able to create two different vehicles on a single platform, Mazda is developing a special architecture that will debut in 2019. It’s designed with batteries in mind, which will make it suitable for both EVs and hybrids.

Source: Automotive News

Categories: Mazda

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63 Comments on "Mazda Rotary Engine To Return As Range Extender"

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How loud are these engines?

Mart Shearer


Was this before “zoom zoom”?

Mart Shearer

Yeah, think early 1970s.




Would like to see a Phev where the rotary is coupled in to provide power to the wheels. The power characteristics would be a perfect complement. No need for multigeared transmission and accerleration would continue well after the electric drive acceleration tapers.


Rotary Engines are “PROVEN FAILURES” Nothing but Problems. They just won’t give up on .. So Stubborn ! They Burn Oil Make lots of Noise, Bad seals , run Hot ,Back Fire, Heavy on fuel, Etc: They are Proven inherently “NO GOOD” They just Don’t wanna get it through their Fool Heads!..Besides “ICE” will be historectomy in time to come …Why bother playing with Junk ? ..


Because they rev to infinity (almost).

My first engine rebuild was a Mazda rotary–I agree that there are many disadvantages to a rotary engine, mostly due to the wide rpm range that is desired. Yes, a rotary must have a rich mixture to idle, but a range extender can run at a single rpm.

The new rotary engines use peripheral porting which eliminates overlap from the engines with rotor ports.

Dave K

In this application a rotary works well, compact, smooth and high power/weight. As a seldom used range extender who cares if it lasts a long time or uses a little oil? The only question is when pure EVs have 200+ mile ranges how necessary is a range extender?


All you saïd might be true, but rotary has avantage like high power to weiht ratio, low vibration, compactness and simplicity.
If they improve their drawback, it coupe be a better choice than a piston engins.
Will never béat pure BEV thought


In a primitive way the Rotary engine is imitating the Electric motor in the form of a fossil fuel burner…


That does not make sense.


Then Go ahead & buy one! I wouldn’t touch it with a 20foot stick..


No one’s telling you to buy one either.


Now, you are a professional troll!

The early rotary had a problem with seals but they corrected and then rotary become the very reliable engine. Mr. Troll, hopefully, you can speak the truth from now and on.


You paint a bit of a rosy picture. The RX-8 is more reliable then the line ever was in the past, but still not a reliable car.


Most rotary engine problems can be traced back to RPM related issues. They should be very reliable when operated at a constant RPM.

Emissions problems related to operation at idle will be non-existent, because like the BMW i3 range extender, it won’t sit and idle when not in operation.


Gee, I thought the Mazda RX7 was a popular car that many just loved to drive with little problems.


Rotary will be a good range extender. MPG will rise with a steady load profile.





Well, I’ll be happy if they can do it. But I am not a fan of the Wankel for a variety of reasons. On the bright side, if I use the range extender as often as I use the one in my Volt (approx 6 times per year), it shouldn’t be a problem. I’m actually more interested in the piston design that Toyota is working on that has no crankshaft. That should eliminate a lot of weight and be very efficient.


I wonder whatever happened with the wave-disk engine.


Yeah, I thought that one would be a winner also. Paid for by GM and Ford, then it sits as an R&D museum curiosity. Must be some reason (just guessing but not enough torque for its size?) for its disappearance.


Unless they’ve come up with some breakthroughs with efficiency, the Wankel has terrible MPG, even its wiki lists bad fuel economy under disadvantages…EPA for the last RX8 base (1.3l w/turbo), 18mpg…Many owners flooded them, Mazda had major defects and had to extend the warranty…What this tells me is the Wankel engineers have been working tirelessly to improve efficiency, couldn’t get there so Mazda Corp threw the team a bone by making it into a EREV…

A subcompact hatchback is not the right segment for the States…


Tidbits about the latest Mazda rotory, the SkyActive-R…

Gist of it is now they flipped it 180 degrees so now that intake is on the bottom and exhaust is on the top which translates to short intake and exhaust plumbing…Also each side features common intake/exhaust and individual intake/exhaust runs which somehow creates a supercharger like affect…They claim it’s comparable to a typical ICE as far as emissions and MPG…Yet do not mention what typical means (A 2.0 NA 4 banger? V8?)


But most PHEVs use a Atkinson cycle, which is even more efficient than typical ICE. Unless the changes you describe surpass a typical ICE, they’re not enough to match the Atkinson. Maybe there is a benefit of power or vibration, but that would be a trade-off.


I think they’re thinking of i3 REx, though not necessarily serialized. In that case it could be a good fit.


Seems to me the main issue with this, by the time it arrives in 2019 or 2020, >250 miles will be routine on battery for the cars coming out then, and a range extender will be pretty much unnecessary.


Different segment of buyers…I mean why does anyone buy even buy a Volt (or any EREV) when there’s the Bolt EV?


Because you can drive anywhere you want any time you want to.


God, because it takes the Chevy Bolt over an hour and a half to charge to 80% on a 50 KW charger.


Are you kidding? I have an i3 REX and it’s still more convenient to have a gas range extender than a longer range EV for long drives. DCFCs are too few and far between, occupied, broken, and take too long to recharge the car compared to a quick gas up.
Once fast chargers are ubiquitous and can charge the car in 10 minutes then there will be no need for gas range extenders.

Brave Lil' Toaster

Ah. Evidently, using a rotary engine is a solution to the problem of the EV’s over-reliability that threatens to put car dealerships out of business.







I’m still waiting for the Audi A1 e-tron with Wankel engine, announced in 2009. If anything, after reading clean tech articles for 10 years, I am disappointed at the speed with which this industry grows.

What year?

Yes, it is funny. An article from 2017… oops, 2010:

“Another world premiere in Geneva is the A1 e-tron design study, which shows that Audi’s expertise in electric drive systems extends down into the compact car segment. At the end of 2012 Audi will launch the e-tron electric car that was seen last year at the Frankfurt Motor Show (IAA).”

“Every year Audi invests around two billion euros in development projects […] Electric mobility is a further priority: In this area the e-tron show car seen at the IAA was a dramatic signal. At the same time, the various activities are being grouped together strategically. Audi has established the e-performance project house to deal with electric mobility topics”


Rotary engines inject oil to lubricate the APEX seals, so that gives them bad emissions. Not sure that is a good fit for an EV.

Empire State

Actually, it’s Range-Extended EVs which make a good home for the rotary. Although the rotary may have a poorer emissions spectrum from reciprocating piston engines, the overall vehicle emissions for something that is primarily a BEV but occasionally uses petroleum power can easily best a PHEV. Together, the relative light weight of the rotary engine, and the fact that it’s weight specific output being good means that the electric motors are hauling around less inactive engine weight while it’s not in use, means that the engine can be a more optimized design for the occasional-use application in a Range-Extended BEV. Clever.

You are making probably wrong assumption about “occasionally uses petroleum power”. Unless they design it like Volt, it could kick in the gasser on every drive by lightly tapping on the pedal.

And if the electric is strong enough, it will need hefty battery, which means smaller weight rotary engine is not significant. Rotary makes no sense as range extender unless the goal is to waste more fuel and emit more pollution (I mean real pollution like burned oil and soot, not CO2)


It isn’t the same engine from last century. I imagine they have improved it significantly, or so they claim. Operating at constant RPM would eliminate part of the problems as well.


What a waste of financial and engineering resources.

I second the motion. It’s a dinosaur before it goes into production.


Mazda with it’s rotary engine fetish and Elon’s door fetish.


If only Mazda had actually put that into production…

Hans Hammermill

I applauded Mazda for trying to improve the rotary; it seemed like a good technological hedge (if they developed a break-through in efficiency or emissions).

Now that we have 200+ mile pure EVs that are not insanely priced, it just seems like a solution in search of a problem.


The beauty of an BEV is it’s simple, clean and efficient. Why introduce the complication, pollution and additional expense of an inefficient, ICE, especially an unproven rotary.

Hybrids have been obsoleted by quick charging and better batteries.


” However, given the much longer daily drives in North America, a version of the model with a range extender is believed to be crucial for a market success in the United States.”

This is false. The average daily mileage in most European countries & the US is about the same. In fact, because a lot more (percentage wise) Europeans use public transport and/or bicycles for their daily commute, cars tend to be used for fewer but longer trips.


No, an electric car does not need a range extender if it has a 90kWh+ battery.
With a 300 mile range, thats pretty much the maximum we really need. Then its all about having well-placed 150kW fast chargers, and ideally having an 80 amp on-board charger so we can keep our 5 hour home charging times.


90kWh+ batteries will be far too big, heavy and expensive for a while yet, and not suited for the majority of cars.

A 40mi electric range is enough for 70% of miles to be electric, already cutting two-thirds of fuel use and emissions, as the Volt demonstrates.

A PHEV/serial-hybrid that can do ~50-80mi on battery (for cars 1-2 size classes larger than the Volt) can probably do 80%-90% of its miles on electric… Until batteries are light & cheap enough, it’s far better that the majority of people drive PHEVs than only a few percent will. There are 2-3 decades — several generations of cars — where PHEVs make much more sense than BEVs as all-rounder vehicles, certainly for 1-car households. The latter are the normal case in most of the world.

And before people start saying “but the Model 3”, it’s not a car for the masses — it’s still far too expensive for most of the world.


We already have 100 KWh and the roadster is anouced with 200 KWh. In the same time we will have Megachargers. A Rex is yesterday’s solution, now oilies will have to face the full blow of pure BEV. They will also be cheaper very fast.

“it’s still far too expensive for most of the world”

I suspect whatever PHV Mazda produces with Wanker (yes, Wanker!) engine will probably be similarly priced as base Model 3.


As much a I like rotary engines for their mechanical simplicity, they are notoriously bad when it comes to emissions.

I really really wish this wasn’t the case, but the sad reality is that (so far) anything that improves their emissions degrades their fuel economy, and don’t get me started on gas turbine engines.

As far as I know, Atkinson cycle engines are among the more efficient and cleaner ICE engines.

And this is why we we need to get to BEV’s.

Doug Bostrom

Having driven and much enjoyed a factory-fresh RX-2 (yes I’m that old) I get a nostalgic glow reading this.

However, the awesome zip and smooth operation of the RX-2 came at a cost: 17MPG for a car that could not have weighed more than 3,000 lbs.

The engine simply wasn’t very efficient. Presumably this has been improved?

Doug Bostrom

Addendum: the physical form of the Wankel does seem better suited to this application than does the awkwardly shaped piston engine. Plus few parts, of course.

Josh Bryant

This would be a good idea for trucks or large SUVs. But seems foolish for a small car unless they are sticking with 100ish mile range for the BEV. similar to the current i3 optional range extender.


This is 2017 notre 1997.
To late for that Kind of system.


Come on Mazda. All I want is a BEV MX-5. Is that so Hard?

I’m sure all the engineers that have commented know exactly how efficient the new engine is. But presuming that’s not true, let’s assume Mazda has actually fixed the emissions and efficiency issues. If that’s the case then there are obvious advantages. 1. For the same power, it can be half the size and half the weight of a regular Rex. 2. It has fewer moving parts and doesn’t reciprocate so should have longer engine life and greater reliability than a regular reciprocating piston engine. 3. Cheaper to build. 4. Suited to running at a constant RPM ala the Nissan Note e-Power…perfect for a Rex. IF that’s the case then there is both a cost and environmental argument for doing it. If you take the setup of the i3 Rex, it can be improved by making the battery smaller. Give it 50 miles of range and a 5 gallon gas tank. The only reason it has such a small gas tank and large battery is that BMW is getting it classified for CARB as a rex EV rather than PHEV which is greater tax credit. Drop that artificial incentive that doesn’t exist in most states and the better economic argument is… Read more »
Doug Bostrom

Yes to all of that.

Fairly sure that Mazda has not somehow overlooked the efficiency problem (which presumably will solve many of the pollution problems which had a lot to with unburned/poorly burned fuel).

Low thermal efficiency is inherent in the design, due to combustion chamber shape and large swept area. But thermal efficiency is unimportant in a seldom-used range extender. You can still come out ahead in terms of overall vehicle efficiency if the rotary reduces weight and takes up less space. REx is most compelling at the low end. It’s absurd for people to claim BEV will now dominate when the lowest cost 200 mile BEV is a $20k Sonic variant priced at $37k. (It’s even more absurd for someone to claim the 200 kWh pack in the 2021 quarter-million dollar Roadster2 has any relevance to this discussion). Build cost for a practical, low end car (e.g. Ford Focus, Honda Fit, etc.) is less than $10k. Much less in developing countries. The Bolt battery alone costs more than that. Cut battery costs in half by 2025 and you’re still way too high. An 80 mile rotary REx could cost almost the same as a low end gascar. Since people rarely take small, low end cars on long trips, 80-90% of miles would be EV. Low cost EVs would enable cities to ban ICE much sooner, spurring the transition. Personally, I’d rather address… Read more »