8 ms·

Mazda’s rotary engine in the age of the electric car

240 points by gascoigne 2y ago

rootusrootus 2y ago
Almost feel bad for GM, the article did not mention the Volt when talking about series hybrids. But I guess it is a Japan-focused news source.
- jmspring 2y ago
  The funning thing is, people I know who have a Volt love their cars. Haven't tried one myself. My family has a couple of paid of Toyota gas vehicles that are 8+ years old and will probably live longer than we will.
  - joking 2y ago
    Vehicles with range extenders are the exception, even if they seem a good option, they didn’t gain market share.
  - Tagbert 2y ago
    I drive a 2017 Volt gen 2 and love it. I drive about 90+% of miles in EV mode and mostly use the gas engine for road trips. It is fun to drive and (other than a couple of common, and easily fixed issues) has been reliable. I do plan to replace it in the next year because it sits very low and has a very low roofline. My spouse is uncomfortable getting into it so we almost never drive it when together.
    - nradov 2y ago
      I don't understand why GM never put the Voltec drivetrain into a compact SUV. It would have sold much better than an odd looking hatchback with little interior space.
      - Tagbert 2y ago
        Word is that PHEVs are expensive to build but customers didn't seem to be flocking to them. Traditional buyers didn't see the need to save money on fuel and didn't believe that climate change "stuff". More adventurous buyers were flocking to the new full EV coolness. I think GM decided that the future was BEV that they would be able to come out strong with EV version of their products and sell them at reasonable prices. With the component shortages and inflation, their price targets became untenable. Then they ran into assembly problems with their battery packs so they couldn't even deliver at any price. Now they have backtracked and said that they will bring out hybrids (maybe PHEV?). It's not clear which platform they'll use for that. I think that they have an Equinox-sized hybrid in China that they might bring over. The flailing around EVs vs hybrids and the on again off again story on the Bolt don't make it look like they know what they are doing, sadly. BTW the Bolt actually has a surprising about of room in it, but even so, its on the small side. Equinox would fit more customers.
  - illegalsmile 2y ago
    My friend has a few volts from 2013-2018 (that he loves) and I usually borrow one for trips to see family and friends 12-16 hours away rather than drive my truck. I think they're great vehicles. ~40mpg at 80-90mph on the highway is really good though it does take premium for that 40+ mpg and it has a smallish tank so you have to stop a little more often. Once you reach your destination all driving is done on electric and charges overnight on a regular outlet/level 1. Their maintenance is surprisingly low for what seems like a complex system. Crazy to me that Chevy has abandoned their PHEV platform considering others, like Toyota, are in such high demand. Speaking of which I spent a week with a Rav4 Prime and found that equally as impressive range-wise as a volt.
- tokai 2y ago
  The point is the wankle engine. No sense in mentioning the Volt.
  - rootusrootus 2y ago
    They did mention a couple other series hybrids, however, neither of which has a Wankel.
- seabrookmx 2y ago
  As mentioned elsewhere in this thread, the Volt is not actually a series hybrid despite being marketed as such. There is a planetary gear set (ala. Toyota hybrids) connecting the engine to the wheels at most speeds.
486sx33 2y ago
Does it produce more low end torque verses a traditional gasoline combustion engine? If not then why is it better suited for electrical generation? Is it more efficient with less load? The article mostly makes it sound like Mazda just loves the wankle and wants to find any possibly way to bring it back - even though it has “high” emissions… so coupling it with a hybrid electric motor makes it happen.. That can’t be the whole story?
- jpgvm 2y ago
  Wankels can be made extremely compact so that might have something to do with it, i.e it has both very high power to weight and power to volume specs. I honestly don't know if that is the reason though, perhaps someone more knowledgeable of the specifics of range extenders might chime in but I imagine that is an important factor.
  - sethhochberg 2y ago
    They have a pretty narrow power band (produce efficient max power at a small range of RPMs) which always somewhat limited their use for normal ICE cars, but is a pretty workable constraint for an electrical generator. So you have compact size, good power to weight ratio, and power limitations that don't really matter for range extender purposes. Lots of potential. I can't find the article right now, but I'd swear I remember discussion here a handful of months ago about a startup marketing a similar EV range extender engine design.
    - HPsquared 2y ago
      They have low compression though, which really hurts the thermal efficiency.
    - coryrc 2y ago
      Then you may as well use a gas turbine, which is pretty much better in every way that matters for generating purposes.
      - 2y ago
Projectiboga 2y ago
I was always impressed by this engine in my childhood, but it never really caught on. Here is a variation I've seen on the internet, i'm not sure how practible it would be. https://arstechnica.com/cars/2023/11/this-inside-out-design-solves-most-of-the-rotary-engines-problems/ https://arstechnica.com/cars/2023/11/this-inside-out-design-...
- explorigin 2y ago
  https://www.youtube.com/watch?v=X5UOqZn43gY https://www.youtube.com/watch?v=X5UOqZn43gY It has longevity-issues due to an internal roller bearing on the main shaft.
  - knodi123 2y ago
    wow, thanks. I didn't expect to watch the whole thing, but I did.
  - fragmede 2y ago
    Depending on how it's being used. Rotary engines are better in some ways when being run hard (ie as a track car) compared to more traditional layouts.
Projectiboga 2y ago
Mazda and Toyota formed an alliance to share technologies to fill gaps they each had. I'm guessing this is fruit of that partnership.
- vpribish 2y ago
  Where do read Toyota into this announcement?
mattmaroon 2y ago
I have never understood why the Volt Series Hybrid idea never took off. It is more efficient to turn gasoline into electricity and then drive the car with that than to directly connect the engine to the wheels. Is it perhaps that the cost involved is just too much more than a plugin hybrid to make the small extra fuel savings worth it?
- HPsquared 2y ago
  Surely the "generator -> charger -> battery -> inverter -> motor" chain is less efficient than a driveshaft. Perhaps the only benefit is the engine can run at an optimal speed, but an appropriate gear ratio should handle that.
  - dragontamer 2y ago
    > but an appropriate gear ratio should handle that. See Prius's "Powersplit Device". I'd describe the Powersplit device to be a combination of generator/alternator, starter/electric motor, reversed-differential (2x power inputs -> 1x driveshaft), and effective gear-ratio. All in one planetary gearset. EV motor2 determines the speed of the car. The ICE motor can spin at any speed that the computer determines to be useful. If EV Motor2 is 0-rpm, then the ICE is 100% in generator mode (2000rpm but the car isn't moving: all the energy goes to charging the battery). If the EV motor is at 10mph but ICE is off (0-rpm), then its 100% electric drive mode. And any combination in-between is possible. EV Motor1 (a smaller, weaker motor) controls the 3rd set of gears (I think the planet gears?? I forget), which determines how ICE relates to EV (changes the effective gear-ratio) https://eahart.com/prius/psd/ https://eahart.com/prius/psd/ --------- So yeah, the PSD allows the ICE to always function at the appropriate speed (which is either 0rpm or ~2500rpm for efficiency). While the combination of EV-motor1 (changes effective gear ratio of ICE) and EV-motor2 (hard-wired to the final speed) handle the different speeds the user wants in practice. All in like, 15 gears or so. https://www.youtube.com/watch?v=jofycaXByTc https://www.youtube.com/watch?v=jofycaXByTc --------- I do think that the Prius (and Prius Prime) have surpassed the Volt's design, and the proof is in the pudding. Prius Prime has 52mpg, a figure far more efficient than the Volt ever had. Prius Prime also has 220 horses today for a 0-to-60 time of 6.6 seconds. So today's Prius Prime is a lot faster than the Volt too. Volt was good when it came out, but technology has gotten better since then. Toyota has seemingly perfected this "power split device", and its beginning to lead into exceptional acceleration and good driving feel (as opposed to being 100% economy focused like before). Volt had better feel than the 2010-era Prius, but 2024-Prius is a totally different car. I think all Volt fans are in "but what if GM didn't kill the Volt and kept investing in the technology?". And... yeah... that's a fun what-if. But... GM killed the Volt. It sucks, because it seemed like great tech. Apparently GM has kept the drivetrain technology ("Ultium") and has continued to provide R&D, but Toyota's recent advancements are jawdroppingly good.
shanusmagnus 2y ago
What was the purpose of using the rotary engine in the first place, for ICE cars? From the comments it seems it's maybe lighter for a given power output. Is that it, other than just the novelty of it?
- 20after4 2y ago
  It's about double the power output for a given size / displacement. It's very smooth and high-revving so that makes for a really fun driving experience in a light-weight sports car.
- jdblair 2y ago
  Lighter and mechanically simpler were the selling points. Poor fuel efficiency and trouble with the seals were the downsides. My uncle had an RX-7 back in the 80s when I was a kid. I remember when it was idling I could see the exhaust puffing, in pulses. It only had a single combustion chamber after all.
  - LarsDu88 2y ago
    It's mechanically simpler until the apex seals blow out. Then you are fucked
  - samdunham 2y ago
    I've had three RX-7s. A first generation and two second generations. I drove the first until the wheels literally fell off (I was a young, stupid kid that ignored the crunching sounds of the rear wheel bearings falling apart. The rear wheel(s) seized while I was driving down a bridge causing the axel to snap in half. That was an interesting "drive" down the rest of the bridge). The second was a base model second gen that I gave up when I suddenly had two cars because of getting married, then divorced. The third was my favorite. A late model second gen fully loaded. That one eventually caught on fire due to negligence at a tire place. I loved that car. The third generation never got cheap enough for me to consider one, but oh, I wanted one badly. The RX-8 never really caught me. Plus they had some early issues. That Iconic concept definitely has my attention, though.
  - 2y ago
dragontamer 2y ago
A good article. It barely addresses the elephant in the room however: The Toyota Prius and its Atkinson engine. The Atkinson engine is 99% the same as a regular engine (aka: Otto cycle), except the timing is different. Instead of closing the valves when the piston+cylinder is full of gasoline+air mix... the Atkinson engine waits a bit and "leaks" some gasoline+air back out before closing the intake valve, effectively burning only 70% of the fuel, but getting maybe 85%+ of the power of a regular Otto-cycle engine. Its a simple and cheap tweak to a traditional engine that grossly improves efficiency (but at huge costs to low-end torque). Basically, any regular ol' carmaker who is mass producing Otto cycle / regular ICE engines can easily tune their piston timing to be an Atkinson engine instead. I believe Toyota even has computerized controls today that switches between efficient Atkinson (lower-power but higher efficiency) modes and powerful Otto cycle (higher power but lower efficiency) modes, though this control isn't really used too often in practice. --------- This article makes a good point that Mazda has a culture of this... rotary engine. It does compare it (somewhat unfairly) to the Atkinson engine though (inside the Prius and RAV4), I don't think anyone expects any traditional engine (Otto or Rotary) to keep up with Atkinson Engine efficiency. Its a good try however. But it does raise the question of what benefits can this rotary engine give over other engine types.
- aidenn0 2y ago
  I am mildly annoyed that Toyota calls late intake valve closing (LIVC) an "Atkinson-cycle" Atkinson made 3 engines none of which are anything like a 4-stroke with LIVC. The closest is perhaps his two-stroke engine, which kept the exhaust valve closed during the power stroke and open for part of the compression stroke. The Miller-cycle is much closer to what the Prius uses than anything Atkinson made; it was a traditional 4-stroke with LIVC, but required a super-charger to generate power at low RPMs. The Prius has a CVT and electric motor, overcoming any issues at low RPMs. Also now that VVT is more common, many engines run with LIVC under certain conditions.
  - jeffbee 2y ago
    And, of course, Mazda had been selling LIVC engines for years before the Prius appeared. Like all of Mazda's other weird engines they were expensive, bad, and unreliable.
SebFender 2y ago
I have so many bad memories from this engine. I finally brought them to court to win. But all this to say Mazda has been out of the game so long living on dreams with this engine.
- busterarm 2y ago
  Mine went 110k miles without ever blowing up and then I decided to rebuild it. It's got as much longevity as other cars from the era if you pay attention to oil/omp and (over)boost (if you have a turbo). Everyone puts in at least a downpipe and then neglects all of the other mods (wastegate mod, better fuel bump, bigger injectors, wideband o2 sensor and new fuel map, better intercooler, etc) that you'll be forced to do along the way or suffer from boost creep and an eventual grenaded engine. It's all of the other things under the hood that I've had to replace from all that heat though. Three alternators. A wiring harness that caught fire...
ngcc_hk 2y ago
Is the rotary better or worst with pollution ?
- linsomniac 2y ago
  The long combustion chamber, according to an ex-petrolium engineer co-worker of mine, is inherently less efficient because the charge along the walls of the combustion chamber doesn't burn as well.
1970-01-01 2y ago
The problem with the Wankel is and has always been apex seals. You need to rebuild it at least once during a vehicle lifetime. I would not say it is safe from this fate, even with modern seals and a hybrid application.
- aunty_helen 2y ago
  I thought it was the horrible compression and oil burning. Apex seals seem to last if you don’t do silly things to them but you can’t solve inherent issues with the cycle design. For comparison, rotaries get about 100psi of compression, a modern gas car can more than double that. More compression, more efficient burn.
  - 1970-01-01 2y ago
    I've read that oil burning (which is directly tied to the apex seals) has been fixed in modern engines. Compression is a somewhat configurable matter, and can be high in a low-torque generator (battery hybrid) application.
seany 2y ago
Can you buy it as an EV and then drop in the generator later? It makes a big difference for registration in some places.
SeanLuke 2y ago
> Despite all this, though, the MX-30 R-EV still falls somewhat short, with a catalog fuel efficiency of 15.4 kilometers per liter (as measured in WLTC mode). With no similar vehicles on the market, like-for-like comparison is not possible, although the Toyota RAV4 plug-in hybrid gets 22.2 km/l, while the Prius plug-in hybrid gets 26.0 km/l. The MX-30 R-EV is clearly inferior in terms of its fuel economy. That's because the engine serves an entirely different purpose. The Prius plug-in hybrid is a 13.6kWh battery mated to a regular engine. The MX-30 R-EV is a 17.8 kWh battery mated to a tiny ultralight emergency range extender. As to similar designed cars, um, hello, the BMW I3 Hybrid? Exactly the same design. The failing of the MX-30 R-EV is that its battery size is pathetically small for what amounts to an EV with a range extender. It is an embarrassment.
- tom_ 2y ago
  I wonder how many people drive far enough to regularly need the range extender before they have a chance to plug it in. The fuel economy of this thing is not great if you drive it far enough that it runs out of petrol and you need to fill it up again - but what if you rarely do that? What if you usually drive less than about 50 miles before the next opportunity to recharge it?
awful 2y ago
_
- ryukoposting 2y ago
  A Wankel with a turbo at redline sounds you just violently shook a big metal can full of hornets.
dbg31415 2y ago
The mid-90s RX-7 was sexy as hell. But the RX-8 just wasn't. A cool engine still needs to be wrapped in a car that people want to drive. The MX-30 doesn't quite fit the bill... just seems so mundane to look at.
mikewarot 2y ago
Instead of a Wankel, why not use a small custom turbogenerator, like the APU in aircraft?
- AYBABTME 2y ago
  They're efficient at higher power levels but really not at small-power-generator level. An 8kw jet powered generator I saw recently used 0.5kw-hr per kg, which is 5x more than an equivalent one based on a traditional diesel engine. Their main advantage is high power for low mass of generator, but consume massive amount of fuels.
  - willis936 2y ago
    Seems unreasonable for a powertrain, but pretty reasonable for a series hybrid generator.
    - AYBABTME 2y ago
      Not really because the power rating at which they start to make sense is in the multiple hundreds of kW. Cars don't need that much average continuous power while driving, on the order of 15-30kW depending on speed and grade. So a "more efficient than piston" turbine engine would be way too big and powerful and would cycle about once per hour. Overall excess mass and bad reliability due to frequent cycling. It's better to have a smaller engine that's sized for slightly over 15-30kW continuous duty. Realistically this will be a piston engine, or a fuel cell. I would love to use a turbine engine for my own application but the math doesn't work, unfortunately.
johgoy 2y ago
I like the LiquidPiston engine technology as an inverse Wankel engine. A lot more efficient.
wkat4242 2y ago
One of the cool things about this engine is that it can run on hydrogen with minimal modifications. Not sure if the article mentions this, I don't have time to read it now. But that could make it more interesting when renewable hydrogen becomes common (right now it's not)
- m463 2y ago
  Have you looked at hydrogen prices? when the first hydrogen cars came out it was about $17/kg, and I think last time I looked it was around $33. I think that's a LOT more expensive than gasoline per mile.
  - wkat4242 2y ago
    Meh, market forces can go either way. By the time green hydrogen actually becomes available it might have changed again. The problem is more finding a less lossy way to create it out of water with electricity. Also I don't advocate hydrogen as a 'solution'. To me the solution is less cars and nmuch better public transport. I could see it work for buses though.
- adrianN 2y ago
  Why would you burn hydrogen in a car? It's more efficient to burn it in a power plant and run the car on electricity.
  - wkat4242 2y ago
    I'm sure there's some niche uses where it makes sense. Fast refueling for example because batteries are so slow. And much heavier than a Wankel engine plus hydrogen tank. Like in a public transport bus that needs to be on the go all day. In fact I'm pretty sure that's what the hydrogen buses in my city do, they're way too noisy to be fuel cell electric. Besides, if you can run on electric you can bypass the whole hydrogen step altogether.
m463 2y ago
It's worth mentioning that serial hybrids, like the BMW i3 rx, might not be able to drive on the freeway on the output of their generator. That's why it's a "range extender" - at some point you have to pull over and charge. EDIT: this is a big secret that none of the marketing materials (want to) make clear. I'm uncertain the output of the wankel, but maybe with its power-to-weight it might get closer to being able to drive on gasoline in a self-sufficient way.
- danans 2y ago
  The Mitsubishi Outlander plug-in hybrid can do up to 60mph on a flat road in serial hybrid mode.
- bruce511 2y ago
  Weeelll, "freeway driving" depends on the freeway and time of day. For too many freeways, for too much of the day, I can ride a bicycle at speeds greater than the surrounding traffic. And in those conditions hybrids, and electric cars are perfect.
- adrianN 2y ago
  Does that matter in practice? What's the effective range for highway driving in these cars?
  - m463 2y ago
    I recall the i3 rx only had about 2 gallons of gas.
- connicpu 2y ago
  I don't know where you get this idea, my Chevy Volt is perfectly capable of reaching 70mph+ while holding the battery level steady (in the Hold mode)
  - m463 2y ago
    The volt is not a serial hybrid. The motor is physically connected to the wheels (in an interesting way btw), so it can drive on gasoline alone.
golemiprague 2y ago
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npunt 2y ago
I've always seen rotary engines as one of the best examples of a particular approach to design that solves something very elegantly but relies too much on one critical component where all the pressure of the design is applied. In the case of a rotary engine, it's the apex seals. They're a great warning for designers/architects/engineers to not get too enamored with the elegance of a system if parts of it are not yet completely solved. It's so easy when designing to try to shove aside some complex problem and say you'll solve it later, or play some shell game where every time you hit some hard to solve problem you wind up shuffling it around to someplace else [1], but that kind of instinct ultimately leads to unworkable things in practice. [1]: 'we'll solve the seals problem later.. maybe materials has an answer' or 'just add oil in the mix to protect the seals there, we'll solve emissions later'
- hatsunearu 2y ago
  No, rotary engines are terrible. For one, the equivalent of variable valve timing doesn't exist/cannot exist for rotary engines, unless Mazda creates a miracle. VVT and VVL lets you do some insane things in terms of efficiency and good engine behavior, so the rotary falls behind a lot. The rotor is pretty much unable to be cooled too.
  - seabrookmx 2y ago
    I'm not saying rotaries are great, but two stroke piston engines can have variable port timing (typically called a "power valve"). I don't see why the same method couldn't be applied to a rotary.
    - TylerE 2y ago
      The same reason we don’t use two strokes anymore? They’re environmental disasters and wildly inefficient.
      - seabrookmx 2y ago
        The comment I replied to said a rotary couldn't have variable timing and so I was simply refuting that claim. I'm not trying to make a case for either engine here.. there's clear reasons why four cycle piston engines won out for the most part (other than a few powersport and power equipment niches).
speedgoose 2y ago
I used to own the first gen electric i3 with its tiny range. I didn’t wish to have the hybrid ICE version to drive further, but I did wish for more electric range and more fast chargers along the road. Nowadays, I have a cheaper car with a lot more range, almost 4 times more in real life conditions, and plenty of fast chargers everywhere. I don’t see why I would bother with an ICE. It makes no sense for me. It’s because I live around Oslo in Norway, a place where it’s the age of electric cars. I think ICE for cars has a very limited future in the age of electric cars. I see it reserved for specific applications where the energy density is a must, and some car enthusiasts activities. Hybrids are some kind of temporary solutions for places where the EV infrastructure aren’t good enough yet. Once the infrastructure is good enough, some people will still buy ICE for a little while as they are unsure, but most switch to full electric eventually. At least that what happened around Oslo and happens now in the country side of Norway.
- trevyn 2y ago
  Is this intended to be an anecdote about life in Oslo, or are you suggesting that you expect the world outside of Scandinavia will somehow become more like Scandinavia over time?
  - speedgoose 2y ago
    Yes, with the right political decisions most countries could switch to electric vehicles. EVs also are nicer to drive and cheaper over the vehicle lifetime. It’s just a matter of time in my opinion.
- deergomoo 2y ago
  I am a big proponent of EVs, but I personally think hybrids will have a really long tail, especially as the technology improves: we could feasibly end up with a situation where much city driving in a hybrid is zero-emission EV-mode. Two reasons: First, in relation to your point > Once the infrastructure is good enough I live in the UK and I think this is gonna take a long, long time here. Not only will we need to build an enormous amount of fast chargers, but there will need to a significantly greater number of them than petrol stations, to offset the fact that even the fastest chargers take 5-10x as long as filling up with petrol (2-3 mins vs 20-30). Of course, the ideal scenario with EVs is that most charging is done at home, with fast chargers used only on long journeys. Problem is, by some estimates 2/3 of UK households do not have off-street parking. We would need to roll out en-masse solutions for on-street charging and, to my knowledge, we have not even began to think about this outside limited trials. Second is cost. Almost all cars have got crazy expensive over the last few years (I’m unsure if the rise of the PCP is a cause or effect of this), but over here full EVs are still not affordable for a huge number of people—myself included. I really wanted to go electric, and was looking at the MG4; widely considered to be the best value in EVs in the UK right now. But for the model with a range that would suit us, and the cost of installing a charger, you’re looking at close to £30,000. I just don’t have that sort of money, and a finance deal would be half my mortgage again. And for context, I make nearly double the median UK salary.
abruzzi 2y ago
> NSU and Mazda are the only manufacturers ever to have mass-produced rotary engine vehicles. Not quite true. Suzuki also made and sold a rotary engined vehicle--specifically the RE5 motorcycle. https://en.wikipedia.org/wiki/Suzuki_RE5 https://en.wikipedia.org/wiki/Suzuki_RE5
bobx11 2y ago
I think I heard this pitched by Neil Diamond 15 years ago. He had an f body or similar old big body car from the early 80 retrofitted with a rotary engine charging the battery… I’m so glad to hear this finally making production.
dunekid 2y ago
The fortnine video about this type of engine is quite interesting:https://youtu.be/-3HBAvkc4a0?feature=shared https://youtu.be/-3HBAvkc4a0?feature=shared Mazda might be one company with the expertise to make it work. The range extender, not directly driving wheels, can work in its optimum temperature, rpm and on a pretty constant load. The ability to work with multiple types of fuel adds to its versatility as a range extender. Since Mazda has alliances with other Japanese car makers, if it is indeed a good proposition, I reckon it would appear on other Japanese cars too, and maybe in BMW as well.

240 points by gascoigne 2y ago

Almost feel bad for GM, the article did not mention the Volt when talking about series hybrids. But I guess it is a Japan-focused news source.

jmspring 2y ago
The funning thing is, people I know who have a Volt love their cars. Haven't tried one myself. My family has a couple of paid of Toyota gas vehicles that are 8+ years old and will probably live longer than we will.
- joking 2y ago
  Vehicles with range extenders are the exception, even if they seem a good option, they didn’t gain market share.
- Tagbert 2y ago
  I drive a 2017 Volt gen 2 and love it. I drive about 90+% of miles in EV mode and mostly use the gas engine for road trips. It is fun to drive and (other than a couple of common, and easily fixed issues) has been reliable. I do plan to replace it in the next year because it sits very low and has a very low roofline. My spouse is uncomfortable getting into it so we almost never drive it when together.
  - nradov 2y ago
    I don't understand why GM never put the Voltec drivetrain into a compact SUV. It would have sold much better than an odd looking hatchback with little interior space.
    - Tagbert 2y ago
      Word is that PHEVs are expensive to build but customers didn't seem to be flocking to them. Traditional buyers didn't see the need to save money on fuel and didn't believe that climate change "stuff". More adventurous buyers were flocking to the new full EV coolness. I think GM decided that the future was BEV that they would be able to come out strong with EV version of their products and sell them at reasonable prices. With the component shortages and inflation, their price targets became untenable. Then they ran into assembly problems with their battery packs so they couldn't even deliver at any price. Now they have backtracked and said that they will bring out hybrids (maybe PHEV?). It's not clear which platform they'll use for that. I think that they have an Equinox-sized hybrid in China that they might bring over. The flailing around EVs vs hybrids and the on again off again story on the Bolt don't make it look like they know what they are doing, sadly. BTW the Bolt actually has a surprising about of room in it, but even so, its on the small side. Equinox would fit more customers.
- illegalsmile 2y ago
  My friend has a few volts from 2013-2018 (that he loves) and I usually borrow one for trips to see family and friends 12-16 hours away rather than drive my truck. I think they're great vehicles. ~40mpg at 80-90mph on the highway is really good though it does take premium for that 40+ mpg and it has a smallish tank so you have to stop a little more often. Once you reach your destination all driving is done on electric and charges overnight on a regular outlet/level 1. Their maintenance is surprisingly low for what seems like a complex system. Crazy to me that Chevy has abandoned their PHEV platform considering others, like Toyota, are in such high demand. Speaking of which I spent a week with a Rav4 Prime and found that equally as impressive range-wise as a volt.
tokai 2y ago
The point is the wankle engine. No sense in mentioning the Volt.
- rootusrootus 2y ago
  They did mention a couple other series hybrids, however, neither of which has a Wankel.
seabrookmx 2y ago
As mentioned elsewhere in this thread, the Volt is not actually a series hybrid despite being marketed as such. There is a planetary gear set (ala. Toyota hybrids) connecting the engine to the wheels at most speeds.

486sx33 2y ago

Does it produce more low end torque verses a traditional gasoline combustion engine? If not then why is it better suited for electrical generation? Is it more efficient with less load? The article mostly makes it sound like Mazda just loves the wankle and wants to find any possibly way to bring it back - even though it has “high” emissions… so coupling it with a hybrid electric motor makes it happen.. That can’t be the whole story?

jpgvm 2y ago
Wankels can be made extremely compact so that might have something to do with it, i.e it has both very high power to weight and power to volume specs. I honestly don't know if that is the reason though, perhaps someone more knowledgeable of the specifics of range extenders might chime in but I imagine that is an important factor.
- sethhochberg 2y ago
  They have a pretty narrow power band (produce efficient max power at a small range of RPMs) which always somewhat limited their use for normal ICE cars, but is a pretty workable constraint for an electrical generator. So you have compact size, good power to weight ratio, and power limitations that don't really matter for range extender purposes. Lots of potential. I can't find the article right now, but I'd swear I remember discussion here a handful of months ago about a startup marketing a similar EV range extender engine design.
  - HPsquared 2y ago
    They have low compression though, which really hurts the thermal efficiency.
  - coryrc 2y ago
    Then you may as well use a gas turbine, which is pretty much better in every way that matters for generating purposes.
    - 2y ago

Projectiboga 2y ago

I was always impressed by this engine in my childhood, but it never really caught on. Here is a variation I've seen on the internet, i'm not sure how practible it would be. https://arstechnica.com/cars/2023/11/this-inside-out-design-solves-most-of-the-rotary-engines-problems/ https://arstechnica.com/cars/2023/11/this-inside-out-design-...

explorigin 2y ago
https://www.youtube.com/watch?v=X5UOqZn43gY https://www.youtube.com/watch?v=X5UOqZn43gY It has longevity-issues due to an internal roller bearing on the main shaft.
- knodi123 2y ago
  wow, thanks. I didn't expect to watch the whole thing, but I did.
- fragmede 2y ago
  Depending on how it's being used. Rotary engines are better in some ways when being run hard (ie as a track car) compared to more traditional layouts.

Projectiboga 2y ago

Mazda and Toyota formed an alliance to share technologies to fill gaps they each had. I'm guessing this is fruit of that partnership.

vpribish 2y ago
Where do read Toyota into this announcement?

mattmaroon 2y ago

I have never understood why the Volt Series Hybrid idea never took off. It is more efficient to turn gasoline into electricity and then drive the car with that than to directly connect the engine to the wheels. Is it perhaps that the cost involved is just too much more than a plugin hybrid to make the small extra fuel savings worth it?

HPsquared 2y ago
Surely the "generator -> charger -> battery -> inverter -> motor" chain is less efficient than a driveshaft. Perhaps the only benefit is the engine can run at an optimal speed, but an appropriate gear ratio should handle that.
- dragontamer 2y ago
  > but an appropriate gear ratio should handle that. See Prius's "Powersplit Device". I'd describe the Powersplit device to be a combination of generator/alternator, starter/electric motor, reversed-differential (2x power inputs -> 1x driveshaft), and effective gear-ratio. All in one planetary gearset. EV motor2 determines the speed of the car. The ICE motor can spin at any speed that the computer determines to be useful. If EV Motor2 is 0-rpm, then the ICE is 100% in generator mode (2000rpm but the car isn't moving: all the energy goes to charging the battery). If the EV motor is at 10mph but ICE is off (0-rpm), then its 100% electric drive mode. And any combination in-between is possible. EV Motor1 (a smaller, weaker motor) controls the 3rd set of gears (I think the planet gears?? I forget), which determines how ICE relates to EV (changes the effective gear-ratio) https://eahart.com/prius/psd/ https://eahart.com/prius/psd/ --------- So yeah, the PSD allows the ICE to always function at the appropriate speed (which is either 0rpm or ~2500rpm for efficiency). While the combination of EV-motor1 (changes effective gear ratio of ICE) and EV-motor2 (hard-wired to the final speed) handle the different speeds the user wants in practice. All in like, 15 gears or so. https://www.youtube.com/watch?v=jofycaXByTc https://www.youtube.com/watch?v=jofycaXByTc --------- I do think that the Prius (and Prius Prime) have surpassed the Volt's design, and the proof is in the pudding. Prius Prime has 52mpg, a figure far more efficient than the Volt ever had. Prius Prime also has 220 horses today for a 0-to-60 time of 6.6 seconds. So today's Prius Prime is a lot faster than the Volt too. Volt was good when it came out, but technology has gotten better since then. Toyota has seemingly perfected this "power split device", and its beginning to lead into exceptional acceleration and good driving feel (as opposed to being 100% economy focused like before). Volt had better feel than the 2010-era Prius, but 2024-Prius is a totally different car. I think all Volt fans are in "but what if GM didn't kill the Volt and kept investing in the technology?". And... yeah... that's a fun what-if. But... GM killed the Volt. It sucks, because it seemed like great tech. Apparently GM has kept the drivetrain technology ("Ultium") and has continued to provide R&D, but Toyota's recent advancements are jawdroppingly good.

shanusmagnus 2y ago

What was the purpose of using the rotary engine in the first place, for ICE cars? From the comments it seems it's maybe lighter for a given power output. Is that it, other than just the novelty of it?

20after4 2y ago
It's about double the power output for a given size / displacement. It's very smooth and high-revving so that makes for a really fun driving experience in a light-weight sports car.
jdblair 2y ago
Lighter and mechanically simpler were the selling points. Poor fuel efficiency and trouble with the seals were the downsides. My uncle had an RX-7 back in the 80s when I was a kid. I remember when it was idling I could see the exhaust puffing, in pulses. It only had a single combustion chamber after all.
- LarsDu88 2y ago
  It's mechanically simpler until the apex seals blow out. Then you are fucked
- samdunham 2y ago
  I've had three RX-7s. A first generation and two second generations. I drove the first until the wheels literally fell off (I was a young, stupid kid that ignored the crunching sounds of the rear wheel bearings falling apart. The rear wheel(s) seized while I was driving down a bridge causing the axel to snap in half. That was an interesting "drive" down the rest of the bridge). The second was a base model second gen that I gave up when I suddenly had two cars because of getting married, then divorced. The third was my favorite. A late model second gen fully loaded. That one eventually caught on fire due to negligence at a tire place. I loved that car. The third generation never got cheap enough for me to consider one, but oh, I wanted one badly. The RX-8 never really caught me. Plus they had some early issues. That Iconic concept definitely has my attention, though.
- 2y ago

dragontamer 2y ago

A good article. It barely addresses the elephant in the room however: The Toyota Prius and its Atkinson engine. The Atkinson engine is 99% the same as a regular engine (aka: Otto cycle), except the timing is different. Instead of closing the valves when the piston+cylinder is full of gasoline+air mix... the Atkinson engine waits a bit and "leaks" some gasoline+air back out before closing the intake valve, effectively burning only 70% of the fuel, but getting maybe 85%+ of the power of a regular Otto-cycle engine. Its a simple and cheap tweak to a traditional engine that grossly improves efficiency (but at huge costs to low-end torque). Basically, any regular ol' carmaker who is mass producing Otto cycle / regular ICE engines can easily tune their piston timing to be an Atkinson engine instead. I believe Toyota even has computerized controls today that switches between efficient Atkinson (lower-power but higher efficiency) modes and powerful Otto cycle (higher power but lower efficiency) modes, though this control isn't really used too often in practice. --------- This article makes a good point that Mazda has a culture of this... rotary engine. It does compare it (somewhat unfairly) to the Atkinson engine though (inside the Prius and RAV4), I don't think anyone expects any traditional engine (Otto or Rotary) to keep up with Atkinson Engine efficiency. Its a good try however. But it does raise the question of what benefits can this rotary engine give over other engine types.

aidenn0 2y ago
I am mildly annoyed that Toyota calls late intake valve closing (LIVC) an "Atkinson-cycle" Atkinson made 3 engines none of which are anything like a 4-stroke with LIVC. The closest is perhaps his two-stroke engine, which kept the exhaust valve closed during the power stroke and open for part of the compression stroke. The Miller-cycle is much closer to what the Prius uses than anything Atkinson made; it was a traditional 4-stroke with LIVC, but required a super-charger to generate power at low RPMs. The Prius has a CVT and electric motor, overcoming any issues at low RPMs. Also now that VVT is more common, many engines run with LIVC under certain conditions.
- jeffbee 2y ago
  And, of course, Mazda had been selling LIVC engines for years before the Prius appeared. Like all of Mazda's other weird engines they were expensive, bad, and unreliable.

SebFender 2y ago

I have so many bad memories from this engine. I finally brought them to court to win. But all this to say Mazda has been out of the game so long living on dreams with this engine.

busterarm 2y ago
Mine went 110k miles without ever blowing up and then I decided to rebuild it. It's got as much longevity as other cars from the era if you pay attention to oil/omp and (over)boost (if you have a turbo). Everyone puts in at least a downpipe and then neglects all of the other mods (wastegate mod, better fuel bump, bigger injectors, wideband o2 sensor and new fuel map, better intercooler, etc) that you'll be forced to do along the way or suffer from boost creep and an eventual grenaded engine. It's all of the other things under the hood that I've had to replace from all that heat though. Three alternators. A wiring harness that caught fire...

ngcc_hk 2y ago

Is the rotary better or worst with pollution ?

linsomniac 2y ago
The long combustion chamber, according to an ex-petrolium engineer co-worker of mine, is inherently less efficient because the charge along the walls of the combustion chamber doesn't burn as well.

1970-01-01 2y ago

The problem with the Wankel is and has always been apex seals. You need to rebuild it at least once during a vehicle lifetime. I would not say it is safe from this fate, even with modern seals and a hybrid application.

aunty_helen 2y ago
I thought it was the horrible compression and oil burning. Apex seals seem to last if you don’t do silly things to them but you can’t solve inherent issues with the cycle design. For comparison, rotaries get about 100psi of compression, a modern gas car can more than double that. More compression, more efficient burn.
- 1970-01-01 2y ago
  I've read that oil burning (which is directly tied to the apex seals) has been fixed in modern engines. Compression is a somewhat configurable matter, and can be high in a low-torque generator (battery hybrid) application.

seany 2y ago

Can you buy it as an EV and then drop in the generator later? It makes a big difference for registration in some places.

SeanLuke 2y ago

> Despite all this, though, the MX-30 R-EV still falls somewhat short, with a catalog fuel efficiency of 15.4 kilometers per liter (as measured in WLTC mode). With no similar vehicles on the market, like-for-like comparison is not possible, although the Toyota RAV4 plug-in hybrid gets 22.2 km/l, while the Prius plug-in hybrid gets 26.0 km/l. The MX-30 R-EV is clearly inferior in terms of its fuel economy. That's because the engine serves an entirely different purpose. The Prius plug-in hybrid is a 13.6kWh battery mated to a regular engine. The MX-30 R-EV is a 17.8 kWh battery mated to a tiny ultralight emergency range extender. As to similar designed cars, um, hello, the BMW I3 Hybrid? Exactly the same design. The failing of the MX-30 R-EV is that its battery size is pathetically small for what amounts to an EV with a range extender. It is an embarrassment.

tom_ 2y ago
I wonder how many people drive far enough to regularly need the range extender before they have a chance to plug it in. The fuel economy of this thing is not great if you drive it far enough that it runs out of petrol and you need to fill it up again - but what if you rarely do that? What if you usually drive less than about 50 miles before the next opportunity to recharge it?

awful 2y ago

ryukoposting 2y ago
A Wankel with a turbo at redline sounds you just violently shook a big metal can full of hornets.

dbg31415 2y ago

The mid-90s RX-7 was sexy as hell. But the RX-8 just wasn't. A cool engine still needs to be wrapped in a car that people want to drive. The MX-30 doesn't quite fit the bill... just seems so mundane to look at.

mikewarot 2y ago

Instead of a Wankel, why not use a small custom turbogenerator, like the APU in aircraft?

AYBABTME 2y ago
They're efficient at higher power levels but really not at small-power-generator level. An 8kw jet powered generator I saw recently used 0.5kw-hr per kg, which is 5x more than an equivalent one based on a traditional diesel engine. Their main advantage is high power for low mass of generator, but consume massive amount of fuels.
- willis936 2y ago
  Seems unreasonable for a powertrain, but pretty reasonable for a series hybrid generator.
  - AYBABTME 2y ago
    Not really because the power rating at which they start to make sense is in the multiple hundreds of kW. Cars don't need that much average continuous power while driving, on the order of 15-30kW depending on speed and grade. So a "more efficient than piston" turbine engine would be way too big and powerful and would cycle about once per hour. Overall excess mass and bad reliability due to frequent cycling. It's better to have a smaller engine that's sized for slightly over 15-30kW continuous duty. Realistically this will be a piston engine, or a fuel cell. I would love to use a turbine engine for my own application but the math doesn't work, unfortunately.

johgoy 2y ago

I like the LiquidPiston engine technology as an inverse Wankel engine. A lot more efficient.

wkat4242 2y ago

One of the cool things about this engine is that it can run on hydrogen with minimal modifications. Not sure if the article mentions this, I don't have time to read it now. But that could make it more interesting when renewable hydrogen becomes common (right now it's not)

m463 2y ago
Have you looked at hydrogen prices? when the first hydrogen cars came out it was about $17/kg, and I think last time I looked it was around $33. I think that's a LOT more expensive than gasoline per mile.
- wkat4242 2y ago
  Meh, market forces can go either way. By the time green hydrogen actually becomes available it might have changed again. The problem is more finding a less lossy way to create it out of water with electricity. Also I don't advocate hydrogen as a 'solution'. To me the solution is less cars and nmuch better public transport. I could see it work for buses though.
adrianN 2y ago
Why would you burn hydrogen in a car? It's more efficient to burn it in a power plant and run the car on electricity.
- wkat4242 2y ago
  I'm sure there's some niche uses where it makes sense. Fast refueling for example because batteries are so slow. And much heavier than a Wankel engine plus hydrogen tank. Like in a public transport bus that needs to be on the go all day. In fact I'm pretty sure that's what the hydrogen buses in my city do, they're way too noisy to be fuel cell electric. Besides, if you can run on electric you can bypass the whole hydrogen step altogether.

m463 2y ago

It's worth mentioning that serial hybrids, like the BMW i3 rx, might not be able to drive on the freeway on the output of their generator. That's why it's a "range extender" - at some point you have to pull over and charge. EDIT: this is a big secret that none of the marketing materials (want to) make clear. I'm uncertain the output of the wankel, but maybe with its power-to-weight it might get closer to being able to drive on gasoline in a self-sufficient way.

danans 2y ago
The Mitsubishi Outlander plug-in hybrid can do up to 60mph on a flat road in serial hybrid mode.
bruce511 2y ago
Weeelll, "freeway driving" depends on the freeway and time of day. For too many freeways, for too much of the day, I can ride a bicycle at speeds greater than the surrounding traffic. And in those conditions hybrids, and electric cars are perfect.
adrianN 2y ago
Does that matter in practice? What's the effective range for highway driving in these cars?
- m463 2y ago
  I recall the i3 rx only had about 2 gallons of gas.
connicpu 2y ago
I don't know where you get this idea, my Chevy Volt is perfectly capable of reaching 70mph+ while holding the battery level steady (in the Hold mode)
- m463 2y ago
  The volt is not a serial hybrid. The motor is physically connected to the wheels (in an interesting way btw), so it can drive on gasoline alone.

golemiprague 2y ago

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npunt 2y ago

I've always seen rotary engines as one of the best examples of a particular approach to design that solves something very elegantly but relies too much on one critical component where all the pressure of the design is applied. In the case of a rotary engine, it's the apex seals. They're a great warning for designers/architects/engineers to not get too enamored with the elegance of a system if parts of it are not yet completely solved. It's so easy when designing to try to shove aside some complex problem and say you'll solve it later, or play some shell game where every time you hit some hard to solve problem you wind up shuffling it around to someplace else [1], but that kind of instinct ultimately leads to unworkable things in practice. [1]: 'we'll solve the seals problem later.. maybe materials has an answer' or 'just add oil in the mix to protect the seals there, we'll solve emissions later'

hatsunearu 2y ago
No, rotary engines are terrible. For one, the equivalent of variable valve timing doesn't exist/cannot exist for rotary engines, unless Mazda creates a miracle. VVT and VVL lets you do some insane things in terms of efficiency and good engine behavior, so the rotary falls behind a lot. The rotor is pretty much unable to be cooled too.
- seabrookmx 2y ago
  I'm not saying rotaries are great, but two stroke piston engines can have variable port timing (typically called a "power valve"). I don't see why the same method couldn't be applied to a rotary.
  - TylerE 2y ago
    The same reason we don’t use two strokes anymore? They’re environmental disasters and wildly inefficient.
    - seabrookmx 2y ago
      The comment I replied to said a rotary couldn't have variable timing and so I was simply refuting that claim. I'm not trying to make a case for either engine here.. there's clear reasons why four cycle piston engines won out for the most part (other than a few powersport and power equipment niches).

speedgoose 2y ago

I used to own the first gen electric i3 with its tiny range. I didn’t wish to have the hybrid ICE version to drive further, but I did wish for more electric range and more fast chargers along the road. Nowadays, I have a cheaper car with a lot more range, almost 4 times more in real life conditions, and plenty of fast chargers everywhere. I don’t see why I would bother with an ICE. It makes no sense for me. It’s because I live around Oslo in Norway, a place where it’s the age of electric cars. I think ICE for cars has a very limited future in the age of electric cars. I see it reserved for specific applications where the energy density is a must, and some car enthusiasts activities. Hybrids are some kind of temporary solutions for places where the EV infrastructure aren’t good enough yet. Once the infrastructure is good enough, some people will still buy ICE for a little while as they are unsure, but most switch to full electric eventually. At least that what happened around Oslo and happens now in the country side of Norway.

trevyn 2y ago
Is this intended to be an anecdote about life in Oslo, or are you suggesting that you expect the world outside of Scandinavia will somehow become more like Scandinavia over time?
- speedgoose 2y ago
  Yes, with the right political decisions most countries could switch to electric vehicles. EVs also are nicer to drive and cheaper over the vehicle lifetime. It’s just a matter of time in my opinion.
deergomoo 2y ago
I am a big proponent of EVs, but I personally think hybrids will have a really long tail, especially as the technology improves: we could feasibly end up with a situation where much city driving in a hybrid is zero-emission EV-mode. Two reasons: First, in relation to your point > Once the infrastructure is good enough I live in the UK and I think this is gonna take a long, long time here. Not only will we need to build an enormous amount of fast chargers, but there will need to a significantly greater number of them than petrol stations, to offset the fact that even the fastest chargers take 5-10x as long as filling up with petrol (2-3 mins vs 20-30). Of course, the ideal scenario with EVs is that most charging is done at home, with fast chargers used only on long journeys. Problem is, by some estimates 2/3 of UK households do not have off-street parking. We would need to roll out en-masse solutions for on-street charging and, to my knowledge, we have not even began to think about this outside limited trials. Second is cost. Almost all cars have got crazy expensive over the last few years (I’m unsure if the rise of the PCP is a cause or effect of this), but over here full EVs are still not affordable for a huge number of people—myself included. I really wanted to go electric, and was looking at the MG4; widely considered to be the best value in EVs in the UK right now. But for the model with a range that would suit us, and the cost of installing a charger, you’re looking at close to £30,000. I just don’t have that sort of money, and a finance deal would be half my mortgage again. And for context, I make nearly double the median UK salary.

abruzzi 2y ago

> NSU and Mazda are the only manufacturers ever to have mass-produced rotary engine vehicles. Not quite true. Suzuki also made and sold a rotary engined vehicle--specifically the RE5 motorcycle. https://en.wikipedia.org/wiki/Suzuki_RE5 https://en.wikipedia.org/wiki/Suzuki_RE5

bobx11 2y ago

I think I heard this pitched by Neil Diamond 15 years ago. He had an f body or similar old big body car from the early 80 retrofitted with a rotary engine charging the battery… I’m so glad to hear this finally making production.

dunekid 2y ago

The fortnine video about this type of engine is quite interesting:https://youtu.be/-3HBAvkc4a0?feature=shared https://youtu.be/-3HBAvkc4a0?feature=shared Mazda might be one company with the expertise to make it work. The range extender, not directly driving wheels, can work in its optimum temperature, rpm and on a pretty constant load. The ability to work with multiple types of fuel adds to its versatility as a range extender. Since Mazda has alliances with other Japanese car makers, if it is indeed a good proposition, I reckon it would appear on other Japanese cars too, and maybe in BMW as well.