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'
I would just add that sometimes ideas exceed the technology of their time. So revisiting a design that had deficiencies (weak points, high production costs, bad emissions, etc.) with new tools, materials, etc. can lead to breakthroughs. Not that that's what is happening here, just why some ideas that previously didn't work seem to circle back around.
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.
In hub motors might be another automotive example of this. They were used by Ferdinand Porsche and invented in 1896. Ever since engineers keep trying them out as a simple elegant solution. Eventually they will break through I think, but there’s the same allure in the simplicity of it all.
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..
Wankels have tremendous power-to-weight and power-to-size ratios. Their main problem is reliability. The generally accepted solution to improve rotary engine reliability (oil injection) results in poor emissions. The wide, flat-ish combustion chamber doesn't help the emissions problem, either.
The Wankel is at its most efficient and its most reliable when operating at a constant RPM. Conveniently, the EV generator application demands a pretty flat RPM band. As a result, the engine doesn't need to lean as hard into those emissions-increasing compromises.
Thus, EVs allow the Wankel's benefits over a reciprocating-piston engine to be reaped without the same costs as before. In theory, at least. It remains to be seen if the benefits will outweigh the drawbacks. I'm glad they're at least going to give it a try.
> 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?
You've got it backwards.
The Prius's Atkinson engine makes low-end torque *worse*, and then relies upon the EV Motor to drive the car at low speeds (0mph to 10mph) before the ICE kicks back in.
If ICE is operating, its at higher RPMs where the generator can still be useful (low RPMs like 500 are too low for the Atkinson engine to be effective in any way, the computer instead increases the RPM to maybe 2000, and uses all the power to drive a generator instead)
------------
So you see, the name of the game is efficiency at all costs, with EV-motors assisting whatever compromise you built into the motor. In the case of Toyota, its absolutely undrivable crap for low-end torque ICE, but a powerful enough 60hp to 100hp electric-motor that can handle the low-speeds and stop-and-go traffic, smoothing out any problems.
------
IE: The engineers build a highly compromised ICE engine (the Atkinson engine) that has a far narrower band of usable RPMs than a normal vehicle. Then they smooth out those problems with electric motors.
It sounds like Mazda is doing the same trick here with their Rotary engine, but the Rotary engine doesn't have the crazy-good efficiency curves that the Toyota Atkinson engine has. Efficiency isn't the "only" name of the game however, but Mazda now needs to find out a good way to market this engine / highlight its strengths.
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.
Low end torque is not that relevant to electrical generation, which typically involves the motor constantly running at a constant rpm. So, since low end torque is a weakness of the Wankel engine, that actually makes it more suitable for electrical generation than for driving directly.
Engineering organizations fall in love with superficial attributes of solutions that worked especially well for them in the past. When RIM/BlackBerry realized the iPhone was a serious threat, they built a touchscreen phone where the entire display produces a physical clicking effect because they were so convinced that what people really want from a smartphone is the click of a keyboard.
Mazda is BlackBerry, and the rotary engine is their clicky keyboard.
Wankels have only one advantage - they are about two times more powerful on same volume (you could consider them as very clean two stroke engines).
Unfortunately, Wankels have extremely huge mechanical problems - complex geometry (classic ICU are very close to just cylinders), need of better materials, depend on much better oil.
And also big problem is production scale, as I talked with people, they considered Wankels as toy, you will just utilize when it run out guarantee term.
For example, for standard ICU, considered big repair, sleeves, so they will continue working, sure, less heavy duty than new.
One interesting detail is that Mazda never designed a wankel after the 90s. They have claimed since then that computer design and simulation has allowed for dramatic performance gains.
Low end torque tends to be the rotary's Achilles heel. I think the claim being made is that efficiency is better at high, steady RPMs, but tbh, I've always found that claim a bit dubious. If you love the rotary engine, this does have some nice perks as the electric motor basically fixes the rotary engine's main weakness.
Having said that, I'd have been much more excited about this 10-15 years 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.
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.
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?
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?
This was how the BMW i3 worked. It was a rather novel design that included an optional small electric scooter motor in the rear that had a 2.5 gallon gas tank. When the battery was low, it would be charged by running the small generator.
This was clearly a wonderful idea but it was hamstrung by a silly California rule requiring the gas range to be less than the electric range to qualify for rebates. With a 6 gallon tank, the car would have been able to do ~300 miles instead of 170 and would have been parked in everyone’s driveway.
An added benefit was that the car could use existing gas station infrastructure when you needed to travel long distances.
> 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
I thought so too, but my research suggested that the efficiency is pretty much the same if not worse and power delivery is worse. Do you have some links? I‘d like to be wrong on this one.
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.
The Volt worked best as an EV with an ICE range extender. As an EV, the 40-52 mile range was sufficient for 90+% of daily driving. Adding more range would have little true benefit. It was a series hybrid, but it was mediocre as a hybrid due to the added battery weight.
Nissan has the E-power hybrid that is the pure series hybrid that you describe. AFAIK it is not as efficient as a regular, parallel hybrid. The advantage is in cost as running the gas engine as a generator uses fewer components than running it in a parallel hybrid system.
That seems unlikely. A mechanical coupling should be close to near perfect efficiency where as using the engine to drive electric motors requires several conversion steps.
Aside from your suggestion violating the laws of physics, that's actually not how the Volt worked.
The original concept for the volt was that the engine would only generated electricity, but in production models, the engine was connected to the drivetrain.
“It is more efficient to turn gas into electricity”
I don’t think that’s correct. It may be true for highly variable/low loads where the pumping losses in the pistons dominates. However the majority of fuel consumption in a car happens at traveling speed (highway miles). That is the area that needs to be optimized for.
My 2015 Honda Accord Hybrid takes this approach. At below-freeway speeds the gas motor runs in series to drive an electric motor. At highway speeds, it engages a clutch and directly connects the engine to a low-loss 1-speed transmission.
Stellantis (Dodge) has an upcoming version of the RAM 1500 that does this. It's an electric truck with a 145 mile range on electric battery; once that is expended the gas engine kicks on to run a 130 kilowatt generator.
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.
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.
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.
The fortnine video about this type of engine is quite interesting: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.
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.
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.
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.
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.
If the engines are direct injected rather than port injected, they can just delay fuel injection until the intake valve is closed, and no fuel should be pushed back into the intake manifold.
I have read that modern Toyota engines use both port and direct injection, but am not sure what the Prius does.
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?
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.
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.
Power density is indeed the main advantage. It's also much easier to balance; hunks of metal changing direction many times per second (6000 RPM is 100Hz) is somewhat mechanically exciting.
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)
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.
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.
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.
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...
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.
> 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.
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?
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.
npunt|1 year ago
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'
class3shock|1 year ago
hatsunearu|1 year ago
The rotor is pretty much unable to be cooled too.
twobitshifter|1 year ago
486sx33|1 year ago
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?
ryukoposting|1 year ago
Wankels have tremendous power-to-weight and power-to-size ratios. Their main problem is reliability. The generally accepted solution to improve rotary engine reliability (oil injection) results in poor emissions. The wide, flat-ish combustion chamber doesn't help the emissions problem, either.
The Wankel is at its most efficient and its most reliable when operating at a constant RPM. Conveniently, the EV generator application demands a pretty flat RPM band. As a result, the engine doesn't need to lean as hard into those emissions-increasing compromises.
Thus, EVs allow the Wankel's benefits over a reciprocating-piston engine to be reaped without the same costs as before. In theory, at least. It remains to be seen if the benefits will outweigh the drawbacks. I'm glad they're at least going to give it a try.
dragontamer|1 year ago
You've got it backwards.
The Prius's Atkinson engine makes low-end torque *worse*, and then relies upon the EV Motor to drive the car at low speeds (0mph to 10mph) before the ICE kicks back in.
If ICE is operating, its at higher RPMs where the generator can still be useful (low RPMs like 500 are too low for the Atkinson engine to be effective in any way, the computer instead increases the RPM to maybe 2000, and uses all the power to drive a generator instead)
------------
So you see, the name of the game is efficiency at all costs, with EV-motors assisting whatever compromise you built into the motor. In the case of Toyota, its absolutely undrivable crap for low-end torque ICE, but a powerful enough 60hp to 100hp electric-motor that can handle the low-speeds and stop-and-go traffic, smoothing out any problems.
------
IE: The engineers build a highly compromised ICE engine (the Atkinson engine) that has a far narrower band of usable RPMs than a normal vehicle. Then they smooth out those problems with electric motors.
It sounds like Mazda is doing the same trick here with their Rotary engine, but the Rotary engine doesn't have the crazy-good efficiency curves that the Toyota Atkinson engine has. Efficiency isn't the "only" name of the game however, but Mazda now needs to find out a good way to market this engine / highlight its strengths.
jpgvm|1 year ago
porphyra|1 year ago
skellera|1 year ago
A true electric successor to the RX-7 would capture so much attention.
pavlov|1 year ago
Engineering organizations fall in love with superficial attributes of solutions that worked especially well for them in the past. When RIM/BlackBerry realized the iPhone was a serious threat, they built a touchscreen phone where the entire display produces a physical clicking effect because they were so convinced that what people really want from a smartphone is the click of a keyboard.
Mazda is BlackBerry, and the rotary engine is their clicky keyboard.
simne|1 year ago
Unfortunately, Wankels have extremely huge mechanical problems - complex geometry (classic ICU are very close to just cylinders), need of better materials, depend on much better oil.
And also big problem is production scale, as I talked with people, they considered Wankels as toy, you will just utilize when it run out guarantee term.
For example, for standard ICU, considered big repair, sleeves, so they will continue working, sure, less heavy duty than new.
pengaru|1 year ago
What does low end torque have to do with electrical generation?
jqpabc123|1 year ago
There are better designs than Wankel for "series hybrid" application.
https://newatlas.com/automotive/innengine-one-stroke-engine-...
WillAdams|1 year ago
One (potential?) advantage not mentioned in the article is lighter weight relative to a similar traditional engine.
brucethemoose2|1 year ago
It does prefer a narrow RPM band, which is fine.
Reliability is the biggest concern TBH, but maybe that's not a huge bummer if its more of a backup/assistant engine.
agloe_dreams|1 year ago
_ea1k|1 year ago
Having said that, I'd have been much more excited about this 10-15 years ago.
markhahn|1 year ago
speedgoose|1 year ago
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.
deergomoo|1 year ago
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.
trevyn|1 year ago
mattmaroon|1 year ago
jeremymims|1 year ago
This was clearly a wonderful idea but it was hamstrung by a silly California rule requiring the gas range to be less than the electric range to qualify for rebates. With a 6 gallon tank, the car would have been able to do ~300 miles instead of 170 and would have been parked in everyone’s driveway.
An added benefit was that the car could use existing gas station infrastructure when you needed to travel long distances.
ch_sm|1 year ago
I thought so too, but my research suggested that the efficiency is pretty much the same if not worse and power delivery is worse. Do you have some links? I‘d like to be wrong on this one.
HPsquared|1 year ago
Tade0|1 year ago
Here are the differences explained in more detail:
http://roperld.com/science/ChevyVolt.htm
Tagbert|1 year ago
Nissan has the E-power hybrid that is the pure series hybrid that you describe. AFAIK it is not as efficient as a regular, parallel hybrid. The advantage is in cost as running the gas engine as a generator uses fewer components than running it in a parallel hybrid system.
https://www.nissan-global.com/EN/INNOVATION/TECHNOLOGY/ARCHI....
deelowe|1 year ago
themerone|1 year ago
The original concept for the volt was that the engine would only generated electricity, but in production models, the engine was connected to the drivetrain.
callalex|1 year ago
I don’t think that’s correct. It may be true for highly variable/low loads where the pumping losses in the pistons dominates. However the majority of fuel consumption in a car happens at traveling speed (highway miles). That is the area that needs to be optimized for.
My 2015 Honda Accord Hybrid takes this approach. At below-freeway speeds the gas motor runs in series to drive an electric motor. At highway speeds, it engages a clutch and directly connects the engine to a low-loss 1-speed transmission.
ryandvm|1 year ago
https://www.cnbc.com/2023/11/07/new-ram-pickup-ev-has-gas-po...
dragosmocrii|1 year ago
m463|1 year ago
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.
bruce511|1 year ago
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.
connicpu|1 year ago
danans|1 year ago
adrianN|1 year ago
Projectiboga|1 year ago
explorigin|1 year ago
Projectiboga|1 year ago
vpribish|1 year ago
1970-01-01|1 year ago
aunty_helen|1 year ago
For comparison, rotaries get about 100psi of compression, a modern gas car can more than double that. More compression, more efficient burn.
dunekid|1 year ago
rootusrootus|1 year ago
jmspring|1 year ago
tokai|1 year ago
seabrookmx|1 year ago
johgoy|1 year ago
dragontamer|1 year ago
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|1 year ago
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.
pmsh|1 year ago
I have read that modern Toyota engines use both port and direct injection, but am not sure what the Prius does.
shanusmagnus|1 year ago
20after4|1 year ago
jdblair|1 year ago
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.
aidenn0|1 year ago
abruzzi|1 year ago
Not quite true. Suzuki also made and sold a rotary engined vehicle--specifically the RE5 motorcycle.
https://en.wikipedia.org/wiki/Suzuki_RE5
wkat4242|1 year ago
adrianN|1 year ago
m463|1 year ago
bobx11|1 year ago
SebFender|1 year ago
busterarm|1 year ago
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...
dbg31415|1 year ago
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.
seany|1 year ago
mikewarot|1 year ago
AYBABTME|1 year ago
SeanLuke|1 year ago
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_|1 year ago
ngcc_hk|1 year ago
linsomniac|1 year ago
awful|1 year ago
ryukoposting|1 year ago
golemiprague|1 year ago
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