Similarly you could ask why we're wasting time building software prototypes. Just like in software, building prototypes in other industries can uncover unknown unknowns, solicit feedback and help build marketing hype.
Wouldn't the best type of ICE be a flexible fuel backup generator to extend range of otherwise electric vehicles? Which should call for altogether new designs, for example optimization for single RPM and torque to spin a dynamo rather than having to handle rapidly changing load of direct driving. Then over time we can find cleaner fuels and, if one day we have batteries that charge in 15 minutes and something to charge them from eveywhere, ditch it all together without having to revamp every car's design.
He's describing a particular kind of hybrid, where the ICE acts purely as a power generator. Most hybrids don't work this way. They tie the output shaft of the ICE into the powertrain directly, so it can operate the wheels by itself if needed.
This setup allows them to make the electric motors much smaller and let the triple-rotor engine lay down power for acceleration, while the small motors handle the cruising.
just wanted to add interesting detail:
hybrid cars use slightly different engine construction that is more efficient but lacks power in low rpm making them useless in regular cars albecause you would not be able to move from full stop, hybrids just use electric motor to solve that issue
> He's describing a particular kind of hybrid, where the ICE acts purely as a power generator.
That's pretty much how diesel railway locomotives work, they just ditch the batteries and throttle the engine to control power. For regenerative braking (that isn't) they just have giant resistors with fans.
That's called a plug-in hybrid (as opposed to normal hybrids which switch from electric to combustion operation depending on power output needs). They're quite good and clever vehicles, but their name has caused a gigantic amount of confusion and problems for them, and they seem to be in serious trouble because of that.
I think they are actually talking about a series hybrid (https://en.wikipedia.org/wiki/Hybrid_vehicle_drivetrain#Seri...), which is different than a plug-in hybrid (though it would be somewhat crazy to make a series hybrid that was not also a plug-in hybrid).
.. as to why those never caught on: I have no idea. Plug-in series hybrids seem like a brilliant solution to most issues with both ICE cars/parallel hybrids and electric cars. My honest theory is that Tesla started pushing all-electric cars much earlier than anyone else would have, and that caused most people to skip plug-in series hybrids.
The problem is that by going with that, you lose many of the benefits of an EV, like not lugging around several hundred pounds of cast iron, or having oil to change.
Totally fair. My thinking is that means you could lug around a lot less battery weight (ie, make the all-electric range 60 miles or so), basically just enough to complete the average amount of driving a car does in a day and operate on the assumption that most cars would get plugged in every night. In return, you'd get the ability to use the existing energy distribution infrastructure built around roadways (ie, gas stations) whenever you wanted to drive your car further than it could go on a charge. I'd also assume that the ICE/generator combo could be tuned to operate entirely within whatever window results in highest efficiency for the ICE engine, which should be a notable improvement on the way ICE efficiency varies by speed in traditional cars.
I'm not saying that there aren't tradeoffs, just saying that it feels like an interesting idea. Enough so that I'm not at all sure why it didn't take off.
If the engine is able to always operate at peak efficiency, there is little reason to bother with batteries beyond a bit for handling transient peaks.
I guess what it comes to down for me is that the hybird as you described, while it has advantages over pure ICE, it's sorta the worst of both worlds - all the moving parts, all the complexity, the fire risk from both li-ion AND gasoline, more expensive (since two drivetrains, essentially).
A constant RPM motor for an extended period isn't a super enjoyable sound, either.
> If the engine is able to always operate at peak efficiency, there is little reason to bother with batteries beyond a bit for handling transient peaks.
My thinking here is that most of these theoretical cars would spend a good part of their life only operating on battery power - basically, all of the home-to-work-to-supermarket-to-home trips would be pure electric in my mind. So much so that I've wondered if the ECU would need to occasionally run the ICE for a bit just to make sure it doesn't ever spend so much time without being turned on that entirely different problems arise.
> it's sorta the worst of both worlds
I get this. This idea is very much the best of both worlds/worst of both worlds depending on your point of view.
> more expensive (since two drivetrains, essentially)
I'm not sure about this. I think the right comparison here is to imagine a battery that has (say) 25% of the range of a Model 3 battery, but is (say) 30 or 35% of the cost. Based on EV battery replacement cost, could you buy a cheap 3-cyl ICE engine and generator for that? Intuitively this feels possible, though I'll admit I don't have access to the data to be able to say, for sure how these costs would compare at scale.
> A constant RPM motor for an extended period isn't a super enjoyable sound, either.
The sound should be similar to the sound a pure ICE car makes on the freeway when on cruse at a constant speed and not changing gear. Yeah, you'd need to tune the exhaust to make sure the sound is pleasing, but this feels like a solvable problem also.
(As an aside, sorry if it feels like I'm hassling you. I'm honestly not, this is just an idea that has lived in the back of my brain for a bit and I'm enjoying the discussion.)
An ICE places a lot more constraints on design and manufacter...since it has to be behind a firewall, it's large, it has all kinds of fluids that need routing out... it's a nightmare. For comparison a typical EV battery is just a bunch of bricks inside the skateboard base.
Ah good to know about the name "Series Hybrid", I've only ever heard people call a Series Hybrid a "Plug-In Hybrid" even in somewhat official and educational contexts, but I suspect that's just a symptom of the problem I was complaining about.
For sure. And, at the risk of being pedantic, a plug-in hybrid can still be a parallel hybrid - series vs. parallel is about how the ICE power gets to the ground, whereas plug-in vs not is about the existence of a way to charge the hybrid battery packs separate from the ICE engine or regenerative breaking (or whatever else that's not electric power from a wall outlet).
And most plug-in hybrids are (parallel). The "plug in" part is usually referring to (even if technically wrong) the electric subset being able to reasonably move the car alone, instead of being just a substitute to the ICE in near-idle cruise and an assistance at peak load. The combination of reasonable utility electric-only and serial is usually referred to as "electric with range extender" instead of hybrid.
Nissan make a series hybrid (which they call "e-power"), although with a very small (2.1 kWh) battery, so it doesn't work as a plug-in hybrid, and sadly it is apparently rubbish:
This is sort of what Edison Motors[1] is doing. They have built what is essentially a diesel electric locomotive in truck form, where they have a CAT diesel generator charging two battery sets which then power two electric axles in the rear, two traction motors per axle. The generator runs at a constant efficient speed (when needed) and has no mechanical connection to anything other than the alternator.
I once came across an ancient genset based on the original Willy's jeep engine, it was an interesting little device, the cam rockers were very sharp because it only had to run at a very narrow band of RPMs and this made the valve timing very tight.
It's neat how given a chance to optimize instead of just sticking the standard camshaft in there the engineers immediately went for the efficiency gains.
that's also would allow broader adoption in countries where charging infrastructure is not yet ready.
eg. in my country we have very little charging stations because there is just not enough demand, and we do not have much electric cars because not many people want to pay that much for car that you have no way to charge (especially when you do not have garage)
I like this idea, especially the flex fuel aspect. Something purpose designed to easily convert to run gasoline, natural gas, pure ethanol, you name it. Though it might have to have some sort of cycle to ensure you don't have 2 year old gas in your tank when you finally need to charge the batteries on the road.
I don't know what fuels it takes, but the "optimized for a single RPM and torque to spin a dynamo" is pretty much describing Mazda's MX-30 R-EV which does this with a rotary engine.
Won't be coming to the US though, and the EV version is dropped here as well. Now that they have PHEVs in the CX-90 and upcoming CX-70. Previously the MX-30 was available in California as a compliance car.
The problem with doing that in the purest sense is that mechanically connecting the engine to the wheels is always more efficient than turning a dynamo, then running the power through an inverter and a motor. Honda and Mitsubishi actually do pretty much what you're saying, but they both couple the engine to the front wheels at high speed. And at low speed, the efficiency in hybrid mode is not that great. It is a very simple, elegant design though, so I'm still fond of it.
I agree that the path from engine mechanical output to wheels certainly seems less efficient. We might be wrong about that, underestimating the losses in gear sets, but that's not my point and I also suspect that in that case we would hear more about gear set cooling solutions/issues.
But the path from fuel to engine output can be made far more efficient by designing the engine for a very narrow band of usage conditions instead of the crazy wide range from cruising at near idle to showing off what you paid extra for. Diesel trains have been diesel-electric for almost a century.
I have a plug-in hybrid (Toyota RAV4 Prime). It doesn't support flex fuel, but it's an awesome implementation- I typically drive for months before having to refuel the 10 gallon tank, with most of my driving on the battery. There's no dynamo, it switches from charging to discharging smoothly.
> if one day we have batteries that charge in 15 minutes
We're actually pretty close to that already. the Ioniq 6 Long Range adds 340km of range in 16 minutes. [0] The Porsche Taycan Plus adds 330km in 17 minutes [1]
How much battery life do you lose if you always fast charge? I thought batteries strongly prefer the kind of slow overnight charging that needs a garage.
Tesla used to tell users to avoid overusing the fastchargers, but they no longer include such language on the site.
A recent study by Recurrent Auto which looked at data from 12,500 Tesla vehicles said that there is "no statistically significant difference in battery degradation between Tesla Model 3 vehicles that charged at least 90% of the time using Superchargers and Model 3 vehicles that charged no more than 10% of the time using Superchargers."
Other brands might have different technology and might degrade differently. Tesla's aren't the fastest chargers, so perhaps the data for Ioniq or Porshe would be different.
If a series hybrid were optimal in a sports car or performance car, then I would expect to see them used in the 24 Hours of Le Mans and 24 Hours of Rolex, where maximizing fuel economy without sacrificing speed is essential to winning the race. Instead, they mostly use the hybrid system for energy recovery, and it sounds to me like the new RX-9 might be more similar to those systems than what we are used to seeing on the street.
FWIW, I have endurance raced a hybrid vehicle -- a stock Toyota Prius with a roll cage. Under racing conditions, it mostly keeps the engine at a constant 4000 rpm as it struggles to keep the battery charged. Racing a Prius is a little odd, because you end up doing a few laps to charge the battery, then strategically executing a pass once the battery is charged enough to give you power. In a series hybrid, you would only get power from the electric motor(s) rather than getting the combined power of the MG and ICE.
> then I would expect to see them used in the 24 Hours of Le Mans and 24 Hours of Rolex
Powertrains in these leagues are heavily, heavily regulated. Outside of baja, there haven't been "unlimited" high budget racing leagues since like the 70s or 80s.
Hence crazy 80s Group C Le Mans cars (before they got banned) got similar lap times similar to modern Le Mans prototypes with much worse tyres, and the 70s Porsche 917 still holds the lap record at Talladega, by a wide margin, because such a nutty unregulated engine never lapped it again.
Also, the performance targets for a pure racecar are totally different than a sports car or even a luxury supercar. They are either at high RPM full throttle, full brake, or in a turn 24/7, with no concern for any other kind of load (like puttering down a highway at low RPM) or any kind of sane maintenance schedule. And weight is absolutely critical.
No (I think), unless your are just talking about hybrid vehicles which have been in use for a very long time. You are proposing a vehicle with redundant drive systems and two primary sources of fuel. This only makes sense in very specialized cases where some odd sort of asymmetrical failure mode is worth the extra complexity and weight.
The only reason these exist on the market today in the form of Plug-in Hybrids is that power generation in a hybrid vehicle requires some intermediary storage to be effective. Manufacturers can add a plug and allow the vehicle to run directly off the intermediary storage for a very short distance (usually less than the distance provided by single gallon of fuel), however as far as I know this is basically done as a form of greenwashing. Given the ranges allowed, you might as well ride your bicycle.
Yeah, this is a good setup for a rotary. Its kinda like the Porsche 918, with its super high revving, tiny racecar V6 that only made power at high RPM, compensated by a electric motor everywhere else... Though I question if Mazda will really be able to keep the curb weight down. Other manufacturers just can't seem to help themselves, and stuff tons if heavy junk in modern cars.
Maybe tuners (or Mazda themself?) will put a centrifugal supercharger on it later. They seem to be en vogue, they are simple and light, and they don't butcher timings/compression and such as much as a turbocharger or other superchargers, with was a major pain point with the RX-8 Wankel.
How about supercharger (or turbocharger) + exhaust energy recovery turbine? Perhaps coupled to an electric generator? Would be a nice match to the hybrid electric system.
That would be a turbocharger. And electric turbocharger and driveshaft turbochargers are also a thing.
The problem with turbo is backpressure from the exhaust energy recovery part, which compromises some other engine tuning. And the problem with traditional superchargers is low efficiency + high boost in low RPMs, same issue.
A centrifugal supercharger is relatively efficient and basically only does anything at high RPM, so from what I understand it won't "upset" the compression of the rotary or highly tuned NA engines as much as a traditional turbo/supercharger.
I wonder if they could use multiple rotors in series, like a gas turbine engine does with stages of compression/expansion, to improve efficiency.
A "compression" rotor, a "combustion" rotor and an "expansion rotor" perhaps? That would give more chance to extract useful work and a lower exhaust temperature.
Still have a lot of thermal losses though (lots of surface area in all those combustion chambers, and a long residence time of the hot gases allowing heat transfer to happen... not ideal)
This has been done in order to make a Diesel Wankel (a Mercedes prototype engine, IIRC), since there's a fundamental upper limit on the compression ratio of a Wankel rotor, which isn't high enough for a reasonably running Diesel. Though, the "compression rotor" and "expansion rotor" were the same rotor. A pair of ports allowed the lower pressure rotor to empty itself at peak compression into the intake of the higher pressure rotor. The higher pressure rotor exhausted itself into that same high-compression space of the low pressure rotor for a second expansion.
Note that the original Wankel rotor invention was a supercharger for a piston engine, so it's use in staged compression was thought of from the beginning.
Too late to edit, but it was Rolls Royce trying to stage Wankel rotors for a Diesel engine, not Mercedes. The Mercedes (Daimler-Benz) attempt was a modified rotor shape to increase compression.
Less than 100hp from the electric motors? That might not be bad, but maybe that shouldn't have been the headline figure. More interesting would be the torque data.
I'm guessing that is fairly good, as it would solve the rotary's problems with lacking low end torque.
I still think they'd have been better off with a 100% BEV, though. I doubt this will do particularly well in the market.
Although he's basically a motorcycle blogger, the production values manage to pump a lot of great physics[1] / MechEng information into the entertainment. There's not many mediocre videos on his channel, but this is one of the better ones.
The gist of this video: the Wankel does have some[0] fundamental problems as a concept. There's workarounds (none of which I could find in the OP, although using a Wankel as an ePMU is probably ideal) but also a point of diminishing returns apart from specialized platforms like UAS.
Rotational, high-flow, high-rpm . . turns out you're already halfway to a gas turbine anyway.
[0] Rather a lot
[1] The host is a physics major, IIRC, rather than mecheng, which was interesting.
Yeah, I'll buy that. I use F9 to sneak some moto knowledge into my nephews, who have . . I don't even know what they call attention spans these days. . negative attention? Unless it's some incomprehensible card game. Anyway, good vids!
Targeted at nerds who ride motorcycles perhaps? Other than the Revzilla guys, what motorcycle tech/errata video channels do you recommend for the discerning and mature?
I had the same thought. Nobody wants to touch those used rx-8's with a 10 foot pole. But I guess that doesn't matter so much for people who don't care about the trade in value down the road. Which is a surprisingly high percentage of new car buyers I've observed.
I so was hyped for the RX8 back in 2003. For its time it looked pretty cool and the interior layout was even better. But I kept hearing about the reliability issues after just a couple of years. So I ended up going with a 6spd Nissan 350Z instead. That car was solid as a rock, and man did that VQ engine sound beautiful. I wish Mazda didn't half-ass the RX8, as the RX7 was such a classic.
If they pull this off (especially if it's possible to do all-electric at low speeds for short distances) I'll be on the preorder list for sure. A manual would be preferable, but that may be too complicated to allow given the powertrain setup.
I'll bet you a beverage of your choice that it will have at least a 6-speed transmission (whether that's manual, automatic or manumatic). A 4- or 5-speed isn't out of the question (The RX-8 had a version with a 4-speed automatic), so I'm giving you a bit of edge over your prediction of a 2-speed.
To be fair, I should point out that TFA predicts an 8-speed automatic.
That would be interesting because I see no way how you'd have a hybrid (either series or parallel) with multiple motors and gearboxes. What you could do is to have an automatic transmission in a parallel setup and maybe a gear (or two) for the electric motors or a series version where the ICE drives a generator to drive the electric motors (which is how I understand this one works). In that case there would be no gears at all or maybe just two to match the electric motors better to the speed you are driving at.
Can you explain how you think an actual 6 speed transmission (manual or automatic, not 'fake' gears from a CVT) would work with a parallel hybrid? Because the only way that would work is if the electric drive system is entirely optional and just there to relieve the ICE a bit.
Edit: Ah ok, I see it now, so the in-hub electric motors aren't geared at all (they can't be) and the ICE can run across a regular gearbox. So this is a parallel hybrid with the electric motors only coupled in right at the hubs rather than somewhere further upstream. So indeed the electric motors are 'optional', and they are managing the balance by either switching the automatic gearbox to neutral and then use the electric motors to drive the vehicle, not power the electric motors but just use the ICE or a combination of both. This does indeed allow for a variety of different geartrains.
Per TFA it's 3 electric motors (2 front, one rear), so I imagine something like:
6-speed going from ICE to rear-differential, with an electric engine on the either between the engine and the transmission (like the Insight IMA) or between the transmission and the wheels.
2 electric motors in front, one going to each front wheel.
I rather suspect that if it has an electric-only mode it will be FWD.
[edit]
From an earlier article:
> Two of those will power each of the front wheels individually, while the third one is positioned between the transmission and rotary engine, and will have an assist function like in a mild-hybrid. Car vlogger and YouTuber, Kirk Kreifels, noted that this is a similar setup to the now-discontinued, second-generation Honda NSX with the main difference being that the mid-engine NSX was a F-HEV while Mazda’s latest patents suggest a P-HEV architecture.
You may be interested to read about the first generation Honda Insight and/or the Honda CRZ. Both were hybrids that were available with a manual transmission. But as another commenter has already explained, Mazda's setup here is very different from anything currently in production.
I recently took delivery of a Mazda CX-90 PHEV. My other car is a 2012 Acura TSX. I wasn’t ready to jump fully into EV simply because I wanted a larger family hauler that didn’t break the bank. My driving is limited to less than 15 km per day. Therefore, the EV portion of the CX-90 was more than enough, with the ICE portion available if we ever need it.
I really like Mazda and I’m glad they exist to push things like the rotary. Maybe I’ll consider the RX-9 as a fun vehicle.
I want EVs to succeed but they simply don’t make sense for all use cases yet. But they don’t have to. Maybe I’ll get an EV to replace the TSX if it ever dies.
But, Mazdas are great cars. I wouldn’t sleep on them.
I hear there are concerns about plug-in hybrid's that don't use their engines often developing issues because those engines never get used. Does the CX-90 have any features to help with that?
Not that I’m aware of but to be honest, I doubt I’ll have that problem. 42km of EV-only range means that every so often, I’ll need the ICE. Plus, I have a heavy foot, so if I want to experience all 340 ponies, I gotta fire up the ICE.
That said, the appeal of EV-only and adaptive cruise control means I drive more calmly. Most of the time.
Just need to get a Comma 3X running on this and I’ll be set!
My PHEV just runs the engine for no reason, if it hadn't run in a long time. Also it comes on for surprising reasons, such as when the battery is fully charged and you apply the brakes.
> I want EVs to succeed but they simply don’t make sense for all use cases yet.
I think they do? There's a couple really small corner cases, like if you're on the road 99% of the time for work, or live in sub-zero temperatures all year long, or something exceptional like that. But EVs are already there right now for everything non-exceptional people use cars for. The things people think EVs can't do are the kinds of things people think they need to be able to do, but don't actually ever do, like go on 400 mile road trips every week with zero stops. YAGNI.
I really like Mazda, too. They make good stuff, and their recent "anti-touchscreen" stance really jives with me[1].
As someone that wants to go on ski trips, it's the exact nightmare scenario for EVs. In nominal conditions it's a long, cold trip with lots of people inside, lots of shit in the trunk, and potentially stuff on the roof harming aero greatly, while also being cold and driving through mountains with potentially limited fast charging.
Oh and god forbid the road gets shut down and you need to stay in the car for a few hours as they drag out someone from the ditch!
What’s the difference for being stuck in the cold in an EV to an ICE car? The time you can keep the heating running is very similar (around 1,5 days with a full tank of gas or a full battery).
The only benefit of the combustion engine is that you can keep some extra fuel in the trunk. But who has 50l extra fuel in their trunk?
Setting aside the cold, being stuck in general is easier to recover from in an ICE car. It’s very easy for AAA, emergency services, etc, to bring you a container of gasoline at the side of the road.
I honestly don’t know, what’s the solution for EVs? Will AAA bring a generator? Can they charge you off the engine of the tow truck?
Yes, you can charge an EV from a generator, there are already devices for that on some service trucks.
There is another option (although not recommended by any manufacturer): If the EV still goes into drive mode, just tow it for a short distance and use regenerative breaking. You should be able to gain 2-5 times the towed distance as range.
Edit: this technique is not recommended, although it seems to work. It’s very important that the car still turns on and you can select D. Otherwise the car may get severely damaged. If the car is off, it should not be towed more than about 5 time its length. When you tow it, there is a lot of electricity generated in the engines, even if it’s off. (There are exceptions from this rules though).
It's not needed for EVs, they just work, though with faster drain and slower charging speeds (though battery heaters/conditioners help mitigate this). Batteries wear out more quickly from long-term cold exposure, which is why I said "year round subzero temps". For typical American winters, even up here in Minnesota, it's not a significant issue.
Now I get it, you're talking about subzero fahrenheit temperatures. So sub -17,7 temperature in normal people's units ;)
Because subzero celsius temperatures are not an issue. Scandinavia and Finland have a lot of EVs, and also big distances to drive. Doesn't seem to be a big issue.
Some would argue this is not a use case...but my use case is that I don't want to buy a new car every 5yrs (or pay a fortune to replace the batteries).
I have a 2005 Honda that's still running great, I plan to keep driving it a long time. I just got a 2021 Honda (ICE) as the family car, I expect to keep driving that one just as long.
I want to see longevity in EVs before I make the switch. Or they need to be significantly less expensive.
Depending on your locale, EV batteries last about 8-15 years[1], not five. EVs are cheaper to maintain and run than ICEs[2]. I think right now, it's a toss-up which will come out cheaper after 20 years when including a battery replacement. But EV components will only go down in price as we massively scale up manufacturing, so I expect EVs will be the clear price winner within the next 5-10 years, which is about when you'd maybe start thinking about replacing the battery if you purchased an EV today.
I live in an apartment, and none of the parking lots near us have charging spaces…so unfortunately we’re stuck with gas cars until that situation changes.
Good point! Don't have a great story there right now today, unfortunately. I think the goal will be for most shopping and workplace parking lots to have chargers, so you can charge up while you're out doing other stuff. I've also seen newly built apartment parking lots in my city (Minneapolis/St Paul) often contain a handful of charging spots. We're definitely not there today, but a bunch of money is going into building out the charging networks right now[1], so hopefully that changes very soon.
In Central Europe a lot of supermarkets and malls already have DC charging (sometimes AC charging too). So during a regular (20-30 min) visit at the supermarket you can easily charge the battery up to 80%.
Where I live every town with more than ~1000 inhabitants got at least one AC charging spot operated by the local electricity provider. Charging there may be cumbersome though, because you may need to walk back 5-10 minutes to your apartment and pick up the car a few hours later.
Oh yeah! Give a throttle blip during shutdown and you could cause a huge back-fire, sometimes occurring after you already exited the car! Always a crowd pleaser.
How does Mazda have the mental energy and monetary budget for their endless series of fruitless journeys into weird forms of combustion? They still haven't made that Skyactiv-X thing work, their Miller cycle engines never worked right even though everyone else now makes Miller cycle engines, and rotary engines are only good for the track where the owner is willing to rebuild it hourly.
The "Skyactiv-X thing" absolutely works and is available on Mazda 3s in Europe now. It doesn't work in the US because of our very stringent NOx emission rules (which, incidentally, is one of the reasons diesels are less popular here). I'm not aware of Mazda trying a Miller cycle engine outside of one trim level on the Millenia. I have heard that their experiments with that helped the development of their Skyactiv engines in general though. I'm also not aware of anyone else making Miller cycle engines currently. Perhaps you're thinking of Toyota's heavy use of the related but not the same Atkinson cycle engine.
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[ 2.8 ms ] story [ 225 ms ] threadhttps://www.rideapart.com/news/618464/erex-one-stroke-engine...
This is the simplest, lightest, most efficient ICE yet.
https://hackaday.com/2023/09/10/new-electric-motor-tech-spin...
Population is now too dense around the world in most cities to handle all the exhaust.
This setup allows them to make the electric motors much smaller and let the triple-rotor engine lay down power for acceleration, while the small motors handle the cruising.
The MX-30 R-EV operates the way you describe (https://www.caranddriver.com/news/a42485033/mazda-mx-30-r-ev...)
That's pretty much how diesel railway locomotives work, they just ditch the batteries and throttle the engine to control power. For regenerative braking (that isn't) they just have giant resistors with fans.
.. as to why those never caught on: I have no idea. Plug-in series hybrids seem like a brilliant solution to most issues with both ICE cars/parallel hybrids and electric cars. My honest theory is that Tesla started pushing all-electric cars much earlier than anyone else would have, and that caused most people to skip plug-in series hybrids.
I'm not saying that there aren't tradeoffs, just saying that it feels like an interesting idea. Enough so that I'm not at all sure why it didn't take off.
I guess what it comes to down for me is that the hybird as you described, while it has advantages over pure ICE, it's sorta the worst of both worlds - all the moving parts, all the complexity, the fire risk from both li-ion AND gasoline, more expensive (since two drivetrains, essentially).
A constant RPM motor for an extended period isn't a super enjoyable sound, either.
My thinking here is that most of these theoretical cars would spend a good part of their life only operating on battery power - basically, all of the home-to-work-to-supermarket-to-home trips would be pure electric in my mind. So much so that I've wondered if the ECU would need to occasionally run the ICE for a bit just to make sure it doesn't ever spend so much time without being turned on that entirely different problems arise.
> it's sorta the worst of both worlds
I get this. This idea is very much the best of both worlds/worst of both worlds depending on your point of view.
> more expensive (since two drivetrains, essentially)
I'm not sure about this. I think the right comparison here is to imagine a battery that has (say) 25% of the range of a Model 3 battery, but is (say) 30 or 35% of the cost. Based on EV battery replacement cost, could you buy a cheap 3-cyl ICE engine and generator for that? Intuitively this feels possible, though I'll admit I don't have access to the data to be able to say, for sure how these costs would compare at scale.
> A constant RPM motor for an extended period isn't a super enjoyable sound, either.
The sound should be similar to the sound a pure ICE car makes on the freeway when on cruse at a constant speed and not changing gear. Yeah, you'd need to tune the exhaust to make sure the sound is pleasing, but this feels like a solvable problem also.
(As an aside, sorry if it feels like I'm hassling you. I'm honestly not, this is just an idea that has lived in the back of my brain for a bit and I'm enjoying the discussion.)
https://www.arenaev.com/nissan_qashqai_epower_confirms_what_...
I don't know what their engine is; if this is a normal car engine repurposed to drive a generator, this is not a great test of the idea.
[1]: https://www.edisonmotors.ca
It's neat how given a chance to optimize instead of just sticking the standard camshaft in there the engineers immediately went for the efficiency gains.
However Mazda has started releasing PHEV designs as you design over the past few years, with the RX-9 being a performance optimized variant.
https://www.autocar.co.uk/car-review/mazda/mx-30-r-ev
Won't be coming to the US though, and the EV version is dropped here as well. Now that they have PHEVs in the CX-90 and upcoming CX-70. Previously the MX-30 was available in California as a compliance car.
But the path from fuel to engine output can be made far more efficient by designing the engine for a very narrow band of usage conditions instead of the crazy wide range from cruising at near idle to showing off what you paid extra for. Diesel trains have been diesel-electric for almost a century.
https://en.wikipedia.org/wiki/BMW_i3
We're actually pretty close to that already. the Ioniq 6 Long Range adds 340km of range in 16 minutes. [0] The Porsche Taycan Plus adds 330km in 17 minutes [1]
[0] https://ev-database.org/car/1718/Hyundai-IONIQ-6-Long-Range-...
[1] https://ev-database.org/car/1924/Porsche-Taycan-Plus#chargin...
A recent study by Recurrent Auto which looked at data from 12,500 Tesla vehicles said that there is "no statistically significant difference in battery degradation between Tesla Model 3 vehicles that charged at least 90% of the time using Superchargers and Model 3 vehicles that charged no more than 10% of the time using Superchargers."
Other brands might have different technology and might degrade differently. Tesla's aren't the fastest chargers, so perhaps the data for Ioniq or Porshe would be different.
[0] https://cleantechnica.com/2023/10/01/tesla-supercharging-not...
[1] https://www.tesla.com/ownersmanual/model3/en_us/GUID-7FE78D7...
FWIW, I have endurance raced a hybrid vehicle -- a stock Toyota Prius with a roll cage. Under racing conditions, it mostly keeps the engine at a constant 4000 rpm as it struggles to keep the battery charged. Racing a Prius is a little odd, because you end up doing a few laps to charge the battery, then strategically executing a pass once the battery is charged enough to give you power. In a series hybrid, you would only get power from the electric motor(s) rather than getting the combined power of the MG and ICE.
Powertrains in these leagues are heavily, heavily regulated. Outside of baja, there haven't been "unlimited" high budget racing leagues since like the 70s or 80s.
Hence crazy 80s Group C Le Mans cars (before they got banned) got similar lap times similar to modern Le Mans prototypes with much worse tyres, and the 70s Porsche 917 still holds the lap record at Talladega, by a wide margin, because such a nutty unregulated engine never lapped it again.
Also, the performance targets for a pure racecar are totally different than a sports car or even a luxury supercar. They are either at high RPM full throttle, full brake, or in a turn 24/7, with no concern for any other kind of load (like puttering down a highway at low RPM) or any kind of sane maintenance schedule. And weight is absolutely critical.
The only reason these exist on the market today in the form of Plug-in Hybrids is that power generation in a hybrid vehicle requires some intermediary storage to be effective. Manufacturers can add a plug and allow the vehicle to run directly off the intermediary storage for a very short distance (usually less than the distance provided by single gallon of fuel), however as far as I know this is basically done as a form of greenwashing. Given the ranges allowed, you might as well ride your bicycle.
Maybe tuners (or Mazda themself?) will put a centrifugal supercharger on it later. They seem to be en vogue, they are simple and light, and they don't butcher timings/compression and such as much as a turbocharger or other superchargers, with was a major pain point with the RX-8 Wankel.
That would be a turbocharger. And electric turbocharger and driveshaft turbochargers are also a thing.
The problem with turbo is backpressure from the exhaust energy recovery part, which compromises some other engine tuning. And the problem with traditional superchargers is low efficiency + high boost in low RPMs, same issue.
A centrifugal supercharger is relatively efficient and basically only does anything at high RPM, so from what I understand it won't "upset" the compression of the rotary or highly tuned NA engines as much as a traditional turbo/supercharger.
Dare I say it, it would be better than the RX8/RX9 if they just put a big wankel in it.
A "compression" rotor, a "combustion" rotor and an "expansion rotor" perhaps? That would give more chance to extract useful work and a lower exhaust temperature.
Still have a lot of thermal losses though (lots of surface area in all those combustion chambers, and a long residence time of the hot gases allowing heat transfer to happen... not ideal)
Note that the original Wankel rotor invention was a supercharger for a piston engine, so it's use in staged compression was thought of from the beginning.
https://en.wikipedia.org/wiki/Wankel_Diesel_engine
I'm guessing that is fairly good, as it would solve the rotary's problems with lacking low end torque.
I still think they'd have been better off with a 100% BEV, though. I doubt this will do particularly well in the market.
https://youtu.be/-3HBAvkc4a0?si=9NJd4B-VK1LxfXWy
Although he's basically a motorcycle blogger, the production values manage to pump a lot of great physics[1] / MechEng information into the entertainment. There's not many mediocre videos on his channel, but this is one of the better ones.
The gist of this video: the Wankel does have some[0] fundamental problems as a concept. There's workarounds (none of which I could find in the OP, although using a Wankel as an ePMU is probably ideal) but also a point of diminishing returns apart from specialized platforms like UAS.
Rotational, high-flow, high-rpm . . turns out you're already halfway to a gas turbine anyway.
[0] Rather a lot
[1] The host is a physics major, IIRC, rather than mecheng, which was interesting.
I really liked these two:
How rotary engine works (Mazda RX-7): https://www.youtube.com/watch?v=sd6pJtR4PaY
What new to RX-9 from RX-7: https://www.youtube.com/watch?v=-3gzQVGEqF4
Wasn't the principal flaw of the rotary engine that it tends to die?
I'd love to see some new engine concepts like an electric drive vehicle. I think I heard some cars do this but need to double check.
To be fair, I should point out that TFA predicts an 8-speed automatic.
Can you explain how you think an actual 6 speed transmission (manual or automatic, not 'fake' gears from a CVT) would work with a parallel hybrid? Because the only way that would work is if the electric drive system is entirely optional and just there to relieve the ICE a bit.
Edit: Ah ok, I see it now, so the in-hub electric motors aren't geared at all (they can't be) and the ICE can run across a regular gearbox. So this is a parallel hybrid with the electric motors only coupled in right at the hubs rather than somewhere further upstream. So indeed the electric motors are 'optional', and they are managing the balance by either switching the automatic gearbox to neutral and then use the electric motors to drive the vehicle, not power the electric motors but just use the ICE or a combination of both. This does indeed allow for a variety of different geartrains.
6-speed going from ICE to rear-differential, with an electric engine on the either between the engine and the transmission (like the Insight IMA) or between the transmission and the wheels.
2 electric motors in front, one going to each front wheel.
I rather suspect that if it has an electric-only mode it will be FWD.
[edit]
From an earlier article:
> Two of those will power each of the front wheels individually, while the third one is positioned between the transmission and rotary engine, and will have an assist function like in a mild-hybrid. Car vlogger and YouTuber, Kirk Kreifels, noted that this is a similar setup to the now-discontinued, second-generation Honda NSX with the main difference being that the mid-engine NSX was a F-HEV while Mazda’s latest patents suggest a P-HEV architecture.
https://www.topspeed.com/a-mazda-rotary-sports-car-is-happen...
I really like Mazda and I’m glad they exist to push things like the rotary. Maybe I’ll consider the RX-9 as a fun vehicle.
I want EVs to succeed but they simply don’t make sense for all use cases yet. But they don’t have to. Maybe I’ll get an EV to replace the TSX if it ever dies.
But, Mazdas are great cars. I wouldn’t sleep on them.
That said, the appeal of EV-only and adaptive cruise control means I drive more calmly. Most of the time.
Just need to get a Comma 3X running on this and I’ll be set!
I think they do? There's a couple really small corner cases, like if you're on the road 99% of the time for work, or live in sub-zero temperatures all year long, or something exceptional like that. But EVs are already there right now for everything non-exceptional people use cars for. The things people think EVs can't do are the kinds of things people think they need to be able to do, but don't actually ever do, like go on 400 mile road trips every week with zero stops. YAGNI.
I really like Mazda, too. They make good stuff, and their recent "anti-touchscreen" stance really jives with me[1].
[1] https://www.motorauthority.com/news/1121372_why-mazda-is-pur...
Oh and god forbid the road gets shut down and you need to stay in the car for a few hours as they drag out someone from the ditch!
The only benefit of the combustion engine is that you can keep some extra fuel in the trunk. But who has 50l extra fuel in their trunk?
I honestly don’t know, what’s the solution for EVs? Will AAA bring a generator? Can they charge you off the engine of the tow truck?
There is another option (although not recommended by any manufacturer): If the EV still goes into drive mode, just tow it for a short distance and use regenerative breaking. You should be able to gain 2-5 times the towed distance as range.
Edit: this technique is not recommended, although it seems to work. It’s very important that the car still turns on and you can select D. Otherwise the car may get severely damaged. If the car is off, it should not be towed more than about 5 time its length. When you tow it, there is a lot of electricity generated in the engines, even if it’s off. (There are exceptions from this rules though).
Because subzero celsius temperatures are not an issue. Scandinavia and Finland have a lot of EVs, and also big distances to drive. Doesn't seem to be a big issue.
I have a 2005 Honda that's still running great, I plan to keep driving it a long time. I just got a 2021 Honda (ICE) as the family car, I expect to keep driving that one just as long.
I want to see longevity in EVs before I make the switch. Or they need to be significantly less expensive.
[1] https://www.edmunds.com/electric-car/articles/electric-car-b...
[2] EV maintenance costs are about 60% of ICE https://www.energy.gov/eere/vehicles/articles/fotw-1190-june...
and fueling costs are about 50% of ICE https://www.caranddriver.com/shopping-advice/a32494027/ev-vs...
[1] https://arstechnica.com/cars/2023/02/heres-how-the-governmen...
In Central Europe a lot of supermarkets and malls already have DC charging (sometimes AC charging too). So during a regular (20-30 min) visit at the supermarket you can easily charge the battery up to 80%.
Where I live every town with more than ~1000 inhabitants got at least one AC charging spot operated by the local electricity provider. Charging there may be cumbersome though, because you may need to walk back 5-10 minutes to your apartment and pick up the car a few hours later.
I bought a used ‘79 RX-7 in 1990 with about 130,000 miles on it. When it started up, it emitted a large cloud of white vapor.
When I turned it off, usually at the gas station, that un burned fuel ignited in the exhaust line. It was not unlike a gunshot.
I’d like to apologize to those whose hearts I stopped.
source? i thought it's shipping with mazda 3's