[HN Gopher] Mazda's rotary engine in the age of the electric car
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Mazda's rotary engine in the age of the electric car
Author : gascoigne
Score : 210 points
Date : 2024-03-28 12:22 UTC (2 days ago)
(HTM) web link (www.nippon.com)
(TXT) w3m dump (www.nippon.com)
| 486sx33 wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| They have low compression though, which really hurts the
| thermal efficiency.
| coryrc wrote:
| Then you may as well use a gas turbine, which is pretty
| much better in every way that matters for generating
| purposes.
| iamthirsty wrote:
| Except extremely complex and usually hard to repair and
| inefficiently sized for a consumer car.
| userbinator wrote:
| Actually far simpler than a piston engine; the fuel
| consumption and high production cost was what made them
| become extinct.
|
| https://en.wikipedia.org/wiki/Chrysler_Turbine_Car
| kyleee wrote:
| Of course Jay Leno has one; not sure if he's featured it
| on his youtube channel (I don't recall seeing it).
| Awesome
| 01HNNWZ0MV43FF wrote:
| Yep I've seen it on his YouTube. The "EcoJet"
| https://www.youtube.com/watch?v=10q9_pB6unU
|
| He said that they had to put really big brakes on it. I
| guess for some reason you can't just have a clutch.
| Personally if I was going for eco I'd want something more
| clever than "bigger brakes" but maybe building something
| like a Hybrid Synergy Drive is harder than building a
| turbine.
| SoftTalker wrote:
| > He said that they had to put really big brakes on it.
|
| There's no compression braking (engine braking) with a
| turbine engine.
| jasonwatkinspdx wrote:
| Here's his video on his 1960's one, which is worth
| watching and some neat animation footage from the period
| talking about the design:
| https://www.youtube.com/watch?v=b2A5ijU3Ivs
|
| You can tell Jay genuinely loves cars and the history of
| the auto world. He's indulging his hobby interest in a
| way that will preserve these vehicles for future
| generations to see and learn about. As far as ways rich
| people can spend their money that's a pretty cool one in
| my book.
| WalterBright wrote:
| Gas turbine cars have been built, but they tend to set
| anyone on fire if they walk behind the car.
|
| https://bandimere.com/previewing-the-brakes-plus-jet-car-
| nat...
| coryrc wrote:
| You're probably being silly, but for anyone else, gas
| turbines as used for generators don't have jet exhausts
| on them, i.e. https://www.youtube.com/watch?v=yR5oVn-Fvvg
| philwelch wrote:
| So what do they do with the exhaust?
| elevatedastalt wrote:
| The reason jet engines have that sort of exhaust is
| because the primary purpose of the gas turbine there is
| to dump all the excess energy into the exhaust to make it
| go fast (so that the plane can be pushed ahead by the
| reaction force). They produce very little power, just
| enough to power the Auxiliary Power Unit (that manages
| the plane electronics, air-conditioning etc.).
|
| If you want to use a gas turbine for producing power, you
| will set it up such that most of the energy goes into the
| work generated, rather than the exhaust, so it would be a
| cooler, slower exhaust, similar to an IC-engine.
| 01HNNWZ0MV43FF wrote:
| Depending on the plane and engine. Big jetliners have
| high-bypass turbines where they do intentionally produce
| a lot of torque, to spin a large compressor fan, but most
| of the fan air does not go through the combustion step,
| it's just used to react off of.
| WalterBright wrote:
| It's ironic how propeller airplanes evolved into jets for
| for thrust and back to propellers.
|
| (A ducted fan is still a propeller.)
| pfdietz wrote:
| We may go to unducted fans soon. The latest iteration of
| this concept has two sets of fans, one set of which
| doesn't rotate.
| philwelch wrote:
| Other people have already mentioned the distinction
| between turbojets (what you're describing) and turbofan
| engines, but I think there's another inaccuracy:
|
| > They produce very little power, just enough to power
| the Auxiliary Power Unit (that manages the plane
| electronics, air-conditioning etc.).
|
| The APU is a completely separate gas turbine that doesn't
| rely on the main engines. As a consequence, the APU on an
| airplane will also have its own exhaust.
|
| > If you want to use a gas turbine for producing power,
| you will set it up such that most of the energy goes into
| the work generated, rather than the exhaust, so it would
| be a cooler, slower exhaust, similar to an IC-engine.
|
| Yes, obviously. At the same time, I was under the
| impression that turboprops and turboshafts on airplanes
| and helicopters still produced enough jet exhaust to
| represent a safety hazard, and in those applications you
| would also expect that most of the energy would go into
| the work generated rather than the exhaust. So is it just
| that this residential generator is even more efficient
| than the main engine of a heavy-lift helicopter? Is it
| because it's a less powerful machine in the first place?
| I could continue to speculate about this but I don't
| actually know.
| londons_explore wrote:
| [delayed]
| mrighele wrote:
| Some models do, some others do not:
| https://www.youtube.com/watch?v=b2A5ijU3Ivs,
| https://www.youtube.com/watch?v=CdCudNSti_Q
| JALTU wrote:
| Oh! The Batmobile!
| fodkodrasz wrote:
| Except for consumption, waste heat generated, size.
| mrighele wrote:
| If all you need is power generation, use a nuclear
| reactor. Time to bring back the Ford Nucleon ! [1]
|
| Comes with daily free health checkup (in form of an
| X-Ray).
|
| [1] https://en.wikipedia.org/wiki/Ford_Nucleon
| xattt wrote:
| Aaahktually, the radiation given off the reactor would be
| too "hard" and useless in soft-tissue imaging.
|
| Maybe neutrino imaging?
| user_7832 wrote:
| Apparently they really don't scale well. I found this
| reddit post explaining it better:
|
| > Gas turbines scale extremely poorly. They rely on small
| clearance between the rotating blades and the housings
| for efficiency. The smaller the turbine, the greater the
| relative clearance and the more energy is lost. Gas
| turbines, at least with established technology, make very
| little sense below 300ish HP. As a real life comparison:
| A Robinson R44 piston helicopter and an R66 turbine
| Helicopter have almost identical design, dimensions, and
| weights. Power is around 250 / 300hp. The former burns
| between 50-60L of gas per hour at cruise, the latter
| around 90-110L of Jet fuel.
|
| 1 - https://old.reddit.com/r/cars/comments/s8vkv8/are_wan
| kel_eng...
| bob1029 wrote:
| 300 HP = ~220 kW
|
| I believe a Tesla can charge its battery pack at
| approximately this rate.
| avalys wrote:
| What's your point?
|
| There's no reason to have a generator that charges the
| pack in a hurry. It really only needs to cover the
| maximum sustained average draw - driving up an extended
| grade at high speed. That's a lot less than 300 hp - it's
| probably not more than 80 hp or so at most.
| Baeocystin wrote:
| I remember back in the 90's in auto shop we calculated
| that you'd only need 15-25hp continuous to essentially
| power all of a car's needs if you could smooth demand for
| power from the peaks over the length of the trip. It
| stuck with me as a surprisingly small number, but it
| mathed out, even including heating and AC. Cars are both
| larger and more aerodynamic nowadays; I wonder if the
| amount would still be the same?
| DarmokJalad1701 wrote:
| A Model 3 or Model Y's "rated efficiency" of 250-300
| Wh/mi corresponds to 16-20 kW assuming a 65 mph speed.
| That's well within that range you quote.
| defrost wrote:
| For _many_ 'standard' driving patterns ( _relatively_
| 'flat' urban commutes with approx balanced medium length
| up and down grades) there are lightweight optimal
| solutions for EV's that can minimise both battery pack
| size (and weight) and the need to draw on a small rotary
| engine for recharge.
|
| The UK's drone engines come in light and small with
| models that range from 5 BHP to 120 BHP with 40 BHP being
| suitable for broad swathe of "typical" driving.
|
| https://www.aieuk.com/wankel-rotary-uav-engines/
| UniverseHacker wrote:
| Thank you, I've wondered for years why we didn't have
| tiny gas turbine engines...
| pfdietz wrote:
| There are companies that have tried, like Capstone
| (formerly Capstone Turbine, then Capstone Green Energy).
| Capstone declared chapter 11 bankruptcy last year (since
| emerged and continuing under new leadership.)
| londons_explore wrote:
| I still believe it's possible - for example by having all
| the blades enclosed in a ring you can avoid gas escaping
| 'round' the blade.
|
| And with metal 3d printers rapidly falling in price, I
| think it will get within the scope of university students
| to prototype soonish.
| ckozlowski wrote:
| They did come about, in the late 60s. Williams worked on
| these to varying degrees of success. One of their designs
| became quite famous. The F107 powers the BGM-109 Tomahawk
| and AGM-86 ALCM.
|
| https://www.smithsonianmag.com/air-space-magazine/the-
| little...
| bobthepanda wrote:
| Fun fact, before the oil crisis the French TGV was
| originally a gas turbine train.
| Merad wrote:
| They definitely exist for small RC aircraft, but they're
| very expensive.
| rgmerk wrote:
| And chew through fuel at truly extraordinary rates.
|
| This one, for example, weighs 450 grams, but can consume
| its own mass in fuel every three minutes!
|
| https://www.kingtechturbinesaustralia.com.au/product-
| page/k4...
| alexose wrote:
| Cosworth appears to have developed a microturbine for
| this purpose. And it (maybe?) has found a home in Ariel's
| latest insane car:
| https://www.carscoops.com/2022/09/ariel-hipercar-is-
| an-1180-...
| cjbgkagh wrote:
| AFAIK I think there is some difficulty in getting
| turbines to scale down efficiently with a need of a
| recouperator to maintain a higher core temperature for
| better efficiency. The recouperator is additionally
| expensive on top of the already expensive turbine cost.
|
| Having a rotary with a turbo should be able to work
| better at a lower scale for a pretty cheap production
| cost.
| cranky908canuck wrote:
| Want to comment explicitly, though I upvoted a similar
| comment ... a gas turbine in a consumer car will be a
| maintainability nightmare (where do you find the
| technicians that can do anything with it?), at least in
| the current automotive ecosystem.
| simne wrote:
| Gas turbines are economically effective when larger than
| about 300hp. This border with time slow lowered, but I
| don't know, when it will appear somewhere about 50Kw of
| most popular automobiles (Toyota Corolla, WV Golf, Ford
| Focus).
|
| When scaling down, gas turbines become much more
| expensive than ICE. For example on small planes market,
| exist many dual-powered models (in range 200-300hp), and
| with gas turbine it typically priced twice of ICU-powered
| with very similar parameters. Range of 1000hp+ on planes
| are near totally gas turbines.
| bluedino wrote:
| Chrysler tried it in the 50's and 60's
|
| https://en.m.wikipedia.org/wiki/Chrysler_Turbine_Car
|
| The ideas and innovations back then seemed amazing
| eep_social wrote:
| Maybe you're thinking of the Edison kits? They seem to be
| putting a genset into the truck bed to do EV conversions:
| https://news.ycombinator.com/item?id=38893567
| seltzered_ wrote:
| > I'd swear I remember discussion here a handful of months
| ago about a startup marketing a similar EV range extender
| engine design.
|
| Possibly https://liquidpiston.com
|
| Prior discussions: https://hn.algolia.com/?dateRange=all&pa
| ge=0&prefix=true&que...
| speed_spread wrote:
| In a hybrid vehicle, the gas engine can be run mostly as a
| generator, which makes it possible to further optimize it for
| a very specific load. It's possible that such an
| updated+tuned Wankel could be a great fit for certain
| applications where space and weight are at a premium.
|
| They can simulate lots of it but to get real answers, they
| have to build the engine and see how it holds up.
|
| Also Mazda is a small-ish manufacturer at the Japanese scale.
| Since Wankels are part of their identity they could decide to
| build a car with it even though the downsides wouldn't make
| sense for a "rational" brand like Toyota. It can give them
| that creative freedom that help make desirable cars and keep
| Mazda relevant.
| tokai wrote:
| I bet wankle development is also excellent for internal
| education of their engineers.
| DonHopkins wrote:
| Mazda Rotary 'Launch':
|
| https://www.youtube.com/watch?v=Hdjj52FUsEo
|
| >These are some of the earliest ads I wrote and directed.
| Many of these ads cost our client just a couple of hundred
| dollars. When you look at this early attempt ant animation,
| it's not surprising that it didn't cost much more as a
| decent lunch these day!
|
| >It's hard to believe now how absolutely 'revolutionary'
| the rotary engine appeared to be in those days. Many of us
| expected that they would eventually take over from
| reciprocating engines completely.
|
| >This ad was produced just before the moon landing.
|
| >The Agency was Hayes Advertising, Sydney. My producer (and
| dear friend) was Max Cleary and the Account Director was
| Vic Violet.
|
| Mazda RX-3 Commercial:
|
| https://www.youtube.com/watch?v=oHzeGEHWMjo
|
| >Piston engine goes boing, boing, boing, boing.
|
| >Mazda engine goes Hmmmmmmmmmmmmmmmmmmmmmmmmmm.
|
| Felix Wankel:
|
| https://en.wikipedia.org/wiki/Felix_Wankel
|
| >Wankel and the Nazi Party
|
| >During the early 1920s Wankel was a member of various
| radical anti-Semitic organizations. In 1921 he joined the
| Heidelberg branch of the Deutschvolkischer Schutz- und
| Trutzbund and in 1922 he became a member of the NSDAP, the
| National Socialist German Workers Party (or "Nazi Party"),
| which was banned soon afterwards. Wankel founded and led
| youth groups associated with a cover-up organization of the
| NSDAP. With them he conducted paramilitary training,
| scouting games and night walks.[3] When his high esteem for
| technical innovations was not widely shared among the
| German Youth Movement, he was offered instead the
| opportunity to talk about the issue of technology and
| education to Adolf Hitler and other leading National
| Socialists in 1928.[4]
|
| >In the meantime Wankel's mother, Gerty had helped founding
| the local chapter of the NSDAP in his hometown of Lahr.
| Here Wankel not only rejoined the party in 1926, but also
| met the local Gauleiter, i.e. regional head of the NSDAP
| party, Robert Heinrich Wagner. In 1931 Wagner entrusted
| Wankel with the leadership of the Hitler Youth in Baden.
| But they soon fell out with each other, because Wankel
| tried to put a stronger emphasis on military training,
| whereas Wagner wished for the Hitler Youth to be a
| primarily political organization. In a particularly bitter
| and ugly controversy Wankel publicly accused Wagner of
| corruption. Wagner retaliated by stripping Wankel of his
| office by early 1932 and managed to have him expelled from
| the party in October 1932.
|
| >Wankel, who sympathized with the social-revolutionary wing
| of the NSDAP with Gregor Strasser, then founded his own
| National Socialist splinter group in Lahr and continued his
| attacks on Wagner. Since the Nazis' seizure of power on 30
| January 1933 had strengthened his position, Wagner had
| Wankel arrested and imprisoned in the Lahr jail in March
| 1933. Only by intervention of Hitler's economic adviser
| Wilhelm Keppler and Hitler himself, was Wankel set free in
| September 1933.[5] A fellow native of Baden and member of
| Reichstag from 1933 to 1945, Keppler had been a friend of
| Wankel and an ardent supporter of his technological
| endeavors since 1927. He now helped Wankel to get state
| contracts and his own Wankels Versuchs Werkstatten
| experimental workshop in Lindau.
|
| >Wankel tried to rejoin the NSDAP in 1937, but was turned
| down.[6] With the help of Keppler, however, he was admitted
| to the SS in 1940 in the rank of Obersturmbannfuhrer.[7]
| Two years later his membership was revoked for unknown
| reasons.[6]
| porphyra wrote:
| nit: it's spelt Wankel not Wankle.
|
| Also for those who don't know, it's pronounced /'vaNGkl/ or
| /'vaNGk@l/ in the International Phonetic Alphabet (IPA). In
| German, "W" is pronounced as "V" in English, and the "e" in
| the syllable "kel" is reduced to a schwa ([@]) sound, common
| in many German pronunciations of unstressed vowels.
| jpgvm wrote:
| Sadly enough I did know that but wrote it wrong anyway!
| Fixed, thanks. :)
| pengaru wrote:
| > Does it produce more low end torque verses a traditional
| gasoline combustion engine? If not then why is it better suited
| for electrical generation?
|
| What does low end torque have to do with electrical
| _generation_?
| jiveturkey wrote:
| It's not a direct connection.
|
| You do want efficient horsepower to drive a generator. More
| low end torque means the HP comes at lower RPM, which should
| mean less fuel consumption.
|
| Sibling says the achilles heel of the Wankel rotary is low
| end torque, but you don't take the direct output from the
| engine, it goes through gear reduction for final drive
| output. The real achilles heel is the awful emissions. It's
| more or less a 2 cycle engine from that POV.
|
| When driven at variable speeds it's hard to wrangle.
|
| The reason it's well suited for electrical generation is its
| mechanical simplicity, compactness, low weight, low NVH, and
| not least important, "rotary" brand value. I suppose that
| when run at constant RPM and constant or smoothly changing
| load, the emissions is easier to deal with.
| pengaru wrote:
| The side-port exhaust used in the rx-8 generation RE
| substantially improved the emissions situation, but the
| fuel efficiency is still trash by modern ICE standards.
|
| It's been awhile since I gave a damn about wankels (or ICEs
| in general), but ISTR there being a relatively low limit to
| achievable static compression ratio due to the fundamental
| geometry of the swept volume. Modern ICE engines are
| largely exploiting the combination of direct injection and
| the high compression ratios it enables to improve their
| thermal efficiency. Between the relatively low compression
| ratio and sub-optimal combustion chamber shape and the fact
| that it migrates around the housing with the power stroke,
| the wankel is pretty much doomed in a world that cares
| about efficiency.
|
| disclaimer: I've worked hard to discard all my gearhead
| knowledge, but went fairly deep down the rx-7 rabbithole in
| my 20s-30s. Take the above with a big grain of "I may be
| senile and overconfident in stale once-deep knowledge"
| salt.
| jiveturkey wrote:
| to the best of my knowledge, you are correct on all
| counts. the new rotary used as a generator does also have
| direct injection, but i don't think they gain much
| compression ratio from that, for the reasons you stated.
| it's more for efficiency. without reading up on it, i
| believe the combustion chamber mixture and flame front
| propagation is not great in a rotary (hence RX8 has 2
| plugs per chamber, leading and trailing) and DI should
| improve on it.
| WillAdams wrote:
| Pretty much.
|
| One (potential?) advantage not mentioned in the article is
| lighter weight relative to a similar traditional engine.
| joking wrote:
| Would be good as a range extender motor. I think smaller
| battery cars with range extenders should be a better option
| than what we have now.
| thehappypm wrote:
| Oh my God, if Tesla sold a range extender gas generator
| that sat in the frunk, and could add an extra 150 miles..
| take my money.
| jsight wrote:
| 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.
| ianai wrote:
| A YTer said it allows the rotary engine to operate in its
| best circumstances. It's essentially a range extender while
| battery tech improves.
| lostlogin wrote:
| It fixes the terrible efficiency by having an entirely
| different power source?
|
| As others have pointed out, the article doesn't do a great
| job of explaining how the rotary helps.
| suprjami wrote:
| It really isn't. Go and drive a 13BT car. They make almost
| all their torque by 2500rpm and the curve is flat. They're
| more torquey than any 4 cylinder I've driven.
| skellera wrote:
| I don't understand why Mazda doesn't just make a drift-tuned
| electric car. You could do amazing stuff with software focused
| on that driving style.
|
| A true electric successor to the RX-7 would capture so much
| attention.
| HPsquared wrote:
| The unique sound is a key selling point for rotary
| enthusiasts. Kind of raspy, almost like a 2-stroke.
| mikestew wrote:
| _Kind of raspy, almost like a 2-stroke._
|
| That's not what the TV commercials from the 70s told me:
|
| "Piston engine goes 'boing, boing, boing, boing'"
|
| "But the Mazda goes 'hmmmmmmm'"
|
| (Oh, of course there's a YouTube video:
| https://www.youtube.com/watch?v=oHzeGEHWMjo)
| porphyra wrote:
| Sports cars, in general, are much loved but seldom bought.
| kjkjadksj wrote:
| You'd think its a different time now that the kids who grew
| up lusting over these cars now have money for one, enough
| money to create a new car market where even a pickup truck
| can be almost six figures optioned out
| porphyra wrote:
| Yeah but by the time you're able to afford one you will
| be married with kids and therefore prioritize
| practicality over drifting.
| Prcmaker wrote:
| I'm literally waiting for it, have been for quite a while.
| Small cars have numerous benefits over just being sporty.
| An electric, or even a hybrid 86/BRZ or miata would be
| great, but can't be compared to the mini or fiat, and while
| tesla might be fast, it's huge. Even with a price increase
| these could be more affordable than a lot of sports cars.
| The 86/BRZ has been a huge seller too.
| dkjaudyeqooe wrote:
| The EV market is so frustrating right now. Everything
| seems to more or less be an SUV.
|
| I wish someone would deliver something small, light,
| aerodynamic, stripped down and without features of
| marginal utility. Sportiness sort of comes for free.
|
| The only important features for an EV are (excluding
| safety issues) are change speed and range. I might add a
| heat pump for the cabin (and battery in cold climes).
| Skip the screen and just let me use my phone and give me
| physical controls.
|
| If a car marker thought seriously for a moment and
| resisted the full techno wank that is inflicted upon us
| at the moment, they'd make a lot of money.
|
| It's a car, it's not that complicated, get back to
| basics.
| PaulDavisThe1st wrote:
| I'm not really that interested in cars. We drive a Honda
| Fit (Jazz for the rest of the world). I was really
| excited 8+ years ago when Honda said they might do an EV
| version of the Fit/Jazz - just perfect for my wife and I,
| combining the great utility of the Fit/Jazz with our
| preferred power source, all in a reasonable sized and
| reasonably slick package (incredibly internal visibility
| also).
|
| Not only has this not happened, Honda have even stopped
| selling the ICE version of the Fit in the USA. The
| closest thing to this concept - the Nissan Leaf - has
| also been discontinued in the N. American marketplace.
|
| Truly pathetic.
| lagadu wrote:
| The MG Cyberster is coming out pretty soon, also the
| electric Cayman, though it's a completely different price
| bracket.
| ggreer wrote:
| Several reasons.
|
| First, like most of the Japanese manufacturers, Mazda bet
| against electric vehicles. They focused R&D on improving
| engine efficiency and getting their engines to run on
| hydrogen. If Mazda wants to make electric vehicles now, they
| have to play catch-up, or license key technologies from other
| manufacturers.
|
| Second, batteries are heavy. For sedans and mid-size
| crossovers, this isn't much of a problem. EVs of that class
| are about the same weight as combustion vehicles. But for a
| lightweight sports car with decent range, batteries would be
| a big chunk of the total weight. Tesla's 85kWh battery weighs
| around 1,200lbs. If your desired weight is 2,500lbs, that
| only leaves 1,300lbs for the actual car. Yes you can save
| some weight by making the battery part of the structure, and
| you don't need an exhaust system, engine block, alternator,
| intake, etc, but it's still a tough set of constraints to
| work within.
|
| Why do customers want sports cars to be light? Well all else
| equal, a lighter vehicle will have better performance. But
| even when all else isn't equal, vehicle weight can
| drastically affect driving enjoyment. I have a 4,048lb Model
| 3 Performance and a 2,182lb Mazda Miata. In terms of specs,
| the Model 3 is better in every way. It can accelerate, brake,
| and turn better than the Miata. It even has more range than
| the Miata. But the Model 3 feels like it's using brute force
| to beat inertia into submission. (Don't get me wrong, that
| can be fun.) The Miata is the opposite. Its light weight
| means that there's very little inertia to overcome, and
| something about that is extremely satisfying. It's almost
| like having a street legal go-kart. Until battery technology
| improves, an electric version just won't have the same
| appeal.
| lostlogin wrote:
| Going with this theme, the idea of a battery car with
| longer range is appealing to me. However a smaller battery
| but quick charging would mostly remove the need.
|
| I'm not sure I want to drive around with a capacitor in the
| boot, but a huge battery isn't ideal either.
| gambiting wrote:
| That's the whole thing right - most people don't actually
| care about having 600 miles of range, they care about
| being able to "refuel" quickly. My Mercedes AMG would
| only do like 200 miles on a tank of fuel and I don't ever
| recall having any kind of range anxiety with it, because
| you could gain all of it back within like 5 minutes and
| keep going.
| user_7832 wrote:
| It would be theoretically possible to have a small battery
| ("just a 60 mile/100km range, or even smaller) combined
| with a generator, but I don't know if markets would
| appreciate that.
| 01HNNWZ0MV43FF wrote:
| This company Toyota started a pretty popular line of
| hybrid gas-electric cars, maybe 20 years ago, called
| Priuses. I think they sell pretty well. I see a lot of
| them running as taxis. The new ones can plug in and drive
| a few miles on the highway on pure electric before
| starting the gas engine.
| gambiting wrote:
| Priuses do use the ICE to drive the wheels though, no?
| pfdietz wrote:
| Yes, they are parallel hybrids.
| dragonwriter wrote:
| Its called a series hybrid, there have been a small
| number of plug-in hybrids that used that design, they
| weren't successful in the US and are no longer in the US
| market. But that may not be anything particular about the
| technology; I wouldn't generalize from such a small set.
| narag wrote:
| It seems Mazda is going ahead with an electric Miata, they
| just don't know how electric it will be:
|
| https://www.motortrend.com/news/2026-mazda-mx-5-miata-
| electr...
| eggsboenk wrote:
| The McMurtry Speirling is claimed to be under 1000kg. A
| lightweight electric car may not be an oxymoron after all.
| Just some concessions to make.
| ggreer wrote:
| The McMurtry Speirling is not street legal and it costs
| $1 million.
| fragmede wrote:
| And what a car it is!
| greggyb wrote:
| The Bugatti Veyron launched in 2005 with 1K horsepower
| and cost > $1M. As of last year, you could get a Dodge
| Challenger with 1K horsepower for <$100K. Those prices
| are unadjusted for inflation, so the price difference is
| even greater than 10x.
|
| While it is not a guarantee, the innovations in today's
| supercars do tend to become much more common with time.
| inhumantsar wrote:
| I think you're drawing a lot of conclusions from that
| correlation.
|
| what innovations did the Veyron introduce that the
| Challenger used?
| gambiting wrote:
| Our VW e-Up is just below 1200kg and has 150 miles range
| from a 36kWh battery, fits two of us, baby seat, and
| Costco shopping. You can absolutely have a lightweight
| electric car, just be realistic about what you're
| getting.
| discreteevent wrote:
| "Adding power makes you faster on the straights.
| Subtracting weight makes you faster everywhere." - Colin
| Chapman (Lotus)
| ggreer wrote:
| I agree with the adage, but brute force seems to win in
| this specific case. Even though it's the lightest model
| made, my Miata only gets 0.82g on the skidpad.[1] The
| Model 3 Performance gets 0.96g thanks to its wide tires,
| which are needed to transfer all its power to the
| asphalt.[2] This difference isn't just due to the 1990
| Miata's older suspension and tire technology. Even the
| latest Miatas only get 0.90g of lateral acceleration.[3]
|
| 1. https://www.caranddriver.com/reviews/a15141519/1990-ma
| zda-mx...
|
| 2. https://www.caranddriver.com/reviews/a36329678/2019-te
| sla-mo...
|
| 3. https://www.caranddriver.com/reviews/a22678665/2019-ma
| zda-mx...
| giobox wrote:
| > I agree with the adage, but brute force seems to win in
| this specific case. Even though it's the lightest model
| made, my Miata only gets 0.82g on the skidpad
|
| The current ND2 (2019+) Miata regularly pulls ~0.95 stock
| in magazine tests, almost identical to your model 3
| Performance number.
|
| > https://www.motortrend.com/reviews/2019-mazda-
| mx-5-miata-clu...
|
| You can exceed 0.95 and get ~1 on an ND Miata with
| slightly wider than OEM tires (still on stock rims) and a
| little more negative camber, which is widely done to the
| car by the enthusiast community. Similarly, you can get
| more out of your very own NA (1990) Miata with simple
| tire/alignment changes, even more with cheap new sway
| bars or springs etc.
|
| > https://help.flyinmiata.com/align-your-suspension-
| chakras-By...
|
| The ND2 is a ~1070kg car.
|
| To use a more fitting Lotus example here, the ~900kg
| Lotus Elise (50% of the weight of the Model 3
| Performance) pulls 1g when tested by Car and Driver:
|
| > https://www.caranddriver.com/reviews/a15146116/2007-lot
| us-el...
| ggreer wrote:
| Yes and you can modify the Model 3 to increase cornering
| ability, but like in the case of the Miata it means
| increased tire wear, worse comfort, and worse mileage.
| Not to mention money.
|
| My point was simply that even if you know vehicle A is
| twice as heavy as vehicle B, you don't know for sure
| which one is faster in the turns.
| giobox wrote:
| > increased tire wear, worse comfort, and worse
| mileage... Not to mention money
|
| It literally means none of this to change a miata as I
| described - we are talking a single degree of camber here
| not a race car. An alignment is normal maintenance - no
| change in price - and tires stay the same price if you go
| up a single size, so if you do this when getting new
| tires anyway it costs essentially nothing.
|
| It's a minor camber change (done at a standard alignment
| as normal, no extra special bits - just ask tech nicely).
| The tires will last just as long for your driving style
| and gas mileage unaffected. Comfort unchanged - no
| spring, damper or tire pressure changes.
|
| The point this all makes is simple factors beyond weight
| have a huge bearing on constant lateral load car will
| sustain, to the point it's almost pointless to compare
| weight and max corner load. You will never see car
| enthusiasts comparing weights of their cars and arguing
| in favour of more weight, almost ever. This entire
| comparison is pretty odd. No one who knows what they are
| talking about is going to question the classic Colin
| Chapman quote because physics didn't change since his
| death - the concept of same car but lighter was faster in
| the 60s and 70s, and is still faster round a circuit
| today. It's why race cars set faster lap times as the
| fuel tank depletes, which proves the point beyond doubt.
|
| If you haven't had a good alignment done to your NA
| recently get it done and don't be scared of small
| adjustments, they won't ruin anything - it does quite the
| opposite! - and the numbers that work great for all
| miatas are insanely well documented online. Steering feel
| will thank you for it. It's the first thing I will have
| done to any generation of miata - they all benefit a lot,
| and usually arrive from factory not very accurately setup
| at all - you will see this when you have first alignment
| done and brand new car has initial numbers all over the
| place.
|
| I've owned and maintained multiple examples of all four
| generations of the car over the last 20 years - a
| precision alignment with a touch more camber/toe is one
| of the easiest, best and cheapest (100-150 dollars
| typically in major US city) things you can do to the car
| - the miata is all about that steering feel which is
| easily corrupted.
| ksec wrote:
| >A true electric successor to the RX-7 would capture so much
| attention.
|
| Not entirely sure that would be the case even with a Red Sun
| label on it.
| busterarm wrote:
| As someone who owns a white turbo fc, sans stickers, I
| would be interested.
| porphyra wrote:
| 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.
| dragontamer wrote:
| > 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.
| 01HNNWZ0MV43FF wrote:
| It's not like the ICE doesn't do anything at low speeds, HSD
| uses the two motor-generators like a gearbox
| pfdietz wrote:
| Isn't it a Miller cycle engine, not Atkinson? Miller cycle
| exploits variable valve timing to make the compression stroke
| effectively shorter than the expansion stroke (but reduces
| the amount of air being compressed, reducing power); Atkinson
| has some funky extra joints in the rod or crankshaft, I
| think.
|
| Yes: https://en.wikipedia.org/wiki/Atkinson_cycle
|
| However, these modern Miller cycle engines are being called
| Atkinson or Atkinson-Miller cycle for some reason.
| brucethemoose2 wrote:
| Power/Weight is extremely high. A tiny wankel will do the job,
| and weight is everything on cars.
|
| 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.
| suprjami wrote:
| Reliability for rotaries hasn't been a concern for a long
| time. Modern apex seals work well and last a reasonably long
| time. There is a need to stop parroting facts from the 1980s.
| pavlov wrote:
| It can be the whole story.
|
| 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.
| cpursley wrote:
| > Mazda is BlackBerry
|
| No, they're not. Go test drive a Miata. They make the most
| fun cars to come out of Japan. And also have one of the
| better design languages.
| KptMarchewa wrote:
| As much as I love Mazda, if the only thing they'll have for
| them is fun, they are dead as a mass manufacturer.
| interstice wrote:
| Since the achilles heal of the rotary is wearing seals has
| anyone seriously invested in testing coating/material tech
| for this? It may not make sense for mass production but
| spending ~10k to make a bulletproof rx7 would be an
| incredibly good investment.
| ryukoposting wrote:
| It has nothing to do with sentimentality.
|
| 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.
| sanderjd wrote:
| These three paragraphs would have been a far more
| enlightening article than the posted article.
| ghostly_s wrote:
| > 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.
|
| If I understand the article correctly, the "series" hybrid
| configuration means precisely that it cannot operate at the
| ideal rpm when charging the battery, because it is always
| driving the wheels directly as well.
| FooBarBizBazz wrote:
| I think you have series and parallel hybrids backwards.
| Series hybrids have no mechanical connection between engine
| and wheels. It's just an EV with a generator wired in.
| ryukoposting wrote:
| Exactly the opposite. In a series hybrid, there is no
| mechanical connection between the engine and the wheels -
| only an electrical one, with the battery still providing
| considerable power in most cases, even when it's depleted.
|
| No hybrid ever runs its battery all the way to zero, and
| series hybrids are no exception. The Chevy Volt (the other
| notable series hybrid in Western markets) keeps its engine
| at a near-constant RPM by using the battery to supply
| torque, even when the battery is "dead." I would expect the
| MX-30 to do the same.
|
| IME in several thousand miles driving/riding in a Volt, it
| hums away within a very narrow RPM band unless you hoon it
| on a dead battery in cold weather. Even then, it's not
| nearly as wide of a rev band as a conventional hybrid.
| chipsa wrote:
| The Volt is a series/parallel hybrid. It has situations
| where the motor is directly connected to the wheels. The
| BMW i3 does has a series only set up, but that's probably
| because it also has a BEV only version.
| willis936 wrote:
| Reliability is something easily discounted because the data
| to characterize it is much more difficult to capture than
| performance data. In most applications you can work around
| this with redundancies and diverse technologies, but no one
| makes a fault tolerant powertrain due to cost.
|
| I don't think there's a good reason to keep pushing down
| deadend reliability paths. We should be responding to our
| hard earned decades of learning and be pressing advantages.
| Not every novel and viable solution ends up being an
| enhancement.
| 14 wrote:
| Except in Mazdas case the data was there to characterize
| it. They were notorious for failing very early and suffered
| bad seals around the rotary shaft. This has been well known
| for a long time. Many Rx owners knew ride it for 100k miles
| then sell it before it is too late.
| Retric wrote:
| That rate isn't a deal killer for a plug in hybrid. The
| engine might see ~1/4th the ware per mile spending the
| vast majority of its time off.
|
| Meanwhile hybrids really want a small and lightweight
| engine because of all the extra equipment.
| willis936 wrote:
| Right but then why not use a more efficient and reliable
| engine? The motors will last hundreds of thousands of
| miles. The power circuitry should have a similar run if
| kept cool. Why have an ICE that's more likely to fail
| with lower thermal efficiency?
|
| The engine used in Toyota's most popular cars runs in
| Atkinson most of the time with a 40% thermal efficiency.
|
| https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7425626/
| Retric wrote:
| Because the engine isn't the only thing being optimized.
| Suppose your options are 50 miles of effective plug in
| range and a 40% efficient engine or a 35% efficient
| engine and a 100 miles of plug in range. The second
| option might use a lot less gas.
|
| It's not just the cost of batteries that's a concern
| resulting in short plug in hybrid ranges. Weight is a
| real limiting factor when you also need a gas engine and
| large fuel tank.
| willis936 wrote:
| That would be a worthy trade, but that is vastly
| overstating the weight of aluminum block engines compared
| to Li+ and not at all realistic.
| Retric wrote:
| Atkinson engines have poor power to weight ratio at
| maximum efficiency, if you're going to maintain that 40%
| then the engine needs to be oversized and under utilized.
| This is why many hybrids have seemingly much more power
| than they need. Thus the 194HP Prius vs 75 HP on a CX-90
| plug in SUV.
|
| Also it's not just that you can have extra Li+ it's also
| pushing around less dead weight when the engine is off.
| So you can get fairly close to a 50 mile range difference
| depending on exact setup.
|
| Alternatively you can have a smaller Atkinson engine and
| a larger reserve on the battery, but that also costs
| range while still being heavier.
| pfdietz wrote:
| It could make more sense to use a conventional engine,
| but get extra expansion (the kind an Atkinson/Miller
| cycle engine gets from the longer expansion stroke) by
| turbo-compounding. That is, exhaust gases (still at
| greater than ambient pressure) go through a turbine that
| is coupled to the output shaft, or to another generator,
| rather than being used to drive a compressor as in a
| conventional turbo. Or, attach a motor/generator to a
| conventional turbo and be able to have it operate in both
| modes and use the battery to help overcome turbo lag.
| Retric wrote:
| Possibly, but that's a lot of separate systems.
|
| It might make sense to look into a turbine engine on a
| hybrid. Though that's probably been investigated I doubt
| anyone has invested the kind of time and money needed to
| make a real shot of it.
| eptcyka wrote:
| You will never be able to match the weight of a Wankel
| with a regular reciprocating piston engine, all other
| parameters being equal.
| fransje26 wrote:
| > The motors will last hundreds of thousands of miles.
|
| They might, but with the current average build quality of
| the car industry, the rest of the car will die well
| before that..
| everybodyknows wrote:
| > The engine uses port and side direct fuel injection
| systems (PFI/GDI, referred to by Toyota as D-4S); a
| cooled, external exhaust gas recirculation system (cEGR);
| and a wide range of authority variable valve timing with
| electric phasing on the intake camshaft and hydraulic
| phasing on the exhaust camshaft. Atkinson Cycle is
| implemented using late intake valve closing (LIVC).
| Effective compression ratio is varied by varying intake
| camshaft phasing.
|
| Clever indeed.
| Supermancho wrote:
| I had an RX-8 for years. It was made in 2007. Someone
| defaulted on the loan or lost it in a divorce and drove
| it into a lake, marking it salvage.
|
| I bought it for 25k and was the owner from 2009 to 2019,
| from 60k to over 150k mi. The maintenance was a bit
| pricey, due to the fuel injection problems and the
| electronics would fail in extreme heat of sustained 110+
| outside temp (southern california heat) or cold (seattle
| mornings). I eventually sold it for 9k to a collector.
| Not a bad deal at all.
| nogridbag wrote:
| Wait you paid 25k for a used/salvage RX-8 in 2009? That
| sounds crazy. I think I bought one new for around 26k in
| 2008.
| kcrwfrd_ wrote:
| That does sound crazy. The sticker price for the brand
| new Subaru BRZ limited manual transmission I got in 2012
| was $28k.
| amatecha wrote:
| $25k USD? That does sound really high for a salvage RX-8
| in 2009. My 2005 RX-8 was about $12k CAD in 2011 and was
| not salvage status. Though I guess yours was just a
| couple years old, mine was older, but still.
|
| In regards to reliability, not long into owning it I had
| to get the engine rebuilt due to low compression (luckily
| JUST within the extended warranty period which Mazda
| offered due to the very issue everyone in here is
| mentioning, loss of compression due to failing seals).
| fransje26 wrote:
| > I don't think there's a good reason to keep pushing down
| deadend reliability paths. [..] Not every novel and viable
| solution ends up being an enhancement.
|
| That's a strange take.. It took decades to get
| reciprocating engines to be reliable, even deployed at
| scale. It also took decades to get jet engines reliable
| enough to comply with ETOPS requirements, to the point that
| it was long considered a pipe dream.
|
| If it hadn't been for continuous investments over long
| periods of time and incremental adoptions of improved
| technologies, we wouldn't be enjoying any of their benefits
| today.
| ryukoposting wrote:
| >In most applications you can work around this with
| redundancies and diverse technologies
|
| Are you proposing that Mazda should put two engines in
| their cars? Or am I misreading this?
|
| >hard earned decades of learning and be pressing
| advantages. Not every novel and viable solution ends up
| being an enhancement.
|
| That's precisely what Mazda is doing. They poured decades
| of R&D into the rotary engine, and are leveraging that
| research to their advantage. Their engine's diminutive size
| means they can provide more interior space in a compact
| vehicle, which is one of the key benefits of an EV that you
| can't get with a conventional hybrid. There are innate
| material advantages to the rotary in this application, it's
| not just hand-waving.
|
| There's nothing overly novel about series hybrids, either.
| Chevy proved they can deliver EV driving dynamics and
| efficiency with ICE convenience, even at a larger scale
| than Mazda appears to be targeting.
|
| This entire comment perplexes me. I can't tell if you like
| what Mazda's doing, or if you dislike it.
| redwall_hp wrote:
| Formula 1 cars are also series hybrids, for about a
| decade now. Electric motors drive the wheels at all
| times, and power comes from a turbocharged V6.
| TylerE wrote:
| This is incorrect.
|
| The F1 MGU-K is geared to the crankshaft via the timing
| gears. The wheels are absolutely NOT electrically driven,
| it's working as a torque fill for the conventional
| powertrain.
| AtlasBarfed wrote:
| What happened to the inside out rotary that was supposed to
| be extremely compact and would enable cheaper PHEVs? IIRC the
| patents were about 5 years ago.
| ryukoposting wrote:
| If you're referring to Liquid Piston's "X-engine," as they
| call it, it's doing well. It landed a substantial military
| contract and will likely be used to make super compact,
| lightweight diesel generators.
| cookiengineer wrote:
| Technically, the Wankel rotary engine design allows much
| higher power output than an I-4 or even a V-6 engine design
| due to no strains on the rods, and much less strains on the
| piston(s) as those literally blow up all the time in I4
| engine designs in similar power output ranges.
|
| I've seen many very reliable 3 or 4 rotary wankel swaps in
| RX7 FD3S that output far beyond anything imaginable any
| V8/V12 could produce. 2000hp is not a joke here, when being
| run on pure ethanol as fuel input. Apart from fuel injectors,
| clutch and gearbox, these engines run very stable and
| reliable.
|
| There was an RX-8 Blue model being sold in Japan which was
| burning hydrogen directly, effectively producing water as
| output, which, in the prototype was being converted back to
| hydrogen via a fuel cell. And this was in 2004.
|
| I wish there were more Wankel engines being used as "pocket
| generators", because they can reliably run on synthesized
| alcohol and hydrogen and be a potential generator replacement
| for all that Diesel based crap that's being used in rural
| areas.
|
| Imagine a solar roof on your house that produces hydrogen
| with some fuel cells (which also produce heat for your home).
| This could be the optimum cycle for use in a decentralized
| home, as chemical energy storage has no loss compared to li-
| ion batteries that have a limited lifetime. The multiple use
| of hydrogen (e.g. a stove just needs to burn the gas) also
| makes it very low tech, and possibly much more reliable than
| a circuit based system where transformers might fail over
| time.
|
| But of course, can't sell decentralized approaches via gas
| stations, so it will never take off...
| virtue3 wrote:
| While I also share in your love of Wankel engines I think
| you are grossly skipping over their unreliability (mostly
| around the seals).
|
| There's an extremely good reason "rural" applications are
| reliant on diesels. It's not uncommon for a diesel engine
| to hit 300k+ miles and still operate reliably. And not to
| mention simply. They are relatively easier to maintain than
| a standard gasoline engine.
|
| Diesels also greatly benefit from being on a fixed power
| band. It's why they work so dang well on large ships.
|
| Where as rotary engines(rx-7's at least) need a rebuild
| every 80-100k miles. So I think without really knowing what
| you're doing mechanically or having access to a mechanic
| that can repair those kinds of engines you aren't going to
| be super reliable with a rotary.
|
| Green hydrogen approaches via rotary engines does seem
| quite interesting. I think if the reliability of the rotary
| could be improved that could have some serious merit. Or at
| least making small enough generators that you can easily
| ship them out to be replaced/repaired could have serious
| merit.
| ryukoposting wrote:
| My guess is this: Mazda believes its battery-only range
| is enough for most driving situations. If they're right,
| the rotary engine's more limited lifespan would be a moot
| point since it will still last the vehicle's entire
| lifetime. One can only hope.
|
| The maintenance thing is concerning, though. _Nobody_
| knows how to work on these things. As an RX-7 or RX-8
| owner, you 're either doing most of your engine work by
| yourself, or you're driving very long distances to go to
| a specialty shop. We can pray that it's reliable enough
| for this to not be a problem, but if these engines start
| failing, it's going to be a huge mess.
|
| Side note - the geometry of a Wankel rotary engine makes
| a diesel version impossible - you can't get enough
| compression. Diesel rotaries _do_ exist though. An
| American company called Liquid Piston is making them for
| the Army. The intent is to use them in diesel generators,
| since the resulting generator is much smaller and lighter
| than more traditional diesel generators.
| lightedman wrote:
| "The multiple use of hydrogen (e.g. a stove just needs to
| burn the gas)"
|
| Oh, no. You don't want to be cooking over a flame capasble
| of melting platinum. You will utterly destroy your pots and
| pans temper. I do jewelry work, hydrogen gas is one of the
| hardest gases to properly work with. I'd rather let a
| newbie play with oxy-acetylene than a hydrogen torch.
| rootusrootus wrote:
| Could you elaborate on why this is? Naively, the
| temperature of a simple hydrogen flame is not too much
| hotter than a methane flame. And in torch form, it seems
| like MAPP is several hundred degrees (C) hotter? And oxy-
| acetylene a few hundred more on top of that. Any torch
| seems to have way more than enough heat to melt platinum
| (1700C)?
| lightedman wrote:
| A hydrogen-oxygen flame (this is what happens naturally
| since you're burning hydrogen in open atmosphere) burns
| closer to 2800C, and also has the fun property of causing
| embrittlement (which is especially worsened at higher
| temperatures where metal expands and becomes more
| porous.) Your steel pots and pans are essentially toast
| under a hydrogen flame.
|
| People think "Fire is fire" and no, no it is not.
| Grazester wrote:
| Where are you seeing all these magically rotaries? Yeah the
| guys in NZ and maybe some Americans(Rob Dahm) have some
| high horsepower rotaries but let's not pretend it's the
| norm and that they are more reliable than an equivalent
| piston engine.
|
| Built Nissan VR38DETT V6 produces 2000hp. A full billet
| block will produce 3000hp+. Nissan GT-R guys(T1, ETS,AMS)
| Let's not even get into the big block V8's because these
| things will run all day at that hp and be a whole lot more
| reliable than anything mentioned here.
| simne wrote:
| 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.
| agloe_dreams wrote:
| 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.
| markhahn wrote:
| sorry, why would low-end torque be important?
| rootusrootus wrote:
| 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 wrote:
| 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 wrote:
| Vehicles with range extenders are the exception, even if they
| seem a good option, they didn't gain market share.
| Tagbert wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| The point is the wankle engine. No sense in mentioning the
| Volt.
| rootusrootus wrote:
| They did mention a couple other series hybrids, however,
| neither of which has a Wankel.
| seabrookmx wrote:
| 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.
| Projectiboga wrote:
| 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-...
| explorigin wrote:
| https://www.youtube.com/watch?v=X5UOqZn43gY It has longevity-
| issues due to an internal roller bearing on the main shaft.
| knodi123 wrote:
| wow, thanks. I didn't expect to watch the whole thing, but I
| did.
| fragmede wrote:
| 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 wrote:
| 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 wrote:
| Where do read Toyota into this announcement?
| mattmaroon wrote:
| 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 wrote:
| 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 wrote:
| > 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/
|
| ---------
|
| 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
|
| ---------
|
| 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.
| rootusrootus wrote:
| The Volt was a great idea, but I couldn't make it work for
| me. I need a four door car which regularly holds four
| people, and the Volt (especially the newer one, which was
| when I was shopping) has a low roofline. Only time I've hit
| my head harder on a car roof was when I tried to sit in a
| new Supra. So I ended up finding something where the
| physics of getting in and out were more agreeable. Still a
| sedan, just with fewer headaches.
|
| I wish they had offered that same powertrain design in
| something other than a Cruze.
| akira2501 wrote:
| > All in one planetary gearset.
|
| In the first version. In later versions they added a second
| separate gear set. Then even later they merged the two gear
| sets back into one but with two separate planetary
| arrangements.
|
| I'm not a particular fan of EVs in general, but I do very
| much like the Prius and the careful engineering that went
| into this drive train. This video[0] does a great job of
| explaining the overall system in the context of an
| operating vehicle.
|
| [0]: https://www.youtube.com/watch?v=PIYNAroYEk0
| labcomputer wrote:
| > 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.
|
| This is partly because the Prius is optimized as a hybrid-
| first design, while the Volt is optimized as a BEV-first
| design. The difference is in the gear ratios of the
| planetary CVTs: Prius is optimized to minimize the amount
| of energy transmitted electrically, which maximizes overall
| efficiency.
|
| However, that design is sub-optimal for a car that you want
| to act like an EV. As your link shows, the Prius _must_
| have the ICE spinning at speeds greater than 42 mph. Not a
| problem for a hybrid, but that doesn 't work for a "range-
| extender EV" like the Volt. Additionally, (before the
| current model year) Toyota's plug-in hybrids can't provide
| full acceleration in EV mode--they always kick in the ICE
| when you floor it. That's again a consequence of how the
| transmission is optimized for hybrid operation.
|
| By making compromises to the gasoline efficiency, GM was
| able to create a car which acts like a real EV most of the
| time: A 1st gen Volt will go at least 80 mph in EV mode,
| and won't turn on the ICE (come hell or high water) until
| the battery is below 5%. And, it will do that for an honest
| 35 miles of freeway driving.
|
| The second generation Volt uses GM's "2 mode" hybrid
| transmission, which closes some of the MPG gap by adding
| one fixed ratio (100% mechanical transmission) as well as
| high and low speed eCVT ratios (to minimize electrical
| power in those two speed ranges).
|
| https://www.gm-volt.com/threads/gen-2-volt-transmission-
| oper...
| dragontamer wrote:
| > However, that design is sub-optimal for a car that you
| want to act like an EV. As your link shows, the Prius
| must have the ICE spinning at speeds greater than 42 mph.
| Not a problem for a hybrid, but that doesn't work for a
| "range-extender EV" like the Volt. Additionally, (before
| the current model year) Toyota's plug-in hybrids can't
| provide full acceleration in EV mode--they always kick in
| the ICE when you floor it. That's again a consequence of
| how the transmission is optimized for hybrid operation.
|
| True in 2007.
|
| But 17 years later, the Prius Prime 2024 has 100% EV mode
| even at highway speeds. Toyota has improved the design
| since that webpage was made in 2007.
|
| Despite this change, the Prius still achieves 57 mpg,
| even better than ever before.
|
| Prius Prime is a proper EV-only mode, albeit a touch
| underpowered but its EV mode now covers all possible
| driving conditions.
|
| ------
|
| I believe the modern Prius 2024 has 17,000 RPM limits
| now, as well as tweaked gear ratios and far larger EV and
| ICE engines. Despite the larger 220hp aggregate engine,
| the Prius remains absurdly efficient. Both in EV mode and
| in ICE mode.
|
| This is why I was saying that the Volt has wasted it's
| opportunity. GM was ahead in many respects 10 years ago,
| but Toyota has caught up. The GM advantage has been
| squandered.
|
| > By making compromises to the gasoline efficiency, GM
| was able to create a car which acts like a real EV most
| of the time: A 1st gen Volt will go at least 80 mph in EV
| mode, and won't turn on the ICE (come hell or high water)
| until the battery is below 5%. And, it will do that for
| an honest 35 miles of freeway driving.
|
| Prius Prime added a button to enter EV-only mode in this
| 5th generation design starting in 2023.
|
| It took Toyota too long to add this feature, but now that
| it's here the 5th generation Prius is a far better
| choice.
|
| Especially because Prius still has it's trademarked 50+
| MPG and 130+MPGe ratings. Top of the line efficiency.
|
| It's somewhat frustrating to see Toyota catch up when GM
| was so far ahead for so long. Also because GM killed the
| Volt.
| numpad0 wrote:
| Supposedly has rooms for improvements but there is actually
| that system and real world data: Nissan NOTE e-POWER with
| LEAF motor and no mechanical engine->wheels connection has
| actual user reported mileage of 19.72 km/L(46.4 mpg) on
| regular fuel[0]. This is worse than reported 21.25 km/L(50
| mpg)[1] for Prius[2].
|
| 0:
| https://minkara.carview.co.jp/car/nissan/note_e_power/nenpi/
|
| 1: https://minkara.carview.co.jp/car/toyota/prius/nenpi/
|
| 2: The latest one has a worse fuel economy figure than the
| 1st gen, by the way
| ch_sm wrote:
| > 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.
| idontwantthis wrote:
| I thought the idea is that the battery acts as a buffer and
| the engine is always either off or at constant rpms in its
| ideal power band.
| callalex wrote:
| You also have to keep in mind that the average consumer
| is...quite stupid, or more charitably quite sensitive.
| There are lots of cars on the market today with CVTs
| (continuously variable transmissions) that enable the motor
| to always be driven in the most optimal RPM. However in
| software, the engines are intentionally driven at less
| efficient rpm's so that the driver can feel steps and
| lurches as the car accelerates which is somehow more
| "correct" to the average car buyer.
| idontwantthis wrote:
| I just bought a car with a CVT and now I'm upset.
| topspin wrote:
| No need for that. While it's possible to point out
| particular "performance" car CVTs that do indeed
| compromise efficiency for aesthetics, that's not done in
| most cases, at least not to the degree that efficiency is
| significantly compromised. The actual reason for not
| doing as suggested and placing the entire burden of
| acceleration on the CVT (thus keeping the engine at a
| constant RPM) is that this would be a foolish design.
|
| Between the precision electronic fuel delivery and
| ignition, variable valve timing, variable plenums and
| other features of your ICE, all of which are invariably
| present today when an ICE is the prime mover, the ICE
| power curve has wide RPM bands in which its efficiency is
| high. By taking advantage of these wide bands of
| efficiency, the CVT can have less size, mass, mechanical
| loss, cost, etc., than would be the case if the CVT were
| required to precisely enforce a constant engine RPM.
|
| Minimizing the burden on the CVT is crucial because CVTs
| are a mechanical compromise: they are inherently not as
| strong as a conventional transmission and generally have
| higher mechanical losses.
|
| The manufacturers responsible for these designs aren't
| actually fools, slavishly beholden to some old fashioned
| transmission aesthetic. They're responding to a large
| number of pressures and doing the math. The math says
| that constraining the ICE to an efficient, yet non-zero,
| RPM band is better than trying to manufacture
| miraculously agile CVTs.
| 01HNNWZ0MV43FF wrote:
| Priuses do a power split where the engine drives the wheels
| and the motor-generators act sort of like an electrical
| CVT. You would have to be out of the power band a lot to
| make a series hybrid more efficient than a parallel hybrid.
| The reason locomotives are series hybrids is just that
| mechanically switching that amount of power isn't
| practical. To my surprise, even off-highway mining trucks
| mostly use mechanical transmissions.
| themerone wrote:
| 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.
| Tagbert wrote:
| Almost - In production models the engine does act like a
| series hybrid generator under most circumstances. At high
| speeds, the engine was directly connected to the drive train
| as it is more efficient to do that. the transaxle of the
| Voltec system is a marvel of engineering. It supports a
| dynamic switching between series and parallel hybrid mode as
| well as using the two separate electric motors for either
| power delivery or can switch one to regen and can rapidly
| switch between those modes, too.
| rootusrootus wrote:
| That remains true for more recent "series hybrids" as well,
| such as the Honda mentioned in the article. The efficiency
| gain from engaging the ICE when cruising on the highway is
| just too good to pass up.
| seabrookmx wrote:
| Exactly. The Volt uses the same planetary gear set style
| transmission that the Prius does.
|
| Everyone bemoaning the death of the Volt can now just buy a
| Prius Prime (the PHEV variant). It's the same thing just
| newer/better. It even looks sporty-ish now.
| mattmaroon wrote:
| It wasn't my suggestion, but what I read way back in the day,
| and it may not be accurate but it does not violate the laws
| of physics. It's entirely possible that (just as one
| hypothetical example) being able to keep the engine at
| optimal RPMs at all times in a series hybrid creates more
| efficiency even after the extra conversion losses.
| deelowe wrote:
| 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.
| calfuris wrote:
| The trick is having a large buffer, so that typically the
| engine can operate at the point with the best specific fuel
| consumption or shut down entirely. Getting energy from the
| engine to the wheels is less efficient than a mechanical
| transmission, but the increased average efficiency of the
| engine can more than offset that.
| deelowe wrote:
| Still seems like a traditional hybrid would be more
| efficient. I'm not sure what's gained by removing the
| mechanical coupling altogether (other than
| cost/reliability).
| Electricniko wrote:
| Honda has an interesting solution in their latest gen
| hybrids, where the electric motors power the wheels at
| lower speeds, the combustion engine runs at its optimum
| RPMs as a generator while the electric motors are
| working, and at higher speeds a clutch activates that
| changes the coupling so that the combustion engine
| directly drives the wheels.
| 01HNNWZ0MV43FF wrote:
| Whatever the Prius HSD does is great. It'll do 50 MPG
| city and highway. No clutch at all.
| jeremymims wrote:
| 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.
| davewritescode wrote:
| That and the fact that in the US the car is tuned to only
| turn on the range extender when the battery is nearly dead
| and it can't always keep up.
|
| Thankfully it's trivial to change.
| labcomputer wrote:
| > it was hamstrung by a silly California rule requiring the
| gas range to be less than the electric range to qualify for
| rebates.
|
| The problem is that BMW wanted to get the same amount of
| credits as a pure-BEV. California anticipated that a car with
| 300 miles of gas range might spend much of it's life being
| driven on gas if there was no penalty for doing so... and in
| fact that is _exactly_ what happened with many European plug-
| in hybrids sold as company cars.
|
| California never gave BMW the credits, but BMW decided to
| keep the dinky gas tank anyway, so that's on them.
| Cthulhu_ wrote:
| > and in fact that is exactly what happened with many
| European plug-in hybrids sold as company cars.
|
| The counter force to that is that lease car drivers have to
| meet certain fuel efficiency goals, so, adopt an efficient
| driving style and plug in the plug-in hybrid instead of
| ragging it around; I'm not sure what the consequences were
| though, probably more taxes. Either way, enough of a push
| for my colleagues with plug-in / hybrids to do the thing.
| jessekv wrote:
| I'm curious which country it is that has these fuel
| efficiency goals.
| jasonwatkinspdx wrote:
| Some friends of mine in the Seattle area had one and
| absolutely loved it. It was a very practical car for
| commuting within its range. The extender was barely audible
| when running.
|
| I think the goofy styling was probably as much of an issue as
| the tank size.
| Tagbert wrote:
| 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.
|
| https://www.nissan-
| global.com/EN/INNOVATION/TECHNOLOGY/ARCHI....
| gimmeThaBeet wrote:
| I got my honda partially because it has the closest thing to
| nissan's e-power (in many ways the same, but with a couple
| twists).
|
| At low speeds (< 45 mph) it's either off the battery the
| whole time, or the motor runs and directs power to the
| traction motor or the battery. One wrinkle is that the motor
| assembly has a clutch that can engage the engine direct to
| the wheels, but like in city driving, the engine isn't going
| to be connected to the wheels. But I def would say that at
| least Honda's hybrid doesn't feel as simple as e-power.
|
| Now this probably isn't really accurate, but architecturally
| I think I like it because the only thing keeping it from
| being a BEV is the battery size (only a couple kWh); the
| electric motor is strong enough to be usable on its own.
|
| I think Toyota has increased the power on the normal prius,
| and definitely on the prime, but it used to be as part of the
| power split system, the electric drive motor wasn't sized to
| be enough on its own.
| Tagbert wrote:
| Yes, that was one of the limitations of the Honda Clarity.
| The EV motor wasn't big enough and it was all too eager to
| switch to the gas engine. Looked like it was a comfortable
| car, though.
|
| GM setup the Volt to alway have full power in EV mode and
| the vehicle would never automatically switch to gas unless
| the battery was discharged.
| ryandvm wrote:
| 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.
|
| https://www.cnbc.com/2023/11/07/new-ram-pickup-ev-has-gas-po...
| dragosmocrii wrote:
| have a look at the new Mitsubishi outlander EV, it kinda works
| like the volt
| callalex wrote:
| "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.
| darby_eight wrote:
| > However the majority of fuel consumption in a car happens
| at traveling speed (highway miles).
|
| Unless of course you drive primarily in stop-and-go traffic,
| e.g. delivery drivers, taxis, commuter cars, etc. Quite often
| you won't exceed 50 kph. For whatever reason, I've never seen
| (or have and forgotten) a car marketed towards this market--
| probably for exactly the reason that plug-in hybrids perform
| better in this scenario.
| labcomputer wrote:
| > > "It is more efficient to turn gas into electricity"
|
| > I don't think that's correct.
|
| You're right, it's not.
|
| In fact, GM wrote an SAE paper about their "2-mode hybrid"
| transmission (which was used in their 2008-2013 light-duty
| trucks and SUVs, and then in later modified form in the 2nd
| gen Volt), where this is plainly explained.
|
| In the paper they describe exactly the tradeoffs made to
| optimize fuel efficiency in an eCVT... it turns out that you
| want to set up the planetary gears to minimize the energy
| transmitted from input to output via electricity and maximize
| the amount transmitted mechanically because that is most
| efficient. You especially want to avoid a round trip through
| the battery in most cases (except when that allows installing
| a smaller, more efficient ICE).
|
| That has implications for the CVT's mechanical ratio: GM's "2
| mode" which has what basically amounts to an auxiliary
| overdrive integrated in the eCVT so that it can use smaller
| motor-generators over a wider range of speeds. Smaller motor-
| generators means more energy is transmitted mechanically,
| which means higher efficiency.
|
| This is also basically the same reason the 1st gen Volt gets
| _significantly_ worse highway MPG in range-extender mode than
| the (contemporary) Prius Hybrid (~35MPG vs ~50MPG): The 1st
| gen Volt eCVT was envisioned as an EV with a range extender
| (where energy usually comes from a battery), while the Prius
| 's eCVT was optimized for driving primarily on the ICE, with
| the battery only supplementing acceleration.
| Tade0 wrote:
| Both the Chevy Volt and Toyota's hybrids rely on a planetary
| gear set to blend power between the gasoline engine and
| electric motors.
|
| Here are the differences explained in more detail:
|
| http://roperld.com/science/ChevyVolt.htm
| maxerickson wrote:
| At least one version could run as a series hybrid or as a
| torque combining hybrid, depending on which clutches were
| engaged.
| shanusmagnus wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| It's mechanically simpler until the apex seals blow out. Then
| you are fucked
| samdunham wrote:
| 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.
| ed_balls wrote:
| rx-7 had two combustion chambers.
| linsomniac wrote:
| >It only had a single combustion chamber after all
|
| Just to be clear: At had two combustion chambers. Both the
| 12A and 13B engines had two rotors (1.2 and 1.3L
| "displacement" respectively), each one has a combustion
| chamber. I had an '84 GSL-SE (13B), I don't remember it
| particularly "puffing", not saying it didn't just don't
| remember it.
|
| The engine in this article they say is an "8C", which I
| assume means 0.8L displacement.
| aidenn0 wrote:
| 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.
| dragontamer wrote:
| 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 wrote:
| 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 wrote:
| 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.
| pmsh wrote:
| 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.
| pfdietz wrote:
| You want both to keep the intake valves clean, yes?
| SebFender wrote:
| 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 wrote:
| 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 wrote:
| Is the rotary better or worst with pollution ?
| linsomniac wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 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.
| SeanLuke wrote:
| > 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_ wrote:
| 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 wrote:
| _
| ryukoposting wrote:
| A Wankel with a turbo at redline sounds you just violently
| shook a big metal can full of hornets.
| dbg31415 wrote:
| 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 wrote:
| Instead of a Wankel, why not use a small custom turbogenerator,
| like the APU in aircraft?
| AYBABTME wrote:
| 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 wrote:
| Seems unreasonable for a powertrain, but pretty reasonable
| for a series hybrid generator.
| AYBABTME wrote:
| 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 wrote:
| I like the LiquidPiston engine technology as an inverse Wankel
| engine. A lot more efficient.
| wkat4242 wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 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.
| bruce511 wrote:
| 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 wrote:
| Does that matter in practice? What's the effective range for
| highway driving in these cars?
| m463 wrote:
| I recall the i3 rx only had about 2 gallons of gas.
| danans wrote:
| The Mitsubishi Outlander plug-in hybrid can do up to 60mph on a
| flat road in serial hybrid mode.
| connicpu wrote:
| 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 wrote:
| 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.
| seany wrote:
| Can you buy it as an EV and then drop in the generator later? It
| makes a big difference for registration in some places.
| npunt wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| The same reason we don't use two strokes anymore? They're
| environmental disasters and wildly inefficient.
| trimethylpurine wrote:
| I think it only turns to charge the battery, so probably it
| turns at it's most efficient speed at all times. Does
| variable valve timing help in that case?
|
| That said, the article doesn't describe any benefit to using
| the rotary engine here either.
|
| I wonder if we're missing something?
| class3shock wrote:
| 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.
| newsclues wrote:
| It's hard to tell if you can improve technology until it's
| good enough (jet engines) or if it's a futile dead end.
|
| Kelly Johnson of Skunkworks had a keen mind for
| differentiating between them.
| class3shock wrote:
| It is indeed and sometimes it can go either way depending
| on the time point. A good example is what eventually became
| the PW GTF, the PW8000, discussed here:
|
| https://cornponepapers.blogspot.com/2006/04/short-life-
| and-u...
|
| Just a little bit to early but when they came back to the
| idea they ended up with a technology that they use on all
| their new (big) commercial engines.
|
| For anyone that doesn't know the name Kelly Johnson I
| recommend "Kelly: More Than My Share of It All". A rare
| person who combined technical genius with an ability to get
| large scale things done.
| runlaszlorun wrote:
| I feel like software is the poster child for this. My hunch
| is that a lot of techniques have been dropped for performance
| penalties that may be on the order of 20-30% (totally
| guessing here) when Moore's Law often has covered that gap in
| mere months.
|
| I read a comment on HN a while back that you can look like a
| genius in software by going back about 10 years and finding
| something forgotten. The whole web development shift from
| server-side to client-side and now drifting back to server-
| side as if it's something new seem to validate this. Though
| in this case it just seems like the extension of the decades
| long back and forth of going from mainframe with super
| minimal client, to PC only, to networked, to client/server,
| to server-side web, etc, etc.
| throwaway11460 wrote:
| This factoid about web dev misses the fact that the JS
| developers today are often the same people who were writing
| CGI, Perl and PHP, some of us also ASP and later ASP.NET,
| or some Java. We always knew there are good parts about the
| old ways and merging the two was _always_ the goal - it
| just takes some time to get the client side right and then
| to get the merging right.
|
| This especially applies to React core devs. Remember XHP?
| wredue wrote:
| >20-30%
|
| Your total guess is orders of magnitude off.
|
| Most software today is in the ballpark of 10,000x slower
| than it should be.
| Narishma wrote:
| That's not what they're saying. They're talking about
| things that couldn't be done due to performance issues
| but are now possible thanks to improved hardware.
| wredue wrote:
| Software developers rarely question the hardware they are
| developing on/for. Unless you were developing in the
| pentium and earlier era, it has almost definitely not
| been true for you that "the hardware is not capable of
| running this idea" (ignore certain obvious high
| performance sectors).
| Ntrails wrote:
| 10 years ago we designed a system to approximate a chunk
| of maths we did not have time to do every second, too
| slow.
|
| If you started from scratch you'd never even consider
| doing anything other than the original obvious "correct"
| maths. Approximation be damned.
| cobalt60 wrote:
| Adding to the list of deficiencies, Apex seals!!
| twobitshifter wrote:
| 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.
| markhahn wrote:
| I admire the idea of hubmotors as well, but once mentioned
| them to a car engineer, who basically said "think about
| unsprung weight".
|
| Which, now that I think of it again, is a bit silly because
| most EV mass is battery, not motor.
| zrobotics wrote:
| Shaving unapeung weight down, even by a small fraction of
| the total vehicle weight, will dramatically affect handling
| and perceived ride quality. Even though the battery makes
| an EV heavier than an equivalent ICE car, there is still
| the need to reduce unsprung weight. Thus, it would be
| better to have the motor inboard and run a cv axle out to
| the wheel than have the entire mass of the motor out on the
| wheel.
| lelanthran wrote:
| Unsprung weight does not have a linear impact.
|
| Increasing the unsprung weight by 10% causes a 100%
| deterioration in handling and ride quality.
|
| You're suggesting increasing the unsprung weight by about
| 400%.
| rootusrootus wrote:
| > once mentioned them to a car engineer .... now that I
| think of it again, is a bit silly
|
| No offense, but this right here is peak HN.
| speedgoose wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 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
| PS30,000. 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.
| speedgoose wrote:
| If you think about cost, long term it's cheaper to skip the
| ICE and have a slightly better electric power train with a
| bigger battery capacity. That's what Carlos Tavares said to
| the French government many years ago. Hybrids have two
| systems and that's expensive and complex.
|
| Installing electric power plugs everywhere isn't that
| challenging. I'm sure UK can manage it if the local
| government decides to do it seriously.
|
| By the way, 35kEUR for a brand new car that is cheap to run
| isn't a bad deal. New cars are expensive. Maybe you can wait
| a decade or two before switching with a cheap used EV that
| has enough range.
| grecy wrote:
| > _even the fastest chargers take 5-10x as long as filling up
| with petrol (2-3 mins vs 20-30)_
|
| I just drove to the airport in a bit of a rush. Drove
| straight up to pump, tapped credit card, authorized for $100
| and opened cap at same time. Stuffed the pump in and held it
| at max flow. 45l of gas later (small car), cap back on, pump
| away and moving again.
|
| I don't think it would be possible to be faster.
|
| Total time stopped: 7 minutes.
| abruzzi wrote:
| > 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
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