[HN Gopher] "Inside-out Wankel" rotary engine delivers 5X the po...
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"Inside-out Wankel" rotary engine delivers 5X the power of a diesel
Author : geox
Score : 213 points
Date : 2023-04-05 14:55 UTC (8 hours ago)
(HTM) web link (newatlas.com)
(TXT) w3m dump (newatlas.com)
| clort wrote:
| looks neat and I am in no way any kind of expert; I wonder why
| there is an external counterweight? It seems to me that the
| rotating 'piston' has hollow chambers in one side only to allow
| passage of gases and therefore needs a counterweight to balance
| it; is there a reason they cannot have some hollows in the other
| side but not have them connected to the burn chamber so that the
| piston is balanced by design, and the external weight not
| required?
| garaetjjte wrote:
| Photo clearly shows spark plugs on it, and they claim it runs on
| diesel, so which is it? I don't think spark ignited diesel would
| work very well.
| CharlesW wrote:
| How do you know they're spark plugs and not glow plugs?
| garaetjjte wrote:
| Glow plugs don't have HV insulator.
| LesZedCB wrote:
| they also claim it runs on gas and propane and hydrogen.
| probably the photo is set up for only on of the 4 options?
| Cockbrand wrote:
| Surely the engineers who came up with this are a lot smarter than
| myself, but to me it looks like the lower half of the rotor
| rotates into the combustion and thus has to work _against_ its
| force. If this is true, I'd assume that this takes away a lot of
| effectiveness.
| jutrewag wrote:
| [dead]
| qbrass wrote:
| It actually happens less on this engine than piston engines
| because the lobe on the rotor kind of rotates over the
| combustion chamber for a while instead of moving towards or
| away from it.
|
| On the other hand, it exposes a lot of surface area to heat,
| which gets absorbed by the rotor but isn't used to turn the
| engine. It's a problem it shares with wankel engines. The
| advantage over wankels is the extra time air and fuel spends
| burning in the combustion chamber before the chamber volume
| expands. It means it gets more time to combust evenly which
| should help reduce both hydrocarbon and nitrogen oxide
| emissions.
| eYrKEC2 wrote:
| I know this goes towards steam-engine design, but why can't
| that heat be re-captured as steam? When the engine heat gets
| above a threshold, inject [distilled?] water instead of fuel.
| coryrc wrote:
| Water injection is a thing, it gains a little efficiency.
| Generally not worth the complexity.
| KAMSPioneer wrote:
| I'm not sure what you mean -- are you referring to at the end
| of the combustion cycle during the exhaust phase? If so, then
| because the exhaust channel is open, the gases in the
| combustion chamber won't be exerting appreciable force on the
| shaft/rotor, the gasses will simply escape through the exhaust
| channel. At least, that's how I see it.
|
| But maybe I've understood you wrong.
| Cockbrand wrote:
| Yes, it's a bit hard to explain, and I'm not a native
| speaker. But you got me right, and now I see that too. Thanks
| for the heads up!
| mywittyname wrote:
| A non-turbo diesel is an interesting choice of competitor. The
| big selling point of the Kohler motor is that it's almost silent
| - even the valve train is belt-driven to reduce noise.
|
| Not sure a rotary engine screaming at 6500RPM is comparable here
| to a diesel with a peak torque at 2000 and peak power at 3600.
|
| > LiquidPiston has been working on these X-engines for nearly 20
| years now,
|
| I'm guessing they will never actually release a commercially
| viable product. 20 years to design an ICE is...too much.
| toss1 wrote:
| Seems likely. Several years ago when working on a hybrid-
| powered UAV, I was checking out high power/weight engine
| platforms, and actual Wankels in development or available did
| better.
|
| A 30sec DDG search turned up options that are definitely
| better, e.g., the AIE 80S, with 15BHP/11.2kW at 5kg or their
| 225CS, with 40BHP/30kW at 10kg [0]. In contrast, this weighs
| 19kg to produce 26HP/20kW. The net power - weight for these
| Wankels is 2.24kW/kg and 3.0 kW/kg vs Liquid Piston's
| 1.05kW/kg.
|
| While IDK about availability from AIE (it just turned up at the
| top of the search), I know there are others on the market that
| are/were available. Meanwhile the LP prototype still isn't
| available 7+ years after I was first looking at them, and the
| were suppose to ship "real soon now".
|
| We'll see...
|
| [0] https://www.aieuk.com/225cs-40bhp-wankel-rotary-engine/
| astral303 wrote:
| rotary engines do not really scream at peak power... this is
| why Mazda has plans to use rotary at peak power to generate
| electricity for their hybrid EVs.
|
| re 20 years to make a new engine point, compare investment $ in
| traditional ICE across the car industry vs investment $ into
| rotary or other alternative engines (the former is order of
| magnitudes more)
| rgmerk wrote:
| As cool as the rotary engine is, Mazda's attempt at a rotary
| hybrid is flogging the deadest of dead horses.
| heelix wrote:
| We will be driving an old RX7 in the '24 hours of Lemons'
| this year. Looking forward to pushing it in a nice casual
| race. Mechanically, we were not at a point where it was
| solid enough for 2022. I think the rotary engine was the
| only thing that was working. :)
| jacquesm wrote:
| Good luck with the seals! Between rotary and Stirling I
| find it hard to pick a favorite and both of them have
| similar problems despite the completely different
| geometry.
| red-iron-pine wrote:
| Mazda still holding on to those rotary engines, eh?
|
| Still, call my interest piqued. I'll keep an eye out for
| their Wankel-EVs
| shortsightedsid wrote:
| https://www.youtube.com/watch?v=-3gzQVGEqF4 explains the
| details. As usual Jason's awesome at explaining the
| details.
| m463 wrote:
| btw: I had a mazda rotary engine car, and the 7000rpm shown on
| the tach seemed exciting compared to a piston engine... except
| it wasn't really true. It really ran at 1/3 that speed.
| stronglikedan wrote:
| If it's truly a 5x size reduction, then there's still plenty of
| room for sound dampening materials!
| Zak wrote:
| The specific version described in the article appears to be a
| Diesel rotary that runs on jet fuel with military UAVs as a
| primary application.
| Cthulhu_ wrote:
| I think a lot of commenters in articles like this will only
| think about automotive as a use case for alternative engine
| designs.
|
| I'm reminded of a linear piston engine (iirc two pistons that
| just go back and forth without their motion being translated
| into rotation; one where they were side-by-side moving
| alternately, the other one where they'd actually move towards
| each other and share a combustion chamber). The use case for
| that was to have the pistons move through coils, thus
| generating electricity. We used to have a flashlight that
| works with the same principle, shake it to generate
| electricity.
| themaninthedark wrote:
| My first thought went to cargo ships. They require huge
| motors, so I imagine that if you can keep or gain
| performance while reducing size they would be very
| interested.
| adgjlsfhk1 wrote:
| this is backwards. the reason cargo ship engines are big
| is because they don't care about size. they would rather
| have a 2x bigger engine that was 1% more efficient
| lb1lf wrote:
| There's an awful lot of room on a cargo ship. They don't
| care too much about size. They only care about total cost
| of ownership.
|
| Edit: ninja'd!
| hommelix wrote:
| Yes this ils comparing apple and banana. 2-stroke vs 4-stroke,
| supercharged vs naturally aspired.
| BWStearns wrote:
| Sounds like it could be awesome for some GA applications given
| the lack of weight budget and it seems like they did solve the
| issues with rotaries. Hopefully someone starts cramming them in
| some experimentals!
| stametseater wrote:
| General aviation are perhaps the most cautious and wary ICE
| users around. Most of the engines used in GA, Lycomings and
| Continentals, are essentially 1960s designs with very well
| known cost, performance and reliability characteristics.
|
| That is not to say change is impossible, GA's overdue
| changeover to unleaded gasoline seems like an inevitability.
| Unleaded gas is already being approved for many of these
| engines, like new production O-360 engines (which date back to
| the 1950s.)
| soliton4 wrote:
| about 5 decades to late, but non the less impressive
| davidbanham wrote:
| A commodity chainsaw (Stihl ms660) returns 1.4kg per kw from 2
| stroke fuel. Before any performance tuning takes place.
|
| That's at about a quarter of the size of this. I bet there's
| efficiencies to be had if it were scaled up.
|
| I'm just not sure this is the game changing breakthrough the
| article's tone suggests.
| kortex wrote:
| Two-strokes are extremely dirty, due to blow-through of the
| fuel-oil mixture, incomplete/less efficient combustion due to
| crude fuel metering, and inability to use conventional
| catalytic converters (due to fouling from the above two
| points). But they do afford roughly double the power-per-RPM of
| four-stroke engines, and a further power-to-weight multiplier
| due to their simpler design.
|
| AFAIK there's nothing _mechanically_ stopping you from scaling
| a 2-stroke, but it would very quickly render the immediate area
| noxious.
|
| But they are simple, lightweight, and easy to shrink.
|
| This is actually a really important point as we are trying to
| clamp down on VOC/NOx emissions. Ignoring CO2, two-strokes emit
| way more emissions than cars per unit work. But a 4-stroke
| engine, in addition to expense, does not lend itself to tools
| like chainsaws. In theory this engine could fill that niche.
| [deleted]
| AceyMan wrote:
| TFA didn't seem to hint how they addressed the hot-side/cold-side
| issue that troubles Wankel designs. Anyone who knows more, please
| share.
| causi wrote:
| Ok, so they're "shooting for" a performance of 1hp per 1.57 lbs
| of engine weight. A Toyota Camry engine produces 1hp for every
| 1.41 lbs of engine weight. It produces 1ft-lb of torque for every
| 1.94 pounds of engine weight, compared to 1.58 for the Camry.
|
| How is this revolutionary motor being outdone by a mid-range
| sedan engine?
| bell-cot wrote:
| Their target market is the military - which has plenty of
| kerosene / jet / diesel fuels as part of its standard supply
| chain. The Camry engine will only run on gasoline - which the
| military neither carries, nor wants to.
| bluGill wrote:
| Toyota makes some great diesel engines (they don't put them
| to the US bound products in general), which could run on jet
| fuel with some small modifications.
| Syonyk wrote:
| > _How is this revolutionary motor being outdone by a mid-range
| sedan engine?_
|
| Go ask your Camry engine to make 100% rated power indefinitely,
| and see how long it holds up. That's the difference.
|
| A typical car engine is designed to make 30-50hp sustained, and
| occasionally generate more power for reasonably short periods
| of time.
|
| An aviation engine, generator engine, or any sort of
| "industrial" engine is going to be able to sit there, making
| full rated horsepower, for thousands of hours without any
| trouble at all.
| kube-system wrote:
| IIRC some automakers do test automotive engines at 100% duty
| cycle (in a test stand configuration). And more than a few
| automotive engines are used in slightly modified variants for
| marine and aviation applications.
|
| As I understand, the reason a typical car engine can't sit at
| 100% duty cycle isn't the engine itself, but usually the
| cooling and oiling configuration.
|
| Examples:
|
| https://youtu.be/GNPB3RtHN2M
|
| https://www.vikingaircraftengines.com/engine-options
| bluGill wrote:
| 100% duty cycle doesn't really exists as stand alone
| concept. It is always in reference to the application. A
| typical car engine is at 100% duty cycle at around 30
| horsepower, but the engine can produce 200+ horsepower for
| short bursts (enough to do the 0-60 test that everyone
| loves to quote). With more cooling you can run more power
| from the same engine, but the additional stress will mean
| the engine doesn't last as long before it breaks.
|
| Marine applications generally means salt water, so they
| will run at higher power is the salt is what gets the
| engine eventually not the stress of high power output.
| Airplane engines are expected to be reliable and so they
| run at relatively lower power output. There are many small
| niches in between that have their own idea of what 100%
| duty cycle is.
| kube-system wrote:
| I agree, it can mean different things. To be more
| specific, the video I linked says Kia tests at full load,
| WOT, and maximum engine speed for 300 hours continuously.
| Then they run it 10-20% faster than the specified maximum
| engine speed for another 10-20 hours.
|
| This exceeds most definitions of "100% duty cycle".
| ghostpepper wrote:
| The first time I learned you can increase, sometimes
| significantly, the performance of a car by upgrading the
| oil cooler blew my mind a little bit, but of course in
| hindsight it makes perfect sense.
| Syonyk wrote:
| I'm aware of some auto engine conversions - the 13Bs out of
| the RX-7s and related could do it, the older Subaru engines
| (EA81) would do it, but they're just a small aircraft
| engine in a car, design-wise...
|
| Looking over the Viking engines, I don't think it's fair to
| call those "automotive engines," because my read of the
| description of what they do means they're pulling it apart
| and replacing an awful lot of pieces. They claim they're
| "based on" the latest Honda engines, and once you're
| starting to change the cylinder bore offset, custom hone
| the cylinders, replace your pistons and conrods, etc, it's
| no longer a car engine.
| kube-system wrote:
| If changing those minor attributes makes an engine "not a
| car engine" then the majority of race cars also don't
| have car engines.
|
| On their About page, they themselves say:
|
| > Companies like Honda and Mitsubishi have spent millions
| of dollars refining and testing. We don't claim that we
| can outsmart either company when it comes to the design
| of any internal running component of these engines. We
| don't change vital engine parameters around and claim we
| have different models. The compression, etc. is all
| stock. Every part is OEM Honda / Mitsubishi, nothing is
| new aftermarket from unknown origins.
|
| > We start with the most up to date year engines with
| super low mileage, derived from fender benders across the
| US. When customers want the information about where there
| engine core came from and how many miles it had - we have
| all that documentation readily available to show.
|
| Literally, every one of these engines _came out of a
| car_. I think that plainly qualifies it as a car engine.
| abfan1127 wrote:
| those mods sound very similar to typical mods found in
| drag race cars.
| causi wrote:
| _going to be able to sit there, making full rated horsepower,
| for thousands of hours without any trouble at all._
|
| The XTS-210 can do that?
| Syonyk wrote:
| If it's an aviation engine, it'd better be able to!
| someweirdperson wrote:
| Multiple thousand at max power? Typically, overhaul at
| 2000 hours. And maximum continous power isn't usually
| full load.
| Syonyk wrote:
| It really depends on the engine, but almost all the
| general aviation engines you'll find (Lycoming and
| Continental 4s, and the smaller 6s) are rated for
| continuous operation at full power, and if they're flown
| regularly, will typically make well past the 2000-3000
| hour TBO (which is a recommendation/expectation, not a
| legal requirement, though I believe some of the small
| diesels can't be operated past it).
|
| Our flying club engines in the 172s typically make at
| least 3000, if not 3500 hours, and I think some of the
| overhauls at that point have been a "Well... it's still
| perfectly fine... but..." thing where the board was just
| starting to get uncomfortable with the hours on it.
|
| And, yes, they spend a lot of time making less than rated
| power, because of density altitude, but they're still
| rated for full power operation, and since there's
| basically no wear going on with an engine in operation
| (almost all the wear is during starting), there's no real
| difference there.
|
| It's not until you get into the really large engines
| where "maximum continuous" is a different thing from
| "takeoff power." The turbocharged 500s are about the
| smallest I know of with that sort of rating, and even
| then I don't think it's all of them. Most of the big
| radials have that limit, though. If you find a smaller
| plane with that sort of limit, it's either a possible
| resonance issue between the engine and prop, or a noise
| regulation for certification.
| SV_BubbleTime wrote:
| Add 10,000 or 20,000 lbs to the vehicle weight, does it all
| scale the same?
| causi wrote:
| I'm not sure what your point is. The XTS-210 hasn't been put
| in a vehicle as far as I know.
| [deleted]
| codeflo wrote:
| I know this is off-topic, but I'm curious. I always had the
| impression that even in the US, standard units are used for
| engineering. Reading about "ft-lb" makes me think I was wrong
| (and my head hurt, tbh). Do you really compute stuff like
| _torque_ in imperial units? Don 't you need weird factors in
| every formula to make that work?
| bluGill wrote:
| There are lots of weird factors in engineering anyway. We
| have different factors, but there are still factors. Besides,
| nobody is calculating this, they are measuring and that is
| just a matter of what label you put on the dial.
|
| Most engineering in the US is done in metric units. Then
| marketing applies a metric to imperial conversion.
|
| I suspect China does more engineering in imperial than the
| US, both in total an per capita: most things I buy made in
| America are all metric (cars are all metric except for parts
| designed in the 1960s and the adapter bracket to make them
| fit on a modern metric car). Most things I buy made in China
| are imperial. I don't really know for sure, but that is my
| impression of industry.
| codeflo wrote:
| > Besides, nobody is calculating this, they are measuring
| and that is just a matter of what label you put on the
| dial.
|
| That's why I asked about engineering, not driving. Nobody
| converts torque to power etc.?
| bluGill wrote:
| The engineers who do that are using metric. Marketing
| might do this conversion, but they just plug it into a
| converter and have no reason to know anything more than
| bigger is better.
| mcronce wrote:
| Torque to power is just (torque * RPM) / (some constant
| depending on the units inolved). With ft-lbs and
| horsepower, that constant is 5252; with N-m and kW, it's
| 9549. The only thing that changes is the constant.
| codeflo wrote:
| You make it sound like you'd have to remember a 4-digit
| constant in either case. That's stupid, it's simply
| (torque * RPS * 2 * PI).
| raketenolli wrote:
| No, power is just torque times angular velocity. No
| constants involved.
| mcronce wrote:
| If you ignore units, sure.
| shadycuz wrote:
| The engine is the size of a push mower.
|
| > XTS-210 is about the size of a basketball, weighs in at 19 kg
| (42 lb), and displaces 210 cc.
|
| So you are talking about a 26HP lawn mower.
|
| While the Camry might make more power at its normal size. It
| would not if you scaled it down to the size of a basketball.
| I'm guessing it would make 1-3HP at that size.
| ww520 wrote:
| The Camry engine has 4-6 cylinders for its size. A single
| cylinder is not much bigger than a basket ball.
| 93po wrote:
| A Traxxas 5407 TRX 3.3 engine used in RC cars makes 1.42
| horsepower, weighs 305 grams, and fits in the palm of your
| hand.
|
| This is 1hp per 0.46 pounds of engine weight, nearly three
| times better than the camry engine.
|
| Granted an RC engine runs on a mixture of fuel and
| nitromethane, and doesn't have any reasonable durability
| compare to a Camry engine. But it also only costs $200.
| kortex wrote:
| > Granted an RC engine runs on a mixture of fuel and
| nitromethane
|
| That's a _huge_ difference. The main limiting factor in
| engine power is mass air flow, not fuel. Engines are as
| much air pumps as they are containers for extracting
| expansion from explosions. Nitromethane provides extra
| oxidizer in liquid form, putting nitro engines in some ways
| closer to rocket engines in terms of power-to-weight ratio.
| seabird wrote:
| You can't just make the Traxxas 18x bigger and get linear
| performance improvement. Trying to compare power/weight
| between engines with radically different weight constraints
| is silly.
| 93po wrote:
| Ok, a Kawasaki H2R engine makes 326 horsepower and weighs
| about 160 pounds running regular fuel. That's almost
| identical to the Traxxas - 1hp for 0.49 pounds.
| syrrim wrote:
| If you had 18 such engines it would get you precisely 18x
| the performance, at precisely 18x the weight.
| aidenn0 wrote:
| And precisely 1/18 the MTBF
| pas wrote:
| but it fails gracefully, right? (only one engine fails at
| a time)
|
| it's like RAID, great until the RAID card itself fails
| aidenn0 wrote:
| It's probably most like losing power in a single
| cylinder; the effects vary from engine to engine.
| jacquesm wrote:
| They tend to seize and when they do and you gang them
| they'll likely break stuff in the other ones unless you
| add a freewheel or some other luxury like that.
| 93po wrote:
| In a way, sure. Often when a car engine fails people just
| replace it. If you were to replace all 18 when the first
| one failed, the same way you would with a regular car
| engine, it's not 1/18 the MTBF. And if it was just 1
| failing prematurely and you replaced only that one, you
| also see that same dynamic with car engines.
| Retric wrote:
| No, because you would need to add structural elements,
| some way of combining power output, and cooling if you're
| aiming for a similar form factor.
| m463 wrote:
| I'm not familiar with that engine, but I remember having
| little glow-plug engines and they didn't even have piston
| rings. (and were not efficient)
| cjbgkagh wrote:
| I've read about a lot of people complaining about the
| difficulty of getting the mixture right, perhaps that might
| be a show stopper for a UAV that must reliably work
| unattended for a long time. Though the military should also
| be able to get such mixtures down to a science - so I don't
| know.
| bluGill wrote:
| Every motorcycle mechanic I've seen has a sign in the shop:
| speed costs money, how fast do you want to go. That sign
| isn't referring to the costs to modify an engine to go faster
| so much as the cost to constantly rebuild the engine after
| they modify it to go fast. I've seen two identical engines,
| one rebuilt to stock and one rebuilt to max speed - the cost
| for both rebuild jobs was about the same (the parts for speed
| were more - but not much more compared to the labor which was
| the same), but the engine rebuilt to stock ran for thousands
| more hours, while the one rebuilt for speed has the mechanic
| bragging that it lasted a whole 80 hours!
| 0cf8612b2e1e wrote:
| What is done to modify an engine for speed? What kind of
| improvement can be seen for speed (accelerates XX faster?
| YY higher top speed)?
| qup wrote:
| Bigger cylinders, forced air systems, lighter weights,
| etc.
| mcronce wrote:
| Simplifying things in this comment a fair amount, but...
|
| Extracting more power is, most commonly, a matter of
| burning more fuel, which requires more oxygen. This
| increases combustion chamber pressure, which drives the
| piston down with more force; that force is converted to
| rotational torque and ultimately drives the wheels
| harder, pushing the vehicle forward faster.
|
| More oxygen can be added in any number of ways; less
| restrictive intake/exhaust parts, larger valves, cams
| that are more optimized for whatever load/engine speed
| you want to produce peak power (or are more optimized for
| output than, say, economy or emissions), supercharger,
| turbocharger.
|
| Adding fuel is more straightforward: A higher capacity
| pump and/or bigger injectors/carbs.
|
| You can also switch to pistons that will compress the
| air/fuel charge more. This also increases combustion
| chamber pressure.
|
| You can also run the engine at a higher speed, which will
| often warrant different cams, stronger valve springs,
| etc. May also require bottom end uprated components that
| can handle that task (connecting rods, pistons, bearings,
| crankshaft).
|
| On the subject of bottom end components, depending on how
| much you increase cylinder pressure, you may need to
| upgrade those.
|
| You can also increase output power by reducing losses - a
| lighter flywheel is a common example with enthusiasts.
|
| Every single one of these involves a trade-off. A lighter
| flywheel impacts drivability; removing intake/exhaust
| restrictions and adding forced induction components will
| both make more noise; etc.
| madog wrote:
| Right. Generally more air and more fuel, produces bigger
| explosions and bigger forces, so the engine would output
| more power and torque.
|
| These greater forces cause more stress to factory engine
| components, so generally at a certain level you will need
| to replace engine internals with uprated parts e.g.
| stronger rods and pistons.
| davidthewatson wrote:
| Surely, I can't be alone in reading this having driven an RX-7,
| numerous turbos, but no diesels, thinking this is EXACTLY what I
| need to replace the 310cc single cylinder in my BMW motorcycle
| that gets 70 MPG consistently, sits comfortably at 70 MPH on the
| highway, but is slow on the uptake in a crowded on-ramp. I
| remember the BMW single being a revelation because it's a single,
| DOHC, eats corn gas for breakfast without indigestion and has
| plenty of breathing room at the top end of the tach, which is
| unusual in single cylinders at redline, 10.5K RPM IIRC. One can
| only hope since one has less-than-zero mechanical engineering
| skills.
| jldugger wrote:
| I guess the "inside out" is that the rotary block is also the
| fuel injector? Would have to read more to figure out how they get
| fuel into a thing moving at thousands of rpm.
| bagels wrote:
| That is unlikely, it's probably in the housing, just like a
| wankel.
| HWR_14 wrote:
| A traditional Wankel engine has a rotary block in the shape of
| a reuleaux triangle moving in a more cylindrical stationary
| chamber. The "inside out" refers to how this engine is a more
| cylindrical rotary block moving inside a stationary reuleaux
| triangle chamber.
| [deleted]
| Etheryte wrote:
| We do this all the time with cylinders, no? I don't see how
| this is any different.
| bagels wrote:
| They were, I think, imagining placing the fuel injector on
| the moving part itself (eg the piston) which doesn't makes
| much sense to do, taking the inside out bit to the extreme.
| jutrewag wrote:
| [dead]
| bagels wrote:
| To the dead comment, no, the injector is not on the moving
| part, it's attached to the housing, clearly seen at 2:27 in
| their video.
| [deleted]
| swamp40 wrote:
| _> As electrification takes off, it 's a difficult time to be
| working on new combustion engine concepts_
|
| Turn it into a portable battery charger...
| [deleted]
| Zigurd wrote:
| They were advertising on Twitter for crowdfunded investment,
| which is a very small-time vibe.
| debacle wrote:
| My understanding is that everyone acknowledges that rotary
| engines are great, bt in comparison to piston based engines they
| have far shorter longevity.
| msandford wrote:
| The folks in the article seem to have figured some of the
| longevity problems out.
| jandrese wrote:
| That's what they claim, but since this engine isn't in
| general use yet it's impossible to verify. In the past
| "supercharged" and "Wankel" have been a combo prone to
| maintenance issues.
| Gordonjcp wrote:
| They're not great, at all. They have very few moving parts and
| they are very smooth because there are no reciprocating parts.
|
| Other than that, they have emissions like 2-stroke engines
| because of the incomplete combustion and we have never been
| able to devise any kind of material to make the apex and side
| seals last anything like as long as piston rings.
|
| Piston engines are a terrible way to power vehicles, but
| everything else we've tried is worse.
| himinlomax wrote:
| Wankel engines are great in one respect, power density. But
| they have terrible reliability and fuel efficiency.
|
| Turbine engines also have great power density and terrible
| fuel efficiency, but they are very reliable.
|
| Diesel engines are reliable and fuel efficient but heavy.
|
| This one appears to have improved reliability and fuel
| efficiency over the Wankel without sacrificing power density.
| jabl wrote:
| Large turbines running at close to rated power actually
| have pretty good efficiency. Turbines are bad at scaling
| down to smaller sizes due to e.g. boundary layer friction,
| and also part load efficiency is poor. Recuperators help
| somewhat, though still not nearly as good as a piston
| engine.
| projct wrote:
| LiquidPiston addressed both of those issues.
| Gordonjcp wrote:
| Mazda addressed both of those issues, Rotax addressed both
| of those issues, Norton addressed both of those issues, NSU
| addressed both of those issues, Comotor addressed both of
| those issues...
|
| The issues remain fundamental, and largely unaddressed.
| rascul wrote:
| Some years past, a friend who worked for Mazda explained to me
| that the engines need to be driven for a bit because until
| they're warmed up fully there can be a lot of carbon buildup
| and it needs to be run some amount of time to get the carbon
| through. Once they're warmed up and running for a bit they're
| fine. Supposedly it's the short trips of only a few miles that
| can kill them over time.
|
| Not sure if that's correct.
| Enginerrrd wrote:
| Yeah I talked to some race mechanics that said the mazda
| rotary engines had much better longevity if you really drove
| the piss out of them. They liked to rev high and hard, which
| would be basically consistent with that notion.
| devnullbrain wrote:
| If we lived in a world of rotaries and BMW came out with the
| S85 we'd say that piston engines were emotive and fun but too
| unreliable for mainstream use. When we refer to rotary engines
| we mostly talk about two generations of one engine from one
| manufacturer used in sports cars that were designed before
| emissions targets changed.
| tudorw wrote:
| I understand this too, however, the technology might be worth
| revisiting with modern techniques, I understand the power
| output is 'smoother', which can reduce vibration, some
| applications might need that?
| brodouevencode wrote:
| Nearly all engines need some level of vibration reduction if
| anything just to prevent it from damaging itself.
| ww520 wrote:
| The problem with rotary engine is that its max power efficiency
| is at a very narrow rpm range and loses power at most other rpm
| ranges. This is due to the constant air intake inherent in the
| design. Piston engine has variable valve air intake to ensure
| optimal air oil mixture compression to deliver max power
| efficiency at a long range of rpm's. That's why rotary design
| is not popular for cars.
|
| Mazda is reviving small single cylinder rotary engine design
| for HEV by running it at a constant speed with max power
| efficiency to charge the battery.
| djaychela wrote:
| They also have issues meeting emissions targets - both because
| of the basic design (there isn't the ability to actively
| control valve timing events), and also because they typically
| need some sort of lubrication for the combustion chamber. They
| are similar to two-stroke engines in these respects.
| skullone wrote:
| Running them at a pre-determined RPM constantly can resolve
| lack of VVT, but that limits their applications. New
| materials for apex seals being researched could alleviate
| their longevity issues too. But, I have a big soft spot for
| rotaries and would love to see them applied more :(
| vvillena wrote:
| Isn't this how the range extender in the MX-30 works?
| skullone wrote:
| Ohhhhh interesting, this would be a perfect fit for a
| range extender!
| HPsquared wrote:
| I guess the range-extender application is also less
| likely to suffer from the effects of lots of short trips.
| manarth wrote:
| Whilst also being worse-performing?
|
| Take a two-stroke Moster 185 engine: 25 HP at 7.800 RPM, for
| a 15kg package.
|
| I'd be keen to understand how (if) this outperforms a typical
| two-stroke.
| busterarm wrote:
| My '88 RX-7's engine went 120k miles before I decided to
| rebuild it and it still probably had a good 30k miles before it
| would have 'gone'.
|
| This is completely normal through the 70s and 80s when these
| engines were popular. We didn't start getting million-miler
| cars until the Lexus LS400 came out.
|
| The problem with the rotary is heat and the damage it does to
| other components. The RX-8's engine design was actually bad and
| doesn't adequately lubricate, but that gets 'fixed' in the last
| three model years.
|
| The biggest reason that RX-7 owners have seal failures are
| often due to adding on too much power without adequately
| upgrading the fuel system. Keep in mind that Wankel engines are
| absurdly popular in the world of amateur aviation without any
| of the stigma.
| Supermancho wrote:
| My near-mint condition 2009 Mazda RX-8 never had a Wankel
| engine problem (over 100k miles). It would have easily lasted
| another 5 years without a doubt or hiccup.
|
| Wankels are usually excluded from all engine comparisons,
| because it's a considered a different class...for piston engine
| marketing reasons.
|
| I sold off my RX8 in 2018 because my fiancee and I moved to
| Seattle (passing emissions testing wasn't anything special). We
| needed the money and we had her car, which was more functional.
| I do miss it.
| mywittyname wrote:
| More antic-data: i worked with a guy whose brand new RX-8
| needed two engines in the time we worked together. Granted,
| his was a 04 automatic, which is the worst combo. But still,
| Mazda didn't go out of their way to extend the engine
| warranties on the early RX-8s for no reason.
|
| Did you happen to have an 08+ model with the updated engine
| and/or remove teh catalytic converter?
| Supermancho wrote:
| Yes, the model was 2009 (updated my initial post for
| clarity). No, I did not remove the converter.
| nogridbag wrote:
| My RX-8 needed a new engine at 50k miles. As you likely
| know, if you start and stop an RX-8 engine without allowing
| it to warmup you risk flooding the engine.
|
| In my case, I was taking a trip with my family and my RX-8
| was blocking the driveway. We were running late for the
| flight, so I pulled it out, parked it back in the driveway,
| and let it idle there for 30 seconds knowing I'm not
| supposed to shut it down so quickly. But I had people
| waiting for me and what am I supposed to do, say "Sorry I
| own a strange car and I need to drive around the block for
| a bit to let it warm up!".
|
| Of course that flooded the engine, but I didn't know until
| I got back from the trip. I followed all the instructions
| to de-flood the engine but it wasn't working for me so I
| had it towed to Mazda where they probably screwed it up
| further. It was there 2 weeks before they told me the
| engine needed to be replaced. They eventually had to fly an
| engineer from Japan to replace the engine since the dealer
| apparently had no one capable of dealing with rotaries. I
| think my car was at the dealer for a good 2 months.
| Thankfully all covered by warranty.
| mmetzger wrote:
| Long since mattering, but you could move them like this
| if you started it, rev'd it beyond 4k RPM, and then shut
| the motor off prior to it dropping below 4k. Basically,
| the idea was the rotors would force the fuel / oil
| mixture out of the crankcase and keep the spark plugs
| from fouling.
|
| I loved my RX-8, but it was a pain in the rear. Switched
| to a WRX and got 50% better gas mileage, more power, more
| torque, and way more room. This of course bypassed the
| need to check / refill the oil every other fill up (aka,
| every 300-ish miles) all while trying desperately not to
| burn your hand.
| elihu wrote:
| Kind of weird article that doesn't talk about either the main
| benefits or design hurdles. The advantage of the LiquidPiston
| design is that at the time of ignition, the combustion chamber is
| a roughly round shape, as opposed to a traditional rotary where
| it's a long crescent. This should theoretically improve the
| emissions and fuel economy to be more like piston engines.
|
| I don't think Liquid Piston was talking about a 2-stroke version
| before. That's news to me, and it seems like it would throw out
| the efficiency/emissions benefits in exchange for more power.
| Maybe the author of the article was confused and this isn't
| actually a 2-stroke design?
|
| The main design hurdle has been longevity. Their prototypes in
| the past only work for a short time and wear out. That's probably
| just a matter of doing the necessary R&D to figure out the best
| alloys to make the engine out, and the best ways to lubricate
| everything. It's not clear from the article if this new version
| has this solved so it can last a normal amount of time or not.
| m3047 wrote:
| 2 stroke has poor unburned emissions because of mix flow-
| through when ports are open. If air charge / purge is completed
| before fuel is injected then that doesn't occur; whether that's
| diesel or something else is irrelevant.
|
| As a bonus, built in EGR if properly managed.
| abfan1127 wrote:
| I thought 2-strokes had poor emissions was the injection of
| lubrication oil into the air fuel mixture. traditional
| 2-strokes I'm familiar with pull in air into the crank case
| (which requires lubrication), then uses a portion of the
| exhaust stroke to compress the fuel/air creating forced
| induction. By keeping air out of the crank case and providing
| lubrication delivery outside of the air/fuel mixture,
| emissions can be significantly improved. The article claims
| the design allows external lubrication, but it doesn't say
| how. I'd like to see how the seals are better than apex
| seals.
| mannykannot wrote:
| The basic crankcase-scavenged two-stroke suffers from both
| problems. Typical diesel two-strokes use a separate blower
| for scavenging, so the combustion air inflow never passes
| through the crankcase and does not come in contact with the
| lubricating oil, while the fuel is not injected until after
| the exhaust is closed.
|
| The engine described here can have its shaft and eccentric
| bearings externally lubricated, but its apex seals, like
| those of Wankel engines, seem to be in a situation
| analogous to that of a piston ring. Unlike either of those,
| however, they are mounted in the stator, not the moving
| part, and so may be easier to lubricate precisely.
|
| https://www.cycleworld.com/2015/04/06/two-stroke-
| motorcycle-...
|
| https://auto.howstuffworks.com/diesel-two-stroke1.htm
| ajmurmann wrote:
| All the numbers in the article were really small and seemed to
| aim at use cases that are all about small and reliable. Is
| anything stopping this from being scaled-up to be a light but
| very powerful engine for a sports or supercar? This could be a
| huge innovation in racing if it scaled.
| dsr_ wrote:
| The four strokes of a four stroke cylinder are intake,
| compression, combustion, and exhaust. That's down, up, down,
| up. Since there's no down or up in any of this engine's
| combustion chambers, "strokes" is probably inappropriate.
| RickHull wrote:
| The strokes have nothing to do with up and down (e.g. flat
| motors, like a boxer), but to do with compression and
| expansion. The direction of compression doesn't really matter
| aside from packaging concerns.
|
| As you said, 4 stroke has intake, compression, combustion,
| and exhaust. That's expansion, compression, expansion,
| compression. It fires between compression and combustion.
|
| A 2 stroke motor has compression and expansion. It fires
| between compression and expansion. Intake, exhaust, and
| combustion happen during the expansion phase.
|
| A rotary motor is traditionally 4 stroke, and I'm not sure a
| 2 stroke version is feasible. The LiquidPiston rotary appears
| to be a 4 stroke to me, despite the article text.
| Cthulhu_ wrote:
| I think for comparison, this (and the Wankel) would have to
| do two rotations for a single cycle.
| mcronce wrote:
| Typical Otto cycle 4-stroke piston engines do two rotations
| for a single cycle. Wankels are more complicated; each
| rotor face acts as a separate combustion chamber and all
| four strokes happen in a single rotation. It _looks_ like
| the situation is similar with LiquidPiston 's
| implementation.
| tacroqueen wrote:
| I don't think New Atlas is a reputable site.
|
| https://medium.com/democratizing-finance/liquid-piston-insid...
|
| This is likely all part of a pump and dump. That's why it's a
| weird article.
|
| They've been advertising this heavily of all places on
| instagram and taboola chumboxes. Obviously none of those people
| need this engine, they're looking for marks.
| spydum wrote:
| I suspect a lot of folks confusion on how this works is better
| explained by this from warped perception (first place I heard of
| this inverted rotary):
|
| https://m.youtube.com/watch?v=jLtyNtf9_ew&t=10s
| dingaling wrote:
| Confusion is also possibly due to misuse of the term 'rotary'.
| A true rotary engine turns on its crankshaft. The Wankel is a
| rotating-sleeve-valve engine.
| LesZedCB wrote:
| https://en.wikipedia.org/wiki/Wankel_engine
|
| https://www.britannica.com/technology/Wankel-engine
|
| both seem to disagree with your technical definition. at the
| very least, the colloquial usage is broad enough that
| adhering to some archaic technical definition isn't
| sufficient to explain some confusion.
|
| even this wiki article says it's obsolete
| https://en.wikipedia.org/wiki/Rotary_engine
| tbruckner wrote:
| Surprised they didn't consider the Middle-out wankel.
| stillworks wrote:
| Haven't been exposed to the rigorous competition of TechCrunch
| Disrupt as yet I guess ?
| DesiLurker wrote:
| I know this is targeted towards military/aviation applications
| (now, initially it was different), but, I honestly cannot
| understand why there is so little research on just making a
| hyper-efficient low-maintenance engine that runs at maybe 2
| optimal rpms and powers a small battery bank plus electric motor
| (i.e.. typically series hybrid). None of these gas engines will
| come anywhere near the power-per-pound & torque output of a
| electric motor.
|
| If traditional carmakers had done that research about 10 years
| ago they wouldn't be facing such crisis with EVs today. a high-
| efficiency multi-fuel range extender engine is all we need today
| but still I cant find many automakers jumping on it.
|
| PS: it would have been nice to see a micro-turbine based
| generator with high thermodynamic efficiency but my understanding
| is that need a lot of maintenance so not suitable for consumer
| applications.
| driverdan wrote:
| One of the reasons is government regulation. I'll talk about US
| regulation but similar situations exist in other countries.
|
| 1. US incentives and regulation result in car manufacturers
| having to shift production from hybrids to EVs.
|
| 2. In order to qualify as an EV a vehicle can't have a range
| extending ICE that provides more than a 50% range increase.
| There's also a very low limit to the size of the fuel tank.
|
| These regulations have resulted in very few vehicles with ICE
| range extenders. Existing engines are easily capable of maxing
| out that regulation so there's no incentive to research other
| engines.
| DesiLurker wrote:
| US incentives aside, Nothing was stopping them from doing
| this for more expensive vehicles even if they didn't care
| about environment. I mean wouldn't you want to have a pickup
| truck with acceleration & torque of an EV with 2+1 motors
| powered by series hybrid and also have fuel economy of a
| 40mpg in city?
|
| I think its just institutional laziness & innovators dilemma.
| Even in last 5 years when it was clear Tesla is starting to
| rise they decided to sit on their hands and do nothing. Even
| till last year toyota has been singing BS about hydrogen cars
| and not enough lithium. they deserve whats coming to them.
| [deleted]
| tda wrote:
| Are you aware you are essentially describing the original
| Toyota Prius? the engine is optimised for constant low rpm/low
| torque/high efficiency, whilest relying on the battery/electric
| motor for torque and temporary extra power
| DesiLurker wrote:
| yes I am well aware of Prius series configuration but it is
| still a regular engine shrunk down and fine tuned. What I am
| asking for is something very ground up redesigned for
| maximizing one thing only efficiency of energy conversion.
| couple of examples of this are Aquarius engines or [1].
| basically you cut out all the unnecessary stuff and all the
| maintenance/repair plus cost with it. Current engines are
| complex because they are operating over a large range or rpms
| and optimizing for other factors like torque etc. the you
| have losses in mechanical power transfer at each stage. Cut
| that all out and make something thats super easy to
| manufacture & replace and you have added another 50 years to
| ICE.
|
| 1: https://www.youtube.com/watch?v=u4b0_6byuFU
| Tade0 wrote:
| Actually it just keeps the engine at/close to minimal brake-
| specific fuel consumption:
|
| https://en.m.wikipedia.org/wiki/Brake-
| specific_fuel_consumpt...
|
| Which covers a range of RPMs.
| joshuaheard wrote:
| Too bad internal combustion engines are being banned throughout
| the United States.
| Synaesthesia wrote:
| This mechanism is really ingenious. I really liked the video
| explanation, it does seem like a very efficient and promising
| design.
| jiveturkey wrote:
| came across this company a few weeks ago. the engine design is
| neat (who doesn't have a soft spot for the wankel). while the
| design is neat, the scammy investors page turned me right off.
| [deleted]
| jsight wrote:
| Kind of looks like a peanut in a Dorito. So yeah, basically the
| opposite of the usual Dorito-powered version.
| andy_ppp wrote:
| I'm surprised the air intake isn't more aerodynamic, more like a
| fan blade to compress the air into the engine?
|
| Could this engine be fitted inside the rear wheel to save space
| and weight as well?
| bmelton wrote:
| That's a really good idea.
|
| Mazda is doing something that I think is fairly novel, which is
| almost exactly what you've described. They've scaled down the
| rotary engine from their RX cars to a single-rotor and put it
| into their new EV (almost tucked into the front wheel well,)
| and letting it act as a 70ish horsepower generator for the
| otherwise battery-powered car to extend range.
| detourdog wrote:
| This was done by BMW for the i3 with REX (range extender)
| equipped models. To be classified as an EV the gas tank range
| can't be greater than battery range. This led to a 2ish
| gallon tank.
| jdmichal wrote:
| I always wondered why "electric with an onboard generator"
| didn't take off as a subset of available vehicles. AFAIK,
| hybrids all work with complex gear boxes to allow the engine
| to directly power the wheels, while also charging the
| batteries.
|
| I suspect the answer is because it's more efficient from a
| MPG perspective to allow the engine to directly power the
| wheels, at the cost of the extra complexity of gearing.
| Converting motion to electricity back to motion is lossy, and
| even more so if you insert battery storage as an additional
| step.
| tromp wrote:
| Presumably this new model:
| https://www.greencarreports.com/news/1138444_mazda-
| mx-30-r-e...
| digdugdirk wrote:
| Mazda really seems like the only company innovating in the
| ICE space (this, wankel rotary engines, skyactive engines)
| and their cars look damn good these days too.
|
| On top of that, they make fun cars. With buttons and knobs on
| the dash!
|
| I'm glad they're still around doing their thing.
| CocaKoala wrote:
| Mazda's also one of the few carmakers that's independent,
| as opposed to being part of a much larger conglomeration!
| slaw wrote:
| Nissan released cars with variable compression engine.
| bmelton wrote:
| Agreed, but there's also Koenigsegg, which has managed to
| eliminate the need for cams, and complete heads from ICEs,
| replacing them with their 'freevalve' tech (which basically
| replaces the timing chain with computers so that instead of
| having one or two modes that a camshaft can opt into, you
| can precisely dial in bespoke timings for every RPM, or
| every RPM and speed, or ever RPM / speed / gear
| combination. They've also practically reinvented the
| transmission to invent a new transmission that eliminates
| moving gearsets and gives you a dual-clutchish transmission
| with a 6 speed manual AND a 9 speed automatic in the same
| device.
|
| IIRC, the Freevalve tech is like a 30% efficiency hack for
| any ICE you put it on, and it's a part of how Koenigsegg
| are managing to squeeze 600 brake horsepower out of just a
| 2L, 3-cylinder engine.
|
| Wesley Kagan reimplemented their freevalve technology on
| his Mazda Miata, and it's probably the coolest hobby
| automotive project I've seen in years.
| https://www.youtube.com/watch?v=E9KJ_f7REGw
|
| Here's a really cool explainer on the transmission -
| https://www.youtube.com/watch?v=Hvb6J96KiSM
| aidenn0 wrote:
| People have made test engines with camless electrically
| actuated valves for a long time; it's just been too
| expensive to put in production cars...
| digdugdirk wrote:
| Absolutely love Koenigsegg, and their new engines are
| probably the current state of the art in (small scale)
| production ICE engines.
|
| I just feel like Mazda doesn't get enough credit for the
| innovation they manage to accomplish at a truly mass
| produced scale. It's almost like they're too "normal" to
| get the attention they deserve.
| coryrc wrote:
| Wankel is noticeably worse in about every metric,
| especially pollution and lifetime, so I wouldn't be too
| excited about it.
| hoosieree wrote:
| Actually mounting an engine inside a wheel increases "unsprung
| weight" which is bad for handling. But putting such small
| engines near the wheels (but still on the body so the
| suspension can do its job) that could indeed improve cargo
| space. Pushing the engine weight outward toward the wheels
| would also make the vehicle harder to rotate, which is bad for
| track cars and go carts, but good for passenger and freight
| vehicles.
| AnotherGoodName wrote:
| You want the unsprung mass to be as low as possible. As in you
| want the wheels to be much lighter than the rest of the car for
| a smooth ride. The wheels should bounce around but the rest
| shouldn't. Newtons law and all.
|
| Putting engines in wheels causes a very rough ride. Even if the
| engine is light you're still likely creating an order of
| magnitude more unsprung mass. That's an order of magnitude
| rougher ride.
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