[HN Gopher] Animated Engines
       ___________________________________________________________________
        
       Animated Engines
        
       Author : marcodiego
       Score  : 653 points
       Date   : 2021-03-06 17:29 UTC (1 days ago)
        
 (HTM) web link (animatedengines.com)
 (TXT) w3m dump (animatedengines.com)
        
       | prashnts wrote:
       | Quite interesting! Reminds me of http://507movements.com/
       | 
       | Edit: It's linked in the website as a "sister site".
        
         | ourcat wrote:
         | I was about to say the exact same thing. :) 507 Movements is a
         | work of art and inspirational.
        
       | cstross wrote:
       | Needs more Napier Deltic:
       | 
       | https://en.wikipedia.org/wiki/Napier_Deltic
       | 
       | (It's a two-stroke cycle diesel but not as we know it -- three
       | cylinders arranged in a triangle with a crankshaft at each
       | vertex, one of them counter-rotating relative to the other two,
       | and _six_ pistons, two of them opposed in each cylinder! There is
       | an animation on the wikipedia page. Tracking it will make your
       | head hurt. This thing was a mainstay of the British railway
       | industry in the late 1950s to 1960s ...)
        
         | vvanders wrote:
         | That's pretty incredible, and here I though the Wankel was a
         | fairly unique engine.
         | 
         | Not directly related but learning about the diesel-electric
         | locomotives and the transition from PWM DC to 3-phase VFD with
         | the traction improvements(I seem to recall they doubled
         | available traction but would have to check my sources[1]) was
         | also something that caught me by surprise. All these EVs out
         | there now owe a lot to the work that happened back in that
         | industry.
         | 
         | Edit: found the one of the sources I remember reading.
         | 
         | [1] http://www.republiclocomotive.com/ac-traction-vs-dc-
         | traction...
        
         | nimbius wrote:
         | Diesel engine mechanic here and I learned about these during my
         | apprenticeship. "high strung" is the understatement of the
         | fucking century. Deltics are garbage compared to a modern
         | inline 8 or 16 cylinder locomotive diesel.
         | 
         | cheerleaders for deltics will always measure their
         | effectiveness in the guesome "miles per casualty" figure,
         | completely ignoring the fact this system had astronomical
         | service costs as the design compounds stress on cast parts. you
         | had to have starter cartridges (explosives) to start the
         | things, and it wasnt uncommon for them to give up the smoke
         | just cranking them.
         | 
         | they have horrendous emissions as well compared to inlines.
         | diesel and lube oil would roll out of the exhaust in massive
         | plumes (you would never get these approved in the US today.)
         | Usually on startup large diesels have monitored exhaust
         | temperatures but in a Deltic your eyes had to be glued to the
         | meter because the stack was always a blond one away from
         | runaway (catching fire.) As tolerances drifted during service
         | most fleets just fed these things more lube oil and in turn,
         | worse emissions and efficiency.
         | 
         | again, complexity. Your tolerances for a deltic were insane
         | compared to what you had at the time for an off-the-shelf
         | diesel. repair parts too had to be custom fitted to the engine
         | as it had worn and take into account things like piston bore
         | cavitation damage from overprimed starter
         | cartridges/overspeed/overtemp/etc...The shop down the road
         | could not fabricate deltic parts so lead times were
         | considerable. Whoever worked on these had a dedicated machinist
         | (not just a miller) cutting parts off a dialed-in colchester
         | lathe or something with a very good tolerance.
        
           | [deleted]
        
           | willyt wrote:
           | Yes but you are comparing 1950s technology to 2020
           | technology. Sounds like the mechanical design was a bit ahead
           | of the capabilities of materials science and readily
           | accessible metal fabrication technology at the time. I expect
           | if you could add the amount of refinements and digital
           | augmentation that modern diesels have, you could get the
           | maintenance down to similar levels, but like the Wankel
           | rotary engine no-one is willing to bear the cost of redoing
           | the last 70 years of engineering optimisations that have been
           | done to the standard Diesel engine configuration.
        
             | Judgmentality wrote:
             | > but like the Wankel rotary engine no-one is willing to
             | bear the cost of redoing the last 70 years of engineering
             | optimisations
             | 
             | Mazda tried bringing this back with the RX-8. It was a
             | failure, and while everybody loves the "spirit" of the
             | wankel, outside of the infamous 787B I think people are
             | always going to remember it for the theory instead of the
             | application.
             | 
             | If we're going to talk about using modern engineering
             | capabilities, perhaps we should be discussing the
             | quasiturbine engine? At least in theory it solves many of
             | the problems of the rotary engine, although I suspect it
             | will be a nightmare of complexity that never becomes
             | reliable.
             | 
             | https://en.wikipedia.org/wiki/Quasiturbine
        
         | ggm wrote:
         | Absolutely amazing engine noise, you couldn't mistake it
         | pulling out of Waverley station in Edinburgh. As a trainspotter
         | I stood on the platform and saw all 22 over the years. I
         | believe the tested engine used to be in the science museum in
         | London but is now in the York museum.
         | 
         | The baby deltic was a more prosaic workhorse, the deltics
         | delivered the 100mph Edinburgh London service for decades.
        
           | totetsu wrote:
           | the noise for the curious https://m.youtube.com/watch?time_co
           | ntinue=54&v=gtv0s1JQ0D4&f...
        
             | ggm wrote:
             | I swear you can hear three notes in the thrummm. I know
             | it's a projection from my memory and desire, but in both
             | pitch, and it's tonality it isn't like normal diesel
             | locomotives.
             | 
             | I don't think the YouTubes do it justice, a bit like rocket
             | launches: you have to be there to get a chest-beating
             | throb.
        
           | quercusa wrote:
           | The York RR museum is an excellent place to spend a day.
        
           | redis_mlc wrote:
           | > As a trainspotter
           | 
           | OK, limey. :)
           | 
           | Maybe you can explain the appeal of trainspotting to a US
           | audience. Haven't heard much about that over here.
        
         | jacquesm wrote:
         | That's a pretty clever design, thank you for posting this, I
         | never even heard of it before. I really like the opposing
         | piston trick to get rid of the heavy head, but it does make you
         | wonder how they dealt with the spot where the fuel has to be
         | injected, it's hard enough to get reasonably efficient
         | combustion when you're injecting into the center of the cavity.
         | Did it use multiple injectors per cylinder?
        
           | rleigh wrote:
           | This part is dead simple and quite clever. It's on the
           | animated diagram in dark blue, and you can also see one port
           | on the cutaway engine block photo (I've been to see this in
           | real life; the engineering is phenomenal). On the blue
           | diagram I think it's air+fuel at one end and exhaust at the
           | other.
           | 
           | When the pistons reach their maximum opposing distance, the
           | injection and exhaust ports are briefly exposed, allowing for
           | entry of fuel/air and exit of exhaust in a single linear
           | movement from one end of the cylinder to the other. Maybe the
           | air is injected before the fuel or at a higher pressure. And
           | if you time the speed of the exchange just right in time for
           | the exhaust ports to be closed over before the compression
           | stroke, you get complete exchange with no fuel wastage.
           | Absolutely nothing like a 4-stroke engine, and not much like
           | common 2-stroke designs either.
        
             | jacquesm wrote:
             | Clever, and no valves to adjust. I really like this design,
             | and I'm wondering why it never caught on more, it looks as
             | though it would have worked well in a boxer like engine as
             | well, instead of two camshafts and one crank you'd end up
             | with no camshafts and two cranks.
        
               | Judgmentality wrote:
               | > While the Deltic engine was successful in marine and
               | rail use and very powerful for its size and weight, it
               | was a highly strung unit, requiring careful maintenance.
               | This led to a policy of unit replacement rather than
               | repair in situ. Deltic engines were easily removed after
               | breakdown, generally being sent back to the manufacturer
               | for repair, although after initial contracts expired both
               | the Royal Navy and British Railways set up their own
               | workshops for overhauls.
               | 
               | I guess nobody wanted to maintain them.
        
               | cstross wrote:
               | What you describe is the Junkers Jumo 204, and the Deltic
               | design was allegedly directly inspired by it.
               | 
               | https://en.wikipedia.org/wiki/Junkers_Jumo_204
        
               | jacquesm wrote:
               | Wow, what a beast. The displacement to weight ratio is
               | incredible, unfortunately it doesn't seem to produce a
               | whole lot of power for all that weight, though since it
               | is a diesel the torque is probably quite impressive (even
               | though it is for aircraft, where engines typically are
               | fairly low torque). Add a supercharger or a turbo
               | assuming the pistons can stand it and this could very
               | well still be a competitive engine. What a nice design.
               | Thank you once again.
        
               | Judgmentality wrote:
               | Not to take away from how neat that design is, but my
               | favorite thing about that link is learning that it was
               | manufactured by a now defunct company called Junkers.
               | 
               | https://en.wikipedia.org/wiki/Junkers
        
               | jacquesm wrote:
               | The English language association is a pretty negative one
               | but in German it's just another name. Coincidentally, the
               | house I am in right now is heated by a Junkers 'Eurostar'
               | central heating unit.
               | 
               | And in Polish 'Junkers' is pretty much synonymous with
               | water heater.
        
         | martinmunk wrote:
         | My dad collects old kerosene engines, and used to have a
         | simplified version of this. A 2 cylinder, 2 crankshaft, 4
         | piston, 2 stroke Diesel engine.
         | 
         | Used by German forces to power plane-spotting projectors, so
         | presumably manufactured in the late 30s or 40s.
        
           | userbinator wrote:
           | The general type is known as
           | https://en.wikipedia.org/wiki/Opposed-piston_engine
        
       | fartcannon wrote:
       | We used these animations as visual aids in my undergrad
       | approximately 18 years ago, give or take a year. It's marvelous
       | that they're still here.
        
       | AlexFielder wrote:
       | Surprised nobody mentioned the MYT engine:
       | http://angellabsllc.com/
        
       | Judgmentality wrote:
       | This is neat. If someone wants a slightly more comedic take on
       | automotive engine designs, Donut Media has some interesting
       | content.
       | 
       | https://www.youtube.com/watch?v=8YIDOjD0oBI
       | 
       | EDIT: Removed erroneous claim.
        
         | berniemadoff69 wrote:
         | > If someone wants a slightly more comedic take
         | 
         | it seems sort of rare on the Internet, particularly in videos,
         | for someone to NOT be doing a 'comedic' take, along with a jump
         | cut every 5 seconds, background music; all kinds of stuff that
         | feels like it is desperately trying to do everything it can all
         | at once to make someone not hit the back button. ironically,
         | hitting the back button is the first thing i do when a video
         | starts with 'Wats up Guyz' or something along those lines. the
         | original post is a breath of fresh air, straight to the point.
         | I wish the Internet was more like this in general.
        
           | marcodiego wrote:
           | These "jump cut every 5 seconds" is the reason I've been
           | watching less youtube everyday. It completely breaks
           | continuity and are so frequent that a significant part of the
           | video is wasted.
           | 
           | Reading and watching an animation is better than video
           | tutorials in almost every regard.
        
         | capableweb wrote:
         | > Donut Media pioneered the "suck squeeze bang blow" descriptor
         | of the 4 stroke engine
         | 
         | Someone please correct me if I'm wrong but I think I've heard
         | the term "suck squeeze bang blow" way before Feb 23, 2021 and
         | also before 2015 (creation of that Youtube channel) so I find
         | that claim hard to believe.
        
           | pen2l wrote:
           | This text dated 1981 mentions it (page viii): https://link.sp
           | ringer.com/content/pdf/bfm%3A978-1-349-06976-...
           | 
           | edit: and googling some more, there are instances of in being
           | used it 1950s. And the likely first author of the saying
           | might well be the inventor of the 4 stroke engine himself,
           | Nicolaus Otto, who used a similar saying to describe it:
           | _Saugen, Drucken, Knall, Schlag._
        
             | wizzwizz4 wrote:
             | Only source I can find for your last claim is
             | https://mechanics.stackexchange.com/a/28690/33924:
             | 
             | > Actually, I wouldn't be surprised if the great Nikolaus
             | August Otto, inventor of the four-cycle engine had a
             | similar saying to explain his engine: _Saugen, Drucken,
             | Knall, Schlag_...
             | 
             | So I think this is apocryphal.
        
               | pen2l wrote:
               | You might be right, I'm not sure. At least in Otto's
               | patent filing (which is found in English here: https://pa
               | tentimages.storage.googleapis.com/1f/3f/4c/821c6da... ) I
               | don't see such an expression.
               | 
               | I do see though that the breakdown of the Otto cycle on
               | most sites including German ones
               | (https://de.wikipedia.org/wiki/Ottomotor) is usually made
               | in a way that just sorts of lends itself to being
               | transformed that way.
               | 
               | Well, thanks for making me go through his writings, this
               | was fun!
        
           | cableclasper wrote:
           | Yeah. I've seen it in an old BBC documentary: The secret life
           | of machines - Internal Combustion Engine
           | https://www.youtube.com/watch?v=gfr3_AwuO9Y
        
           | NikolaeVarius wrote:
           | Wow screw this channel for such dumb shit.
        
           | bagels wrote:
           | It predates that channel by decades.
        
           | Judgmentality wrote:
           | Sorry, it's just the first place I'd heard it. I'll edit my
           | comment. I wasn't speaking on behalf of them.
           | 
           | Weird. I've been talking to people about cars for decades and
           | I'd never heard it before them. Is it just something that
           | people don't say anymore?
           | 
           | https://mechanics.stackexchange.com/questions/28682/who-
           | came...
           | 
           | I guess for whatever reason it's just not used as much, or at
           | least not enough that I've heard it before.
        
           | mhh__ wrote:
           | Even top gear referred to it as such probably a decade prior
        
         | spike021 wrote:
         | Something to keep in mind: several sources of actual topics
         | have contradicted Donut Media views on certain things and DM
         | has been known to steal video clips without crediting where
         | they got them or use Wikipedia articles as established sources.
         | 
         | Not that all their videos have these issues, but some do and it
         | gets pretty ridiculous.
        
       | varenc wrote:
       | I love this site! It reminds me on the "early" internet.
       | Dedication to a niche interest without any other fluff.
        
         | Dudideloo wrote:
         | It's actually a website from the early internet :
         | http://animatedengines.com/history.html
        
         | [deleted]
        
         | jacquesm wrote:
         | Exactly my choice of words :) But you beat me to it by an hour
         | or so, have an upvote.
        
       | coolgeek wrote:
       | Do not miss the sister site http://507movements.com/
        
       | hliyan wrote:
       | A long shot, but hope they could include the Wave Disk Engine
       | (https://en.wikipedia.org/wiki/Wave_disk_engine). I could never
       | wrap my head around the operating principle. Also, the research
       | appears to be either slow going, or halted.
        
         | ActorNightly wrote:
         | >the rotation of the disk creates shockwaves
         | 
         | The engineer in me cringed at this. While you can definitely
         | use shockwaves to compress the air, dealing with the repeated
         | stresses to the engine casing and other parts is a nightmare.
        
       | tim333 wrote:
       | Cool though their turbofan isn't going to work very well with the
       | compressor being much larger than the turbine - the gas would
       | find it easier to flow the wrong way. The Wikipedia animation has
       | more promising dimensions https://en.wikipedia.org/wiki/Turbofan
        
         | mrfusion wrote:
         | This has baffled me since I was two years old. The burning fuel
         | should push in all directions equally. What makes it go more
         | out the back than the front?
        
           | benlivengood wrote:
           | It's easier if you imagine identical fans for the compressor
           | and turbine but gearing so the turbine can spin faster. Of
           | course the gasses will take the easy way out the turbine. At
           | some speed, air stops going out the compressor and comes in
           | instead. Burning fuel keeps the gas expanding so there's
           | still a lot more volume to go through the turbine. Then
           | adjust blade angles and turbine diameters to get rid of the
           | gearing.
        
             | mrfusion wrote:
             | That's an interesting way to look at it. I can kind of see
             | that. Thanks!
        
               | tim333 wrote:
               | Or another way. If the thing was symmetrical the pressure
               | would push both ways and it wouldn't move so the
               | designers have to make it asymmetrical so it's easier to
               | get out the exhaust. I think in practice the compressor
               | blades are closer to perpendicular to the flow than the
               | exhaust turbine ones.
               | 
               | It's also important that there is a larger volume of gas
               | leaving the engine than going in as it expands when the
               | fuel heats it. So while the pressure is the same the
               | energy is greater on the turbine side due to the greater
               | volume so it has power to run the compressor as well as
               | fly the plane.
        
           | rleigh wrote:
           | That's what all the compressor stages are for. There's a
           | pressure differential so the combustion pushes against that
           | and exits in one direction, turning the lower pressure discs
           | on its way out.
        
         | zxczxczxcf wrote:
         | After remarking on how boring jet engines are, the page gets
         | vague and states that the turbofan increases "fuel efficiency",
         | without explaining why or how. I've seen it assumed elsewhere
         | that the efficiency of turbofans is due to thermodynamic
         | effects. In this case, what the author wrote is vague about the
         | mechanics of it, at best.
         | 
         | In fact, turbofans have better _propulsive_ efficiency because
         | they accelerate more air to a lower speed. Fuel efficiency
         | follows from that.
         | https://en.wikipedia.org/wiki/Propulsive_efficiency#Jet_engi...
        
       | benlivengood wrote:
       | Lol at the hate that jet engines get for being too "simple" and
       | "boring".
       | 
       | I think some of the compressor/turbine blades are drawn the wrong
       | angle but jet engines have always looked to me like they
       | shouldn't work at all. I know that the turbine extracts more
       | force from exhaust than the compressor exerts on the air (while
       | spinning up) but it's all in the diameter and blade shape since
       | they're attached to the same shaft, and my intuition has trouble
       | wrapping around the concept.
        
       | amelius wrote:
       | How do you drive the fuel into the highly compressed chamber, in
       | case of the Diesel engine?
        
         | jcampbell1 wrote:
         | Until very recently, the injector works by a push rod from the
         | cam shaft, meaning it is powered the same way the valves are.
         | 
         | In modern engines you have other options such as an electric
         | piezo stack hammer to force the fuel.
        
           | SigmundA wrote:
           | You might be conflating how an injector turns on and if with
           | how the fuel is pressurized. Unit injectors create the high
           | pressure for injection in the injector, combining the high
           | pressure pump and injector in one, fed by a low pressure
           | rail. Theses are driven mechanically via cams to create
           | pressure.
           | 
           | Common high pressure rail injectors have a separate high
           | pressure pump connected to engine elsewhere and the injectors
           | just turn on and off fed by a high pressure common rail.
           | 
           | The injector itself can be actuated mechanically or via
           | solenoids or piezo, but there are no injectors that create
           | pressure electrically that I know of (the closest I have seen
           | are voicemail medium pressure gas injectors used in ETEC
           | engines). That is the electric part of the injector only lets
           | the fuel through, it does not force it.
        
         | dugditches wrote:
         | via a 'fuel/injector pump'. Can click through this to get an
         | idea of just how complicated(and analog) they are.
         | https://www.youtube.com/watch?v=DKZL7Y0b5-U
        
         | cityofdelusion wrote:
         | The fuel injectors operate at very high pressures (200+
         | megapascals). Interestingly, it makes working on these systems
         | dangerous since the atomized fuel can inject and slice through
         | human tissue.
        
         | capableweb wrote:
         | The diesel engine is found here for the record:
         | http://animatedengines.com/diesel.html
         | 
         | Short answer: you need a fuel injector that can handle
         | injection into the highly-compressed air. Longer answer:
         | https://www.britannica.com/technology/diesel-engine/Fuel-inj...
        
         | jacquesm wrote:
         | The 'oldfashioned' way was using a high pressure fuel pump,
         | basically a needle sized piston pushing a tiny little bit of
         | fuel into a high pressure metal fuel line, the springloaded
         | ballbearing return valve at the tip of the injector would be
         | pushed open by the fuel and then the fuel could stream past the
         | ballbearing to the injector nozzle.
        
       | mcguire wrote:
       | Adding to the "if you like this" chain, the vbbsmyt YouTube
       | channel has 3d animations of historic guns and other weapons.
       | 
       | https://www.youtube.com/channel/UCFOZwUakpRbIH2zisiRU0Dw
        
       | eigenvalue wrote:
       | I really love the content here but it looks so pixelated on my
       | high-dpi monitor. It would be awesome is someone remade something
       | like this but using modern web technologies (maybe Lottie from
       | Airbnb) that uses vectorized images that can scale to any size.
        
       | mrfusion wrote:
       | If we ever had a high altitude electric plane do we think
       | electric motors with huge props? Or would we try to recreate the
       | turbo jet? Maybe resistive heating elements instead of fuel?
        
         | mberning wrote:
         | It would most likely emulate a turbofan, replacing the core
         | with an electric motor and possibly a gearbox.
        
       | dang wrote:
       | If curious, past threads:
       | 
       |  _Animated Engines_ -
       | https://news.ycombinator.com/item?id=7127953 - Jan 2014 (34
       | comments)
       | 
       |  _Animated Engines_ - https://news.ycombinator.com/item?id=701186
       | - July 2009 (11 comments)
        
       | TimBurr wrote:
       | If you like this, you'll probably enjoy Elmer's Engines. It's an
       | old book full of steam engine plans, designed for people who are
       | new to machining.
       | 
       | I used some of them as blueprints when I took drafting in high
       | school.
       | 
       | http://www.john-tom.com/html/ElmersEngines.html
        
       | jonplackett wrote:
       | It would be cool to see some Heath Robinson contraptions animated
       | like this!
        
         | mhh__ wrote:
         | One of my dreams for the next few years is that computers are
         | now fast enough to have physically realistic simulations in
         | games - you might not be waiting for too long to be building
         | Heath Robinson machines in VR!
        
           | jonplackett wrote:
           | First thing I would build: recreation of the mousetrap board
           | game.
        
       | carapace wrote:
       | No Tesla turbine? I guess it would be too boring.
       | 
       | (I know it's bad form to explain a joke, but I'm going to anyway.
       | The Tesla turbine used to be legendary (as in "urban legend")
       | before the Internet. Anyway, it has only one moving part which is
       | radially symmetrical and rotates about its center so there would
       | be nothing to see in the animation!)
        
       | p1mrx wrote:
       | The FPLG might be a good addition, though it's interesting
       | because of how boring it is:
       | 
       | https://en.wikipedia.org/wiki/Free-piston_linear_generator
       | 
       | https://www.youtube.com/watch?v=eV7f3tOUEbU
        
       | Vektorweg wrote:
       | These are pretty cool.
       | 
       | Worth to spend some time turning these into continuous SVG.
        
         | cableclasper wrote:
         | I'd like to do this. Can you recommend a good starting place to
         | learn how?
        
           | bobsterman wrote:
           | Start with drawing a single frame with SVG [1], then add
           | animation with CSS [2] or Javascript.
           | 
           | [1] https://developer.mozilla.org/en-
           | US/docs/Web/SVG/Tutorial/Ba... [2]
           | https://developer.mozilla.org/en-
           | US/docs/Web/CSS/CSS_Animati...
        
             | cableclasper wrote:
             | Thank you!
        
       | elwell wrote:
       | When I stare at these animations I can almost hear sounds.
        
         | marcodiego wrote:
         | Possibly related effect:https://www.cambridgebrainsciences.com/
         | more/articles/why-mos...
        
       | elihu wrote:
       | Probably worth mentioning LiquidPiston's new rotary engine design
       | (which has been discussed on HN before):
       | 
       | https://www.liquidpiston.com/how-it-works
       | 
       | (It's like an inside-out Wankel engine. Instead of a triangular
       | rotor in an oval housing, it's an oval rotor in a triangular
       | housing. The advantage is you get a more optimally-shaped
       | combustion chamber, which ought to improve fuel economy and
       | emissions. Also the apex seal-equivalents are easier to lubricate
       | as they're attached to the housing rather than the rotor. They've
       | made a few prototypes and they're working on durability.)
        
         | mberning wrote:
         | Interesting twist on a Wankel style design. It looks like the
         | apex seals are moved to the block rather than rotor. I'm also
         | curious as to the benefit/drawback of having the flow of intake
         | and exhaust perpendicular to the rotor.
        
       | jacquesm wrote:
       | I love websites like these. No fluff, just good quality content.
        
       | mrfusion wrote:
       | So I'm the two stroke what pushes the exhaust out? Wouldn't it
       | mix with the intake?
       | 
       | Also Is it possible to build a clean two stoke?
        
         | TimBurr wrote:
         | You're asking really good questions :)
         | 
         | In my layman's understanding, those are related. Playing with
         | the piston dimensions limits (but doesn't entirely prevent)
         | fuel/exhaust mixing. Unburned fuel in the exhaust makes them
         | dirty.
         | 
         | The site says:
         | 
         | > ... This expels the exhaust gasses out the exhaust port,
         | usually located on the opposite side of the cylinder.
         | Unfortunately, some of the fresh fuel mixture is usually
         | expelled as well.
         | 
         | Another factor - since the fuel enters through the crankcase,
         | it needs to be mixed with oil for lubricating the moving parts.
         | That oil burns when it gets to the combustion chamber. Pretty
         | sure that also increases unwanted emissions.
         | 
         | It's entirely possible modern CFD and chemistry could improve
         | on those issues... I'd be curious if anyone else knows about
         | recent R&D on two-strokes. They're hard to beat on power-to-
         | weight.
        
           | SigmundA wrote:
           | Direct injection two-strokes like ETEC's avoid the burnt fuel
           | in the exhaust by not injecting any fuel until the exhaust
           | port is closed. They also typically have specific oil
           | injection points reduce the amount of oil needed to be
           | burned. They are generally as clean as modern 4-stroke
           | engine.
        
             | TimBurr wrote:
             | Thanks for the reference! I'll have to read about those
             | more.
             | 
             | Sounds like that also eliminates any fuss with oil/fuel
             | ratios, since they're introduced separately.
        
       | jimkleiber wrote:
       | It's posts like this that keep the nerd in me glued to HN.
        
       | retsibsi wrote:
       | This is excellent, thanks for sharing it.
       | 
       | One neat feature it took me a moment to notice: you can step
       | through the animations manually, if you hit the pause button and
       | then either drag the slider or click the arrow buttons.
        
       | MattSayar wrote:
       | There's a lot of engines I've never heard of here, but my new
       | Subaru Outback has a CVT (Continuously Variable Transmission)
       | which isn't represented here which is somewhat disappointing
        
         | h2odragon wrote:
         | You might enjoy this: https://hackaday.com/2021/02/05/building-
         | a-continuously-vari...
        
         | grkvlt wrote:
         | not an engine, but (in the name...) a transmission - a mechnism
         | for transmitting power from the engine to the wheels. normally
         | cars use a gearbox (automatic or manual) and possibly a
         | driveshaft (to connect to the wheels that are at the other end
         | from the engine.)
        
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