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New two-stroke engine design could help keep internal combustion around longer

153 points by clouddrover 6y ago

rbanffy 6y ago
Well... If we cut too much carbon emissions it's a relief we can count on such engines to fill in the void. ;-)
holstvoogd 6y ago
Clutching at straws to make dead dinosaurs go boom!
- chrisseaton 6y ago
  Oil isn’t from dinosaurs that’s a myth. https://www.thoughtco.com/does-oil-come-from-dinosaurs-1092003 https://www.thoughtco.com/does-oil-come-from-dinosaurs-10920...
  - deleted 6y ago
    [deleted]
geekuillaume 6y ago
Link to the video: https://www.youtube.com/watch?v=oiUnqlGzLw8 https://www.youtube.com/watch?v=oiUnqlGzLw8
aww_dang 6y ago
How would the ignition piston be preheated from a cold start?
- kwhitefoot 6y ago
  Glowplug?
01100011 6y ago
Would a 14% increase in thermal efficiency translate into a meaningful reduction in carbon emitted per mile driven? This is interesting technology, but I'm not sure it will prolong the internal combustion engine, at least as far as mass market consumer transportation is concerned.
- m_mueller 6y ago
  I'm thinking this might have interesting applications as a range extender of EVs, like e.g. available for the BMW i30. A vehicle with 150-200km electric range and an optional extender could be quite compelling for lots of usecases.
  - wtallis 6y ago
    It looks like this would make for a pretty heavy engine, with four cylinders to do the work of 1-2 in a more traditional engine. So it might not be worth the trouble in a car, but may be useful in stationary or marine applications.
  - 1bc29b36f623ba8 6y ago
    Yes, hybrids are definitely a viable use-case. There are also other applications where a combustion engine makes much more sense, especially if this design can be used for smaller engines like chainsaw engines and lawnmower engines. The article doesn't mention what kind of fuel this new engine uses, but if it can run on ethanol, or synthesized hydrocarbons like E-diesel then this could definitely be a good thing.
    - henearkr 6y ago
      Chainsaws and lawnmowers do need to go electric now. They are the ones that ought to go electric first. The easier ones.
      - TomMarius 6y ago
        Thankfully electricity is not available everywhere, e.g. in the middle of a forest.
mangecoeur 6y ago
History is littered with the corpses of 'better' IC engine designs... the basic problem is you need to retool your entire factory and re-design your vehicles. If you are doing that today, why not just jump straight to electric motors?
- sneak 6y ago
  Aviation comes to mind, where the power density of batteries is not yet anywhere near sufficient for long-haul or cargo.
  - pjc50 6y ago
    Aviation tends to use turbines. Tiny general aviation aircraft tend to use small volumes of old proven designs.
- close04 6y ago
  > why not just jump straight to electric motors Because they can't satisfy every need just yet. Imagine we still have horses even with engines being around for more than a century. And adapting to a newer IC tech might actually be cheaper and easier than redesigning for EV tech. Manufacturers already have the experience, logistics chains, much of the designs, etc. Some transitions are never complete because sometimes there's no "one size fits all" option for the manufacturer or the consumer.
  - nicoburns 6y ago
    Yeah, but in 10 years when this technology is productionised, the use cases for it are going to be increasingly niche. Just like horses.
    - close04 6y ago
      Perhaps generators or heavy construction equipment would benefit from something like this. Lower pollution, lower costs for the operator, while still offering some flexibility that electric tech may not even in a decade. There are still hundreds of thousands to millions of work horses around the world. I'm still very much for improving old tech where it's possible and makes sense, even if it's niche.
safgasCVS 6y ago
Between this, camless motors, motors that can switch between different combustion cycles and variable compression ratios there is technically still a lot of improvement to be had. Whether or not the political climate will allow those improvements to come forth is unfortunately uncertain
- clarry 6y ago
  I think it's less a matter of political climate and more just that these improvements are "too little, too late" when electrics are already taking over markets. How long would I need to wait for these theoretical improvements to go from lab to reliable, mass market cars? Why aren't they here already, why would I wait a decade or two (for what, a 10%-20% improvement?) if I can buy a full electric car tomorrow? I don't object to improvements, but it's a race, and it seems like ICEs are losing that race unless they can do something impressive on a very short timescale.
  - close04 6y ago
    I don't think this benefits ICs at winning the race, that ship has sailed. Rather it benefits "us". ICs are going to be around for a while depending on the application. They might as well get more efficient and less polluting. We're still improving on DSL and coax as long as they have to be around even if fiber is better.
    - clarry 6y ago
      I'm not sure that's an apt analogy; if you have DSL instead of fiber, it's probably because fiber wasn't available at your location (or would've required you to pay some company thousands to dig up trenches and lay new infra). If electrics take the mass market, as I think they will, then new ICEs will largely just vanish from the market, and anyone who needs a normal family car can and will buy electric. Improvements to ICE tech don't go into old used cars because we don't upgrade their engines. The only ICEs that would be sold new are ones built to meet special needs, but they're probably going to be uncommon enough that improvements in them don't benefit "us" in a meaningful way; instead they become something you can largely ignore. Like, nobody is campaigning for fuel efficiency / pollution mandates for ATVs, tractors, supercars, or excavators, because they aren't a blimp on the radar. In these applications, fuel economy tends to be a very secondary concern anyway.
thecleaner 6y ago
Why is this not a welcome change even considering the supply chain difficulties ? The thing is combustion engine fumes make up for a tiny fraction of carbon emissions. The major part is from industrial production (like cement factories, steel plants etc.) In fact, electric vehicles will only help if the electricity powering it was generated from renewable sources which is a significant fraction in certain countries but not most. Considering these facts I guess good combustion is still a welcome change.
- cranekam 6y ago
  > combustion engines fumes make up for a tiny fraction of carbon emissions Not true. Transport (road/sea/air) accounts for 29% of US emissions. That’s hardly “tiny”. Of that, 59% is from light duty road transport. Burning fossil fuels for transport is a major contributor to global warming. https://www.epa.gov/greenvehicles/fast-facts-transportation-greenhouse-gas-emissions https://www.epa.gov/greenvehicles/fast-facts-transportation-...
- technicaldonut 6y ago
  >In fact, electric vehicles will only help if the electricity powering it was generated from renewable sources which is a significant fraction in certain countries but not most. That statement is false. If an EV is run on electricity generated from coal only, the overall emissions output is close to that of a comparable ICE car [0]. Introduce some friendlier methods into the mix and your beating ICE by quite a margin. The main source of emissions from an EV come from the manufacturing process. Even those can be significantly reduced when proper methods are applied. [0] https://www.forbes.com/sites/jamesellsmoor/2019/05/20/are-electric-vehicles-really-better-for-the-environment/#48b8b99776d2 https://www.forbes.com/sites/jamesellsmoor/2019/05/20/are-el...
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- mcv 6y ago
  ICEs are very inefficient. Even when powered by electricity from a coal plant, an electric car has less emissions than an ICE, simply because the coal plant burns coal more efficiently than an ICE. A more efficient ICE certainly helps, but coal to more efficient fossil fuels, like gas, helps even more. And many countries are rapidly moving to cleaner electricity. But you're right that there are many other sources of CO2 and other greenhouse gasses. Those also definitely need to be addressed, but that does not mean car emissions don't need to be addressed as well.
leoedin 6y ago
Even with the increased electrification of transport, there's still a very strong case for liquid fuel - it just offers an energy density so much higher than batteries, especially in off-grid or remote situations. Electric drivetrains open up an interesting potential for range-extenders which charge the batteries. The constraints are different than conventional engines - lower peak power, more-or-less continuous power output operation, no sudden torque changes. Different constraints generally mean a different optimal solution.
- henearkr 6y ago
  There is not a huge gap at all. Li-metal batteries [edit: still an immature tech] are at around 14 MJ / kg, and gasoline is at 47.5 MJ / kg. Moreover, suppose that you are really "off-grid". Meaning, you are off any fuel supply network!! In this case precisely, you would be saved by electric-related techs, such as photovoltaic.
  - leoedin 6y ago
    I was using off-grid in the most straightforward of senses - off the electricity grid. That doesn't necessary mean stationary or without weight limits (as solar would require) - it could mean long distance trucking, or logging, construction, or even the maintenance of electricity pylons (which probably can't be turned on during that process). All those require huge amounts of energy, and batteries are not yet nearly there (as others point out, your numbers for battery energy density are out by a factor of 30).
  - avhon1 6y ago
    Or saved by combustion-related techs, such as biofuel, biogass, wood gas, or just plain-old "burn organic matter".
    - henearkr 6y ago
      But, using electric, I just have to charge it by plugging in a solar panel. With existing OTS products. If I want to burn dead leaves to run my car... well that sucks right now (moreover that isn't anymore 0 emission).
henearkr 6y ago
- Hi, I've found an improved NP primality test algorithm!! - Uh, but, years ago, a P algorithm has been found... - Yes, but if you want to stay in NP, I have a better one!! This is the way I feel... We have a 0 emission motor -- electric engine-- and people telling us that, if ever we would not like to use 0 emission, then they have a better IC engine...
- mcv 6y ago
  Exactly. It feels like it's just trying to offer some hope for the oil industry. I'm not convinced society needs this. Though if there really are use cases where electric cannot work and we are forced to accept fossil fuels, I guess a slightly more efficient engine is nice.
- avhon1 6y ago
  ICEs have a lot of life left in them yet. Hydrocarbon fuels are energy-dense and easily transported, stored, and transferred. It will be a long time before every use case can be practically and economically covered by electric motors.
  - henearkr 6y ago
    Electrons are energy-dense and easily transported, stored, and transferred. That's probably what a lot of people have missed about the technological revolution that just happened. > ICEs have a lot of life left in them yet. > [...] > It will be a long time before every use case can be practically and economically covered by electric motors. Let the near-future prove you wrong on both statements ;) The maximum density of Li-metal batteries [edit: still an immature tech] is around 14 MJ / kg, whereas gasoline is the highest energy-density fossil fuel at 47.5 MJ / kg. This is not a huge gap at all.
    - jhoechtl 6y ago
      More than three times higher sounds like a massive advantage to me? Or say 330%. That's huge!
    - 6y ago
mtgx 6y ago
Too little, too late. There's no way these will arrive in time on the market in volume and be good enough (power, reliability, etc) by the time EVs reach critical mass. Stats say that something like 90% of the people that drove an EV want to buy one next. I doubt this would be true for the two-stroke engine.
mcv 6y ago
> "Of course, it's not like we're going to be seeing entry ignition engines popping up in road cars any time soon. The method is unproven, and carries a bunch of unknowns regarding cooling, balancing, and reliability. Still, it's a sign not all is lost in the world of fuel-powered engines." Electric cars are well on their way to proving themselves. This new technology is too late to slow down the electric takeover. Its only use is to make those vehicles that are unable to switch to electric (probably because of fuel density or a need for rapid refueling) cleaner. Which is still useful, I guess. Though I'm hoping they won't be necessary at all.
londons_explore 6y ago
Investment into productionizing these kind of advances has pretty much stopped. It's a bit like hard drives... As soon as the SSD arrived, everyone saw that hard drives would eventually die out, so manufacturers pretty much stopped new technology development. Sure, there have been a few small advances, but seek times and data read speeds haven't gone up for a decade, and capacities have only crept up. IC engines are the same. It might take them 30 years to die out, but in those 30 years there won't be any significant tech advances, because every company that makes them is only optimizing for cost in a shrinking market.
- Hamuko 6y ago
  SSDs have been mainstream products for at least a decade now. Ten years ago, the largest HDD we had was like 2 TB. We currently have 16 TB HDDs and people are expecting us to have 50 TB HDDs in 2026. And not only that, 16 TB HDD is quite affordable. Just 500 dollars for a Seagate IronWolf. Meanwhile a 3.2 TB Seagate Nytro will set you back about $1800. SSD mass storage is an option for only those with deep pockets. Hell, not even tape drives have gone away yet. Amazon Glacier is just one example.
  - pg-gadfly 6y ago
    It's also to note that SSD capacity hasn't strictly improved, it's been gained through massive compromises that severely impact their lifetime and performance. More than that, a 5 year old nas drive can outperform a modern cheap ssd in throughput easily.
    - wtallis 6y ago
      Most, but not all of the capacity and affordability increases of SSDs have been due to compromises elsewhere. If you plot the characteristics of "the cheapest flash you can buy" over the years, few of the curves are monotonic. Physical memory cell dimensions decreased steadily until the arrival of 3D NAND, whereupon cell sizes jumped back up and have been relatively stable since. SSDs incorporate more advanced error correction with each generation of controllers, so today's drives can get more usable write endurance out of the same physical cell size. Number of bits that can be stored per cell has been increasing. Each time we cram another bit into each memory cell, performance and write endurance drop. But in between those major shifts, successive generations of flash tend to get faster and more energy-efficient over time. Today's 3 bit per cell TLC NAND is much faster than the TLC from 5 years ago, and has better write endurance thanks to the transition to 3D NAND. Today's SLC NAND has comparable performance and write endurance to the planar SLC that disappeared from the market over 5 years ago, but now it's several times cheaper. And most of the compromises that have been made with NAND flash over the past 10+ years are purely academic. The vast majority of use cases do not need flash rated for 100k P/E cycles, and excess endurance beyond your needs provides no tangible benefit. Most of the endurance that has theoretically been sacrificed was never needed in the first place. Most of the performance lost has been offset by using more flash in parallel and by eliminating bottlenecks elsewhere. The only metric by which a 5 year old NAS hard drive—or any hard drive—will outperform a modern cheap SSD is in long-term sustained sequential write throughput. Even the slowest modern cheap SSD will offer at least twice the sequential read throughput, and orders of magnitude better random read or write throughput. And it's not like the write throughput of modern SSDs is abysmal: gigabit Ethernet is a more significant bottleneck when filling a 1TB or larger dirt-cheap consumer SSD. So unless you're trying to use cheap consumer SSDs in an expensive NAS with 10GbE, the poor write performance of low-end SSDs won't come into play.
sanatgersappa 6y ago
How dare you!
tyho 6y ago
Boring. Even an IC engine operating at the Carnot limit would still emit carbon. Convert every IC on earth to a one with theoretically perfect efficiency and we still blast past 1.5deg warming in a few decades.
- ReticentVole 6y ago
  Plus the cognitive impacts of higher CO2, plus ocean acidification, plus the noise and pollution being exhausted at ground level inside cities, plus supporting barbaric regimes that mine the oil. Just scrap it all and go full electric. Coming out of COVID lockdown is a great time to invest and mandate.
- baq 6y ago
  Many people can’t believe that if we improve IC engines a couple percent a year we’ll be at the Carnot limit in a few decades.
- rootusrootus 6y ago
  We're an awful long way from having battery storage on par with liquid energy storage, and battery tech improves steadily but not exponentially. Having good IC engine designs is going to be important for decades. We will need to start generating liquid fuel that is carbon neutral.
trhway 6y ago
It is basically a split cycle engine and the "New" is a bit overblown by more than 100 years. Even similar non-spark based hot ignition was used back then: https://en.wikipedia.org/wiki/Split_cycle_engine https://en.wikipedia.org/wiki/Split_cycle_engine "The Backus Water Motor Company of Newark, New Jersey was producing an early example of a split cycle engine as far back as 1891. The engine, of "a modified A form, with the crank-shaft at the top", was water-cooled and consisted of one working cylinder and one compressing cylinder of equal size and utilized a hot-tube ignitor system."
- avhon1 6y ago
  The Backus engine shares the pre-compressor piston with this design, but this engine also has the pre-pre-compressor piston (with different geometry) and also the low-pressure power piston. It seems to still be novel, despite sharing characteristics with previous designs.
- throwaway0a5e 6y ago
  "Fuel injection has been tried for 50yr, there's no way it will be commercially successful now" -some guy in 1980. History is littered with inventions that didn't gain widespread use initially then some little advancement(s) came along that make the inventions workable when revisited and tweaked. Repeating firearms and electric lightbulbs are two good examples. I don't pretend to know which bucket this "new" engine advancement will fit into but I think your judgement is premature.
  - jacquesm 6y ago
    Bosch fuel injection was commercialized in 1967.
    - throwaway0a5e 6y ago
      You're not wrong but to imply that Boch fuel injection was successful would be to wear some really rose colored glasses. Boch fuel injection was such a small improvement over contemporary cabruerators and such a downgrade in terms of maintenance and cost of ownership that it was more or less universally reviled by everyone who was not into technology for technology's sake. It never really achieved widespread use. If you wanted a glass half full perspective you could say it gave 1st generation throttle body based injector systems a low bar to exceed. Bosch mechanical fuel injection is almost a perfect example of an implementation of a technology not ready for mass market adoption that later became ready for mass market with the advent of new technology (cheap digital electronics in this case).
avhon1 6y ago
All of the skeptical comments I've read here are talking about how ICE are already obsolete, since electric cars are cleaner, quieter, and simpler. I'm picturing this engine being used in other applications (even though the website, and the journal the engine is publushed in, are automotive). Stationary generators and marine drivetrains come to mind. Those are less sensitive to the greater size and weight that this engine might have, and they benefit greatly from the ability to load fuel, store it, burn it as needed, and be refueled at any time, even while running. As an example, my local university's datacenter has two rooms full of batteries for power backup. They instantly switch on, but can only power the datacenter for a short time. To protect against extended blackouts, there are two redundant diesel generators in the sub-basement, and enough fuel to run the datacenter for several months. Battery technology seems to have a ways to go before it'll be worthwhile to just have a basement full of batteries as long-term backup power. People with those sorts of use cases are probably going to be relying on ICEs for a long time to come. In the meanwhile, efficiency improvements can make them less harmful to own and operate. And even after 150 years of developing ICEs, engineers are still coming up with ideas, maybe even practical ones, to gain those improvements.
- cameldrv 6y ago
  Flow batteries are a possible solution. Energy density is substantially less though, so they may not be practical for applications where the battery is only rarely used.
  - avhon1 6y ago
    The development of flow batteries with lightweight, inexpensive electrodes and efficient, dense electrolytes would definitely change the situation a lot. Fuel would be pumpable again, and you could transfer large amounts energy without it being integrated with the catalyst that can unsafely release all of that energy.
  - barbegal 6y ago
    Whats the advantage of a flow battery over a fuel cell which has higher energy density?
otagekki 6y ago
Is this patented?
imdoor 6y ago
The theoretical efficiency gain appears to be greater than the stated 14%. The article cites a video [1] which in turn cites 49% vs 63% maximum theoretical thermal efficiency for a traditional engine and for the Entry Ignition engine, respectively. That makes it a 14 percentage point increase which is 29% increase in efficiency. [1] https://www.youtube.com/watch?v=oiUnqlGzLw8 https://www.youtube.com/watch?v=oiUnqlGzLw8
- ksec 6y ago
  Thank You I had the exact same question in mind. ~30% increase is a lot. I wonder how much more efficiency can we continue to squeeze out from ICE?
russellbeattie 6y ago
I'm not sure which is worse, YouTube videos where all they do is summarize a written news article, or a written news article summarizing a YouTube video...
- avhon1 6y ago
  I'm pleased with a YouTube video that visually, verbally, and efficiently explains the contents of a paper that costs $33 to read.
- mdszy 6y ago
  If you've never watched Engineering Explained, I'd recommend it highly. It's very high-quality content that deeply explains how engines and other components in cars work. The video was released well before the article, and I believe the article was posted to spread the video more widely.
Jemm 6y ago
All this debate of electric vs internal combustion when the article is about a theoretical design that has yet to be proven.
- ReactiveJelly 6y ago
  Only Consumer Reports can tell us which car is better: One with batteries that don't exist, or one with a gas engine that doesn't exist
taylodl 6y ago
Jason Fenske's Engineering Explained is an excellent YT channel. I especially enjoy his physics for gearheads.
mrfusion 6y ago
So how does this efficiency compare to gas turbines? Should gas power plants switch to this if it pans out? Or it might be good for portable generators. Does two stroke mean it won’t need oil changes?
- johnatwork 6y ago
  This particular two stroke would need oil changes. Some of the traditional ones did not because the oil was mixed with fuel to lubricate the seals that exist between the piston (part that moves up and down) and the cylinder (which houses the piston). In most engines that we refer to in cars, the lubrication happens from the bottom in the crankcase (where you see the rod beneath the piston).
- rootusrootus 6y ago
  > Does two stroke mean it won’t need oil changes? This is not the same kind of two-stroke engine. The one you're thinking of pumps the fuel air mixture through the crankcase, which is why it cannot use the same oiling system that a typical four-stroke engine does. The oil would be diluted with fuel pretty quickly, and also carried into the combustion chamber and burned off. So adding the oil to the fuel is how you get around that, but then you're constantly burning oil.
liammonahan 6y ago
Isn’t this much like how Diesel engines work? They compress air first to heat it to the point that when mixed with fuel it spontaneously ignites. Maybe glow plugs can make a comeback.
- gsnedders 6y ago
  In the diesel case, fuel is immediately at its auto-ignition temperature when introduced. In this, the air-fuel mixture is heated until it reaches its auto-ignition temperature.
- dghughes 6y ago
  Diesel engines are based off a south Pacific people's invention who used a bamboo tube with piston to ignite a sliver of wood. Rudolph used it as inspiration for his engine design. He also intended the fuel for it to be peanut oil or canola oil a crop farmers could grow for their tractors. Glow plugs are still here sort of although now a heating grid. My diesel truck has it to pre-heat the air to make starting easier.
- fnordfnordfnord 6y ago
  It sounds somewhat similar to a supercharged two-stroke design like the formerly very popular Detroit Diesels (8V71, 6V92TA, for example). None of those engines were very efficient though. Also, glow plugs are only used for starting.
thrower123 6y ago
I am relatively certain that people will be rebuilding old Detroit and Cummins diesel engines in heavy equipment for at least the next 50 years, if not 100. I have been surprised at how much 40V/80V electric systems are cutting into what was traditionally two-stroke light engines for string trimmers and mowers. The batteries are expensive though, and I don't know how many you'd need to have in rotation to be able to keep one fully charged and ready to go under continuous usage.
- fnordfnordfnord 6y ago
  The batteries are expensive but when you factor the cost of fuel + oil and the hassle of dealing with it, the case for batteries doesn't look as bad.
- mikestew 6y ago
  For the weed trimmer and lawn mower I purchased at U. S. chain Lowes, the magic number of batteries is 3. The mower came with 2, and the trimmer with 1. The charger can charge a battery almost as fast as the mower can consume them, so the third is needed for a little slack. You could get by with only two if you're content to get a beverage between batteries. Theoretically, anyway; with our tiny yard this is seldom tested. Which why I'm annoyed by neighbors that buy a new gas-powered mower. There is not a yard within at least a 3 mile radius of me that can't be mowed by a modern, lithium-battery push mower.
- vardump 6y ago
  > ...I don't know how many you'd need to have in rotation... My lawn mower 5Ah @56V (EGO power) is good for half an hour. It charges from empty to full in maybe 40 minutes. In a trimmer same battery seems to last forever, maybe at least 2 hours.
mrfusion 6y ago
I just watched the video. Can anyone answer these questions? What prevents the burning from getting into the mixing chamber? It seems like the sliding valve is open while it’s burning. And there’s higher pressure in the cylinder. What prevents the mixing chamber gas from getting into the compression reservoir?
- MontagFTB 6y ago
  I can’t answer the second question, but as to the first my understanding from the video is that the ignition cylinder starts out as much lower pressure that the fuel/air chamber, and as the slide valves open the mixture naturally moves from high to low pressure. The heat contained within the cylinder starts the ignition of the mixture upon entry (hence the name of the engine). I don’t understand how the heat differential between the injection and ignition phases is so great that ignition happens as the slide valve opens, but so little that ignition doesn’t happen within the fuel injection chamber. Perhaps the pressure differential regulates that as well?
- deleted 6y ago
  [deleted]
Dumblydorr 6y ago
Our climate doesn't care if the engine is 14% more efficient. That is still vastly too much carbon emission for people or goods to move from A to B. Consider every time any ICE engine moves anything, those emissions will warm the planet for millennia. We can not afford to use these destructive engines, even though fossil fuel interests make them slightly less damaging. We must have a sustainable transport system, which ultimately means using non-fossil derived fuel. That means way way better batteries, fuel cells, or other up and coming solutions. Any iteration on ICE is just kicking the can down the road.
opwieurposiu 6y ago
Right before jet engines took over the military aviation market, you saw some very complex, high efficiency piston engines. Mechanical marvels they were, only now are automotive engines catching up in performance. Ultimately they were all commercial failures, the jet engine had a lot more headroom for improvement and was mechanically much simpler. https://en.wikipedia.org/wiki/Napier_Nomad https://en.wikipedia.org/wiki/Napier_Nomad
- throwaway894345 6y ago
  I've noticed a very general principle here. Things which are 'before their time' obviously tend to fail, but the interesting bit IMO is that 'before their time' often means "the problem isn't yet constrained such that the efficiencies afforded by the design are economically significant". I think this explains why so much software (my branch of engineering) is miserably inefficient and bug-ridden despite the fact that we have technology to improve efficiency and quality by several orders of magnitude (at a relatively modest cost)--the economic context simply doesn't place a very high value on efficiency and quality, presumably because the market is comparing software against the many, many orders of magnitude worse performance afforded by humans. Perhaps all of this is obvious to many others; it's interesting and novel to me, anyway.
deleted 6y ago
[deleted]
chrismartin 6y ago
It looks like the slider valve is surrounded on all sides by hot air-fuel mixture and combustion gas. Will the fingers of the slider valve need to be lubricated? Might they be lubricated without consuming (burning) excessive oil (with consequent increase of emissions)?
hinkley 6y ago
I recall years ago when someone had rediscovered sleeve valves and was going to apply them to small displacement 4 cycles in order to get the weight down to be more competitive with 2 cycle engines. It wasn't clear that the article author was aware of them either (and in fact I don't think I'd heard of them until the movie Sahara)
hinkley 6y ago
A 2-stroke engine has one ignition per revolution per cylinder. A 4 stroke engine has half an ignition per revolution per cylinder (or two revolutions per ignition). This engine has only one combustion chamber for every four cylinders, which means that it experiences one quarter of an ignition per revolution per cylinder. It's not a 4-stroke, clearly, but I don't see how you can get away with calling it a 2-stroke either. The strokes kind of become beside the point, but if I had to I might want to call this an 8-stroke engine. I see them pilfering ideas from this for 'simpler' engines. That valve design feels like it could be used for about anything. I've seen other engine designs that use a single intake chamber, so that part has in fact already been done before. That recuperation chamber trick I think could be applied to a traditional 4-stroke engine, which you would need every other cycle and therefore could share with another cylinder (opposed by a full revolution, which I hear at least a few 4 cylinders do). And something similar could be applied on the intake side (although you might have to use the ignition cylinder for the second compression) and then fully half of your cylinders fire.
rurban 6y ago
So a multi-chamber diesel. Why should more chambers be more efficient than the single chamber diesel engine? Because per revolution you get double self-ignitions, at the cost of more room and more gas moving around. Hmm, not bad. Bad reminds me on the Wankel. Only better in theory.
- arh68 6y ago
  I'm not sure this [1] is what you're talking about but it reminded me of reading about pre-combustion chambers in diesel cylinders. Interesting stuff. [1] https://en.wikipedia.org/wiki/Indirect_injection#Classification_of_indirect_combustion_chambers https://en.wikipedia.org/wiki/Indirect_injection#Classificat...
  - rurban 6y ago
    Not really interesting. That's from the pre-BOSCH direct injection area. Modern diesel engines are far more efficient than that.

153 points by clouddrover 6y ago

rbanffy 6y ago

Well... If we cut too much carbon emissions it's a relief we can count on such engines to fill in the void. ;-)

holstvoogd 6y ago

Clutching at straws to make dead dinosaurs go boom!

chrisseaton 6y ago
Oil isn’t from dinosaurs that’s a myth. https://www.thoughtco.com/does-oil-come-from-dinosaurs-1092003 https://www.thoughtco.com/does-oil-come-from-dinosaurs-10920...
- deleted 6y ago
  [deleted]

geekuillaume 6y ago

Link to the video: https://www.youtube.com/watch?v=oiUnqlGzLw8 https://www.youtube.com/watch?v=oiUnqlGzLw8

aww_dang 6y ago

How would the ignition piston be preheated from a cold start?

kwhitefoot 6y ago
Glowplug?

01100011 6y ago

Would a 14% increase in thermal efficiency translate into a meaningful reduction in carbon emitted per mile driven? This is interesting technology, but I'm not sure it will prolong the internal combustion engine, at least as far as mass market consumer transportation is concerned.

m_mueller 6y ago
I'm thinking this might have interesting applications as a range extender of EVs, like e.g. available for the BMW i30. A vehicle with 150-200km electric range and an optional extender could be quite compelling for lots of usecases.
- wtallis 6y ago
  It looks like this would make for a pretty heavy engine, with four cylinders to do the work of 1-2 in a more traditional engine. So it might not be worth the trouble in a car, but may be useful in stationary or marine applications.
- 1bc29b36f623ba8 6y ago
  Yes, hybrids are definitely a viable use-case. There are also other applications where a combustion engine makes much more sense, especially if this design can be used for smaller engines like chainsaw engines and lawnmower engines. The article doesn't mention what kind of fuel this new engine uses, but if it can run on ethanol, or synthesized hydrocarbons like E-diesel then this could definitely be a good thing.
  - henearkr 6y ago
    Chainsaws and lawnmowers do need to go electric now. They are the ones that ought to go electric first. The easier ones.
    - TomMarius 6y ago
      Thankfully electricity is not available everywhere, e.g. in the middle of a forest.

mangecoeur 6y ago

History is littered with the corpses of 'better' IC engine designs... the basic problem is you need to retool your entire factory and re-design your vehicles. If you are doing that today, why not just jump straight to electric motors?

sneak 6y ago
Aviation comes to mind, where the power density of batteries is not yet anywhere near sufficient for long-haul or cargo.
- pjc50 6y ago
  Aviation tends to use turbines. Tiny general aviation aircraft tend to use small volumes of old proven designs.
close04 6y ago
> why not just jump straight to electric motors Because they can't satisfy every need just yet. Imagine we still have horses even with engines being around for more than a century. And adapting to a newer IC tech might actually be cheaper and easier than redesigning for EV tech. Manufacturers already have the experience, logistics chains, much of the designs, etc. Some transitions are never complete because sometimes there's no "one size fits all" option for the manufacturer or the consumer.
- nicoburns 6y ago
  Yeah, but in 10 years when this technology is productionised, the use cases for it are going to be increasingly niche. Just like horses.
  - close04 6y ago
    Perhaps generators or heavy construction equipment would benefit from something like this. Lower pollution, lower costs for the operator, while still offering some flexibility that electric tech may not even in a decade. There are still hundreds of thousands to millions of work horses around the world. I'm still very much for improving old tech where it's possible and makes sense, even if it's niche.

safgasCVS 6y ago

Between this, camless motors, motors that can switch between different combustion cycles and variable compression ratios there is technically still a lot of improvement to be had. Whether or not the political climate will allow those improvements to come forth is unfortunately uncertain

clarry 6y ago
I think it's less a matter of political climate and more just that these improvements are "too little, too late" when electrics are already taking over markets. How long would I need to wait for these theoretical improvements to go from lab to reliable, mass market cars? Why aren't they here already, why would I wait a decade or two (for what, a 10%-20% improvement?) if I can buy a full electric car tomorrow? I don't object to improvements, but it's a race, and it seems like ICEs are losing that race unless they can do something impressive on a very short timescale.
- close04 6y ago
  I don't think this benefits ICs at winning the race, that ship has sailed. Rather it benefits "us". ICs are going to be around for a while depending on the application. They might as well get more efficient and less polluting. We're still improving on DSL and coax as long as they have to be around even if fiber is better.
  - clarry 6y ago
    I'm not sure that's an apt analogy; if you have DSL instead of fiber, it's probably because fiber wasn't available at your location (or would've required you to pay some company thousands to dig up trenches and lay new infra). If electrics take the mass market, as I think they will, then new ICEs will largely just vanish from the market, and anyone who needs a normal family car can and will buy electric. Improvements to ICE tech don't go into old used cars because we don't upgrade their engines. The only ICEs that would be sold new are ones built to meet special needs, but they're probably going to be uncommon enough that improvements in them don't benefit "us" in a meaningful way; instead they become something you can largely ignore. Like, nobody is campaigning for fuel efficiency / pollution mandates for ATVs, tractors, supercars, or excavators, because they aren't a blimp on the radar. In these applications, fuel economy tends to be a very secondary concern anyway.

thecleaner 6y ago

Why is this not a welcome change even considering the supply chain difficulties ? The thing is combustion engine fumes make up for a tiny fraction of carbon emissions. The major part is from industrial production (like cement factories, steel plants etc.) In fact, electric vehicles will only help if the electricity powering it was generated from renewable sources which is a significant fraction in certain countries but not most. Considering these facts I guess good combustion is still a welcome change.

cranekam 6y ago
> combustion engines fumes make up for a tiny fraction of carbon emissions Not true. Transport (road/sea/air) accounts for 29% of US emissions. That’s hardly “tiny”. Of that, 59% is from light duty road transport. Burning fossil fuels for transport is a major contributor to global warming. https://www.epa.gov/greenvehicles/fast-facts-transportation-greenhouse-gas-emissions https://www.epa.gov/greenvehicles/fast-facts-transportation-...
technicaldonut 6y ago
>In fact, electric vehicles will only help if the electricity powering it was generated from renewable sources which is a significant fraction in certain countries but not most. That statement is false. If an EV is run on electricity generated from coal only, the overall emissions output is close to that of a comparable ICE car [0]. Introduce some friendlier methods into the mix and your beating ICE by quite a margin. The main source of emissions from an EV come from the manufacturing process. Even those can be significantly reduced when proper methods are applied. [0] https://www.forbes.com/sites/jamesellsmoor/2019/05/20/are-electric-vehicles-really-better-for-the-environment/#48b8b99776d2 https://www.forbes.com/sites/jamesellsmoor/2019/05/20/are-el...
- deleted 6y ago
  [deleted]
mcv 6y ago
ICEs are very inefficient. Even when powered by electricity from a coal plant, an electric car has less emissions than an ICE, simply because the coal plant burns coal more efficiently than an ICE. A more efficient ICE certainly helps, but coal to more efficient fossil fuels, like gas, helps even more. And many countries are rapidly moving to cleaner electricity. But you're right that there are many other sources of CO2 and other greenhouse gasses. Those also definitely need to be addressed, but that does not mean car emissions don't need to be addressed as well.

leoedin 6y ago

Even with the increased electrification of transport, there's still a very strong case for liquid fuel - it just offers an energy density so much higher than batteries, especially in off-grid or remote situations. Electric drivetrains open up an interesting potential for range-extenders which charge the batteries. The constraints are different than conventional engines - lower peak power, more-or-less continuous power output operation, no sudden torque changes. Different constraints generally mean a different optimal solution.

henearkr 6y ago
There is not a huge gap at all. Li-metal batteries [edit: still an immature tech] are at around 14 MJ / kg, and gasoline is at 47.5 MJ / kg. Moreover, suppose that you are really "off-grid". Meaning, you are off any fuel supply network!! In this case precisely, you would be saved by electric-related techs, such as photovoltaic.
- leoedin 6y ago
  I was using off-grid in the most straightforward of senses - off the electricity grid. That doesn't necessary mean stationary or without weight limits (as solar would require) - it could mean long distance trucking, or logging, construction, or even the maintenance of electricity pylons (which probably can't be turned on during that process). All those require huge amounts of energy, and batteries are not yet nearly there (as others point out, your numbers for battery energy density are out by a factor of 30).
- avhon1 6y ago
  Or saved by combustion-related techs, such as biofuel, biogass, wood gas, or just plain-old "burn organic matter".
  - henearkr 6y ago
    But, using electric, I just have to charge it by plugging in a solar panel. With existing OTS products. If I want to burn dead leaves to run my car... well that sucks right now (moreover that isn't anymore 0 emission).

henearkr 6y ago

- Hi, I've found an improved NP primality test algorithm!! - Uh, but, years ago, a P algorithm has been found... - Yes, but if you want to stay in NP, I have a better one!! This is the way I feel... We have a 0 emission motor -- electric engine-- and people telling us that, if ever we would not like to use 0 emission, then they have a better IC engine...

mcv 6y ago
Exactly. It feels like it's just trying to offer some hope for the oil industry. I'm not convinced society needs this. Though if there really are use cases where electric cannot work and we are forced to accept fossil fuels, I guess a slightly more efficient engine is nice.
avhon1 6y ago
ICEs have a lot of life left in them yet. Hydrocarbon fuels are energy-dense and easily transported, stored, and transferred. It will be a long time before every use case can be practically and economically covered by electric motors.
- henearkr 6y ago
  Electrons are energy-dense and easily transported, stored, and transferred. That's probably what a lot of people have missed about the technological revolution that just happened. > ICEs have a lot of life left in them yet. > [...] > It will be a long time before every use case can be practically and economically covered by electric motors. Let the near-future prove you wrong on both statements ;) The maximum density of Li-metal batteries [edit: still an immature tech] is around 14 MJ / kg, whereas gasoline is the highest energy-density fossil fuel at 47.5 MJ / kg. This is not a huge gap at all.
  - jhoechtl 6y ago
    More than three times higher sounds like a massive advantage to me? Or say 330%. That's huge!
  - 6y ago

mtgx 6y ago

Too little, too late. There's no way these will arrive in time on the market in volume and be good enough (power, reliability, etc) by the time EVs reach critical mass. Stats say that something like 90% of the people that drove an EV want to buy one next. I doubt this would be true for the two-stroke engine.

mcv 6y ago

> "Of course, it's not like we're going to be seeing entry ignition engines popping up in road cars any time soon. The method is unproven, and carries a bunch of unknowns regarding cooling, balancing, and reliability. Still, it's a sign not all is lost in the world of fuel-powered engines." Electric cars are well on their way to proving themselves. This new technology is too late to slow down the electric takeover. Its only use is to make those vehicles that are unable to switch to electric (probably because of fuel density or a need for rapid refueling) cleaner. Which is still useful, I guess. Though I'm hoping they won't be necessary at all.

londons_explore 6y ago

Investment into productionizing these kind of advances has pretty much stopped. It's a bit like hard drives... As soon as the SSD arrived, everyone saw that hard drives would eventually die out, so manufacturers pretty much stopped new technology development. Sure, there have been a few small advances, but seek times and data read speeds haven't gone up for a decade, and capacities have only crept up. IC engines are the same. It might take them 30 years to die out, but in those 30 years there won't be any significant tech advances, because every company that makes them is only optimizing for cost in a shrinking market.

Hamuko 6y ago
SSDs have been mainstream products for at least a decade now. Ten years ago, the largest HDD we had was like 2 TB. We currently have 16 TB HDDs and people are expecting us to have 50 TB HDDs in 2026. And not only that, 16 TB HDD is quite affordable. Just 500 dollars for a Seagate IronWolf. Meanwhile a 3.2 TB Seagate Nytro will set you back about $1800. SSD mass storage is an option for only those with deep pockets. Hell, not even tape drives have gone away yet. Amazon Glacier is just one example.
- pg-gadfly 6y ago
  It's also to note that SSD capacity hasn't strictly improved, it's been gained through massive compromises that severely impact their lifetime and performance. More than that, a 5 year old nas drive can outperform a modern cheap ssd in throughput easily.
  - wtallis 6y ago
    Most, but not all of the capacity and affordability increases of SSDs have been due to compromises elsewhere. If you plot the characteristics of "the cheapest flash you can buy" over the years, few of the curves are monotonic. Physical memory cell dimensions decreased steadily until the arrival of 3D NAND, whereupon cell sizes jumped back up and have been relatively stable since. SSDs incorporate more advanced error correction with each generation of controllers, so today's drives can get more usable write endurance out of the same physical cell size. Number of bits that can be stored per cell has been increasing. Each time we cram another bit into each memory cell, performance and write endurance drop. But in between those major shifts, successive generations of flash tend to get faster and more energy-efficient over time. Today's 3 bit per cell TLC NAND is much faster than the TLC from 5 years ago, and has better write endurance thanks to the transition to 3D NAND. Today's SLC NAND has comparable performance and write endurance to the planar SLC that disappeared from the market over 5 years ago, but now it's several times cheaper. And most of the compromises that have been made with NAND flash over the past 10+ years are purely academic. The vast majority of use cases do not need flash rated for 100k P/E cycles, and excess endurance beyond your needs provides no tangible benefit. Most of the endurance that has theoretically been sacrificed was never needed in the first place. Most of the performance lost has been offset by using more flash in parallel and by eliminating bottlenecks elsewhere. The only metric by which a 5 year old NAS hard drive—or any hard drive—will outperform a modern cheap SSD is in long-term sustained sequential write throughput. Even the slowest modern cheap SSD will offer at least twice the sequential read throughput, and orders of magnitude better random read or write throughput. And it's not like the write throughput of modern SSDs is abysmal: gigabit Ethernet is a more significant bottleneck when filling a 1TB or larger dirt-cheap consumer SSD. So unless you're trying to use cheap consumer SSDs in an expensive NAS with 10GbE, the poor write performance of low-end SSDs won't come into play.

sanatgersappa 6y ago

How dare you!

tyho 6y ago

Boring. Even an IC engine operating at the Carnot limit would still emit carbon. Convert every IC on earth to a one with theoretically perfect efficiency and we still blast past 1.5deg warming in a few decades.

ReticentVole 6y ago
Plus the cognitive impacts of higher CO2, plus ocean acidification, plus the noise and pollution being exhausted at ground level inside cities, plus supporting barbaric regimes that mine the oil. Just scrap it all and go full electric. Coming out of COVID lockdown is a great time to invest and mandate.
baq 6y ago
Many people can’t believe that if we improve IC engines a couple percent a year we’ll be at the Carnot limit in a few decades.
rootusrootus 6y ago
We're an awful long way from having battery storage on par with liquid energy storage, and battery tech improves steadily but not exponentially. Having good IC engine designs is going to be important for decades. We will need to start generating liquid fuel that is carbon neutral.

trhway 6y ago

It is basically a split cycle engine and the "New" is a bit overblown by more than 100 years. Even similar non-spark based hot ignition was used back then: https://en.wikipedia.org/wiki/Split_cycle_engine https://en.wikipedia.org/wiki/Split_cycle_engine "The Backus Water Motor Company of Newark, New Jersey was producing an early example of a split cycle engine as far back as 1891. The engine, of "a modified A form, with the crank-shaft at the top", was water-cooled and consisted of one working cylinder and one compressing cylinder of equal size and utilized a hot-tube ignitor system."

avhon1 6y ago
The Backus engine shares the pre-compressor piston with this design, but this engine also has the pre-pre-compressor piston (with different geometry) and also the low-pressure power piston. It seems to still be novel, despite sharing characteristics with previous designs.
throwaway0a5e 6y ago
"Fuel injection has been tried for 50yr, there's no way it will be commercially successful now" -some guy in 1980. History is littered with inventions that didn't gain widespread use initially then some little advancement(s) came along that make the inventions workable when revisited and tweaked. Repeating firearms and electric lightbulbs are two good examples. I don't pretend to know which bucket this "new" engine advancement will fit into but I think your judgement is premature.
- jacquesm 6y ago
  Bosch fuel injection was commercialized in 1967.
  - throwaway0a5e 6y ago
    You're not wrong but to imply that Boch fuel injection was successful would be to wear some really rose colored glasses. Boch fuel injection was such a small improvement over contemporary cabruerators and such a downgrade in terms of maintenance and cost of ownership that it was more or less universally reviled by everyone who was not into technology for technology's sake. It never really achieved widespread use. If you wanted a glass half full perspective you could say it gave 1st generation throttle body based injector systems a low bar to exceed. Bosch mechanical fuel injection is almost a perfect example of an implementation of a technology not ready for mass market adoption that later became ready for mass market with the advent of new technology (cheap digital electronics in this case).

avhon1 6y ago

All of the skeptical comments I've read here are talking about how ICE are already obsolete, since electric cars are cleaner, quieter, and simpler. I'm picturing this engine being used in other applications (even though the website, and the journal the engine is publushed in, are automotive). Stationary generators and marine drivetrains come to mind. Those are less sensitive to the greater size and weight that this engine might have, and they benefit greatly from the ability to load fuel, store it, burn it as needed, and be refueled at any time, even while running. As an example, my local university's datacenter has two rooms full of batteries for power backup. They instantly switch on, but can only power the datacenter for a short time. To protect against extended blackouts, there are two redundant diesel generators in the sub-basement, and enough fuel to run the datacenter for several months. Battery technology seems to have a ways to go before it'll be worthwhile to just have a basement full of batteries as long-term backup power. People with those sorts of use cases are probably going to be relying on ICEs for a long time to come. In the meanwhile, efficiency improvements can make them less harmful to own and operate. And even after 150 years of developing ICEs, engineers are still coming up with ideas, maybe even practical ones, to gain those improvements.

cameldrv 6y ago
Flow batteries are a possible solution. Energy density is substantially less though, so they may not be practical for applications where the battery is only rarely used.
- avhon1 6y ago
  The development of flow batteries with lightweight, inexpensive electrodes and efficient, dense electrolytes would definitely change the situation a lot. Fuel would be pumpable again, and you could transfer large amounts energy without it being integrated with the catalyst that can unsafely release all of that energy.
- barbegal 6y ago
  Whats the advantage of a flow battery over a fuel cell which has higher energy density?

otagekki 6y ago

Is this patented?

imdoor 6y ago

The theoretical efficiency gain appears to be greater than the stated 14%. The article cites a video [1] which in turn cites 49% vs 63% maximum theoretical thermal efficiency for a traditional engine and for the Entry Ignition engine, respectively. That makes it a 14 percentage point increase which is 29% increase in efficiency. [1] https://www.youtube.com/watch?v=oiUnqlGzLw8 https://www.youtube.com/watch?v=oiUnqlGzLw8

ksec 6y ago
Thank You I had the exact same question in mind. ~30% increase is a lot. I wonder how much more efficiency can we continue to squeeze out from ICE?

russellbeattie 6y ago

I'm not sure which is worse, YouTube videos where all they do is summarize a written news article, or a written news article summarizing a YouTube video...

avhon1 6y ago
I'm pleased with a YouTube video that visually, verbally, and efficiently explains the contents of a paper that costs $33 to read.
mdszy 6y ago
If you've never watched Engineering Explained, I'd recommend it highly. It's very high-quality content that deeply explains how engines and other components in cars work. The video was released well before the article, and I believe the article was posted to spread the video more widely.

Jemm 6y ago

All this debate of electric vs internal combustion when the article is about a theoretical design that has yet to be proven.

ReactiveJelly 6y ago
Only Consumer Reports can tell us which car is better: One with batteries that don't exist, or one with a gas engine that doesn't exist

taylodl 6y ago

Jason Fenske's Engineering Explained is an excellent YT channel. I especially enjoy his physics for gearheads.

mrfusion 6y ago

So how does this efficiency compare to gas turbines? Should gas power plants switch to this if it pans out? Or it might be good for portable generators. Does two stroke mean it won’t need oil changes?

johnatwork 6y ago
This particular two stroke would need oil changes. Some of the traditional ones did not because the oil was mixed with fuel to lubricate the seals that exist between the piston (part that moves up and down) and the cylinder (which houses the piston). In most engines that we refer to in cars, the lubrication happens from the bottom in the crankcase (where you see the rod beneath the piston).
rootusrootus 6y ago
> Does two stroke mean it won’t need oil changes? This is not the same kind of two-stroke engine. The one you're thinking of pumps the fuel air mixture through the crankcase, which is why it cannot use the same oiling system that a typical four-stroke engine does. The oil would be diluted with fuel pretty quickly, and also carried into the combustion chamber and burned off. So adding the oil to the fuel is how you get around that, but then you're constantly burning oil.

liammonahan 6y ago

Isn’t this much like how Diesel engines work? They compress air first to heat it to the point that when mixed with fuel it spontaneously ignites. Maybe glow plugs can make a comeback.

gsnedders 6y ago
In the diesel case, fuel is immediately at its auto-ignition temperature when introduced. In this, the air-fuel mixture is heated until it reaches its auto-ignition temperature.
dghughes 6y ago
Diesel engines are based off a south Pacific people's invention who used a bamboo tube with piston to ignite a sliver of wood. Rudolph used it as inspiration for his engine design. He also intended the fuel for it to be peanut oil or canola oil a crop farmers could grow for their tractors. Glow plugs are still here sort of although now a heating grid. My diesel truck has it to pre-heat the air to make starting easier.
fnordfnordfnord 6y ago
It sounds somewhat similar to a supercharged two-stroke design like the formerly very popular Detroit Diesels (8V71, 6V92TA, for example). None of those engines were very efficient though. Also, glow plugs are only used for starting.

thrower123 6y ago

I am relatively certain that people will be rebuilding old Detroit and Cummins diesel engines in heavy equipment for at least the next 50 years, if not 100. I have been surprised at how much 40V/80V electric systems are cutting into what was traditionally two-stroke light engines for string trimmers and mowers. The batteries are expensive though, and I don't know how many you'd need to have in rotation to be able to keep one fully charged and ready to go under continuous usage.

fnordfnordfnord 6y ago
The batteries are expensive but when you factor the cost of fuel + oil and the hassle of dealing with it, the case for batteries doesn't look as bad.
mikestew 6y ago
For the weed trimmer and lawn mower I purchased at U. S. chain Lowes, the magic number of batteries is 3. The mower came with 2, and the trimmer with 1. The charger can charge a battery almost as fast as the mower can consume them, so the third is needed for a little slack. You could get by with only two if you're content to get a beverage between batteries. Theoretically, anyway; with our tiny yard this is seldom tested. Which why I'm annoyed by neighbors that buy a new gas-powered mower. There is not a yard within at least a 3 mile radius of me that can't be mowed by a modern, lithium-battery push mower.
vardump 6y ago
> ...I don't know how many you'd need to have in rotation... My lawn mower 5Ah @56V (EGO power) is good for half an hour. It charges from empty to full in maybe 40 minutes. In a trimmer same battery seems to last forever, maybe at least 2 hours.

mrfusion 6y ago

I just watched the video. Can anyone answer these questions? What prevents the burning from getting into the mixing chamber? It seems like the sliding valve is open while it’s burning. And there’s higher pressure in the cylinder. What prevents the mixing chamber gas from getting into the compression reservoir?

MontagFTB 6y ago
I can’t answer the second question, but as to the first my understanding from the video is that the ignition cylinder starts out as much lower pressure that the fuel/air chamber, and as the slide valves open the mixture naturally moves from high to low pressure. The heat contained within the cylinder starts the ignition of the mixture upon entry (hence the name of the engine). I don’t understand how the heat differential between the injection and ignition phases is so great that ignition happens as the slide valve opens, but so little that ignition doesn’t happen within the fuel injection chamber. Perhaps the pressure differential regulates that as well?
deleted 6y ago
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Dumblydorr 6y ago

Our climate doesn't care if the engine is 14% more efficient. That is still vastly too much carbon emission for people or goods to move from A to B. Consider every time any ICE engine moves anything, those emissions will warm the planet for millennia. We can not afford to use these destructive engines, even though fossil fuel interests make them slightly less damaging. We must have a sustainable transport system, which ultimately means using non-fossil derived fuel. That means way way better batteries, fuel cells, or other up and coming solutions. Any iteration on ICE is just kicking the can down the road.

opwieurposiu 6y ago

Right before jet engines took over the military aviation market, you saw some very complex, high efficiency piston engines. Mechanical marvels they were, only now are automotive engines catching up in performance. Ultimately they were all commercial failures, the jet engine had a lot more headroom for improvement and was mechanically much simpler. https://en.wikipedia.org/wiki/Napier_Nomad https://en.wikipedia.org/wiki/Napier_Nomad

throwaway894345 6y ago
I've noticed a very general principle here. Things which are 'before their time' obviously tend to fail, but the interesting bit IMO is that 'before their time' often means "the problem isn't yet constrained such that the efficiencies afforded by the design are economically significant". I think this explains why so much software (my branch of engineering) is miserably inefficient and bug-ridden despite the fact that we have technology to improve efficiency and quality by several orders of magnitude (at a relatively modest cost)--the economic context simply doesn't place a very high value on efficiency and quality, presumably because the market is comparing software against the many, many orders of magnitude worse performance afforded by humans. Perhaps all of this is obvious to many others; it's interesting and novel to me, anyway.

deleted 6y ago

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chrismartin 6y ago

It looks like the slider valve is surrounded on all sides by hot air-fuel mixture and combustion gas. Will the fingers of the slider valve need to be lubricated? Might they be lubricated without consuming (burning) excessive oil (with consequent increase of emissions)?

hinkley 6y ago

I recall years ago when someone had rediscovered sleeve valves and was going to apply them to small displacement 4 cycles in order to get the weight down to be more competitive with 2 cycle engines. It wasn't clear that the article author was aware of them either (and in fact I don't think I'd heard of them until the movie Sahara)

hinkley 6y ago

A 2-stroke engine has one ignition per revolution per cylinder. A 4 stroke engine has half an ignition per revolution per cylinder (or two revolutions per ignition). This engine has only one combustion chamber for every four cylinders, which means that it experiences one quarter of an ignition per revolution per cylinder. It's not a 4-stroke, clearly, but I don't see how you can get away with calling it a 2-stroke either. The strokes kind of become beside the point, but if I had to I might want to call this an 8-stroke engine. I see them pilfering ideas from this for 'simpler' engines. That valve design feels like it could be used for about anything. I've seen other engine designs that use a single intake chamber, so that part has in fact already been done before. That recuperation chamber trick I think could be applied to a traditional 4-stroke engine, which you would need every other cycle and therefore could share with another cylinder (opposed by a full revolution, which I hear at least a few 4 cylinders do). And something similar could be applied on the intake side (although you might have to use the ignition cylinder for the second compression) and then fully half of your cylinders fire.

rurban 6y ago

So a multi-chamber diesel. Why should more chambers be more efficient than the single chamber diesel engine? Because per revolution you get double self-ignitions, at the cost of more room and more gas moving around. Hmm, not bad. Bad reminds me on the Wankel. Only better in theory.

arh68 6y ago
I'm not sure this [1] is what you're talking about but it reminded me of reading about pre-combustion chambers in diesel cylinders. Interesting stuff. [1] https://en.wikipedia.org/wiki/Indirect_injection#Classification_of_indirect_combustion_chambers https://en.wikipedia.org/wiki/Indirect_injection#Classificat...
- rurban 6y ago
  Not really interesting. That's from the pre-BOSCH direct injection area. Modern diesel engines are far more efficient than that.