5 ms·

weight of diesel piston engines

54 points by mpweiher 4y ago

prottog 4y ago
Surprising that there's still that much efficiency to be squeezed out of internal combustion engines!
- Animats 4y ago
  Yes. Makes you wonder how real this is. And how long it lasts. The military might want it for drones. Even if it's only good for an hour, that's a good survival time in modern combat.
  - smcleod 4y ago
    I think it probably is real, Mazda has a new single rotor engine they've got in the new MX30 hybrid, it's used to extend the range https://www.drive.com.au/news/2023-mazda-mx-30-r-ev-revealed/ https://www.drive.com.au/news/2023-mazda-mx-30-r-ev-revealed...
  - wongarsu 4y ago
    They mention "the XTS-210 engine addresses the fuel efficiency, lubrication, and fuel type limitations of the traditional Wankel rotary engine", but while they quote great fuel compatibility, don't waste more words on efficiency and lubrication. So just based on the marketing fluff I expect those two points to still be worse than traditional diesel engines, just good enough for military applications. And given the other advantages the military might be completely ok with a fuel-guzzling hard-to-maintain engine for certain applications, wouldn't be the first time
    - Phlarp 4y ago
      Adding in the 2 stroke design and wide ranging fuel compatibility to the above military centric specs, I have to imagine the emissions profile is truly stunning.
    - inferiorhuman 4y ago
      Dollars to donuts the rotary will be easier to manufacture and maintain than the diesel. It's got fewer parts and the parts themselves are way simpler. Lubrication's easy if you don't care about efficiency or emissions, which the military doesn't.
      - nine_k 4y ago
        The military does care about efficiency: higher efficiency means longer range, as we seem to be talking about aircraft / rotocraft applications. Higher wear is what they care less about: at peacetime, parts can be replaced more often, and at wartime, many will be destroyed before spending up the spec-dictated operation hours.
        inferiorhuman 4y ago
        Right - they care about range, fuel efficiency is secondary at best. WRT this engine, it's too small for anything but a small-mid sized drone. In that context the specific fuel consumption is likely less of an issue as there's some pretty hefty weight and size savings over the comparable piston engine (and they're claiming better fuel efficiency). The issue with the parts isn't higher wear, it's simplicity. Look at the strain that Ukraine has put on military supply chains. Now take a look at what's involved in building a diesel engine versus a rotary. The rotary engine is a few relatively simple castings*, a piston engine has a ton of small, complex parts. There's no mention if they comparable diesels are two or four stroke, but take a look at a four stroke injection pump and how complex they are (inline pumps are basically mini piston engines). Then take a look at the LiquidPiston motor – at least on one variant they're using the crankshaft for fuel and air delivery. Pretty much everything about it is simpler than a comparable piston engine, and when you've gotta scale up wartime production simpler is better. * okay so it looks like LiquidPiston is milling everything for the time being.
        nine_k 4y ago
        This is right; the simpler, the cheaper and faster to make, and often the harder to break. Very important in the military. Delivering fuel and lubrication via the crankshaft is not uncommon in aircraft motors, or was at times of WWII at least. Delivering air this way is indeed novel and impressive.
- deleted 4y ago
  [deleted]
- bluGill 4y ago
  They are squeezing small size out, not efficiency. You can get more power from a small engine, but you trade long term reliability when you do.
IronWolve 4y ago
My twitter ads have been flooded by this company liquid piston, it looks cool, but if the use case is to replace small engines also, I need to see a drop in crate replacement for a honda or cheap chinese motor for a generator/atv/scooter. I love tote-goats, they use the old 5hp engines, if I could get a diesel version that I could use (for farm use and cheap diesel), count me in if it works.
- Zak 4y ago
  Do the ads want you to buy engines, or invest in the company? Last time[0] I saw this on HN, it appeared very targeted toward military UAV applications rather than anything most consumers would have a use for. [0] https://news.ycombinator.com/item?id=35455286 https://news.ycombinator.com/item?id=35455286
  - IronWolve 4y ago
    Just got one NOW, yes invest. They are still paying to promote their product. 630.7K views, https://twitter.com/LiquidPiston/status/1625932968865693718 https://twitter.com/LiquidPiston/status/1625932968865693718
    - Zak 4y ago
      "The first major innovation to the internal combustion engine in over 100 years" claimed there suggests they're not familiar with the Wankel rotary engine upon which their design is based; the modern eccentric shaft version first ran in 1958.
      - ilyt 4y ago
        It's not just another wankel engine tho, it's significant modification to the idea and comes with few interesting improvements (and some other drawbacks). Basically, the intake and exhaust is delivered thru the rotor, not ports on the sides, and the seals (the achilles heel of the wankel engines are on the outside of it which in theory would make it possible to both replace them without taking apart whole engine, and oil them directly, without putting oil into fuel. The bad part of it is that it would probably be pretty hard to make multi-rotor one
huijzer 4y ago
So the big question is: what’s the fuel efficiency of this thing?
- atlex2 4y ago
  For things that fly, what I’ve seen be more significant is the weight savings (as long as you’re not running too rich).
deleted 4y ago
[deleted]
decafninja 4y ago
Haven't rotary (Wankel?) engines proven to be unreliable? I love the RX-7 (my dream is to own a FD one day), but IIRC even the more refined Renesis engine on the RX-8 seems to have been proven to be ornery. I think Mazda has a rotary acting as a range extender in their MX-30 EV. I wonder how that will fare.
- ilyt 4y ago
  Kinda, kinda not, they have been proven to be vulnerable to mishandling. They have few quirks and require a bit different handling than normal engine, which means that someone treating it as any other car. But at some point it will need to have engine out job and replace apex seals. In motorsports it proven to be very reliable for example. > IIRC even the more refined Renesis engine on the RX-8 seems to have been proven to be ornery. Renesis was evolution in performance but IIRC had some quirks that weren't solved because the car stopped being produced. IIRC the modern apex seals with modern materials do a pretty good job. It also have oil metering pump which just...stole the engine oil and put it into fuel (which was required to oil the seals), which means if you were not on top of filling oil up, you could end up starving the engine. It wasn't a good idea either as 2 stroke oil was better for that use case, so many people removed the metering pump and just added some 2 stroke to the fuel tank every time they filled up
  - 20after4 4y ago
    The oil metering pump was a simple mechanical device on Mazda Wankel engines up to ~1991 (the first and second generation rx-7, and I presume other models in Japan.) This was replaced by an electronically controlled pump on all the later models. The advantage of electronic control is that it conserves oil at low RPM. Unfortunately, the reliability of the pump (and the wiring) became a problem. With the RX-8, they had to dial back the oil supply to meet modern emissions regulations and this lead to premature wear to a lot of engines. I believe this contributed heavily to dwindling sales and ultimately to the decision to discontinue the RX-8 in 2012.
    - ilyt 4y ago
ChuckMcM 4y ago
This is a pretty cool engine. 25hp is about 18.75 kW so a really good fit for a 15kW generator (sometimes marketed as "whole house" generators) its high RPM (typical of rotary engines) makes it a good match foundation for a turboprop engine. A pair of these driving ducted fan turboprop engines would give you an excellent long duration drone platform with good payload capacity. My guess is the Army might be considering them as APUs (Auxiliary power units) on armored vehicles as this would give them long duration "sitting" capability without running the main power plant (but using the same fuel). Similarly bus style RVs could use them to run their in-vehicle electric gear (not a lot of bus RVs are designed for the "dry camping" or boon docking market but it would definitely work well for that. The next thing they have to figure out I'm guessing is how to make them inexpensively (the Army won't care so much but I don't think the company would survive on just Army contracts).
- skykooler 4y ago
  This would definitely be interesting in an RV, it's way more compact than engines in similarly powerful generators in a vehicle where space is at a premium - and the ability to run off the same diesel fuel as the main engine is a huge plus.
- inamberclad 4y ago
  Nit: it's not a turboprop if it's no longer using a turbine.
  - magila 4y ago
    It's also not a turboprop if it's using a ducted fan. Chuck keeps using that word, I do not think it means what he thinks it means.
    - mjevans 4y ago
      Benefit of doubt; they're likely using it as shorthand for 'equivalent to turboprop style/class engine' as an established feature set to have a drop in alternative to.
    - 4y ago
throw2awaymay 4y ago
[dead]
joecool1029 4y ago
I wish they had video of the two-stroke design in operation. There's a bunch of their 4-stroke engines being demonstrated by this youtube channel: https://www.youtube.com/watch?v=TDFAjCOM3iQ https://www.youtube.com/watch?v=TDFAjCOM3iQ This one is interesting as it shows difference between their 4-stroke design and a standard wankel rotary in operation, wondering if the two-stoke variation looks like a combination between the two?
- ilyt 4y ago
  It's rotary. There are no strokes in it.
  - kube-system 4y ago
    The manufacturer calls it a two-stroke. Due to the ubiquity of piston engines most people use "two-cycle" and "two-stroke" interchangeably.
    - ilyt 4y ago
      It's a comparision to the two stroke cycle. There is no four stroke equivalent for rotaries
toss1 4y ago
This is more hype than performance. When I worked on a hybrid-power multirotor drone about eight years ago, I was checking out Wankel engines for their power-weight ratio, and also came across this Liquid Piston crew. They were supposedly ready to ship Real Soon Now. But worse, their power-weight just didn't compare to Wankel options available then. Liquid Piston still do not compare on their headline power-weight ratios. They make a lot of claims about 25 HP (18.6kW) and light weight, but don't actually mention the weight, which is down in their spec sheet - 21.2kg dry [0], which is about 0.877kW/kg. By comparison, just a quick search of small Wankels turns up these: -- AIE model 225CS outputting 40 bhp / 30kW weighing 10kg = 3.0 kW/kg[1] -- AIE model 80S outputting 15 bhp / 11.2kW weighing 5kg = 2.24 kW/kg [2] -- Sorrel Hiperlight Wankel outputting 75 hp / 56 kW weighing 52kg (fully wet with all electric start, reduction drive, and exhaust system, etc. = 1.07 kW/kg [3] -- Crighton CR700W motorcycle engine puts out 220 hp / 164 kW weighing 43kg = 3.8 kW/kg. [4] -- Small Nitto NR20-EP puts out 2.24kW / ~3hp weighing 1.466 kg = 1.53 kW/kg. [5] In short, this is a lot of marketing hype for low pefrofrmance, and they've been working on it since 2003 according to their website. The sole advantage this engine might have is running on a broader range of fuels including JP-8, but I've seen Wankels setup for a wide fuel range also. If I had a funded task to develop a high power-weight engine, I'd start with the Wankel design, not this one. It is already WAAAY ahead, and there's still a lot of performance left on the table. [0] https://uploads-ssl.webflow.com/5f6086e9bbbabd41a20f2984/6427fdcf5c4c4c3d073e9bc4_LPI%20Brochure%2020230331.pdf https://uploads-ssl.webflow.com/5f6086e9bbbabd41a20f2984/642... [1] https://www.aieuk.com/225cs-40bhp-wankel-rotary-engine/ https://www.aieuk.com/225cs-40bhp-wankel-rotary-engine/ [2] https://www.aieuk.com/80s-15bhp-wankel-rotary-engine/ https://www.aieuk.com/80s-15bhp-wankel-rotary-engine/ [3] http://www.ultralightnews.com/sunfun99/hiperlight.html http://www.ultralightnews.com/sunfun99/hiperlight.html [4] https://newatlas.com/motorcycles/dual-rotary-crighton-cr700w-motorcycle/ https://newatlas.com/motorcycles/dual-rotary-crighton-cr700w... [5] https://barnardmicrosystems.com/UAV/engines/wankel.html https://barnardmicrosystems.com/UAV/engines/wankel.html
- majou 4y ago
  How much does that metric matter? Especially in the context of hybrids with regenerative braking. For comparison a Model S weighs over 4,500 lbs.
metadat 4y ago
Also discussed 24 days ago: "Inside-out Wankel" rotary engine delivers 5X the power of a diesel https://news.ycombinator.com/item?id=35455286 https://news.ycombinator.com/item?id=35455286 (203 comments)
thomasjb 4y ago
This would be great for making a light sporting cyclecar around, a category of vehicle that's been sadly neglected this last 100 years.
- nine_k 4y ago
  The problem of (very) light cars is that they can't be strong enough to pass crash tests. 100 years ago regulations around that barely if at all existed.
ilyt 4y ago
That would make cool small dual-sport/dirtbike, super-light and "put anything flammable in the tank".
gnabgib 4y ago
Previously [Efficient Rotary Engine Lands Million-Dollar Darpa Contract](https://news.ycombinator.com/item?id=9431379 https://news.ycombinator.com/item?id=9431379) 76 points, 44 comments, 8 years ago [LiquidPiston: Efficient rotary engine](https://news.ycombinator.com/item?id=11995735 https://news.ycombinator.com/item?id=11995735) 87 points, 20 comments, 7 years ago [LiquidPiston's “inside-out” rotary X-Engine wins Army research contract](https://news.ycombinator.com/item?id=25450477 https://news.ycombinator.com/item?id=25450477) 278 points, 130 comments, 2 years ago [“Inside-out Wankel” rotary engine delivers 5X the power of a diesel](https://news.ycombinator.com/item?id=35455286 https://news.ycombinator.com/item?id=35455286) 255 points, 196 comments, 24 days ago
alsaaro 4y ago
Why did it take them nearly 30 million in grants and 20 years to just now speak about delivering a prototype next year. Engines can be prototyped on the time scale of months not decades. Now they are soliciting the public to "invest" in their business.

54 points by mpweiher 4y ago

prottog 4y ago

Surprising that there's still that much efficiency to be squeezed out of internal combustion engines!

Animats 4y ago
Yes. Makes you wonder how real this is. And how long it lasts. The military might want it for drones. Even if it's only good for an hour, that's a good survival time in modern combat.
- smcleod 4y ago
  I think it probably is real, Mazda has a new single rotor engine they've got in the new MX30 hybrid, it's used to extend the range https://www.drive.com.au/news/2023-mazda-mx-30-r-ev-revealed/ https://www.drive.com.au/news/2023-mazda-mx-30-r-ev-revealed...
- wongarsu 4y ago
  They mention "the XTS-210 engine addresses the fuel efficiency, lubrication, and fuel type limitations of the traditional Wankel rotary engine", but while they quote great fuel compatibility, don't waste more words on efficiency and lubrication. So just based on the marketing fluff I expect those two points to still be worse than traditional diesel engines, just good enough for military applications. And given the other advantages the military might be completely ok with a fuel-guzzling hard-to-maintain engine for certain applications, wouldn't be the first time
  - Phlarp 4y ago
    Adding in the 2 stroke design and wide ranging fuel compatibility to the above military centric specs, I have to imagine the emissions profile is truly stunning.
  - inferiorhuman 4y ago
    Dollars to donuts the rotary will be easier to manufacture and maintain than the diesel. It's got fewer parts and the parts themselves are way simpler. Lubrication's easy if you don't care about efficiency or emissions, which the military doesn't.
    - nine_k 4y ago
      The military does care about efficiency: higher efficiency means longer range, as we seem to be talking about aircraft / rotocraft applications. Higher wear is what they care less about: at peacetime, parts can be replaced more often, and at wartime, many will be destroyed before spending up the spec-dictated operation hours.
      - inferiorhuman 4y ago
        Right - they care about range, fuel efficiency is secondary at best. WRT this engine, it's too small for anything but a small-mid sized drone. In that context the specific fuel consumption is likely less of an issue as there's some pretty hefty weight and size savings over the comparable piston engine (and they're claiming better fuel efficiency). The issue with the parts isn't higher wear, it's simplicity. Look at the strain that Ukraine has put on military supply chains. Now take a look at what's involved in building a diesel engine versus a rotary. The rotary engine is a few relatively simple castings*, a piston engine has a ton of small, complex parts. There's no mention if they comparable diesels are two or four stroke, but take a look at a four stroke injection pump and how complex they are (inline pumps are basically mini piston engines). Then take a look at the LiquidPiston motor – at least on one variant they're using the crankshaft for fuel and air delivery. Pretty much everything about it is simpler than a comparable piston engine, and when you've gotta scale up wartime production simpler is better. * okay so it looks like LiquidPiston is milling everything for the time being.
        nine_k 4y ago
        This is right; the simpler, the cheaper and faster to make, and often the harder to break. Very important in the military. Delivering fuel and lubrication via the crankshaft is not uncommon in aircraft motors, or was at times of WWII at least. Delivering air this way is indeed novel and impressive.
deleted 4y ago
[deleted]
bluGill 4y ago
They are squeezing small size out, not efficiency. You can get more power from a small engine, but you trade long term reliability when you do.

IronWolve 4y ago

My twitter ads have been flooded by this company liquid piston, it looks cool, but if the use case is to replace small engines also, I need to see a drop in crate replacement for a honda or cheap chinese motor for a generator/atv/scooter. I love tote-goats, they use the old 5hp engines, if I could get a diesel version that I could use (for farm use and cheap diesel), count me in if it works.

Zak 4y ago
Do the ads want you to buy engines, or invest in the company? Last time[0] I saw this on HN, it appeared very targeted toward military UAV applications rather than anything most consumers would have a use for. [0] https://news.ycombinator.com/item?id=35455286 https://news.ycombinator.com/item?id=35455286
- IronWolve 4y ago
  Just got one NOW, yes invest. They are still paying to promote their product. 630.7K views, https://twitter.com/LiquidPiston/status/1625932968865693718 https://twitter.com/LiquidPiston/status/1625932968865693718
  - Zak 4y ago
    "The first major innovation to the internal combustion engine in over 100 years" claimed there suggests they're not familiar with the Wankel rotary engine upon which their design is based; the modern eccentric shaft version first ran in 1958.
    - ilyt 4y ago
      It's not just another wankel engine tho, it's significant modification to the idea and comes with few interesting improvements (and some other drawbacks). Basically, the intake and exhaust is delivered thru the rotor, not ports on the sides, and the seals (the achilles heel of the wankel engines are on the outside of it which in theory would make it possible to both replace them without taking apart whole engine, and oil them directly, without putting oil into fuel. The bad part of it is that it would probably be pretty hard to make multi-rotor one

huijzer 4y ago

So the big question is: what’s the fuel efficiency of this thing?

atlex2 4y ago
For things that fly, what I’ve seen be more significant is the weight savings (as long as you’re not running too rich).

deleted 4y ago

[deleted]

decafninja 4y ago

Haven't rotary (Wankel?) engines proven to be unreliable? I love the RX-7 (my dream is to own a FD one day), but IIRC even the more refined Renesis engine on the RX-8 seems to have been proven to be ornery. I think Mazda has a rotary acting as a range extender in their MX-30 EV. I wonder how that will fare.

ilyt 4y ago
Kinda, kinda not, they have been proven to be vulnerable to mishandling. They have few quirks and require a bit different handling than normal engine, which means that someone treating it as any other car. But at some point it will need to have engine out job and replace apex seals. In motorsports it proven to be very reliable for example. > IIRC even the more refined Renesis engine on the RX-8 seems to have been proven to be ornery. Renesis was evolution in performance but IIRC had some quirks that weren't solved because the car stopped being produced. IIRC the modern apex seals with modern materials do a pretty good job. It also have oil metering pump which just...stole the engine oil and put it into fuel (which was required to oil the seals), which means if you were not on top of filling oil up, you could end up starving the engine. It wasn't a good idea either as 2 stroke oil was better for that use case, so many people removed the metering pump and just added some 2 stroke to the fuel tank every time they filled up
- 20after4 4y ago
  The oil metering pump was a simple mechanical device on Mazda Wankel engines up to ~1991 (the first and second generation rx-7, and I presume other models in Japan.) This was replaced by an electronically controlled pump on all the later models. The advantage of electronic control is that it conserves oil at low RPM. Unfortunately, the reliability of the pump (and the wiring) became a problem. With the RX-8, they had to dial back the oil supply to meet modern emissions regulations and this lead to premature wear to a lot of engines. I believe this contributed heavily to dwindling sales and ultimately to the decision to discontinue the RX-8 in 2012.
  - ilyt 4y ago

ChuckMcM 4y ago

This is a pretty cool engine. 25hp is about 18.75 kW so a really good fit for a 15kW generator (sometimes marketed as "whole house" generators) its high RPM (typical of rotary engines) makes it a good match foundation for a turboprop engine. A pair of these driving ducted fan turboprop engines would give you an excellent long duration drone platform with good payload capacity. My guess is the Army might be considering them as APUs (Auxiliary power units) on armored vehicles as this would give them long duration "sitting" capability without running the main power plant (but using the same fuel). Similarly bus style RVs could use them to run their in-vehicle electric gear (not a lot of bus RVs are designed for the "dry camping" or boon docking market but it would definitely work well for that. The next thing they have to figure out I'm guessing is how to make them inexpensively (the Army won't care so much but I don't think the company would survive on just Army contracts).

skykooler 4y ago
This would definitely be interesting in an RV, it's way more compact than engines in similarly powerful generators in a vehicle where space is at a premium - and the ability to run off the same diesel fuel as the main engine is a huge plus.
inamberclad 4y ago
Nit: it's not a turboprop if it's no longer using a turbine.
- magila 4y ago
  It's also not a turboprop if it's using a ducted fan. Chuck keeps using that word, I do not think it means what he thinks it means.
  - mjevans 4y ago
    Benefit of doubt; they're likely using it as shorthand for 'equivalent to turboprop style/class engine' as an established feature set to have a drop in alternative to.
  - 4y ago

throw2awaymay 4y ago

[dead]

joecool1029 4y ago

I wish they had video of the two-stroke design in operation. There's a bunch of their 4-stroke engines being demonstrated by this youtube channel: https://www.youtube.com/watch?v=TDFAjCOM3iQ https://www.youtube.com/watch?v=TDFAjCOM3iQ This one is interesting as it shows difference between their 4-stroke design and a standard wankel rotary in operation, wondering if the two-stoke variation looks like a combination between the two?

ilyt 4y ago
It's rotary. There are no strokes in it.
- kube-system 4y ago
  The manufacturer calls it a two-stroke. Due to the ubiquity of piston engines most people use "two-cycle" and "two-stroke" interchangeably.
  - ilyt 4y ago
    It's a comparision to the two stroke cycle. There is no four stroke equivalent for rotaries

toss1 4y ago

This is more hype than performance. When I worked on a hybrid-power multirotor drone about eight years ago, I was checking out Wankel engines for their power-weight ratio, and also came across this Liquid Piston crew. They were supposedly ready to ship Real Soon Now. But worse, their power-weight just didn't compare to Wankel options available then. Liquid Piston still do not compare on their headline power-weight ratios. They make a lot of claims about 25 HP (18.6kW) and light weight, but don't actually mention the weight, which is down in their spec sheet - 21.2kg dry [0], which is about 0.877kW/kg. By comparison, just a quick search of small Wankels turns up these: -- AIE model 225CS outputting 40 bhp / 30kW weighing 10kg = 3.0 kW/kg[1] -- AIE model 80S outputting 15 bhp / 11.2kW weighing 5kg = 2.24 kW/kg [2] -- Sorrel Hiperlight Wankel outputting 75 hp / 56 kW weighing 52kg (fully wet with all electric start, reduction drive, and exhaust system, etc. = 1.07 kW/kg [3] -- Crighton CR700W motorcycle engine puts out 220 hp / 164 kW weighing 43kg = 3.8 kW/kg. [4] -- Small Nitto NR20-EP puts out 2.24kW / ~3hp weighing 1.466 kg = 1.53 kW/kg. [5] In short, this is a lot of marketing hype for low pefrofrmance, and they've been working on it since 2003 according to their website. The sole advantage this engine might have is running on a broader range of fuels including JP-8, but I've seen Wankels setup for a wide fuel range also. If I had a funded task to develop a high power-weight engine, I'd start with the Wankel design, not this one. It is already WAAAY ahead, and there's still a lot of performance left on the table. [0] https://uploads-ssl.webflow.com/5f6086e9bbbabd41a20f2984/6427fdcf5c4c4c3d073e9bc4_LPI%20Brochure%2020230331.pdf https://uploads-ssl.webflow.com/5f6086e9bbbabd41a20f2984/642... [1] https://www.aieuk.com/225cs-40bhp-wankel-rotary-engine/ https://www.aieuk.com/225cs-40bhp-wankel-rotary-engine/ [2] https://www.aieuk.com/80s-15bhp-wankel-rotary-engine/ https://www.aieuk.com/80s-15bhp-wankel-rotary-engine/ [3] http://www.ultralightnews.com/sunfun99/hiperlight.html http://www.ultralightnews.com/sunfun99/hiperlight.html [4] https://newatlas.com/motorcycles/dual-rotary-crighton-cr700w-motorcycle/ https://newatlas.com/motorcycles/dual-rotary-crighton-cr700w... [5] https://barnardmicrosystems.com/UAV/engines/wankel.html https://barnardmicrosystems.com/UAV/engines/wankel.html

majou 4y ago
How much does that metric matter? Especially in the context of hybrids with regenerative braking. For comparison a Model S weighs over 4,500 lbs.

metadat 4y ago

Also discussed 24 days ago: "Inside-out Wankel" rotary engine delivers 5X the power of a diesel https://news.ycombinator.com/item?id=35455286 https://news.ycombinator.com/item?id=35455286 (203 comments)

thomasjb 4y ago

This would be great for making a light sporting cyclecar around, a category of vehicle that's been sadly neglected this last 100 years.

nine_k 4y ago
The problem of (very) light cars is that they can't be strong enough to pass crash tests. 100 years ago regulations around that barely if at all existed.

ilyt 4y ago

That would make cool small dual-sport/dirtbike, super-light and "put anything flammable in the tank".

gnabgib 4y ago

Previously [Efficient Rotary Engine Lands Million-Dollar Darpa Contract](https://news.ycombinator.com/item?id=9431379 https://news.ycombinator.com/item?id=9431379) 76 points, 44 comments, 8 years ago [LiquidPiston: Efficient rotary engine](https://news.ycombinator.com/item?id=11995735 https://news.ycombinator.com/item?id=11995735) 87 points, 20 comments, 7 years ago [LiquidPiston's “inside-out” rotary X-Engine wins Army research contract](https://news.ycombinator.com/item?id=25450477 https://news.ycombinator.com/item?id=25450477) 278 points, 130 comments, 2 years ago [“Inside-out Wankel” rotary engine delivers 5X the power of a diesel](https://news.ycombinator.com/item?id=35455286 https://news.ycombinator.com/item?id=35455286) 255 points, 196 comments, 24 days ago

alsaaro 4y ago

Why did it take them nearly 30 million in grants and 20 years to just now speak about delivering a prototype next year. Engines can be prototyped on the time scale of months not decades. Now they are soliciting the public to "invest" in their business.