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The thing that makes this so interesting is that it's a 2-stroke, 3-lobe engine. The traditional wankel being a 4-stroke, 1-lobe. I don't expect emissions to b

The thing that makes this so interesting is that it's a 2-stroke, 3-lobe engine. The traditional wankel being a 4-stroke, 1-lobe. I don't expect emissions to be any good since it's fundamentally a 2-stroke, which is perfect for non-road based applications. I don't think we'll see this on the road... ever.

SamBam 6y ago
Could you explain that last part further?
- irjustin 6y ago
  Really small 2 strokes (like leaf blowers) use mixed oil-fuel which is absolutely terrible for emissions. To make a 2 stroke meet emissions while maintaining its primary gain - thermal efficiency, and matching the power density a lot of complexity is needed. This quora post[0] largely sums that up, but quora is only so trustworthy. [0] https://www.quora.com/Why-arent-2-stroke-engines-used-in-cars https://www.quora.com/Why-arent-2-stroke-engines-used-in-car...
topspin 6y ago
> I don't think we'll see this on the road... ever. It's very small and lightweight, so it could serve as a range extender running a generator in an electric vehicle.
- irjustin 6y ago
  The primary limiting factor is emissions for road cars and 2-strokes. 2 strokes have to go oil-sump + direct injection with supercharger to be able to match a 4 stroke when it comes to maintaining thermal efficiency, match power density while meeting emission standards. All that complexity and the 4 stroke atkinson's cycle looks really attractive again. A huge benefit in of the Atkinson's setup is it can switch back to the Otto seamlesssly and directly drive the car for additional power (i.e Hybrid vehciles) If you can parse through the noise of Quora posts, this highlights above[0]. Tesla won't use it gasoline for range extension - it's against their religion - which I subscribe to. [0] https://www.quora.com/Why-arent-2-stroke-engines-used-in-cars https://www.quora.com/Why-arent-2-stroke-engines-used-in-car...
- faeyanpiraat 6y ago
  Why? It's lighter, so less power is required to move the whole car, so it's fine if it provides less power than a regular diesel. It is also easier and cheaper to make. Is durability and maintenance the real issue?
  - topspin 6y ago
    It has the properties of a two stroke engine. I hesitate to call it a two stroke because that isn't strictly true, apparently. However, it has a narrow power band, like a conventional two stroke. This means that it's a poor engine outside its power band; excessive emissions, inefficient, etc. Inside its power band it can be tuned to be clean and efficient. So using it for constant RPM applications such as a generator can make sense. Using it as the prime mover where a wide power band is needed is a bad choice.
- sudosysgen 6y ago
  Actually, Mazda is already working on doing that, so it's quite likely.
grecy 6y ago
Two strokes don't meet emissions because they use the fuel as a lubricant, which means they have to add oil to the fuel and obviously that doesn't burn cleanly. Does this design require oil in the fuel? Certainly in the case of burning diesel I would expect that alone is a good enough lubricant.
- Tor3 6y ago
  It's not a two stroke, it's a four stroke engine. Or near enough, anyway. It doesn't suffer from the two stroke engine issues.
stickfigure 6y ago
This is not correct. If you watch the video, it clearly shows separate intake, compression, expansion, and exhaust strokes in each lobe.
- irjustin 6y ago
  I'm not 100% on this. I caveat that you still could be right. > https://www.liquidpiston.com/how-it-works https://www.liquidpiston.com/how-it-works At 53 seconds, it shows the intake cycle beginning. In the same lobe, the exhaust & the intake ports are both open or "connected" at the same time, which is the 2-stroke cycle. They need to be 100% isolated and it's not super obvious that they are.
  - stickfigure 6y ago
    Look forward to about 1:48 where they run through the whole sequence, flashing intake/compression/expansion/exhaust on the screen for each stroke. Each chamber has four full strokes. It seems clear that there shouldn't be any overlap between the ports. I'm pretty in awe of the cleverness. Hope it works out.
    - Groxx 6y ago
      Yeah, that later sequence is clearer now that I look at it again. The first one animating both intake gasses (presumably into the intake chamber, not the compression area) and exhaust at the same time was just confusing me for some reason.

SamBam 6y ago

Could you explain that last part further?

irjustin 6y ago
Really small 2 strokes (like leaf blowers) use mixed oil-fuel which is absolutely terrible for emissions. To make a 2 stroke meet emissions while maintaining its primary gain - thermal efficiency, and matching the power density a lot of complexity is needed. This quora post[0] largely sums that up, but quora is only so trustworthy. [0] https://www.quora.com/Why-arent-2-stroke-engines-used-in-cars https://www.quora.com/Why-arent-2-stroke-engines-used-in-car...

topspin 6y ago

> I don't think we'll see this on the road... ever. It's very small and lightweight, so it could serve as a range extender running a generator in an electric vehicle.

irjustin 6y ago
The primary limiting factor is emissions for road cars and 2-strokes. 2 strokes have to go oil-sump + direct injection with supercharger to be able to match a 4 stroke when it comes to maintaining thermal efficiency, match power density while meeting emission standards. All that complexity and the 4 stroke atkinson's cycle looks really attractive again. A huge benefit in of the Atkinson's setup is it can switch back to the Otto seamlesssly and directly drive the car for additional power (i.e Hybrid vehciles) If you can parse through the noise of Quora posts, this highlights above[0]. Tesla won't use it gasoline for range extension - it's against their religion - which I subscribe to. [0] https://www.quora.com/Why-arent-2-stroke-engines-used-in-cars https://www.quora.com/Why-arent-2-stroke-engines-used-in-car...
faeyanpiraat 6y ago
Why? It's lighter, so less power is required to move the whole car, so it's fine if it provides less power than a regular diesel. It is also easier and cheaper to make. Is durability and maintenance the real issue?
- topspin 6y ago
  It has the properties of a two stroke engine. I hesitate to call it a two stroke because that isn't strictly true, apparently. However, it has a narrow power band, like a conventional two stroke. This means that it's a poor engine outside its power band; excessive emissions, inefficient, etc. Inside its power band it can be tuned to be clean and efficient. So using it for constant RPM applications such as a generator can make sense. Using it as the prime mover where a wide power band is needed is a bad choice.
sudosysgen 6y ago
Actually, Mazda is already working on doing that, so it's quite likely.

grecy 6y ago

Two strokes don't meet emissions because they use the fuel as a lubricant, which means they have to add oil to the fuel and obviously that doesn't burn cleanly. Does this design require oil in the fuel? Certainly in the case of burning diesel I would expect that alone is a good enough lubricant.

Tor3 6y ago
It's not a two stroke, it's a four stroke engine. Or near enough, anyway. It doesn't suffer from the two stroke engine issues.

stickfigure 6y ago

This is not correct. If you watch the video, it clearly shows separate intake, compression, expansion, and exhaust strokes in each lobe.

irjustin 6y ago
I'm not 100% on this. I caveat that you still could be right. > https://www.liquidpiston.com/how-it-works https://www.liquidpiston.com/how-it-works At 53 seconds, it shows the intake cycle beginning. In the same lobe, the exhaust & the intake ports are both open or "connected" at the same time, which is the 2-stroke cycle. They need to be 100% isolated and it's not super obvious that they are.
- stickfigure 6y ago
  Look forward to about 1:48 where they run through the whole sequence, flashing intake/compression/expansion/exhaust on the screen for each stroke. Each chamber has four full strokes. It seems clear that there shouldn't be any overlap between the ports. I'm pretty in awe of the cleverness. Hope it works out.
  - Groxx 6y ago
    Yeah, that later sequence is clearer now that I look at it again. The first one animating both intake gasses (presumably into the intake chamber, not the compression area) and exhaust at the same time was just confusing me for some reason.