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The animation shows a turbocharger but it also shows that the engine operates on a 2 stroke cycle. Conventional wisdom would say that the turbocharger would be

by ferongr 12y ago

The animation shows a turbocharger but it also shows that the engine operates on a 2 stroke cycle. Conventional wisdom would say that the turbocharger would be a waste since both intake and exhaust ports are open at the same time, preventing the compression of the mixture, while at the same time potentially wasting some of it as it is forced out of the exhaust port. I'd speculate that the turbocharger is small enough and used mainly to introduce the mixture into the chamber with enough velocity to make it swirl, while at the same time improving the removal of exhaust gases.

ams6110 12y ago
On large two-stroke engines a blower/turbocharger is often used to not only introduce additional fresh air for the next combustion cycle but also to more rapidly/completely purge the combustion gasses out the exhaust ports (this is called scavenging).
- semerda 12y ago
  It's not just air, its usually compressed air above atmospheric sea level (bar+). This opposed-piston architecture appears more complicated. Adding an additional crankshaft isn't a small feat. Removing valves that rely on the rotation of a crankshaft is a small win. Add bar+ of pressure into a combustion motor like this and watch it pop. Too many moving pieces! But saying this, what is the drive to keep on overcomplicating things like traditional combustion motors? The Wankel engine was simple, small & powerful (when a turbo hanged off it). The industry killed it to replace it with a more complicated piston engine. And now this more complicated architecture proposal. I would love to see engineering innovation focusing on simplification like that which exists in electric motors. There is still so much more that can be done with magnets & coils.
  - Gravityloss 12y ago
    Emission controls have become a lot stricter. In heavier engines, they are the major technology driver now. Wankels have a crescent shaped combustion space. That is bad for emissions as the far away thin corners dont burn so well.
    - semerda 12y ago
      Yap I understand why Wankel didn't meet emission standards. But neither would have the standard piston architecture if it weren't for innovation i.e. extension of it's complexity. As a ex-fan of combustion motors for many years, and having built a race car, I no longer see investment in combustion motors as sound. Electric motors are far simpler and smaller and are starting to yield similar results to combustion motors. That's where innovation should be heading.
      - jrapdx3 12y ago
        As a past owner (many years ago) of a Wankel-engine powered car I was entertained at the mention of "Wankel". Emissions were the least of its problems, reliability being far less than desirable, as in barely able to keep going at all. Later on there were more reliable rotary engines, e.g., Mazda. If memory serves, there were emission problems and the engine was eventually discontinued for that reason. Rotaries were an interesting idea, hypothetically better, but implementation was obviously difficult and ultimately a failure. In today's world, we need to stop burning fossil fuels and electric-powered vehicles look promising. I'm looking forward to advances that will make electric cars practical. Of course, burning coal or natural methane to make electricity wouldn't be ideal, though possibly more efficient than the distributed combustion we now use.
      - Gravityloss 12y ago
        Audi was considering a Wankel range extender for plugin hybrids around 2010 but they later moved to conventional three cylinder engines. I don't know the specific reasons for that.
    - auxym 12y ago
      I don't have a reference on hand, but everyone I've spoken to who has worked close to engines (in the automotive, recreative and commercial transport industries) has said to me that compliance to emissions is now the leading design consideration. So, not only heavier engines, unless by "lighter" engines you are only referring to lawnmowers and such.
cfallin 12y ago
In addition to what ams6110 said about scavenging, the article talks about how the three crankshafts are phase-offset such that the exhaust valve closes before the intake valve does (this is possible because one piston in a given cylinder pair controls each port). I imagine that this part of the cycle allows for a bit of pressure boost.

by ferongr 12y ago

ams6110 12y ago

On large two-stroke engines a blower/turbocharger is often used to not only introduce additional fresh air for the next combustion cycle but also to more rapidly/completely purge the combustion gasses out the exhaust ports (this is called scavenging).

semerda 12y ago
It's not just air, its usually compressed air above atmospheric sea level (bar+). This opposed-piston architecture appears more complicated. Adding an additional crankshaft isn't a small feat. Removing valves that rely on the rotation of a crankshaft is a small win. Add bar+ of pressure into a combustion motor like this and watch it pop. Too many moving pieces! But saying this, what is the drive to keep on overcomplicating things like traditional combustion motors? The Wankel engine was simple, small & powerful (when a turbo hanged off it). The industry killed it to replace it with a more complicated piston engine. And now this more complicated architecture proposal. I would love to see engineering innovation focusing on simplification like that which exists in electric motors. There is still so much more that can be done with magnets & coils.
- Gravityloss 12y ago
  Emission controls have become a lot stricter. In heavier engines, they are the major technology driver now. Wankels have a crescent shaped combustion space. That is bad for emissions as the far away thin corners dont burn so well.
  - semerda 12y ago
    Yap I understand why Wankel didn't meet emission standards. But neither would have the standard piston architecture if it weren't for innovation i.e. extension of it's complexity. As a ex-fan of combustion motors for many years, and having built a race car, I no longer see investment in combustion motors as sound. Electric motors are far simpler and smaller and are starting to yield similar results to combustion motors. That's where innovation should be heading.
    - jrapdx3 12y ago
      As a past owner (many years ago) of a Wankel-engine powered car I was entertained at the mention of "Wankel". Emissions were the least of its problems, reliability being far less than desirable, as in barely able to keep going at all. Later on there were more reliable rotary engines, e.g., Mazda. If memory serves, there were emission problems and the engine was eventually discontinued for that reason. Rotaries were an interesting idea, hypothetically better, but implementation was obviously difficult and ultimately a failure. In today's world, we need to stop burning fossil fuels and electric-powered vehicles look promising. I'm looking forward to advances that will make electric cars practical. Of course, burning coal or natural methane to make electricity wouldn't be ideal, though possibly more efficient than the distributed combustion we now use.
    - Gravityloss 12y ago
      Audi was considering a Wankel range extender for plugin hybrids around 2010 but they later moved to conventional three cylinder engines. I don't know the specific reasons for that.
  - auxym 12y ago
    I don't have a reference on hand, but everyone I've spoken to who has worked close to engines (in the automotive, recreative and commercial transport industries) has said to me that compliance to emissions is now the leading design consideration. So, not only heavier engines, unless by "lighter" engines you are only referring to lawnmowers and such.

cfallin 12y ago

In addition to what ams6110 said about scavenging, the article talks about how the three crankshafts are phase-offset such that the exhaust valve closes before the intake valve does (this is possible because one piston in a given cylinder pair controls each port). I imagine that this part of the cycle allows for a bit of pressure boost.