https://www.autoweek.com/news/green-cars/a1832081/atkinson-c...
Basically with that cycle they can get massive compression ratios. As an example newer Toyotas are at 14:1 ratio with 41% thermal efficiency. That’s close to diesel territory on a gasoline car.
Naturally when you floor it it goes to Otto cycle and efficiency drops.
Also: start-stop-automatic for free ... I am still somewhat spooked when the motor just turns off going 70 km/h because the ECU decides that the ICE is not needed anymore.
The new 2023 model year Serena from Nissan uses a generator optimized engine in a series hybrid setup. The engine runs at a fixed rpm (except in extreme situations like accelerating a bunch on the highway going from 110 to 140) then it switches to a second higher rpm mode. I bought one, it's a lot of fun to manage the engines heat and battery room. My record is 38km per liter using local driving up and down our hilly community. Pretty incredible when you consider hills are the natural enemy to none hybrid millage.
The car accelerates like an EV. And with Japan's expensive electricity I'm paying only about double the millage cost of an EV. Despite the full size minivan costing us about 20k USD new.
Most hybrids, and all Toyota ones, are not using a special fixed rpm engines. They use a regular motor with different timings. The Nissan fixed rpm engine is actually less powerful than the electric motor powering the wheels. Thus at max acceleration you can deplete the battery faster than it is charged.
It's about a microgram.
https://www.science.org/content/article/where-have-all-insec...
I guess overseas flights will just have to absorb the cost, unless it happens to be economical somehow to operate floating stations for the purpose of collecting dropped batteries.
> The electric pumps are powered by lithium-polymer batteries. The second stage uses three batteries which are "hot swapped", two of the batteries are jettisoned once depleted to shed mass.
Energy density of gasoline is literally 12900 Wh/kg and 9500 Wh/L, Li-ion(not combusted) is ~250 Wh/kg and ~700 Wh/L. That's 50x/14x raw and 17x/13x at 33% efficiency without hybrid/ICE optimization gains.
(23222915000 Wh/kg and 370000000000 Wh/L for Pu239 btw, source[1])
And thank you for the 'x' factor. Had never seen that, outside of everyone stating ICE is only 33% efficient.
Firstly, the newest solid state batteries (relevant because that is what I was responding about) are 2x the density so that is quite good (8.5x/6.5x). Which is already pretty close. They are also going to get better through iteration likely to 3-5x or so (but let’s ignore that for now).
Secondly, the power train also includes regenerative breaking, reduced weight from transmission, in hub motors (reducing axcel weight), reduced center of gravity allowing better drag profiles, no external coolant systems, no engine oil compartments, no fan belts, etc.
I’m happy for you to keep doing the math, but the reality is XXX km or miles per “full tank” is the best measurement because it takes all those factors into consideration.
Seriously, if we could just build 2-3 air-cooled Plutonium fission per each megalopolis core and use e-Fuel on existing hybrids we'd solve everything in modern society ever. The reactor could double as cityscale thermojet ventilation system as well, eliminating heat and atmosphere problems once and for all. It will of course work as a training exercise for coming real Space Age in which humanity builds bunches after bunches of cylindrical habitats fabricated and populated in space. The only two roadblocks towards that path are some NIMBYism/NPT fears and cost.
I’m very happy for there to be really nice and safe fission reactors everywhere for grid scale generation. Including efuel generators for air and space transportation.
The major issue is parasitic drivetrain loss from having to push the cylinder which pushes the cam which turns the flywheel which friction fits against the clutch which friction fits against the transmission flywheel which turns dozens of metal gears which rotates the driveshafts. Direct drive implementations where the engine's output shaft is mated directly to the axle are much more efficient and have been used in massive ships, but are entirely impractical for use in passenger vehicles. There's the Otto, Atkinson, Wankel, Scuderi and diesel cycles for liquid fuel combustion, and all have tradeoffs leaving them competitive with eachother instead of having a clear best solution thanks to everything else required to transfer the power from the initial combustion.
In short, we've hit the mechanical engineering dead end for massive efficiency gains with ICEs. It's all chemical from here, and thus gets much more expensive to run.
https://en.wikipedia.org/wiki/Engine_efficiency#:~:text=Mode....
Something more radical has to be done about the entire crankshaft and a 4 piston design. Believe me, lots of smart people have tried that as well, for many decades. Because the payoffs if you did find something are huge.
There are lots of YouTube channels needing into all of this. Engineering Explained is a good one if you want to understand the level of how advanced modern engines really are.
Mercedes has devised an engine that achieves more than 50 percent efficiency.
https://www.roadandtrack.com/motorsports/a15049580/mercedes-...
The energy density of a gasoline power train is a different measurement taking into account chemistry and physics.
Specifically car engines can only turn 33% of gasoline’s stored energy into motion. Which still puts gasoline ahead in terms of efficiency relative to hydrogen or battery powertrains but reduces the difference a lot.