6 ms·

> although only about half of that reaches the driveshaft. Isn't that more like around 35% on a good day? There are some pure ICE systems that can approach 50

> although only about half of that reaches the driveshaft. Isn't that more like around 35% on a good day? There are some pure ICE systems that can approach 50%, but those aren't in common passenger cars. Hybrid cars do considerably better, but even then 50% is an achievement.

wredue 2y ago
Took me a while to find an estimate of the actual average efficiency of ICE cars, and the number I found was “about 20%”. Some places claim the most fuel efficient vehicles are about 40% (again, on a good day in testing conditions). EVs on the other hand are up around 87% or higher.
- KennyBlanken 2y ago
  They're very high especially if power is coming from solar panels on your roof or excess power from neighbors because there are virtually no transmission losses. Also, most power plants aren't that much better than car engines. Coal plants are about 33% efficient and natural gas plants are about 45%.
  - akoboldfrying 2y ago
    Commercially available solar panels are below 30% in efficiency. If the energy going into the EV battery instead came from a gas turbine, the efficiency drop would be similar, I expect. If you want to say that this factor doesn't count: In what sense should the oft-quoted factor in the final step count? (That is, the loss in converting from petrol to rotational motion in an ICE, or from electric potential to rotational motion in an EV.) I think the only real utility that number has is in estimating the total amount of stored energy in a typical car of each type -- this could be used to estimate the amount of damage that would be caused by the vehicle catching on fire. Other claims strike me as meaningless.
    - 698969 2y ago
      It's fair game to compare if you include the conversion efficiency of the organisms that made the fossil fuels :P We care about the efficiency of converting resources we have a limited amount of, sunlight is unlimited on humanity's scale, so is wind, but how much solar or wind power we can extract from them and transmit has constraints and that is the step where we should start caring about efficiency
      - akoboldfrying 2y ago
        This is indeed a good argument to burn our limited petrol supplies for heat (closer to 100% efficient) instead of using it in today's inefficient ICE cars.
- malfist 2y ago
  Those 40% numbers, if you actually read how they got that, it's almost always that they were running the engine in a fixed point operation with a constant RPM. You can make it a bit more efficient by optimizing an engine for a specific singular output, sometimes up to 50% I think is what nissan claims. One automaker, I forget who, was researching doing a hybrid drive train like the volt had, but where the engine could run in that one single speed and charge a battery. Seems a lot more complicated than just electrifying the system, but I'm not a auto researcher. Nissan's PR about it: https://www.nissan-global.com/EN/INNOVATION/TECHNOLOGY/ARCHIVE/E_POWER50/ https://www.nissan-global.com/EN/INNOVATION/TECHNOLOGY/ARCHI...
  - AdrianB1 2y ago
    I think this is how some Diesel-electric locomotives are built, with Diesel engines creating electricity for electric motors, running the ICE at constant speed and minimum transmission (not sure a reduction is needed, probably not). Looks like solid engineering for the cases when electrification is not possible for various reasons.
    - whaleofatw2022 2y ago
      Diesel electrics can be big enough and with long enough expected lifetimes to go 'all out', I think in some ways they can get closer to CCGT as far as efficiency. Where the challenge comes for smaller vehicles, is the more power you are trying to give, the more you have to build everything up; not just the engine but whatever that engine is inputting into, also trains have somewhat more predictable speed profiles over a trip vs a car. This is why some manufacturers have vehicles that are PHEVS but really BEVs with an 'oh crap' extender that can struggle to keep up a good grade. I gotta give TRD/Toyota/Ford credit, the HSD style drive train does work around a lot of this stuff for PHEVS; in lockup mode you have a 1:1 ratio with minimal losses and at that point it's up to the ability of the engine to adjust profile. Works very well in practice, and far simpler than the setups of others.
    - Animats 2y ago
      Diesel-electric locomotives were the first vehicles to get really good motor control. In what are called "AC" locomotives, the wheel motors are 3 phase variable-frequency AC motors. The power train is Diesel engine -> generator -> really big MOSFETs -> synchronous 3-phase motors. Each motor is separately controlled and they are run as synchronized servomotors, to prevent wheel slip. When multiple locomotives are coupled together, they synchronize at the wheel level. The effect is almost 2x more traction than older technology, which means fewer locomotives per train. Automotive motor controllers now use similar technology, but the locomotives had it first.
jbverschoor 2y ago
Where does the rest go to? Aren’t the pipes and hoses leak free? Seems like an easy win
- smlacy 2y ago
  Wasted heat.
  - jbverschoor 2y ago
    Ahh, I thought he was talking about the actual fuel instead of the watts
    - KennyBlanken 2y ago
      Joules (energy), not watts (power.)
      - andrewflnr 2y ago
        Nah, it's still true for the watts.
  - 1970-01-01 2y ago
    Don't forget sound!
- geertj 2y ago
  Heat
- torpfactory 2y ago
  Thermodynamics places limits on heat engine efficiency. For a gasoline engine it is about 35%. https://en.m.wikipedia.org/wiki/Carnot%27s_theorem_(thermodynamics) https://en.m.wikipedia.org/wiki/Carnot%27s_theorem_(thermody...
- deleted 2y ago
  [deleted]
KennyBlanken 2y ago
38% in the Toyota atkinson cycle engines, which are the top of the industry. Typical is more like 28% for gasoline engines. Then you have automatic transmission efficiency, which is at best ~%80, so now you're down to 30% at best. More typical: 28% engine thermal efficiency, 75% transmission efficiency means 21% overall efficiency. So yes, gasoline energy equivalency is pretty meaningless unless you multiply it by 0.2 first. Gas mileage figures from the EPA and others don't account at all for the time a vehicle spends idling before/after a trip - or even in heavy traffic, just waiting at traffic lights. For example, time parents spend sitting in their cars idling waiting to pick up their kids, time spend idling in coffee and fast food drive-through lines, etc. Start-stop systems help, but a lot of people disable them.
- topspin 2y ago
  Among conventional 4-cycle ICE designs there are some recent generator and marine applications near 50%. F1 designed an amazing hybrid system that achieves 50%. Those are the best figures I've seen. The F1 hybrid design is pretty amazing. The motor–generator is driven by and drives the turbocharger. This allows the turbo to be optimized: When the turbo wants to spin too fast electricity is generated and when the turbo would otherwise not deliver enough pressure (lag) the motor–generator augments the turbo speed. Excess stored power goes to the drive train. This effectively solves turbo charging, recovering waste heat through all operation phases, eliminating lag and delivering high efficiency. F1 chose not to field it, and I don't know why. I don't know if it will ever be seen in normal applications.
  - michpoch 2y ago
    It’s used in the Porsche 992.2 released this year
  - KennyBlanken 2y ago
    F1 engines cost seven figures each and are only required to last roughly 20 hours of race time - 7-8 races, each an hour and a half, plus a qualifying session or two per race (barely 15-20 minutes total session time.)
jiveturkey 2y ago
35% and then drivetrain losses on top. Those losses are fair to include since EV systems are often direct driven.
- m463 2y ago
  and then there's regenerative braking...
- numpad0 2y ago
  btw, battery charging is a lossy process too. Oft-quoted 90% figure for power supply conversion efficiency compounds.
  - heavenlyblue 2y ago
    But it's not relevant to battery capacity
  - XorNot 2y ago
    "Well to wheel" comparisons consistently show EV's coming out on top of ICE despite battery charging losses: e.g. https://www.researchgate.net/figure/Well-to-wheels-efficiency-comparison-between-various_fig4_224712974 https://www.researchgate.net/figure/Well-to-wheels-efficienc...

wredue 2y ago

Took me a while to find an estimate of the actual average efficiency of ICE cars, and the number I found was “about 20%”. Some places claim the most fuel efficient vehicles are about 40% (again, on a good day in testing conditions). EVs on the other hand are up around 87% or higher.

KennyBlanken 2y ago
They're very high especially if power is coming from solar panels on your roof or excess power from neighbors because there are virtually no transmission losses. Also, most power plants aren't that much better than car engines. Coal plants are about 33% efficient and natural gas plants are about 45%.
- akoboldfrying 2y ago
  Commercially available solar panels are below 30% in efficiency. If the energy going into the EV battery instead came from a gas turbine, the efficiency drop would be similar, I expect. If you want to say that this factor doesn't count: In what sense should the oft-quoted factor in the final step count? (That is, the loss in converting from petrol to rotational motion in an ICE, or from electric potential to rotational motion in an EV.) I think the only real utility that number has is in estimating the total amount of stored energy in a typical car of each type -- this could be used to estimate the amount of damage that would be caused by the vehicle catching on fire. Other claims strike me as meaningless.
  - 698969 2y ago
    It's fair game to compare if you include the conversion efficiency of the organisms that made the fossil fuels :P We care about the efficiency of converting resources we have a limited amount of, sunlight is unlimited on humanity's scale, so is wind, but how much solar or wind power we can extract from them and transmit has constraints and that is the step where we should start caring about efficiency
    - akoboldfrying 2y ago
      This is indeed a good argument to burn our limited petrol supplies for heat (closer to 100% efficient) instead of using it in today's inefficient ICE cars.
malfist 2y ago
Those 40% numbers, if you actually read how they got that, it's almost always that they were running the engine in a fixed point operation with a constant RPM. You can make it a bit more efficient by optimizing an engine for a specific singular output, sometimes up to 50% I think is what nissan claims. One automaker, I forget who, was researching doing a hybrid drive train like the volt had, but where the engine could run in that one single speed and charge a battery. Seems a lot more complicated than just electrifying the system, but I'm not a auto researcher. Nissan's PR about it: https://www.nissan-global.com/EN/INNOVATION/TECHNOLOGY/ARCHIVE/E_POWER50/ https://www.nissan-global.com/EN/INNOVATION/TECHNOLOGY/ARCHI...
- AdrianB1 2y ago
  I think this is how some Diesel-electric locomotives are built, with Diesel engines creating electricity for electric motors, running the ICE at constant speed and minimum transmission (not sure a reduction is needed, probably not). Looks like solid engineering for the cases when electrification is not possible for various reasons.
  - whaleofatw2022 2y ago
    Diesel electrics can be big enough and with long enough expected lifetimes to go 'all out', I think in some ways they can get closer to CCGT as far as efficiency. Where the challenge comes for smaller vehicles, is the more power you are trying to give, the more you have to build everything up; not just the engine but whatever that engine is inputting into, also trains have somewhat more predictable speed profiles over a trip vs a car. This is why some manufacturers have vehicles that are PHEVS but really BEVs with an 'oh crap' extender that can struggle to keep up a good grade. I gotta give TRD/Toyota/Ford credit, the HSD style drive train does work around a lot of this stuff for PHEVS; in lockup mode you have a 1:1 ratio with minimal losses and at that point it's up to the ability of the engine to adjust profile. Works very well in practice, and far simpler than the setups of others.
  - Animats 2y ago
    Diesel-electric locomotives were the first vehicles to get really good motor control. In what are called "AC" locomotives, the wheel motors are 3 phase variable-frequency AC motors. The power train is Diesel engine -> generator -> really big MOSFETs -> synchronous 3-phase motors. Each motor is separately controlled and they are run as synchronized servomotors, to prevent wheel slip. When multiple locomotives are coupled together, they synchronize at the wheel level. The effect is almost 2x more traction than older technology, which means fewer locomotives per train. Automotive motor controllers now use similar technology, but the locomotives had it first.

jbverschoor 2y ago

Where does the rest go to? Aren’t the pipes and hoses leak free? Seems like an easy win

smlacy 2y ago
Wasted heat.
- jbverschoor 2y ago
  Ahh, I thought he was talking about the actual fuel instead of the watts
  - KennyBlanken 2y ago
    Joules (energy), not watts (power.)
    - andrewflnr 2y ago
      Nah, it's still true for the watts.
- 1970-01-01 2y ago
  Don't forget sound!
geertj 2y ago
Heat
torpfactory 2y ago
Thermodynamics places limits on heat engine efficiency. For a gasoline engine it is about 35%. https://en.m.wikipedia.org/wiki/Carnot%27s_theorem_(thermodynamics) https://en.m.wikipedia.org/wiki/Carnot%27s_theorem_(thermody...
deleted 2y ago
[deleted]

KennyBlanken 2y ago

38% in the Toyota atkinson cycle engines, which are the top of the industry. Typical is more like 28% for gasoline engines. Then you have automatic transmission efficiency, which is at best ~%80, so now you're down to 30% at best. More typical: 28% engine thermal efficiency, 75% transmission efficiency means 21% overall efficiency. So yes, gasoline energy equivalency is pretty meaningless unless you multiply it by 0.2 first. Gas mileage figures from the EPA and others don't account at all for the time a vehicle spends idling before/after a trip - or even in heavy traffic, just waiting at traffic lights. For example, time parents spend sitting in their cars idling waiting to pick up their kids, time spend idling in coffee and fast food drive-through lines, etc. Start-stop systems help, but a lot of people disable them.

topspin 2y ago
Among conventional 4-cycle ICE designs there are some recent generator and marine applications near 50%. F1 designed an amazing hybrid system that achieves 50%. Those are the best figures I've seen. The F1 hybrid design is pretty amazing. The motor–generator is driven by and drives the turbocharger. This allows the turbo to be optimized: When the turbo wants to spin too fast electricity is generated and when the turbo would otherwise not deliver enough pressure (lag) the motor–generator augments the turbo speed. Excess stored power goes to the drive train. This effectively solves turbo charging, recovering waste heat through all operation phases, eliminating lag and delivering high efficiency. F1 chose not to field it, and I don't know why. I don't know if it will ever be seen in normal applications.
- michpoch 2y ago
  It’s used in the Porsche 992.2 released this year
- KennyBlanken 2y ago
  F1 engines cost seven figures each and are only required to last roughly 20 hours of race time - 7-8 races, each an hour and a half, plus a qualifying session or two per race (barely 15-20 minutes total session time.)

jiveturkey 2y ago

35% and then drivetrain losses on top. Those losses are fair to include since EV systems are often direct driven.

m463 2y ago
and then there's regenerative braking...
numpad0 2y ago
btw, battery charging is a lossy process too. Oft-quoted 90% figure for power supply conversion efficiency compounds.
- heavenlyblue 2y ago
  But it's not relevant to battery capacity
- XorNot 2y ago
  "Well to wheel" comparisons consistently show EV's coming out on top of ICE despite battery charging losses: e.g. https://www.researchgate.net/figure/Well-to-wheels-efficiency-comparison-between-various_fig4_224712974 https://www.researchgate.net/figure/Well-to-wheels-efficienc...