5 ms·

Wow, I had no idea that a car engine produced more than a hundred kilowatts of power, that's ridiculous! (For comparison, an average household consumes somethin

by foota 3y ago

Wow, I had no idea that a car engine produced more than a hundred kilowatts of power, that's ridiculous! (For comparison, an average household consumes something like tens of kilowatt hours per day, so driving for an hour (I guess at peak, which an engine wont always be) may be similar to 5 or 10 days of a household's power usage, and not to mention much less efficiently generated.

infinityio 3y ago
petrol is roughly 9.5kW/litre (~35kWh/US gallon) if that's a better reference for consumption (of which maybe 30% will make it to energy through a modern engine?)
Negitivefrags 3y ago
The rediculoussness of the energy use of transport is especially noticeable when you are driving a Tesla which by default shows you a dial of power consumption and generation in kW. When rolling down a hill with regenerative breaking, the car is generating 50kW. You can literally power many average homes with that.
- m463 3y ago
  On the other hand, pedaling a bicycle, or pushing a car is a lot of work. It's not ridiculous until you compare against people doing it manually. also, teslas are really quite efficient and it's amazing how they recover energy as well. I wonder if there are efficiencies to be had recovering energy to come, since they can only recover what the batteries can absorb.
  - 4gotunameagain 3y ago
    Pedalling a bike is not a lot of work. Old people do it daily. Thrusting a car through air at 100kph though, that takes a lot of work. Drag scales with the square of the velocity and proportionally to the frontal surface area. Cars are a fast, but woefully inefficient means of transport.
    - sokoloff 3y ago
      > Drag scales with the square of the velocity Drag force scales with the square of velocity. Drag power (rate of work or rate of energy consumption) scales with the cube of velocity.
      - 4gotunameagain 3y ago
        Good clarification thanks !
    - TheSpiceIsLife 3y ago
      Perhaps you've never cycled up a hill.
      - 4gotunameagain 3y ago
        Perhaps I've grown up in Europe and have been cycling my whole life.
        bee_rider 3y ago
        You could be from Denmark
        4gotunameagain 3y ago
        I'm not, I've just lived there ;)
  - deleted 3y ago
    [deleted]
  - imoverclocked 3y ago
    You lose a lot of energy to drag, friction and resistance(aka: heat.) Battery capacities are almost never the limiting factor in this equation. This is especially so when you don’t top the battery off to begin with.
  - stefan_ 3y ago
    Of course it's ridiculous to have 300kW car engines racing from light to light averaging 10mph in the city when someone on a bike can do that faster with 100W.
    - IMTDb 3y ago
      Only if the lights are stopping the car but not the cyclist. If you apply regulations that are designed to favour one contestant, it's not longer a fair comparison.
      - rented_mule 3y ago
        I walked to work for over a decade before I retired. I stopped at all the red lights and beat the cars most days. Bikes and pedestrians can go much faster than cars between lights when traffic is bad enough. Sure, there is favorable treatment (pedestrians get their own "roads" and bikes can drive between lanes), but there is no similar treatment that would make sense for cars because they are too big and insufficiently nimble.
      - ornornor 3y ago
        If anything, bicycles are very rarely (in some places, never) favoured over cars in urban planning/design.
    - m463 3y ago
      300kw is peak power. I think teslas are pretty efficient: https://forum.abetterrouteplanner.com/blogs/entry/22-tesla-model-3-performance-vs-rwd-consumption-real-driving-data-from-233-cars/ https://forum.abetterrouteplanner.com/blogs/entry/22-tesla-m... A model 3 LR uses less than 100 watt hours to go 1 mile at 25mph I wonder how efficient bikes become at higher speeds with respect to drag coefficient (without a streamlined fairing)
  - contravariant 3y ago
    > On the other hand, pedaling a bicycle, or pushing a car is a lot of work. One of these is not like the other. Pedalling a bike doesn't come even close. Humans consume several million calories per day at most, now as a rule of thumb a million calories is about the same as a kWh. And the only reason they consume that much energy is because the human body is inefficient at converting this heat to work. Even the best cyclists struggle to produce anything more than a few hundred watt. More to the point, humans struggle to power a light bulb, let alone a house.
    - Wicher 3y ago
      > And the only reason they consume that much energy is because the human body is inefficient at converting this heat to work. The human body does not convert heat to work. We do something entirely different (look up the "ATP/ADP cycle"). But yeah there are certainly conversion losses in the conversion of egg sandwiches to labor. 25% or so. Which is actually pretty good; you won't be able to match that with a steam machine built over the weekend (start with solving the problem of setting eggs on fire?).
lapetitejort 3y ago
And in many cases, that much power transports a single person and occasionally a few bags of groceries. edit: By point of comparison, a good cyclist produces about 100 watts, probably less if they're on a leisurely cruise. That's about 2% of the wattage of a car engine.
- ska 3y ago
  For more direct comparison, there are motorcycles on the market that can produce ~150kW , to transport about the same amount of stuff. Bicycles are really efficient (and those motorcycles are very fast)
- xattt 3y ago
  > And in many cases, that much power transports a single person and occasionally a few bags of groceries. Is there any comparable mode of transport that can accommodate all of this in poor weather (i.e. a snowstorm) without having to wear burdensome clothing? I realize 150 years ago people wouldn’t venture out in those conditions, but they also didn’t move more than 50 km from their birthplace over their lifetime.
  - lapetitejort 3y ago
    Yes: a bus or light rail system can carry tens or hundreds of people at a time for a comparable amount of wattage per person. Build the system underground and inclement weather becomes even less of an issue.
    - throwanem 3y ago
      You're still going to want to bundle up for the parts where you're walking to or from the station. But it's not like that's difficult or burdensome to do, at least for anyone hale enough to walk a couple miles without trouble. I commuted to work daily via light rail for years; with a couple of well-thought-out layers, good gloves and shoes, scarf, and hat, you're good to go down to about 15°F in reasonably still weather, and by adding a parka and balaclava you can take that down to 0° and still be quite comfortable - and with a backpack or satchel, carry quite a lot besides. (If anything, you might find yourself too warm and sweating! Working your muscles puts out a surprising amount of heat, and modern textiles can do an amazing job of keeping it where it does the most good.) Frankly, this is a skill anyone should have who lives where it gets cold enough to be useful. You won't always get to know ahead of time when you might be out in the cold - after a car wreck, for example, and maybe without a running engine for a heater into the bargain - so it pays to dress for what you could end up needing, or at least have the parts of such an outfit close to hand against the chance you might.
carlosjobim 3y ago
The continuation of this thought is to realize what an immense amount of power there is in a gallon of gas. It is basically free energy compared to using serfs or beasts of burden to do the work.
- djaychela 3y ago
  I saw something the other day - the numbers aren't exactly right, but it was along the lines of there's the same amount of energy in a barrel of oil as one man working full time in a manual job FOR SEVEN YEARS. This is why we've (unfortunately) built modern societies on fossil fuels. The amount of work done as a result of it is immense, and probably explains why there aren't vast numbers of people enslaved for manual labour any more.
  - chrisweekly 3y ago
    It's maybe equally mind-blosing to consider the miniscule amount of mass required to generate equivalent energy in nuclear reactions.
AnotherGoodName 3y ago
Modern cars are powerful. Today there's no car on the market today that doesn't have enough power. The cheapest cars you can buy, small sub $20k hatchbacks, are all around 100kw. They all have performance figures that beat sports cars from the 1970s. The limiting factor on early acceleration (0-60kph) today for all cars is now tyres. Beyond that air resistance might make more engine power matter but in general it's all about the tyres. Every car can spin their wheels at the lights if they want to. If you feel the need to floor it at the lights you're showing off your tyres not your engine power (and also wearing them out).
- toss1 3y ago
  "There's nothing like bad tires to make it sound hot off the line..." (racetrack joke — — who needs a big engine to squeal the tires when a set of crummy tires will do it even better?)
  - sokoloff 3y ago
    "There is no such thing as too much horsepower...just not enough traction" ~ Carroll Shelby
- Fatnino 3y ago
  Sub $20k vehicles do not exist in this day and age.
  - mycall 3y ago
    [new cars]
  - wernercd 3y ago
    Nissan Versa is 16k. Kia Rio is 17k. Mitsubishi Mirage is 17k. https://www.caranddriver.com/features/g44830210/cheapest-new-cars/ https://www.caranddriver.com/features/g44830210/cheapest-new... There may not be a LOT of cars in that price range but they definitely exist.
  - 2Gkashmiri 3y ago
wkat4242 3y ago
If you actually run it at that power constantly it's not going to last long though. It's peak power. You're not going to drag race your car, most of the time it's just cruising. This is a big difference to (piston) airplane engines because those are designed to give near 100% a lot of the time.
- chrisweekly 3y ago
  Yeah, marine boat engines (gas outboards -- NOT auxilliary diesels!) are designed to run close to full-throttle ~all the time.
  - wkat4242 3y ago
    Huh I didn't know that. I guess cooling is simple there considering they can just ingest cool water and expel it without having a radiator. I don't know much about boats. It sounds easier than on piston planes even. They run pretty hot when running flat-out while parked, like during a run-up test. We were always told to only do it for 30 seconds or so. They generally use air cooling and despite the huge "fan" on the front it struggles in this scenario. When you're doing 100 knots it's less of a problem.
pornel 3y ago
This is very visible in EVs. They can power a house for multiple days, but last only few hours at highway speeds.
cwillu 3y ago
24 kilowatt•hours/day is better known as simply a kilowatt
- RecycledEle 3y ago
  No. A kilowatt is the instantaneous consumption of 1,000 watts.
  - haneefmubarak 3y ago
    Eh GP is technically correct here if you do the dimensional analysis because the two time units cancel out and you're left with only a power unit.
  - cwillu 3y ago
    Saying a household averages a consumption of 1000 watts over the course of a day makes exactly as much sense as saying someone averaged 30mph over the course of a day on a road trip.
brnt 3y ago
Its why having an EV hookup is so funny: your house is now a tiny percentage of your power bill/load dimensioning. Also why I'd really like to have my car battery be usable by the house: storing solar or winter/night consumption all require a battery. You'll never need a bigger one for your house than the one already in your EV.

by foota 3y ago

infinityio 3y ago

petrol is roughly 9.5kW/litre (~35kWh/US gallon) if that's a better reference for consumption (of which maybe 30% will make it to energy through a modern engine?)

Negitivefrags 3y ago

The rediculoussness of the energy use of transport is especially noticeable when you are driving a Tesla which by default shows you a dial of power consumption and generation in kW. When rolling down a hill with regenerative breaking, the car is generating 50kW. You can literally power many average homes with that.

m463 3y ago
On the other hand, pedaling a bicycle, or pushing a car is a lot of work. It's not ridiculous until you compare against people doing it manually. also, teslas are really quite efficient and it's amazing how they recover energy as well. I wonder if there are efficiencies to be had recovering energy to come, since they can only recover what the batteries can absorb.
- 4gotunameagain 3y ago
  Pedalling a bike is not a lot of work. Old people do it daily. Thrusting a car through air at 100kph though, that takes a lot of work. Drag scales with the square of the velocity and proportionally to the frontal surface area. Cars are a fast, but woefully inefficient means of transport.
  - sokoloff 3y ago
    > Drag scales with the square of the velocity Drag force scales with the square of velocity. Drag power (rate of work or rate of energy consumption) scales with the cube of velocity.
    - 4gotunameagain 3y ago
      Good clarification thanks !
  - TheSpiceIsLife 3y ago
    Perhaps you've never cycled up a hill.
    - 4gotunameagain 3y ago
      Perhaps I've grown up in Europe and have been cycling my whole life.
      - bee_rider 3y ago
        You could be from Denmark
        4gotunameagain 3y ago
        I'm not, I've just lived there ;)
- deleted 3y ago
  [deleted]
- imoverclocked 3y ago
  You lose a lot of energy to drag, friction and resistance(aka: heat.) Battery capacities are almost never the limiting factor in this equation. This is especially so when you don’t top the battery off to begin with.
- stefan_ 3y ago
  Of course it's ridiculous to have 300kW car engines racing from light to light averaging 10mph in the city when someone on a bike can do that faster with 100W.
  - IMTDb 3y ago
    Only if the lights are stopping the car but not the cyclist. If you apply regulations that are designed to favour one contestant, it's not longer a fair comparison.
    - rented_mule 3y ago
      I walked to work for over a decade before I retired. I stopped at all the red lights and beat the cars most days. Bikes and pedestrians can go much faster than cars between lights when traffic is bad enough. Sure, there is favorable treatment (pedestrians get their own "roads" and bikes can drive between lanes), but there is no similar treatment that would make sense for cars because they are too big and insufficiently nimble.
    - ornornor 3y ago
      If anything, bicycles are very rarely (in some places, never) favoured over cars in urban planning/design.
  - m463 3y ago
    300kw is peak power. I think teslas are pretty efficient: https://forum.abetterrouteplanner.com/blogs/entry/22-tesla-model-3-performance-vs-rwd-consumption-real-driving-data-from-233-cars/ https://forum.abetterrouteplanner.com/blogs/entry/22-tesla-m... A model 3 LR uses less than 100 watt hours to go 1 mile at 25mph I wonder how efficient bikes become at higher speeds with respect to drag coefficient (without a streamlined fairing)
- contravariant 3y ago
  > On the other hand, pedaling a bicycle, or pushing a car is a lot of work. One of these is not like the other. Pedalling a bike doesn't come even close. Humans consume several million calories per day at most, now as a rule of thumb a million calories is about the same as a kWh. And the only reason they consume that much energy is because the human body is inefficient at converting this heat to work. Even the best cyclists struggle to produce anything more than a few hundred watt. More to the point, humans struggle to power a light bulb, let alone a house.
  - Wicher 3y ago
    > And the only reason they consume that much energy is because the human body is inefficient at converting this heat to work. The human body does not convert heat to work. We do something entirely different (look up the "ATP/ADP cycle"). But yeah there are certainly conversion losses in the conversion of egg sandwiches to labor. 25% or so. Which is actually pretty good; you won't be able to match that with a steam machine built over the weekend (start with solving the problem of setting eggs on fire?).

lapetitejort 3y ago

And in many cases, that much power transports a single person and occasionally a few bags of groceries. edit: By point of comparison, a good cyclist produces about 100 watts, probably less if they're on a leisurely cruise. That's about 2% of the wattage of a car engine.

ska 3y ago
For more direct comparison, there are motorcycles on the market that can produce ~150kW , to transport about the same amount of stuff. Bicycles are really efficient (and those motorcycles are very fast)
xattt 3y ago
> And in many cases, that much power transports a single person and occasionally a few bags of groceries. Is there any comparable mode of transport that can accommodate all of this in poor weather (i.e. a snowstorm) without having to wear burdensome clothing? I realize 150 years ago people wouldn’t venture out in those conditions, but they also didn’t move more than 50 km from their birthplace over their lifetime.
- lapetitejort 3y ago
  Yes: a bus or light rail system can carry tens or hundreds of people at a time for a comparable amount of wattage per person. Build the system underground and inclement weather becomes even less of an issue.
  - throwanem 3y ago
    You're still going to want to bundle up for the parts where you're walking to or from the station. But it's not like that's difficult or burdensome to do, at least for anyone hale enough to walk a couple miles without trouble. I commuted to work daily via light rail for years; with a couple of well-thought-out layers, good gloves and shoes, scarf, and hat, you're good to go down to about 15°F in reasonably still weather, and by adding a parka and balaclava you can take that down to 0° and still be quite comfortable - and with a backpack or satchel, carry quite a lot besides. (If anything, you might find yourself too warm and sweating! Working your muscles puts out a surprising amount of heat, and modern textiles can do an amazing job of keeping it where it does the most good.) Frankly, this is a skill anyone should have who lives where it gets cold enough to be useful. You won't always get to know ahead of time when you might be out in the cold - after a car wreck, for example, and maybe without a running engine for a heater into the bargain - so it pays to dress for what you could end up needing, or at least have the parts of such an outfit close to hand against the chance you might.

carlosjobim 3y ago

The continuation of this thought is to realize what an immense amount of power there is in a gallon of gas. It is basically free energy compared to using serfs or beasts of burden to do the work.

djaychela 3y ago
I saw something the other day - the numbers aren't exactly right, but it was along the lines of there's the same amount of energy in a barrel of oil as one man working full time in a manual job FOR SEVEN YEARS. This is why we've (unfortunately) built modern societies on fossil fuels. The amount of work done as a result of it is immense, and probably explains why there aren't vast numbers of people enslaved for manual labour any more.
- chrisweekly 3y ago
  It's maybe equally mind-blosing to consider the miniscule amount of mass required to generate equivalent energy in nuclear reactions.

AnotherGoodName 3y ago

Modern cars are powerful. Today there's no car on the market today that doesn't have enough power. The cheapest cars you can buy, small sub $20k hatchbacks, are all around 100kw. They all have performance figures that beat sports cars from the 1970s. The limiting factor on early acceleration (0-60kph) today for all cars is now tyres. Beyond that air resistance might make more engine power matter but in general it's all about the tyres. Every car can spin their wheels at the lights if they want to. If you feel the need to floor it at the lights you're showing off your tyres not your engine power (and also wearing them out).

toss1 3y ago
"There's nothing like bad tires to make it sound hot off the line..." (racetrack joke — — who needs a big engine to squeal the tires when a set of crummy tires will do it even better?)
- sokoloff 3y ago
  "There is no such thing as too much horsepower...just not enough traction" ~ Carroll Shelby
Fatnino 3y ago
Sub $20k vehicles do not exist in this day and age.
- mycall 3y ago
  [new cars]
- wernercd 3y ago
  Nissan Versa is 16k. Kia Rio is 17k. Mitsubishi Mirage is 17k. https://www.caranddriver.com/features/g44830210/cheapest-new-cars/ https://www.caranddriver.com/features/g44830210/cheapest-new... There may not be a LOT of cars in that price range but they definitely exist.
- 2Gkashmiri 3y ago

wkat4242 3y ago

If you actually run it at that power constantly it's not going to last long though. It's peak power. You're not going to drag race your car, most of the time it's just cruising. This is a big difference to (piston) airplane engines because those are designed to give near 100% a lot of the time.

chrisweekly 3y ago
Yeah, marine boat engines (gas outboards -- NOT auxilliary diesels!) are designed to run close to full-throttle ~all the time.
- wkat4242 3y ago
  Huh I didn't know that. I guess cooling is simple there considering they can just ingest cool water and expel it without having a radiator. I don't know much about boats. It sounds easier than on piston planes even. They run pretty hot when running flat-out while parked, like during a run-up test. We were always told to only do it for 30 seconds or so. They generally use air cooling and despite the huge "fan" on the front it struggles in this scenario. When you're doing 100 knots it's less of a problem.

pornel 3y ago

This is very visible in EVs. They can power a house for multiple days, but last only few hours at highway speeds.

cwillu 3y ago

24 kilowatt•hours/day is better known as simply a kilowatt

RecycledEle 3y ago
No. A kilowatt is the instantaneous consumption of 1,000 watts.
- haneefmubarak 3y ago
  Eh GP is technically correct here if you do the dimensional analysis because the two time units cancel out and you're left with only a power unit.
- cwillu 3y ago
  Saying a household averages a consumption of 1000 watts over the course of a day makes exactly as much sense as saying someone averaged 30mph over the course of a day on a road trip.

brnt 3y ago

Its why having an EV hookup is so funny: your house is now a tiny percentage of your power bill/load dimensioning. Also why I'd really like to have my car battery be usable by the house: storing solar or winter/night consumption all require a battery. You'll never need a bigger one for your house than the one already in your EV.