You could also stopping distance on the speedometer. It's roughly proportional to kinetic energy, which is proportional to the square of your velocity. Meaning that if you double your speed, you quadruple your stopping distance.
THE ONLY THING that irks me is... the video is about miles and the picture above is about kilometers.
While the relative values stay the same the range of the speedometer should've been adjusted in the upper picture to ~200kph.
Yes it still serves a purpose but this man tried to make a point about speeding. 130mph is speeding. 130kph is fast but not close to the cretins smooching my back every day on the Autobahn.
The greater the measured distance, the more value is placed on smaller savings. If you save 2 minutes on 10 miles going 80 instead of 60. On a 1000 mile trip that’s 200 minutes saved. 3 hours 20 min. Not insignificant for an otherwise 16h 40min. Worth the increased risk? Debatable I’d say
Really depends on the engine and the gearing for an ICE vehicle. With EVs the slower you go the more efficient you are. Im sure there is some low speed where this stops being true and the energy lost to friction is higher than the energy lost to wind resistance, but in theory the slower the better for an EV when it comes to efficiency (assuming constant speeds).
It depends. 55 is a good guideline for most cars though because the EPA tests highway mileage in that speed area, they actually raised it a few years ago and required the A/C to be on.
So older cars(80s/90s) generally tuned for 45-55 while newer 2010+ tuned around 55-60ish.
My hybrid Maverick gets mid 40s at ~55, but it drops to around 33 at 80. Like my parents are about 220 miles away round trip. At $4 a gallon it's about $30 to take the interstate or $20 to take the highway. About 2 hours vs 2 hours 30 mins. When gas hits $10 a gallon it will be a no brainer.
Depends on the car. This is anecdotal evidence but when I drove from Williamsburg, VA to Las Vegas, I ended up getting the most fuel efficiency around 70. It was strange watching the fuel efficiency go down in Utah where the speed limit is 80.
I was taught this in truck driving school. They even gave us a chart. The guys getting paid by the mile will still drive like maniacs though. And those guys are why you see so many bottles of yellow liquid on the side of highways. They’re losing more if they stop.
This why I always chuckle at people wanting to be able to drive 120kph in the Netherlands. We’re fucking TINY. The width of the Netherlands is around 200km. What are you gaining with 20kph more than is allowed?
I see stuff like this and then I remember the Dukes of Hazard mythbusters testing and I can't help but wonder. How does this car still have a working suspension after that little fling? How does the driver still have clean pants? (Any of them.)
I forget how long I lived there. 4 or 5 years, almost 20 years ago. People would often say something is X miles away, but actually it was km. Old people labelled speed as miles, even though everything was km. I assume because it happened in the 70s after they were young adults.
Yeah, iirc speed limits are in miles and cars have both printed? Been a long time. And there's other stuff. It's not too dissimilar from Canada where colloquially lots of people use imperial, but Canada is more strict on metric being official.
The presentation is in Miles and you can see it when they get closer to the screen. I don't know why the diagram at the top is in Kilometers when the dude keeps talking about Miles. Person who composited the video fucked up.
...why would the values line up differently? If you are going 10 miles per hour it takes you 60 minutes to go 10 miles. The same is true if you are going 10 kilometers per hour, it would take you 60 minutes to go 10 kilometers. Are you confusing it with the *current* inner number displayed in some speedometers which shows the conversion to KPH from MPH?
And this is the point people will miss, they will focus on the “well, I save 1h45m!!!” And not spare a thought that it is still a tiny amount compared to the entire journey itself.
I think it's also important to note, you're not ever going to hit 70-80 mph consistently for a 1000 mile trip no matter where you are or what road you're on. There's going to be traffic you have to slow for at some point, you're gonna likely need to make at least 1 stop, most folks probably more, all of which is going to reduce those supposed time savings even more. I'd be surprised if on average someone even saved a whole hour, you'd probably need a perfect situation for even that much.
and even then, 14 -> 13 hours a ~7% time save. That's a ludicrously small number unless you're racing some kind of concrete deadline like a wedding, funeral or birth. If you spend that extra hour *planning* your trip, you'd likely save more overall time.
Ehhh, the thing is that as you speed up it gets harder and harder to add more speed. It's the inverse with wealth. Give me 30k and I can add a few % over a few years if I'm smart about it. Give me 300k and I can probably add 20-30% in the same time. Give me 3 million and I can probably double it in the same time-frame.
Then if you put it together with the amount of kinetic energy you're adding to your speeding metal doom engine, you'll find the breaking energy required will go up so much faster than any time you'll ever save.
But if you can get to blue shift speed... You would be wise to budget in buffer times for unexpected gravitational distortions. The flip and burn maneuver does always take longer to work than I anticipate. But I do want to figure out an actual answer to the question now that I think about it. My gut says "you're gonna be late regardless" but I'll have to check the math
So we are operating under Terminator rules of time travel in which the desired outcome of time manipulation is that the time flow is ever changing linear
Especially true with an EV - if I drive at the speed limit (120km/h / ~75mph) instead of 90km/56mph, most of the time I'd save is taken up by having to spend longer at the public charger at the motorway services. I actually travel at 100km/h though, as trucks in the EU are limited to 90km/h, so if you cruise at 90, you end up with a truck on your tail, or in your face.
For a electric motor yes. For a combustion engine it depends on the motor. As a example I drive a 2 liter diesel with 150ps. The most fuel efficiency I have at 145 km/h anything below or above is out of the optimal range of transmission and rotation of the motor in combination with the turbo. And some people will see ~ 140 km/h as fast (or slow). There is an efficiency limit to each normal motor since as always you can't beat physics. Anything beyond that point is wasted energy.
Incorrect. Any ICE is limited mostly by wind resistance. Optimal MPG will be within 35-55MPH. REGARDLESS of engine size, capacity, or efficiency. https://www.mpgforspeed.com/
Then you have to factor in traffic (do you have to break a lot and then reaccelerate), and the energy loss caused by tire friction and wind resistance - which increase fast as speed increases. Which probably puts your optimal speed way below the engine’s optimum.
Engineer here. BS. There is no engine with that power output that has peak efficiency at that speed. It's simply not possible, ESPECIALLY a diesel, which typically suffer more efficiency loss at high RPM than petrols do due to being compression ignited (which means they can't advance timing as far).
Peak efficiency will ALWAYS be the lowest speed you can comfortably sit in top gear without labouring the engine. In technical terms, it means when the engine is at about 50% maximum torque output.
Fuel + speed efficiency. Not motor efficiency alone. 100kmh is 5 liter so 140 is 40% more range with only 25% more fuel consumption. Of course I need less energy when I only drive 90. But then I still need 4.5 liters. At 160 I already need > 8l. Anything beyond that loses fuel by being ineffective for the speed + any slow car will exponentially slow you down. You need to ask Peugeot what they did with this motor to be that efficient.
Incorrect. 140 km/h needs nearly double (+100%, not +25%) the power output that 100 km/h needs, and fuel usage goes up accordingly. Engines get progressively less efficient at higher RPM, diesels doubly so, which is one of the reasons industrial engines run at much lower RPM. I have had a diesel Peugeot in the fleet (a T9 308) and there is no way it got more efficient above 100 km/h.
If you live in the real world that means your peak milage will typically be had at around 80 km/h (50 mph), and every 10% faster you go will mean a little over 10% worse milage (power aka fuel flow needed goes up with the square of speed but travel time goes down linearly).
Aerodynamics also has an effect, but yeah, most cars teach peak efficiency between 50-60 mph. However, if you're doing 55 in a 65 for efficiency, you're not a genius, you're an asshole. This is also why the speed limits were reduced during the 80s oil crisis.
Aerodynamics means drag only ever gets worse, there is no escaping it. Really good aero delays this, but cannot ever reverse it, and basically any normal passenger car you car to name will lose laminar flow well before 100 km/h anyway.
I am surprised its that fast though, cos drag squares with speed, and its around that speed that it really starts mattering. Im gonna guess a Golf? Or at least something designed for the autobahn
Ask Ford and Peugeot. I have no idea where that efficiency comes from. It's an Ford Focus from 2018. The profile is pretty low. But the car has an absurd roll distance as well. I have to gear down regularly to the lowest possible gear to not roll into cars on the Autobahn like those damn SUVs that have a wind resistance like a brick wall.
You are correct. Drag is the limiting factor. The other commenter is incorrect. There is no physically possible way that person gets most efficient at around 87MPH unless driving in a vacuum.
WoodORama
Fine. I won't welly it tomorrow.
jshann
This feels like a post about billionaires
Aristocrats
That's why the smart driver focuses on saving precious minutes by running red lights.
diezl97
So where the fuck is my high speed rail network?
turtlefarm
In Europe and China
CrabbyBlueberry
You could also stopping distance on the speedometer. It's roughly proportional to kinetic energy, which is proportional to the square of your velocity. Meaning that if you double your speed, you quadruple your stopping distance.
ellopoppett
This is wrong.
cheidiotou
v = d/t, so t = d/v
t1 = d/v1
t2= d/v2
t_change = t2 - t1 = d/v2 - d /v1 = d(1/v2 - 1/v1)
There's your proof. The reason this absolutely is not wrong is that you're taking the difference of the *inverse* of the speed (aka velocity, v).
Going from 20 (= v2) to 30 (= v1) is:
t_change = d(1/20 - 1/30) = d(3/60 - 2/60) = d(1/60).
That shows the difference per mile traveled (d = 1 mi) is 1/60th of an hour, i.e., 1 minute. 10 miles is then 10 minutes, like he said.
kahooki
THE ONLY THING that irks me is...
the video is about miles and the picture above is about kilometers.
While the relative values stay the same the range of the speedometer should've been adjusted in the upper picture to ~200kph.
Yes it still serves a purpose but this man tried to make a point about speeding. 130mph is speeding. 130kph is fast but not close to the cretins smooching my back every day on the Autobahn.
THEY would argue that even 200kph isn't enough.
petonious
Marginal output. Rule of diminishing returns. Also graphs the golden spiral.
CyberHexx
Don't be a dick.
theskepticinme
The greater the measured distance, the more value is placed on smaller savings. If you save 2 minutes on 10 miles going 80 instead of 60. On a 1000 mile trip that’s 200 minutes saved. 3 hours 20 min. Not insignificant for an otherwise 16h 40min. Worth the increased risk? Debatable I’d say
billiebitkiller
is it miles or km you can't just switch the words without altering anything else
santaferic31415
Speed limit? Move bitch get out da way
jargonmon
I feel like he's giving a lecture to exclusively BMW drivers. I mean... he could be.
Ryzanify
“Nah but I wanna wait at the stoplight faster” -prob some guy who thinks he’s Speed Racer
somerandomhooman
And this is exactly why I floor it in a school zone!
peeopeepeee
That's why I when the limit is 65 I do 125. Almost half the time saved
tinyfootprints
The default speed limit in KSA is 135 kph. I often go around 150. There are no traffic cops and the roads are generally wide, straight, and smooth.
savemebabyjebus
so i have to do 250 to save all the time? /s :)
absolutezero182
You have to do a little over 'c' to save all the time
BallsLikeWatermelonsPeckerLikeAThimble
So I just need to drive 120. Cool.
jalcantara88127001
I think the most fuel efficient speed that cars are tuned for is like 55 too right?
Atomic2
Really depends on the engine and the gearing for an ICE vehicle. With EVs the slower you go the more efficient you are. Im sure there is some low speed where this stops being true and the energy lost to friction is higher than the energy lost to wind resistance, but in theory the slower the better for an EV when it comes to efficiency (assuming constant speeds).
dohcohv
It depends. 55 is a good guideline for most cars though because the EPA tests highway mileage in that speed area, they actually raised it a few years ago and required the A/C to be on.
So older cars(80s/90s) generally tuned for 45-55 while newer 2010+ tuned around 55-60ish.
jalcantara88127001
Nice. Ty
Gibleteousjack
My hybrid Maverick gets mid 40s at ~55, but it drops to around 33 at 80. Like my parents are about 220 miles away round trip. At $4 a gallon it's about $30 to take the interstate or $20 to take the highway. About 2 hours vs 2 hours 30 mins. When gas hits $10 a gallon it will be a no brainer.
KerryCoder
Depends on the car. This is anecdotal evidence but when I drove from Williamsburg, VA to Las Vegas, I ended up getting the most fuel efficiency around 70. It was strange watching the fuel efficiency go down in Utah where the speed limit is 80.
azgrak1
I was taught this in truck driving school. They even gave us a chart. The guys getting paid by the mile will still drive like maniacs though. And those guys are why you see so many bottles of yellow liquid on the side of highways. They’re losing more if they stop.
ToenailClippingsJar
This why I always chuckle at people wanting to be able to drive 120kph in the Netherlands.
We’re fucking TINY. The width of the Netherlands is around 200km.
What are you gaining with 20kph more than is allowed?
Ricdesan
I totally love astute and accurate comparative explanations
DrSharkbite
aquanight
I see stuff like this and then I remember the Dukes of Hazard mythbusters testing and I can't help but wonder. How does this car still have a working suspension after that little fling? How does the driver still have clean pants? (Any of them.)
redundancy
I bet that guy saved 1 whole minute
Endocrom
Bowie Knife99?
Mountons
Fuck sakes, is it miles or km?
somebackup
Welcome to the UK? They're not sure either
Mountons
Ha!
somebackup
I forget how long I lived there. 4 or 5 years, almost 20 years ago. People would often say something is X miles away, but actually it was km. Old people labelled speed as miles, even though everything was km. I assume because it happened in the 70s after they were young adults.
Mountons
We've only partly switched to metric here.
somebackup
Yeah, iirc speed limits are in miles and cars have both printed? Been a long time. And there's other stuff. It's not too dissimilar from Canada where colloquially lots of people use imperial, but Canada is more strict on metric being official.
CurlyBruce
The presentation is in Miles and you can see it when they get closer to the screen. I don't know why the diagram at the top is in Kilometers when the dude keeps talking about Miles. Person who composited the video fucked up.
RatOnnaStick
I can’t get over the fact that someone just took the same pic and replaced miles/h with km/h without changing how the values line up… :/
CurlyBruce
...why would the values line up differently? If you are going 10 miles per hour it takes you 60 minutes to go 10 miles. The same is true if you are going 10 kilometers per hour, it would take you 60 minutes to go 10 kilometers. Are you confusing it with the *current* inner number displayed in some speedometers which shows the conversion to KPH from MPH?
RatOnnaStick
Oh… yea, you are totally right, I got mixed up there.
Amanda55andcows
how much time can I save if I go 80 instead of 70 on a 1000 mile trip?
Quebeker
Around 1h45
schizznatt
It’ll take 12.5 hours instead of 14.3 hours. Not much compared to the overall time.
Pegaxs
And this is the point people will miss, they will focus on the “well, I save 1h45m!!!” And not spare a thought that it is still a tiny amount compared to the entire journey itself.
Xenominim
I think it's also important to note, you're not ever going to hit 70-80 mph consistently for a 1000 mile trip no matter where you are or what road you're on. There's going to be traffic you have to slow for at some point, you're gonna likely need to make at least 1 stop, most folks probably more, all of which is going to reduce those supposed time savings even more. I'd be surprised if on average someone even saved a whole hour, you'd probably need a perfect situation for even that much.
VowelShiftBetch
and even then, 14 -> 13 hours a ~7% time save. That's a ludicrously small number unless you're racing some kind of concrete deadline like a wedding, funeral or birth. If you spend that extra hour *planning* your trip, you'd likely save more overall time.
5050Saint
70 mph would be about 14hr 15min. 80 mph would be about 12hr 30min.
mieper3
you will be there in 7/8ths of the original time
realbrickwall
I mean either way you'll be waiting a fucking long time for the Proclaimers to catch up.
Idontneedrealfacts
top tier right there.
Foolhardyspider
https://media0.giphy.com/media/v1.Y2lkPWE1NzM3M2U1NTY1OWU1aDBxY25zZ3RwN2U1ZzBta2c2d210MGxlZmZxcW45bHJmOCZlcD12MV9naWZzX3RyZW5kaW5nJmN0PWc/sWBzg2D15WwQjHcxbt/200w.webp
Kieralynh
HonHomes
Well, yeah, makes sense. Going from 20 to 30 you're adding 50% to your speed. Going from 50 to 60 you're only adding 20%
HandoB4Javert
Same is true for wealth accumulation...
HonHomes
Ehhh, the thing is that as you speed up it gets harder and harder to add more speed. It's the inverse with wealth. Give me 30k and I can add a few % over a few years if I'm smart about it. Give me 300k and I can probably add 20-30% in the same time. Give me 3 million and I can probably double it in the same time-frame.
HandoB4Javert
Accumulation, not compounding.
CogYang
Then if you put it together with the amount of kinetic energy you're adding to your speeding metal doom engine, you'll find the breaking energy required will go up so much faster than any time you'll ever save.
Zunderfeuer
At what amount of lateness will time dilation occur equal to the speed you are adding to it?
CogYang
Basically anything over a minute will put you into the "still gonna be late" zone, so unless you can get up to blue shift speeds, just take it easy
CogYang
But if you can get to blue shift speed... You would be wise to budget in buffer times for unexpected gravitational distortions. The flip and burn maneuver does always take longer to work than I anticipate. But I do want to figure out an actual answer to the question now that I think about it. My gut says "you're gonna be late regardless" but I'll have to check the math
Zunderfeuer
So we are operating under Terminator rules of time travel in which the desired outcome of time manipulation is that the time flow is ever changing linear
NLOVNI
It’s because of that annoying v-squared thingy
Octomac
Oh, I saw Speeding Metal Doom Engine live in ‘86, that was a great show!
BallSoupHumidity
*braking
IWasGoingToMakeEspresso
… but what if I go from 30 MPH to 90 MPH?
dynamojoe
The faster you go the more fuel (or battery charge) you consume, too. Haste makes waste.
xeoxion
MechKelly
"This" is not entirely accurate.
Yosser
Wind resistance increases exponentially with speed.
Canigetbannedagain2
Must go faster.... I have to poop
MechKelly
Not exactly. Most vehicles get the best fuel efficiency at highway speeds.
Type17
Especially true with an EV - if I drive at the speed limit (120km/h / ~75mph) instead of 90km/56mph, most of the time I'd save is taken up by having to spend longer at the public charger at the motorway services. I actually travel at 100km/h though, as trucks in the EU are limited to 90km/h, so if you cruise at 90, you end up with a truck on your tail, or in your face.
Infinias
For a electric motor yes. For a combustion engine it depends on the motor. As a example I drive a 2 liter diesel with 150ps. The most fuel efficiency I have at 145 km/h anything below or above is out of the optimal range of transmission and rotation of the motor in combination with the turbo. And some people will see ~ 140 km/h as fast (or slow). There is an efficiency limit to each normal motor since as always you can't beat physics. Anything beyond that point is wasted energy.
BuiltonSin
Incorrect. Any ICE is limited mostly by wind resistance. Optimal MPG will be within 35-55MPH. REGARDLESS of engine size, capacity, or efficiency. https://www.mpgforspeed.com/
Anfalicious
Sweet spot on my car is 96km/h. Thats some good engineering.
RatOnnaStick
Then you have to factor in traffic (do you have to break a lot and then reaccelerate), and the energy loss caused by tire friction and wind resistance - which increase fast as speed increases.
Which probably puts your optimal speed way below the engine’s optimum.
RatOnnaStick
*brake a lot
Infinias
Indeed.
Agouti
Engineer here. BS. There is no engine with that power output that has peak efficiency at that speed. It's simply not possible, ESPECIALLY a diesel, which typically suffer more efficiency loss at high RPM than petrols do due to being compression ignited (which means they can't advance timing as far).
Peak efficiency will ALWAYS be the lowest speed you can comfortably sit in top gear without labouring the engine. In technical terms, it means when the engine is at about 50% maximum torque output.
Infinias
Fuel + speed efficiency. Not motor efficiency alone. 100kmh is 5 liter so 140 is 40% more range with only 25% more fuel consumption. Of course I need less energy when I only drive 90. But then I still need 4.5 liters. At 160 I already need > 8l. Anything beyond that loses fuel by being ineffective for the speed + any slow car will exponentially slow you down. You need to ask Peugeot what they did with this motor to be that efficient.
Agouti
Incorrect. 140 km/h needs nearly double (+100%, not +25%) the power output that 100 km/h needs, and fuel usage goes up accordingly. Engines get progressively less efficient at higher RPM, diesels doubly so, which is one of the reasons industrial engines run at much lower RPM. I have had a diesel Peugeot in the fleet (a T9 308) and there is no way it got more efficient above 100 km/h.
Infinias
You want to be an "engineer" and have apparently never seen an engine transmission vs fuel graphic. You are talking absurd bullshit. https://data.motor-talk.de/data/galleries/0/112/8052/23327660/g6-90kw-verbrauch-7926591742525493801.jpg
Agouti
If you live in the real world that means your peak milage will typically be had at around 80 km/h (50 mph), and every 10% faster you go will mean a little over 10% worse milage (power aka fuel flow needed goes up with the square of speed but travel time goes down linearly).
BarryTheCyborg
Aerodynamics also has an effect, but yeah, most cars teach peak efficiency between 50-60 mph. However, if you're doing 55 in a 65 for efficiency, you're not a genius, you're an asshole. This is also why the speed limits were reduced during the 80s oil crisis.
Agouti
Aerodynamics means drag only ever gets worse, there is no escaping it. Really good aero delays this, but cannot ever reverse it, and basically any normal passenger car you car to name will lose laminar flow well before 100 km/h anyway.
Anfalicious
I am surprised its that fast though, cos drag squares with speed, and its around that speed that it really starts mattering. Im gonna guess a Golf? Or at least something designed for the autobahn
Infinias
Ask Ford and Peugeot. I have no idea where that efficiency comes from. It's an Ford Focus from 2018. The profile is pretty low. But the car has an absurd roll distance as well. I have to gear down regularly to the lowest possible gear to not roll into cars on the Autobahn like those damn SUVs that have a wind resistance like a brick wall.
BuiltonSin
You are correct. Drag is the limiting factor. The other commenter is incorrect. There is no physically possible way that person gets most efficient at around 87MPH unless driving in a vacuum.
Anfalicious
Extremely low drag coefficient + extremely high final ratio and you could get there, but yeah, i suspect the drag gets you
Agouti
If you drive a light aircraft... maybe, but even then the most efficient aircraft usually sit around 80-90 km/h.