ICEs and EVs

[boatgeek]

A problem with turbines is they don't start nice and quick like reciprocating engines.

Starting the CFM of a 737 takes about 30-40 seconds.

A large (1000 hp+) diesel really likes to warm up for ten minutes or so before you rev it up. There’s ways to make that faster, but usually at the cost of more maintenance.

 

[Kallahan11]

I will declare bullshit on "near silent" AbramsX anything weighing 65 tons and moving is audible and easy to hear long before it gets to you and feel through the gound, unless its moving about the speed of your average garden slug.

Its a distance related relative matter. Even the current Abrams with just the turbine is considered quiet, while close in the Turbine is louder than a diesel it's also much higher pitched than a diesel engine. This makes it easier to muffle and reduces the range at which the tank can be heard. You need to remember that an Abrams can engage enemies at over a mile.

Another big thing about the hybrid AbramsX will be the reduced thermal signature while the turbine is off.

 

[bwayne64]

Deleted !

 

[Funkworks]

Looks like coal to me. If you have questions or concerns about how a battery is built or powered, feel free to spell it out. The people who support, build and buy EVs know quite well how they work.

I will declare bullshit on "near silent" AbramsX anything weighing 65 tons and moving is audible and easy to hear long before it gets to you and feel through the gound, unless its moving about the speed of your average garden slug.

The link I posted is from those who make the tank. Here's a video, also from those who make the tank. If you have access to the machine, you can easily measure distance (“long”) and sound levels (“silent”) with any smartphone.

 

[bwayne64]

Wow !

 

[Funkworks]

Maybe you'll like the results, maybe you won't.

 

[BEC]

That was fun....

 

[Funkworks]

I can't help but wonder how the best ebikes would have performed. And what if the Chiron was more aerodynamic? The details of what make one EV perform better than another are still somewhat ...nebulous.

Anyway, I'm cranky and tired because a mechanic knocked the shark fin antenna off my car with a half-opened garage door and I won't have it back until Monday. At least my windshield repair will have been free.

 

[Funkworks]

$10k per 100hp is insane. The most efficient cars, physically and economically are electric. The most expensive ones are ICEs. Some people put their money on power and efficiency, some put their money on looks.

 

[kuririn]

Excuse me if this has been answered before, but something popped into my head just now.
As we all know, fuel economy suffers in an ICE when driving or accelerating hard. The fuel mixture is richer and you get more power but at a price.
But EVs don't have an optimal air/fuel mixture for maximum fuel economy.
So does accelerating or driving hard in an EV result in lower miles per charge?
Just curious.

 

[CalebJ]

The biggest factor regardless of how the power is delivered will be the total amount of work done. If you're regularly acceleration and decelerating just to accelerate again, you'll be inefficient. Jackrabbit starts aren't a big deal, just focus on not giving up speed once you've achieved it. Longer gaps between vehicles ahead to react by coasting rather than braking help, as does timing how you approach a traffic light with the goal of not coming to a complete stop.

Regen braking certainly mitigates some of the loss, but it's certainly not 100% efficient.

 

[afadeev]

Excuse me if this has been answered before, but something popped into my head just now.
As we all know, fuel economy suffers in an ICE when driving or accelerating hard. The fuel mixture is richer and you get more power but at a price.
But EVs don't have an optimal air/fuel mixture for maximum fuel economy.
So does accelerating or driving hard in an EV result in lower miles per charge?
Just curious.

Absolutely - Yes!

Just like you drop your ICE mileage on track from ~28mpg to ~6mpg (if you drive with conviction), so will your EV's kWh climb (inverse measure) from ~285 to ~1200.
BTDT.

On the street, you might recoup some of that by decelerating via regen, but it's not 100% efficient.
And if you have the motivation to accelerate at full power, you will likely be motivated to brake at a far greater rate than engine regen can provide.

HTH,
a

 

[kuririn]

Ah, I just remembered about the squaring effect of aerodynamic drag.
Too bad, I was hoping I could be a leadfoot if I bought an EV.

 

[OverTheTop]

If you want more acceleration out of the motor you need more torque. More torque needs more magnetomotive force. MMF has units of ampere-turns. You can't instantaneously change the number of turns in the windings of the motors, but you can increase the current. That increases the resistive loss in the windings (I^2 × R) and other electronics, and also the eddy current losses will go up. I am guessing transmission losses go up with higher power. So I think not dissimilar to ICE cars.

 

[boatgeek]

Ah, I just remembered about the squaring effect of aerodynamic drag.
Too bad, I was hoping I could be a leadfoot if I bought an EV.

Nothing stopping you from being a leadfoot...

 

[BEC]

Excuse me if this has been answered before, but something popped into my head just now.
As we all know, fuel economy suffers in an ICE when driving or accelerating hard. The fuel mixture is richer and you get more power but at a price.
But EVs don't have an optimal air/fuel mixture for maximum fuel economy.
So does accelerating or driving hard in an EV result in lower miles per charge?
Just curious.

Of course it does, as others have noted. The amount of power it takes to accelerate a given mass at a given rate doesn't change with the source of the energy. And of course drag is drag.

That said, since EVs are so responsive, it's nard not to leadfoot it some. It's my own theory that this is at least one major reason why EVs have a reputation for going through tires more quickly....along with higher weights. It's just too hard to avoid temptation to just get up and go.

 

[kuririn]

Reason I ask is that I read somewhere that the amount of energy to traverse a set distance is the same whether you do it in one minute or ten minutes.
Likewise a person burns nearly the same amount of calories whether they walk or run a mile.

 

[jderimig]

Reason I ask is that I read somewhere that the amount of energy to traverse a set distance is the same whether you do it in one minute or ten minutes.
Likewise a person burns nearly the same amount of calories whether they walk or run a mile.

Energy consumed is equal to the work done which is F x d. If F is the same then the energy consumed doesn't have a time (t) factor in it. However F is not the same walking as running.

 

[CalebJ]

I don't see how that's true. There's significantly greater impact on joints and such when running because of the landing forces so I'd expect energy usage to be significantly less efficient.

 

[mbeels]

Reason I ask is that I read somewhere that the amount of energy to traverse a set distance is the same whether you do it in one minute or ten minutes.
Likewise a person burns nearly the same amount of calories whether they walk or run a mile.

That's mostly true (to "first order" as some physicists like to say). The simpler and more perfect your system is, the more true it is. But the more complex your system is (and the more factors you include), the less true it is. Air resistance is one reason it isn't perfectly true, I^2 R losses in a EV is another reason it isn't quite perfectly true.

 

[jderimig]

I don't see how that's true. There's significantly greater impact on joints and such when running because of the landing forces so I'd expect energy usage to be significantly less efficient.

^This. If you consider all the work is applied to just the moving from point A to point B (and neglect air drag) this is true. But a real world machine (like a human body) is doing more work on "other things" as rates go up. Joints is one, work on the elastic parts of your running/walking shoes is another and so on.

For example the car tires heat up a lot more going 50 mph than 5 mph. That energy comes from somewhere and it is not that part is not helping getting your from point A to point B.

 

[afadeev]

There's significantly greater impact on joints and such when running because of the landing forces so I'd expect energy usage to be significantly less efficient.

^This. If you consider all the work is applied to just the moving from point A to point B (and neglect air drag) this is true. But a real world machine (like a human body) is doing more work on "other things" as rates go up. Joints is one, work on the elastic parts of your running/walking shoes is another and so on.

Scientific study to settle the debate:
https://pubmed.ncbi.nlm.nih.gov/15570150/

• Although theoretically walking and running a mile should require the same work, running required more energy than walking for 1600 m, regardless of whether the subject was on the track or the treadmill.
• Running required more energy for 1600m than walking (treadmill: running 481 +/- 20.0 kJ, walking 340 +/- 14 kJ; track: running 480 +/- 23 kJ, walking 334 +/- 14 kJ) on both the track and treadmill.
  • ~43% premium energy consumption while running
• Predictions using the ACSM or Leger equations for running, and the Pandolf equation for walking, were similar to the actual energy expenditures for running and walking (total error: ACSM: -20 and 14.4 kJ, respectively; Legers walking: -10.1 kJ; Pandolf walking: -10.0 kJ).
• Gender differences observed were attributed to the significantly larger metabolically active tissue (fat-free mass) found in the male population. By adjusting for metabolically active tissue, gender differences disappeared.

 

[OverTheTop]

Reason I ask is that I read somewhere that the amount of energy to traverse a set distance is the same whether you do it in one minute or ten minutes.
Likewise a person burns nearly the same amount of calories whether they walk or run a mile.

It is the physics idea of "displacement" (distance). Theoretically moving from one location to another (in a perfect frictionless world), and back again gives you zero displacement. Since (as pointed out above, work = force x distance, then the overall outcome is no work (energy) expended. The losses come from other effects, like mecanical and electrical power losses, drag etc.

In an EV you do get some things on your side. Regenerative braking puts some of the energy back into the batteries, but there are losses associated with that. It does help with range a little, and it really helps with brake pad maintenance. Usually the discs are only needed under about 5kph (based on my traction experience in the Tramways here, years ago) when the motors are not effecient enough as a generator so can't provide any torque to brake with. There is a bit of an art to blending the two braking systems. It isn't as straight-forward as you might think. Some cleverness in the software means it is all handled very well.

 

[jderimig]

It is the physics idea of "displacement" (distance). Theoretically moving from one location to another, and back again gives you zero displacement. Since (as pointed out above, work = force x distance, then the overall outcome is no work (energy) expended.

But work is calculated as W = F dot D where F and D are vector quantities and work is scaler. Assuming 1D motion the trip out work is FD, the trip back is (-F x -D). So the total work is 2FD.

 

[jderimig]

Walking is a special case because no energy is being conserved when you walk or run in a straight line on level ground.
If you consider a perfect frictionless EV in a vacuum with perfect regenerative braking, the work done to accelerate to your coasting speed is [F dot Da], while coasting the work is [0 dot Dc] and when you brake to a stop the work is [-F dot Db]. Sum of work = 0.

 

[OverTheTop]

But work is calculated as W = F dot D where F and D are vector quantities and work is scaler. Assuming 1D motion the trip out work is FD, the trip back is (-F x -D). So the total work is 2FD.

Correct, for a real situation. I have clarified my post with "frictionless".

 

[flyingeagle]

Football game is suspended tonight

 

[bjphoenix]

But work is calculated as W = F dot D

We don't know what the total work is.
Besides moving a mass, and friction and air resistance- how much extra heat is generated? The ICE has reciprocating mass- bits and pieces that move back and forth and have to be accelerated, decelerated, etc. How does the efficiency of converting fuel to movement change when the mechanisms are pushed to their limits?

 

[BEC]

And of course there's the mass of the vehicle as a whole that has to be accelerated and decelerated. To me that's where the "waste" of lead footing goes, regardless of the power source turning the wheels....That an ICE engine is less efficient than normal when you put your foot in it, these days with computer-controlled mixtures and spark and even valve timing, is probably less of a factor than it was back in the good/bad ol' days of four-barrel carburetors (man, I miss the way my Rx-2 felt when those back two barrels opened up....)

 

[OverTheTop]

That an ICE engine is less efficient than normal when you put your foot in it, these days with computer-controlled mixtures and spark and even valve timing, is probably less of a factor than it was back in the good/bad ol' days of four-barrel carburetors (man, I miss the way my Rx-2 felt when those back two barrels opened up....)

Modern engines are great. I have a Hemi 5.7 in the Jeep and it gets the same fuel economy that I used to get in my '82 Toyota Celica. That was a whole 88hp in the earlier car, compared to 360hp in the Jeep. GVM is well on the way to double as well.