Space Ghost GT
Well-Known Member
- Joined
- Aug 4, 2022
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- Delaware Ohio
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- GLE 450, space white GT received 11/04/22
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- Nerd
Here is another picture.
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Only way to coast is to shift to Neutral. Otherwise unless heavy on the brakes regen in 1PD overall is equal to regen in 2Pd. Simple as that!I see where you are going, but you have to check your assumptions. Try to focus on energy loss. In the example earlier where you make the decision to "coast" into the stop in 2P mode, you have the potential energy that is being converted to kinetic energy (moving the car towards the stop), such that it will perfectly run out of energy when you come to a full stop. You are assuming, because you did not apply the brakes that there was no waste other than the friction of the road and the resistance from air which are arguably equal in both 2P and 1P mode.
You then postulate, that if you are slowing down using 1P mode by easing off of the accelerator and thus reducing energy input (but still putting in some energy) and generating some electricity to charge the battery; you are actually worse off because regenerating electricity is not 100% efficient and therefore you were better off with the coasting than you are with the regen.
I agree with that. The problem is with the assumption that you coast to a stop and never touch the brake which is the only way to achieve your coasting efficiency. I cannot guarantee, but I'm pretty certain that your coasting inefficiency far exceeds any regen inefficiency.
One of the early posts for 2P was 90% efficient, versus >98% for 1P. Sounds about right to me.
I thought that might be the article you read. I think the title says it all, "... Isn't Necessarily..." It is not a conclusion from an exhaustive study of 1P vs 2P; it is a thoughtful analysis of different approaches and comparing multiple systems for energy use and capture; Porsche believes their solution doesn't require 1P to be efficient.Talk about a bad look it’s hilarious your telling me I don’t own a Mach e when it’s sitting in my garage.
read and weep I’ll take my 100 dollars. You need to get a handle on your emotions.
https://www.roadandtrack.com/car-cu...rily-the-most-efficient-way-of-driving-an-ev/
Is that true? I have used 2P and coasted (while in drive) and it certainly feels like there is very little regen slowing the car down. I have been amazed (coming out of 1P) how far it will coast. Never tried it in neutral, but I haven't done that with a car since I had a stick.Only way to coast is to shift to Neutral. Otherwise unless heavy on the brakes regen in 1PD overall is equal to regen in 2Pd. Simple as that!
Oh, yes! Another white GT owner!Here is another picture.
There are others who have done sophisticated calculations but think of it this way - you put x amount of energy into you car to accelerate. As you slow down that is either lost to friction or reclaimed by regeneration. So maybe a higher regen has larger heat losses in the regen load but then a longer regen (coast) involves more friction. Bottom line, I believe, as long as you do not hit the friction brakes then the regen from 1PD is equal to 2PD. Unless someone can explain where the energy is lost between the two modes. We are speaking in general and not a special case such as “What about a long downhill drive?” (Which May still be the same but my brain already hurts!)Is that true? I have used 2P and coasted (while in drive) and it certainly feels like there is very little regen slowing the car down. I have been amazed (coming out of 1P) how far it will coast. Never tried it in neutral, but I haven't done that with a car since I had a stick.
I'm not saying you are wrong, because I'm not doing any calculations to defend my statements, but from a conservation of energy perspective, I'm not sure they would be equal between 1P and 2P if you coasted to a stop. My reasoning is that If I am going 50 mph and take my foot off the accelerator in either mode, then measure how far the car rolled in each case: X feet in 2P mode or Y feet in 1P mode. I think we would agree that X > Y. Therefore, more of the energy stored in the car of mass M moving at 50 MPH at time 0 went into moving the car in the case of 2P and more of the energy in the case of 1P went into charging the battery.
If you were correct, wouldn't you guarantee 100% braking efficiency in 1PD(assuming no mechanical brake use by driver).. since we know that's not the case, if we are to believe the car itself, there has to be a loss of efficiency depending on the amount of regen introduced.. ie. Complete depress of accelerator results in max decel.. which is not allowing full recapture of energy... for whatever reason. That's my crude explanation how 1PD could introduce inefficient regen. Although... I assume that same situation could be present in 2PD.. it's just harder to isolate. Or my head just hurts... this is fun!!There are others who have done sophisticated calculations but think of it this way - you put x amount of energy into you car to accelerate. As you slow down that is either lost to friction or reclaimed by regeneration. So maybe a higher regen has larger heat losses in the regen load but then a longer regen (coast) involves more friction. Bottom line, I believe, as long as you do not hit the friction brakes then the regen from 1PD is equal to 2PD. Unless someone can explain where the energy is lost between the two modes. We are speaking in general and not a special case such as “What about a long downhill drive?” (Which May still be the same but my brain already hurts!)
You are correct in that it would be the same in 2PD. So if you are driving light to light you put x amount of energy into acceleration and get Y out in regen and Z in resistive losses and X = Y + Z. My thoughts are that unless you brake hard Y and Z are the same for both modes. Of course if you reef on the brakes in 2PD your resistive loses will be greater and you lose regen.If you were correct, wouldn't you guarantee 100% braking efficiency in 1PD(assuming no mechanical brake use by driver).. since we know that's not the case, if we are to believe the car itself, there has to be a loss of efficiency depending on the amount of regen introduced.. ie. Complete depress of accelerator results in max decel.. which is not allowing full recapture of energy... for whatever reason. That's my crude explanation how 1PD could introduce inefficient regen. Although... I assume that same situation could be present in 2PD.. it's just harder to isolate. Or my head just hurts... this is fun!!
Or even more important - Is it further to Kansas City or by bus?Is it faster to 80 mph if I am using 1PD, or 2PD?
My quick calculation shows a MME at 5000lb driving at 40MPH to a stop has about 200Wh energy to be converted to other type of energy.ok, I am going all nitty gritty here.. please bear with me
Lets say in 2PD:
I am driving 40 mph and I see a red light(about 100 meters) and I remove foot from accelerator, car coasts and I apply brakes at the light (lets ignore 95% regen here)
same scenario in 1PD:
I have to take the foot off the accelerator at (lets say) about 50 meters (regen)
so with 2PD, I drive 100 meters with out consuming energy(coast)
and with 1PD, the regen I got (from 50 meters) will not take me 100 meters(it may take me to 40 meters only)
So I think 2PD is efficient (because of coasting).
Imagine doing this many times while we drive.
I know I am not taking real world example, but I hope you get my point.
Feel free to point my mistakes
I do not know whether to laugh or cry at some of the comments that are being made. Your point about energy needing to be converted is right on and that does not matter if you coast or not. The thing that is driving me crazy; though, is that people do not realize that 2 PD is 100% regenerative braking if done smoothly. So my guess is both methods are close to the same efficiency.My quick calculation shows a MME at 5000lb driving at 40MPH to a stop has about 200Wh energy to be converted to other type of energy.
You 2PD case, the energy mostly converts to heat and releases to the air.
1PD case, mostly goes back to the battery.
I don't know why you think wasting on brakes is better.
This is the answer! Drive mode doesn't reduce efficiency, the way you drive does!So my guess is both methods are close to the same efficiency.