What planet are you people living on?

The next "Las Vegas Prius club" meeting is going to be vastly more exciting than usual.

 

Me thinks this was all a huge publicity stunt to increase attendance at said meeting. B)

 

<div class='quotetop'>QUOTE(PriusTouring07 @ Aug 6 2007, 12:16 AM) [snapback]491076[/snapback]</div>

Thanks so much for sharing your findings. Even with the numbers you have given, you have increased your miles per gallon, but you did not recooperate the actual physical energy that was contained within the gas. I don't know if you were thinking of that. You were accurate on the mpg increase, and the energy saved to teh battery, but it isn't the same as recooperating 100% of your fuel energy used. The battery on the prius is pretty much a very tiny thing. Physics-wise you did not recooperate all the energy, but you certainly increased your mpg! They are going to begin putting the hybrid drive train in the diesel locomotives. They were already regenerating energy, but just making heat with capacitors, instead of storing it. Now the batteries are giving the space for diesel storage a run for it's money. Trains + hills = MAJOR power lol

<div class='quotetop'>QUOTE(PriusTouring07 @ Aug 6 2007, 12:59 AM) [snapback]491096[/snapback]</div>

I just wanted to say, when I drive in the hills of wisconcin my fuel mileage goes up significantly, but here in flat illinois, it's not as nice. However, it's the whole "energy densities" thing that makes the gas so potent and blah blah has lots of energy. Have a good one in Montana

 

I did some mountain driving yesterday, on AZ 89A from Prescott to Cottonwood, AZ.

Here's the terrain profile (from Delorme Topo USA).
[attachmentid=10405]

Here's a picture of the MFD at the end. I had filled the tank and reset the mileage in Prescott. There was an additional 12 miles from Prescott to the beginning of AZ 89A that aren't on the above profile, but it's essentially flat.
[attachmentid=10404]

I averaged about 25mph -- in addition to being steep, this road has tight turns and it was raining. Even with 1700ft freebie of regeneration, I still didn't get past 53.5mpg. The battery was down to 1 bar at the top, and charged up to the full 8 bars on the way down. I had the A/C on low. Most of the trip down was in "B".

 

<div class='quotetop'>QUOTE(PriusTouring07 @ Aug 5 2007, 11:59 PM) [snapback]491096[/snapback]</div>

No one said you were lying. People here are trying to point out a very simple misunderstanding you have about energy and MPG.

Your assumption is that the Prius's MFD miles-per-gallon reading == energy, and that returning to the same MPG, be it 51 MPG or whatever, is the same as not having used any energy.

This isn't true. Miles per gallon is exactly that... miles traveled, over a gallon of fuel consumed, on average, of course.

Your test is to simply observe the MFD to see what your MPG before climbing a hill, and after coming down the other side, however, you need a control case in your experiment.

A suitable control case to your experiment would be : take the same distance traveled as the hill, but flatten it, so there is no elevation difference anywhere from point A to B. So, if your hill was an upside down V, imagine flattening it down to a line, covering the same distance. Measure your MPG from beginning and end of that flat case as your control.

Now, as the meat of your experiment, measure with the elevation change from points A to B. Compare MPGs.

You don't need to yell at people that they haven't performed your same test, since you do have faulty assumptions and lack of a control case.

No one is disputing that you reached the same or higher MPG going up and down this hill... that is not the same as what "experts" are saying about physics. If you did the experiment like i outlined above, because of all of the factors that people here have been saying, MPG going up and down a hill would be worse than if you did a flat shot with no elevation change.

<div class='quotetop'>QUOTE(PriusTouring07 @ Aug 6 2007, 01:28 AM) [snapback]491125[/snapback]</div>

It's entirely possible that the elevation on one side of the hill is lower than the other. That's not the same as a blanket statement saying that you can climb any hill and have the same MPG as you started with. That's WAY too general.

<div class='quotetop'>QUOTE(PriusTouring07 @ Aug 6 2007, 01:28 AM) [snapback]491125[/snapback]</div>

You never said energy, but you certainly hinted at it when you said " Most "experts" here seem to insist that what you lose going up a hill, you can't fully regain going down"

"what you lose" == energy, to most people.

 

<div class='quotetop'>QUOTE(PriusTouring07 @ Aug 5 2007, 09:16 PM) [snapback]491076[/snapback]</div>

Are you serious?
.
.
It sounds like I'm in highschool again. (pinkslips? ha ha ha)
I have done plenty of mountain climbing I live in Southern Colorado for one and Love San Isabel...any way, on to my argument....if you did infact regain all that you lost on the hill climb (which i'm sure wasnt' that long of a climb since your MPG only went down to 46 from 51.) the amount of fuel in your tank would have went back to its original amount!, Since I am POSITIVE this didn't happen, you did not regain all that you used to climb the hill in the first place. All it did was improve your MPG Average since you didn't use any gas coasting down the hill.

besides I'm sure the regenerative braking has a maximum output to re-charge the HV battery. so there is another loss of energy....

Now I'm out!

 

Well, I'm just gonna say that I don't believe you gain MPG by driving in hilly areas. I mean, I have yet to see any person get over 100 MPG in the mountains.

I have an older Prius, so turning on the AC in my car is quite noticeable. If you are referring to highway driving with the AC on, then no there is not much difference. In anything other than highway driving though, there are major loses for using the AC, and I can show you if you want, but I'd rather not waste gas.

Not sure how you all got to arguing about energy vs gas. They are different, and I'm sure he knows that.

I also don't understand why he decided to post this is the first place. In a place like this that's just asking to be flamed.

 

It works!

This weekend I was near empty til I drove up Mount Rainier. By the time I reached the top, I was down to 3 bars of batteries and the tank was dry...

Then I turned around and drove back down. Now the battery's at 10 bars and the tank is full!

It makes mathematical sense too... Infinity minus 25 still equals infinity, just a little less of it. I doubt any of us here would really notice 25 more or less of anything, if we had an infinite amount of it.

 

<div class='quotetop'>QUOTE(PriusTouring07 @ Aug 6 2007, 12:22 AM) [snapback]490991[/snapback]</div>

In fact, the observation you made (which I don't doubt was true) doesn't prove anything. One point is that average MPG is not necessarily the same as total consumption of fuel. The average MPG displayed on the screen of the Prius is likely to be some kind of moving average over a floating time or distance window, perhaps even with a weighting bias towards the most recent data points. Some maths show that, in such a case, if the MPG temporarily goes up and then down again to the same level, you have consumed in total more fuel over that time period than if it would have stayed the same.

Another point is that you don't mention anything about the speed you were driving up and down the mountain. If that average speed is slower than the average you were driving before, your total fuel efficiency may very well have increased indeed, simply because there was less wind resistance.

A third issue similar to the second is about starting and stopping. If you were driving up and down the mountain without any stop, you gain some efficiency compared to a normal (flat) average cycle that contains stops.

So your experiment was a nice try, but, from a scientific perspective, it has some severe issues. Until those are addressed, I stay on the side of 200 years of thermodynamics research that says that, all else equal, it can't be the same.

 

<div class='quotetop'>QUOTE(PriusTouring07 @ Aug 5 2007, 11:16 PM) [snapback]491076[/snapback]</div>

If he has a Prius, he hasn't had it long enough to even know. A/C costs me 2 mpg after 1 year and 18,000 miles. Leaving it at 78 degrees and living in hot Florida.

 

1. I can perfectly believe that going up and down some mountains could, in certain situations, improve ones mileage average. For the up slope, clearly mileage will suffer, and the average will probably go down. however for the downslope, one will be running (simplistically) using no fuel at all and will also be using regenerative braking so the average will be influenced by the 99.9 mpg all the way down and the battery will get charged. Obviously you will not gain energy as you have used energy getting to the top and friction losses etc and energy conversion factors mean that you will be in deficit, but I don't think that was what the OP was saying.

2. Having the A/C on will use more petrol. It takes energy to run the compressor and this eventually has to come from the fuel, and the only fuel one puts into a Prius is petrol. I can fully accept that the efficiency of the compressor in the Prius means that this is a nominal amount but it can be quantified. Won't stop me using mine though!

 

<div class='quotetop'>QUOTE(Alexstarfire @ Aug 6 2007, 02:18 AM) [snapback]491133[/snapback]</div>

Honestly, I don't think anyone has flamed him in response. We have perfectly reasoned posts by several highly experienced members here, including a moderator.

If anything, he's been the one flaming, with one post entirely in CAPS with several profanities.

 

<div class='quotetop'>QUOTE(PriusTouring07 @ Aug 5 2007, 07:15 PM) [snapback]491005[/snapback]</div>

Yes the math is quite simple. In this example you have used 1 gallon of gas going 25 miles up hill and (presumably) no gas coming back down hill the same 25 miles. Therefore you have used 1 gallon of gas to go a total of 50 miles. So that's 50 mpg for the trip. It's not surprising that your mfd displayed the same 51 mpg at the end of the trip as it did at the start, particularly if you already had a decent amount of miles on the reading. As others have noted, if you traveled the same 50 miles over perfectly flat terrain at the same average speed with the same number and manner of stops and all other things being equal, you would have gotten even better mpg (used less than 1 gallon of gas). This is not disputable.

 

<div class='quotetop'>QUOTE(LaughingMan @ Aug 6 2007, 06:57 AM) [snapback]491192[/snapback]</div>

I agree.

 

Lets see:

At the top of the hill his vehicle actually weighs less because some of the fuel has been burned getting to the top of the hill. At the bottom of the hill his vehicle weighs the same as it did at the top of the hill. A dead or fully charged battery weighs the same, so where is this mystery coming from, perhaps a happy hour at a local casino or two??? You know, I had two free drinks when I got to the casino, my wallet was lighter on the way out of the casino even though I consumed free liquid in the form of cheap booze or beer. Could it be the effect of the Las Vegas sun on the light headed gray matter cranium?

I do not now, nor have I ever believed ina perpetual motion machine. Period. There is no free lunch, not in Vegas or in the entire universe as I understand it.

It would be nice to live and work in Las Vegas and have that happen on a regular basis.

I suggest your boss hand you a pinkslip and a week long stay at bellevue, they have AC in the basket weavers lounge......they're coming to take me away ha ha, ho ho hee hee, to the funny farm, where life is merry and happy and gay...ha ha.

Does this qualify as a flame response?

 

Is there a point to this whole thread?

 

<div class='quotetop'>QUOTE(Highly ImPriused @ Aug 6 2007, 10:44 AM) [snapback]491215[/snapback]</div>

I think that was pretty much exactly the point the OP was making and which has been turned around since to mean something else.

He said: "2) Most "experts" here seem to insist that what you lose going up a hill, you can't fully regain going down." Then there was a lot of verbiage up to the conclusion that he has ended at the bottom with the same 51 mpg he started with, and two extra bars of battery SOC, not surprisingly, from the descent.

The subsequent 'argument' has been meaningless since it's largely been cast on interpretations of what the OP meant, not what he said.

Now, if someone had argued 'No, that's not what 'experts' insist....' to his starting post, I think we wouldn't have got to 2 pages of nonsense (so far).