What planet are you people living on?

<div class='quotetop'>QUOTE(ZA_Andy @ Aug 6 2007, 11:48 AM) [snapback]491255[/snapback]</div>

I wasn't trying to prove the OP's point so I'll spell out a few observations that will hopefully clarify things.

1) When "experts insist that what you lose going up a hill, you can't fully regain going down", they are refering to energy being lost (or expended). That energy is provided by gasoline in this case. The laws of physics tell us that it takes more energy to get up and down a hill than it does to travel the same distance over flat terrain, all other things being equal. The prius is able to recapture some of that "lost" energy using the battery, but certainly not all of it.

2) If the OP had gone up a steeper hill over the same distance (all other things being equal) he would have used more gas going up. So lets say 20 mpg going up the steeper grade 25 miles. That's 1.25 gallons consumed. The descent again would be zero gallons consumed. So the same 50 miles with 1.25 gallon cosumed comes out to 40 mpg. The mpg displayed on the mfd would have dropped some in this case.

3) I suspect the OP's rate of acceleration going up the hill was less than he typically uses in daily driving. In this case it just so happened that the combined effect of better mpg at slower acceleration and worse mpg for hill driving approximately canceled each other out. If he had accelerated at the same rate he would typically use on flat terrain he would have had gotten worse mpg for the hill trip.

 

<div class='quotetop'>QUOTE(PriusTouring07 @ Aug 5 2007, 04:22 PM) [snapback]490991[/snapback]</div>

First of all, I live in extreme southwestern Utah, where the temperature is only slightly lower than Las Vegas, and I agree that there is very little difference in mpg with the A/C running.

But regarding your assertion that it is possible to "regain everything ... lost," that would amount to perpetual motion. Simply restoring the average mpg to the value it had in the past does not prove that you regained everything lost. For that to be true, you would have to magically restore the fuel level to exactly the same as it was before your test drive. Rolling downhill can, in fact, restore the same average miles per gallon but it does not restore the gallons consumed in climbing the hill.

 

I remember some surprisingly good mileage in rolling hills, despite the relatively high speed, but it was the batteries being refilled on the way down, not the gas tank. I do not know, people, somebody's got some 'splainin' to do... :mellow:

 

<div class='quotetop'>QUOTE(Highly ImPriused @ Aug 6 2007, 12:22 PM) [snapback]491290[/snapback]</div>

Well thank you, but I'm not much interested in your observations. Nothing personal intended, but I understand what the OP was saying, and to that extent I agree with him. I'm not sure that I would have couched it in terms of 'regained everything lost' since this has simply encouraged armchair physicists to focus on everything but the point (I think) he was making, which is really nothing more that that the MPG read the same at the end as at the start.

 

<div class='quotetop'>QUOTE(ZA_Andy @ Aug 6 2007, 01:08 PM) [snapback]491327[/snapback]</div>

OK fine, lets focus on what he was saying. Here is the exact quote:

<div class='quotetop'>QUOTE(PriusTouring07 @ Aug 5 2007, 06:22 PM) [snapback]490991[/snapback]</div>

He claims to have proved a "theory" wrong. The problem is that what he's arguing against isn't a theory and he doesn't fully understand it. The laws of physics dictate that the energy that is used getting up a hill can't be fully regained going down. That is fact, not theory. That he maintained the same MPG and gained extra charge on his battery at the conclusion of his mountain trip as compared to the start has nothing to do with that fact. Again, there are so many variables associated with MPG achieved (rate of acceleration being a big one) as to make his point utterly meaningless.

 

<div class='quotetop'>QUOTE(Homer Simpson @ April 16, 1995, 08:23 PM)</div>

 

A life long friend's father went to his grave arguing that the moon landing was actually shot on a movie set. He did not believe that man had landed on the moon and would argue vehemently with you his opinion. His son, my friend, tried time and time again to get his dad to change his mind with much proof and data. He wasn't successful as per my first sentence.

Thank you OP for pointing out to us that you are able to maintain or better your MPG and gain more battery charge going up and coming down a mountain.

Thank you physics experts for reminding us of the impossibility of perpetual motion, energy consumption and for sharing your knowledge with the group. Please do not post tables, charts, scan gauge data or quote a Newton’s law here.

If this continues I will understand why the trolls make fun of us.

A wise man knows when enough has been said. For the others reading this, "Put the whips up boys, the horse is starting to stink."

 

<div class='quotetop'>QUOTE(Skinflint @ Aug 6 2007, 02:25 PM) [snapback]491386[/snapback]</div>

Indeed so.

 

I'm surprised no one pointed out the OBVIOUS flaw in his study.
He uses a sample of ONE. No scientific testing equipment, just his own observation and interpretation of the situation. Heck he only talked about one instance on one hill on one drive.

By that same theory, all men are good looking, 5 foot 6", smart, drive great cars and did I mention good looking. Now this is FACT. I can prove it. I studied myself. Study me and it will be proven as FACT. I'll bet /Dr Evil voice [$1 MILLLLIOOON Dollars] \End Dr. Evil Voice to anyone who can prove me wrong.

 

Regardless of what you or anybody else thinks they "measure", the laws of physics are the same everywhere in the observable universe. So who cares what planet I'm on. The laws of physics are the same!

 

Just - remember - that you're standing on a planet that evolving...and revolving at nine hundred miles an hour....
that's orbiting at nineteen miles a second... so it's reckoned...a sun that is the source of all our power....
Now the sun and you and me and all the stars that we can see....are drifting at a million miles a day....
in an outer spiral arm at 40,000 miles an hour in the galaxy we call the milky way.

Now our galaxy itself contains a hundred million stars, it's a hunded thousand light years side to side....
it bulges in the middle 30,000 light years thick, but by us it's just 5,000 light years high.....
we're orbiting around the glaxic central point.... we go around it every 200 million years....
and our galaxy is only one of hundeds of millions in this amazing and expanding universe.

Now the universe, you see, keeps on expanding and expanding.... in all of the directions it can wiz....
as fast as it can go.... the speed of light (you know)....12,000,000 miles a minute and that's the fastest
speed there is...
So remember when you're feeling rather small and insecure.... just remember how unlikely was your birth....
and pray that there's intelligent life somewhere up in space... cause it's all bugger down here on earth.

 

Prius Touring 07-Quick Question. What was your starting elevation and your ending elevation? (This is not a comment in disguise, it is a real question.)

 

<div class='quotetop'>QUOTE(PriusTouring07 @ Aug 5 2007, 10:28 PM) [snapback]491125[/snapback]</div>

My Voodoo adviser said: "... and keep going "

 

<div class='quotetop'>QUOTE(Nda3rdCar @ Aug 6 2007, 11:10 PM) [snapback]491529[/snapback]</div>

I think Eric Idle sang" 'cause there's bugger all down here on Earth" though your version does apply at times!

 

One way to explain why people get better mileage when driving in hilly terrain is this. The engine is operating in a more efficient load range when going up a hill. I think the most efficient load range for the Prius engine is up around 50%? No? When travelling on the flats, the engine is producing much less horsepower, so it is probably less efficient.

Back to the OP. He is clearly confusing mpg as at relates to gaining what you lost going up compared with what you gain coming down.

 

On my planet, its all downhill.

 

He gained all of the bars the battery used on the uphill trip and an additional 2 bars on the way down the hill. To me that means that he had more energy in the battery then when he started.

He never stated that he had more gas (or the same amount of gas) in the tank after going down the hill as he had before going up.

If you use the MFD to measure mpg and you had an average of 51mpg before going up the hill and you still have 51mpg at the bottom of the hill you have gained back (mpg) going down what you lost in mpg going up.

 

<div class='quotetop'>QUOTE(wkramer @ Aug 7 2007, 02:43 PM) [snapback]491939[/snapback]</div>

The problem with your statement that he gained back mpg is that it assumes that MPG is a tangible thing that you can capture back and have... it is not that. It is simply miles traveled per gallon of fuel burned. In the case of the Prius MFD, it is a historical average.

It is an average over miles and time. Gaining or losing MPG doesn't have the same meaning as recovering energy or using energy...

The fact that he said he averaged 51 MPG before the hill and the same after the hill only tells me that the hill probably averaged close to 51 MPG on average for the climb and descent together. It doesn't tell me anything inherent about how he has more of anything than he started out with.

If for example, he had averaged 60 MPG instead of 51 MPG at the very same spot before the hill, certainly he would not have returned to 60 MPG at the end of his experiment (since his climb and decent would have averaged still the same 51 MPG, his average would have fallen and stayed down from 60 MPG) he would have concluded that somehow he "lost" MPG along the way, even though he averaged the same MPG for that distance.

If, for example, he had an average of 20 MPG instead of 51 MPG at the same spot before the hill, he would have ended the experiment EXCEEDING the original 20 MPG because the hill with the climb and descent together averaged 51 MPG. He would have yelled twice as loud that somehow he violated the laws of physics because he ended with "more MPG" than he started even though there was a hill.

This is why his experiment and his confrontational demeanor afterward is sort of meaningless...

Looking at your MPG and making the average number go up or down may be a neat game you can play while you're on a long car ride, but by no means is it hard science.

 

I think all you guys are just jealous because he is so much smarter than everybody on this forum!

Not only has he figured out a way to run his AC using absolutely no energy, most likely he charges his traction battery while running his AC--how come none of you guys can figure that out?

 

I think his Prius is the special Cold Fusion Edition!