How to properly test modifications (AKA: don't believe every MPG claim you read)

[oldbeaver]

Originally Posted by UFO

oldbeaver, you are not interpreting the laws properly.

"You can't win" means you cannot extract more energy out of the system than you put in. Truly, you "cannot win".

"You can't break even" means all energy conversion systems have an intrinsic loss (called entropy), so truly, you "cannot break even".

Forget about "HOH". The conversion efficiencies are easy to calculate, and they add up so badly there is no chance of a mileage improvement. NONE.

You wrote: "You cannot get more energy out from the system than you put in".

Yes, you are completely right.

Now, in a Otto engine you put, say, 100 of gas energy and get 20% out of it as movement, the rest is lost. In the process, some energy is spent in preparing gas to burn (compression), inject gas, etc.. This energy is less than the one we get out of gasoline. Therefore, there is 20% of utility energy. We get some energy out of it all for us to use.

In the case of HOH, we get some energy out of water too. Water is a fuel, just like gasoline. Unfortunately, preparing water (electrolysis) takes a lot of energy, actually more than we get out of it by combustion of H in the engine.

At least, for me is so. In one case algebraic sum is negative, in the other is positive. Is a practical thing. Laws are there and practical things are here. And they BOTH work.

This is the way I see it.

[Cd]

What would be the proper way to test a car too old to use a ScanGuage and no cruise control ?
By the way, I use a SuperMID .

[Nerys]

"In the case of HOH, we get some energy out of water too. Water is a fuel, just like gasoline. Unfortunately, preparing water (electrolysis) takes a lot of energy, actually more than we get out of it by combustion of H in the engine. "

your still not getting it.

100% of all fuel methods you can dream up will ALWAYS take "more energy in" than you will get OUT of combustion (or whatever process you use)

when you make the statement you made you IMPLY directly that gasoline gives you more energy out than was required to GET that gasoline and this is patently false.

ALL ENERGY TRANSFERS ARE SUM NEGATIVE. PERIOD. End of Line.

according to the laws of physics as we know them this is an absolutely inviolate truth of the UNIVERSE AS WE KNOW IT.

energy in versus energy out is NOT RELEVANT.

what IS relevant (in this discussion) is not even what most people think.

TO me at least ecomodder has NOTHING to do with MPG's

it has to do with CPM.

COST PER MILE. it just so happens that higher MPG when using the same fuel always equals LOWER CPM.

but its CPM we are after.

I don't drive a Geo Metro getting 60mpg (last 4 tanks baby) to get 60mpg. I do it because 60mpg COST ME LESS MONEY.

even if HOH is insanely inefficient thats ok if #1 it works (I have no idea if it does in theory it should) and #2 what does it COST what is its CPM.

Electricity is CHEAP compared to gasoline. its darned near FREE compared to gasoline.

would I try HOH? NO. why? because by the time you have a large enough battery pack to make HOH usable you already have a large enough battery pack to go 5 times further with a simple electric motor.

ie with current tech it just can't work ie in a CPM consideration.

[Nerys]

Cd my guess would be LOTS of tests and "average" the results to remove slight errors in runs.

might start with a fuel cell say 1 gallon. get up to speed and when your ready switch over to your 1 gallon fuel cell run till its dry.

that is your MPG. now repeat for consistent results and then make a change repeat several times average the results. switch back ie remove mod and do it again. average the results.

[oldbeaver]

Nery's

You wrote: "ALL ENERGY TRANSFERS ARE SUM NEGATIVE".

This is a nonsense sentence.

All energy transfer is sum zero.

PERIOD. End of Line.

[Nerys]

oldbeaver. your statement ignores the very clear CONTEXT of the statement made. Please reread the post I was replying to and then rereard my post using appropriate context please.

"In the case of HOH, we get some energy out of water too. Water is a fuel, just like gasoline. Unfortunately, preparing water (electrolysis) takes a lot of energy, actually more than we get out of it by combustion of H in the engine.

At least, for me is so. In one case algebraic sum is negative, in the other is positive. Is a practical thing. Laws are there and practical things are here. And they BOTH work."

[MetroMPG]

Originally Posted by Cd

What would be the proper way to test a car too old to use a ScanGuage and no cruise control ?
By the way, I use a SuperMID .

The SuperMID has a "resettable average" fuel consumption function, I assume. You need that.

Without cruise control, you're likely to suffer from more variability in your runs (both speed & fuel consumption), especially if your test route isn't flat & devoid of other traffic (aero effects). You'll see just how much variability there is after you do your first set of "A" runs. If your fuel consumption figures are grouped very tightly / consistently in the set of runs, it may suggest you've got a steady foot.

Does the SuperMID also have a resettable average speed display? You could monitor how accurate your foot is, if it does.

If you're only testing aero mods, you could get around this problem by just doing coastdown testing. It's perhaps not as satisfying as seeing actual MPG figures, but you'd still get a relative indication of whether a mod has any impact vs. coastdown runs in the "control" state.

[UFO]

Originally Posted by oldbeaver

Now, in a Otto engine you put, say, 100 of gas energy and get 20% out of it as movement, the rest is lost. In the process, some energy is spent in preparing gas to burn (compression), inject gas, etc.. This energy is less than the one we get out of gasoline. Therefore, there is 20% of utility energy. We get some energy out of it all for us to use.

In the case of HOH, we get some energy out of water too. Water is a fuel, just like gasoline. Unfortunately, preparing water (electrolysis) takes a lot of energy, actually more than we get out of it by combustion of H in the engine.

At least, for me is so. In one case algebraic sum is negative, in the other is positive. Is a practical thing. Laws are there and practical things are here. And they BOTH work.

This is the way I see it.

So for the 20% utility case, you add the "HOH" system and then get 18% or less utility. And you would consider this an option?

[oldbeaver]

Originally Posted by UFO

So for the 20% utility case, you add the "HOH" system and then get 18% or less utility. And you would consider this an option?

Unfortunately, it comes out that it is not.

What if we have to produce gasoline from oil onboard? Do you think it would be an option? Probably not also.

That is my point.

I don´t discard it "a priori" because of The Law. I discard it because it is not efficient. And if gasoline had to be refined on board, I would probably have to discard it too.

That is my point. I try to be rigorous.

My limited English makes me difficult to express myself.

[jakobnev]

Originally Posted by JRMichler

After suffering through undergrad thermodynamics, the professor was kind enough to translate the laws of thermodynamics into English.

Your professor was

MC Hawking?

(Dammit, that was supposed to be linked but not embedded!)