Water 4 Gas

[quarky]

And what exactly do you think is magic about 40mph? Why didn't you choose 50? Or 30? In any case, what you, or anyone, thinks is irrelevant. The data exists and it says you are wrong.
http://cta.ornl.gov/data/tedb27/Edition27_Chapter04.pdf
Page 23 onwards.

I look forward to reading the data. Thanks for the link.

As per the 40 mph magic; no, I never thought of it as a magical #, much more of a compromise. Slower than that feels like too much to ask. Plus, the air-drag becomes much less significant. If that is false, I'll truly have some egg-on-face.

Off to read up on the data.

 

[quarky]

I read the data. The most recent data had 9 vehicles. It showed a nominal increase between 40 and 50 mph. 60 was worse than 40. All the other data I saw on that page pretty much confirmed my point.

Momentum is significant, certainly. I didn't read enough to know how the tests were conducted, but I'm confident one can increase their mpg by minimizing inertia. Stop and go 40mph driving would surely get worse mpg than non-stop 60 mph driving.

Am I missing some major principle in my understanding?
If so, it wouldn't be the first time, and I would eventually yield, politely, I hope.

 

[TMiguel]

Am I missing some major principle in my understanding?

You are simply missing the fact that because it happens in one case, it doesn’t mean it has to happen in every other case (and in fact it doesn’t).
The optimal valued must be calculated and not taken intuitively, if you change the parameters you most likely will change the result.

 

[Brian-M]

I don't think so. the % of power that's needed to move the air out of the way increases geometricly with the speed.

Remember, just running the engine wastes a huge amount of energy. Driving faster reduces the energy wasted this way.

Draw a graph comparing energy loss to speed. Plot a curve showing wasted energy from wind resistance/friction, and another showing wasted from running the engine to drive at that speed. Where those two graphs intersect should be the most efficient speed. I think.

 

[Toke]

There is also problems with running an engine at low power output.
It gives a lower compression and therefore lower efficientcy and risk of soding up the engine.
The sod problem is probably worst with diesel and heavyer fuels.

I am sure that the manufacturers make a curve for milage/speed for each new car.
I am also sure that they try to optimice it for highway speed, not some hypotetical slow driving.
They might not be eager to part with the data, adverticing and information is a poor mix.

Have you ever seen a battery comercial stating mAh in a alcaline battery?

 

[Brian-M]

Have you ever seen a battery comercial stating mAh in a alcaline battery?

That often annoys me. When I buy batteries, how am I supposed to decide which ones to buy when they almost never give a mAh rating? [/derail]

 

[Cuddles]

Am I missing some major principle in my understanding?

Exactly what TMiguel said. You are trying to insist on there being some universal speed that it must always be more efficient to drive at. However, as explained several times in this thread and demonstrated nicely by that data, this is simply not the case. The most efficient speed to drive at depends on many factors, and it is possible for the most efficient speed to be 60mph or higher.

Also, before deciding that the data supports you, you may want to note that for several cars in the 1997 test, 40mph was just about the worst speed to be driving, with 25mph and 55mph both being far more efficient. Clearly your intuition of around 40mph being a compromise between too slow and too fast is very much wrong.

 

[quarky]

I dig what TMiguel wrote. I think I get it.
My 'intuition' regarding 40 mph is not "very much wrong" however.

That there are vehicle engines and gear ratios built to accomodate certain speeds doesn't minimize the drag of the atmosphere. This is why I mentioned electric cars in a post above.
As I understand, electric motors can put out high tourque at low rpm; internal combustion motors work best at high rpms.

Here's a compromise claim:

In a contest, hypothetical, several electric cars will have a race to see how far they can go, on the same flat, windless track, on an identical amount of stored energy.
Part of the rules is that they are not allowed to go slower than 40mph once they accelerate to it.

The winner will be light and low; shaped like a bullet; on narrow, high-pressure tires...and it will travel at 41 mph.

Can we agree on that?

 

[Cuddles]

Here's a compromise claim:

In a contest, hypothetical, several electric cars will have a race to see how far they can go, on the same flat, windless track, on an identical amount of stored energy.
Part of the rules is that they are not allowed to go slower than 40mph once they accelerate to it.

The winner will be light and low; shaped like a bullet; on narrow, high-pressure tires...and it will travel at 41 mph.

Can we agree on that?

How is this supposed to be relevant? Your claim was that 40mph was better than going faster or slower. Your scenario cannot say anything to support that.

Secondly, electrics are an entirely different kettle of fish, and are in no way relevant to a discussion about oil powered cars. I would completely agree that the most efficient speed will be much lower for electrics. However, you are wrong again because the most efficient speed will be much lower than 40mph for electric cars. Just look at the example I gave earlier:

Going slower is more efficient. Therefore going at 30mph is better than 40mph. And 20mph is better than 30mph. And 10mph is better than 20mph. Now, what would be better than 10mph?

For petrol engines this leads to an obviously silly outcome, since an idling engine still uses some energy, so fuel economy tends to zero as speed tends to zero. However, an electric engine can smoothly power down to zero with no need for idling, so you do not reach the same conclusion. There will likely be some losses and inefficiencies, Ohmic losses for example, that limit the economy for very low speeds, but the sweet spot is likely to be at much, much lower speed than for combustion engines.

 

[quarky]

I think we actually agree, in a disagreeable way.

but enough of this derail.

 

[Sherman Bay]

That often annoys me. When I buy batteries, how am I supposed to decide which ones to buy when they almost never give a mAh rating?

Whenever the topic of which brand of consumer-grade, non-rechargeable alkaline batt to buy comes up in Consumer Reports, IIRC, they say that all brands are pretty much the same, so shop for price.

 

[Psiload]

Moved to avoid a derail...

You know, IF you ran the "hydronaters" with an independent battery, you COULD achieve efficiencies... Recharging the units with ambient braking, collapsable wind turbines, and solar cells...

And yes, I would call such units "advanced technology".

Let's take this apart piece by piece.

We'll look at collapsible wind turbines first. Bolting a pinwheel generator on a car would not generate enough electricity to offset the amount of energy lost due to the increase in wind resistance. So we can chuck this right in the trash.

Covering the entire surface area of a car in solar cells would give you just about enough energy to run your radio... and that's at high noon on a sunny day. While driving your car at night, you'd get nothing.

Regenerative breaking is a great way to reclaim SOME of the energy which would otherwise wasted by an automobile, but it certainly doesn't increase efficiency to a degree approaching anywhere near what anybody would consider revolutionary.

However... none of this applies to "hydronaters", because these are scam products that just plain do not work as advertised... they basically don't work at all.

Whatever energy could be gained through solar, regenerative breaking, etc... would be better applied directly back into the electrical system of the car rather than being run through a useless sham marketing gimmick which would only serve to introduce further energy loss into the system.

Three years later and EVERYONE still isn't scrambling to install "hydronaters' in their cars. And the reason why they're not is quite simple... because they still don't work.

 

[shadron]

Once an engine is running, it is producing 'surplus' electricity.

You can jump a car off that has a dead battery, and once it is running, is begins charging said battery.

If your car is already producing 'surplus electricity', why NOT use it to create a little H and O, that once ported into the intake, INCREASES engine performance?

We aren't producing more energy, we are just using what we have more efficiently...

Let me put your mid at ease...

If you spin a generator that is not hooked to anything, all you are wasting is the energy needed to overcome the bearing friction of the generator. If you then attach a load to the generator, you'll notice your engine spinning the generator will slow. That is the electrical load causing the generator to be harder to turn, slowing down the engine turning it. In other words, as you absorb energy from the generator terminals, the engine has to work harder to turn the generator.

So, if you have an engine idling, and you jump to a dead battery, all of a sudden there will be more load on the generator, which will slow down the idling engine. That engine's computer may compensate, by opening the throttle, thus increasing gasoline intake.

The upshot: if the car and generator are working properly, then you pay in gasoline for all the energy you use. There may be other losses in the system, but they will only increase the amount you pay, never decrease it. All you have "free" is higher electricity production capacity, and actually youo pay for that, too, in higher parts costs and more friction/heating losses (i.e., lower efficiency).

There is no such thing as free electricity in a car's engine-generator system.

 

[davefoc]

Let me put your mid at ease...

If you spin a generator that is not hooked to anything, all you are wasting is the energy needed to overcome the bearing friction of the generator. If you then attach a load to the generator, you'll notice your engine spinning the generator will slow. That is the electrical load causing the generator to be harder to turn, slowing down the engine turning it. In other words, as you absorb energy from the generator terminals, the engine has to work harder to turn the generator.

So, if you have an engine idling, and you jump to a dead battery, all of a sudden there will be more load on the generator, which will slow down the idling engine. That engine's computer may compensate, by opening the throttle, thus increasing gasoline intake.

The upshot: if the car and generator are working properly, then you pay in gasoline for all the energy you use. There may be other losses in the system, but they will only increase the amount you pay, never decrease it. All you have "free" is higher electricity production capacity, and actually youo pay for that, too, in higher parts costs and more friction/heating losses (i.e., lower efficiency).

There is no such thing as free electricity in a car's engine-generator system.

I didn't read the entire thread, for one thing I wasn't quite sure whether King of the Americas was just playing devil's advocate or not.

Assuming he wasn't, I'll add this to Shadron's post which I think was correct. The power output of the car's generator is controlled by the current through the field coils. No current and the generator spin is only restricted by friction. The voltage regulator controls the current through the field coils to control the electrical output of the generator. i.e. more current through the coils, larger magnetic fields, more resistance to turning (no free lunch principle) and more power out of the generator.

As an aside, I've participated in a couple of these Denny Klein threads and it is surprising that yet another one has come to life. There is a lot of information in those threads mixed in, of course, with a lot of gunge, but Denny Klein is not the first with his kind of claims and he probably won't be the last. There is the tiniest bit of truth to these claims in that some much earlier research suggested that there was some possible gains in combustion efficiency by adding hydrogen to the air fuel mix. They were minor and whether there would be any at all for a modern engine hasn't been addressed by any recent credible research that I am aware of. I think it is very doubtful, given the complete failure of mainstream automobile makers to pursue this path.

 

[Furcifer]

I think it is very doubtful, given the complete failure of mainstream automobile makers to pursue this path.

I don't understand how people can get past this simple obvious fact? Companies spend hundreds of millions of dollars researching so they can get a 2% increases in efficiency. What would make anyone think they've overlooked anything? A company that could boast 10% increases stands to make billions over their competitors.