$ per mile: high compression/high test vs. low compression/regular

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The page has an actual PHOTO of a collapsed hose liner, shown from the cut end.

i've already tried that. all it shows is a piece of rough-cut hose with the subscript: "figure 5.44 this hose collapsed on the inside".

if you can see anything other than rubber and fiber shards left over from cutting in that picture, you've got image enhancement software much more powerful than i. i was hoping he was referring to the other image on the basis that it does at least show how someone can think that there's a "flap". the 5.44 image doesn't.

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that pic doesn't show anything except rough cutting. and in poor resolution.

The associated text was quite clear.

Joe Gwinn

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Having actually seen the problem shown, it ( the picture) was pretty clear to me too

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it's not "clear" at all - it's a "technician" explanation dumbed down to the point of idiocy.

there are no "flaps". nobody has ever seen one or ever posted a picture of one, regardless of how it's labeled, because they don't exist. fluid dynamics, material properties, basic mechanical properties, /all/ contradict this bizarre shade-tree legend. and yet simple easily seen swelling constriction, that is entirely in accordance with fluid dynamics, material properties and mechanical properties, is apparently impossible to comprehend.

but i live in hope. are you guys familiar with old-school mechanical spring-loaded diesel injectors? if so, do you understand why the injector can inject, but gas doesn't get blown back through the injector when the fuel burns raising cylinder pressure? i ask because the same principle is at play with a hose constriction. [and because diesel injectors don't have flaps in them!] hopefully if you can understand one, you can understand the other.

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or to try another approach:

the pinching effect you see illustrated in that first example is actioned by the swelling of the contaminated elastomer inside the hose not being allowed to expand outwards by the hose cordage, thus it expands inwards, pinching the internal diameter to zero. any pass-through is determined by the pressure of the brake line reaching a point where elastic stretching of the cordage under pressure allows the internal bore to open enough to allow some flow. if it opens at

1000psi, and brake pressure of 5000psi is applied, a brake caliper will pressurize to 5000psi, but on let-off, will retain 1000psi.

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Lucky you Canadians, getting 5% extra miles per gallon, plus a better running engine.

A full blown racing engine uses the extra volume of 100% ethanol for cooling, but then they could care less how much extra cost or less miles per gallon.

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/some/ race engines use ethanol. most don't. those that do use it do so because it's easier for firefighters to handle, not because it's a better fuel.

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It's used for engine cooling. Fire wise, its flame is nearly invisible, which makes it harder to deal with.

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no more than any other can be used for cooling - its latent heat of vaporization isn't very high.

but the flames are easily extinguished with water. on race tracks, that's a good deal more practical than the foam needed to extinguish other fuels. particularly if you want to quickly restart a race after the paying public have been "entertained" with a crash.

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Pure ethanol has an octane rating around 115, and it produces *some* of the evaporative cooling and densification that methanol does. It produces more horsepower than gasoline. But where you see it in race cars, it's because the ruling body mandates it. If you're going to run alcohol, methanol will produce more power than ethanol.

The firefighting thing has gone back and forth over the years. Yes, you can put out an alcohol fire with water. That is, if you can see it burning. A couple of drivers have burned to death in methanol-fueled cars on bright days because the rescue crews couldn't see the flames until it was too late.

But it was the '64 Indy 500 that changed the equations:

USAC never outlawed gasoline, but they changed the rules on fuel-tank capacity and number of required pit stops for 1965, eliminating the fuel-mileage advantage of gasoline and favoring the higher power obtained with methanol.

Ethanol is purported to burn with a yellower, and more visible flame than methanol, but I don't know about that. In any case, some racing bodies have mandated ethanol largely to answer complaints about not being "green" with methanol. Methanol is toxic as hell.

Advanced fuel cells, Nomex firesuits and Kevlar fabric in the tubs of open-wheeled racers have improved the situation with gasoline, so some classes of racing continue to use it.

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ed, with respect, where do you think that horsepower comes from? ethanol has 76,100BTU/Gal. regular gasoline has 114,000BTU/Gal. "octane rating" has nothing to do with energy content of the fuel - it's simply a quantitative measure of anti-knock. how do you think the thermodynamic efficiency of ethanol combustion compares with that of regular gasoline?

and yet methanol has an even lower calorie content!

which is inherent because of the higher energy content... see above.

the only way you obtain "higher power" is to consume more of it - a /lot/ more.

of course. because street cars use it and it has much better energy density.

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It comes from two places: Higher octane rating, allowing higher compression, and a denser fuel-air mix in the cylinders.

Stoichiometric ratios for air/fuel are 14.7:1 for gasoline (actually

13:1, if you're going to get picky and use lab figures); 9:1 for ethanol; and 6.4:1 for methanol.

So, you burn more alcohol. But the engine makes more power -- if you've adjusted the CR to the optimum for each fuel.

Incidentally, if you work out the energy/gal and relative stoichiometry for each fuel, you'll see that, in terms of power produced, a stoichiometric ethanol-air mix beats out a similar ratio for gasoline by a small amount, IGNORING densification and higher octane ratings. You just have to burn 63% more alcohol than gasoline. If you do, you get 9% more power with ethanol, before even considering compression ratio or densification.

I'm not talking about energy content. I'm talking about how much horsepower you can get out of an engine. We were talking about racing engines over the last few posts, right?

Gasoline has much more energy content, but you can only burn a smaller amount of it each time an engine cylinder fills. In terms of the energy content of the fuel-air mix, the ethanol-air-filled cylinder produces more horsepower than the same cylinder filled with a gasoline-air mix. Even if you don't change the compression ratio to take advantage of ethanol's higher octane rating. Are we on the same page here?

Higher compression can produce more horsepower. I hope we don't have to go over that again, right?

The EPA has researched the thermodynamic efficiency of ethanol and methanol, showing a 20% improvement over gasoline or diesel. Ethanol-fueled engines in the research produced over 40% thermodynamic efficiency:

One caution: I hope you aren't confusing thermodynamic efficiency with the thermal output of a given amount of fuel, are you? Because the thermodynamic efficiency is the ratio of energy produced to the energy

*potential* of the fuel in question. And, as we've said, gasoline has higher energy potential per gallon.

Note the differences in stoichiometric ratios between ethanol (9:1) and methanol (6.4:1). Then do the arithmetic. there's your answer.

Right. Higher energy content, but less potential for producing horsepower, because of (1) the differences in stoichiometric ratios versus energy content per gallon; (2) the higher evaporative cooling of alcohol, which leads to denser charges of fuel-air in the cylinder; and (3) the higher octane rating, and thus the higher potential compression ratios (which relate directly to thermodynamic efficiency) of alcohol fuels.

Right. The volumes are roughly equivalent to the stoichiometric ratios for each fuel. So, roughly, one pound of gasoline must be mixed with

14.7 pounds of air; one pound of ethanol must be mixed with 9 pounds of air; and one pound of methanol must be mixed with 6.4 pounds of air.

In other words, to fill a cylinder with a burnable fuel-air mix requires around 50% more ethanol than gasoline, and more than twice as much methanol as gasoline.

Right. But you mentioned racing a couple of posts ago, and there you have to consider the higher horsepower potential of alcohol fuels.

In caswe that's confusing, the fuel cells I'm referring to are the gas tanks used on racing cars, which contain a self-healing (usually) rubber or plastic bladder that will withstand most crashes.

I'm not referring to the fuel cells that produce electricity from fuel.

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ok...

stoichiometry is only relevant if you're restricted on air. or fuel.

ok, so let's look at some racing engines. from f1, gasoline, v8, 2.4l, they're outputting 740hp or 308hp/l.

and from indy, 100% ethanol, v8, 3.5l, they're outputting 650hp or 185hp/l.

so unless those data sources are completely wrong, or my math is wrong, the higher specific output of f1 on gasoline doesn't support your argument.

ethanol lobby propaganda. go diesel

or prius

i'm not, but i think you are.

um, no, it's T1 -T2 / T1, where T1 is combustion temp, and T2 is the resultant temp after work done. a fuel can have all the "potential" in the world, but if it's not realized with a high combustion temperature, you'll never achieve high efficiency.

no, it's got a higher calorie content. and you're confused about "potential".

that's completely irrelevant unless you're trying to run different fuels with the same availability of air!

???? how?

stoichiometry has nothing to do with it unless you're restricted for air in some way.

you're right that ethanol "cools", but you'd better make that up on charge density or you're going to lose on the adiabatic heating that needs to take place before combustion.

and you start to lose that benefit with modern high compression gasoline engines. the honda k-series have compression ratios up near 12:1. your indy ethanol is ~15:1 naturally aspirated. that's not sufficient to compensate for the substantially lower calorie content.

and????

so why aren't they delivering? 308 vs 185 hp/l?

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That's all good feedback.

How about the wholesale cost (zero markup) of producing various fuels?

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Well, it's relevant if you're talking about fuel consumption rates. If you know the stoichiometric ratios, you're well on your way to knowing the fuel consumption rates for different fuels.

Apples and oranges, Jim. Those are completely different engines, built to sanctioning-body rules. The Indy engine (you're talking about the pre-2012 engine) is a mildly tuned "one design" engine from Honda, built for reliability and low cost. Honda owns the engines and they lease them to the teams. They don't push them for more horsepower; everyone gets the same state of tune, dictated by IndyCar. In other words, IndyCar decides the horsepower, and Honda builds the engine to suit.

The Honda is rev-limited to 10,300 rpm. In six years at Indy, not one engine-related retirement occurred in the race, with 30 - 40 cars using the engine each year.

Formula 1 engines are at the other end of the scale. They turn 18,000 rpm, and are otherwise tuned to within an inch of their lives, in a fierce competition for horsepower. The teams are allowed to use up to

8 engines in one season for each driver. Engines blow up in virtually every F1 race because they are stressed to the limit and beyond. Bore/stroke ratios are around 3:1 and pistons still accelerate at roughly 8,000 G. That's close to twice the piston acceleration rate of the Honda Indy V8.

You're getting sidetracked here. Comparing different engines from different classes of racing, with different engine rules, isn't going to tell you much. If you want details about the basic subject we were talking about, go to SAE's website and peruse their *extensive* research white papers on the subjects of fuels and engine efficiency.

Jim, that's about specific fuel consumption. Your statement was about thermodynamic efficiency.

Alcohol fuels have better thermodynamic efficiency. Gasoline and diesel produce lower rates of specific fuel consumption. They're two completely different things.

Those are pseudo-Atkinson-cycle engines. Honda uses them, too, in their hybrid. If you ran them on alcohol, their thermodynamic efficiency would be even higher.

Atkinson-cycle engines have poor throttle response and other driveability problems. They need the electric motor to smooth them out. That's why they aren't used in conventional cars.

You are, and I'm not. It's clear from your confusion of specific fuel consumption with thermodynamic efficiency.

Look the terms up.

And when you plug the numbers into your equation, what do you get? d8-)

That equation assumes, for a heat engine, that the expansion and compression are isentropic (reversible adiabatic) processes. But they aren't. The cylinder and piston are not insulated. Heat leaks out all over the place. You can't measure it in a practical sense.

Thermodynamic efficiency in practice is usually expressed as e = W/Ein, where W is the useful work extracted from a process, and Ein is the input energy. That's the most useful definition for talking about engines.

Since the BTU potentials of fuels are known, you can measure an amount of fuel burned and the power produced X time, which will give you the energy produced. That's how it's actually done, with a tachometer and a dynamometer. It's much more accurate and meaningful.

Uh, you think so? The energy in fuel is potential energy until it's burned. Then it becomes kinetic energy.

I think you're missing the point. The point there is that methanol has lower caloric content per unit volume, but you burn roughly 40% more of in with the same amount of air. So you get a lot more energy in a cylinder full of methanol-air than in a cylinder full of ethanol-air. That's the result of their different stoichiometric ratios.

Let me try an example, using rounded numbers for clarity.

Say you have two fuels. We'll call them "gasoline" and "alcohol."

Also say that everyone understands what a stoichiometric ratio is. In the case of fuels burning in air, it's the ratio of air to fuel that allows the fuel to burn completely, with no leftover air or fuel. It's usually expressed in terms of masses -- pounds of air to burn a pound of fuel. (don't start with me on "pounds mass" )

Gasoline's stoichiometric ratio is, say, 15:1. The ratio for alcohol is 10:1.

Now, the caloric content of gasoline is 100,000 btu/gallon. The caloric content of alcohol is, say, 70,000 btu/gallon.

Because of their different stoichiometric ratios, if one liter of fuel-air mix for gasoline contains, "x" amount of gasoline, then one liter of fuel-air mix for alcohol contains 1.5x amount of alcohol.

You have 50% more alcohol in a stoichiometric mix than gasoline, in other words. Alcohol, per gallon of fuel, produces only 70% of the btu as gasoline. But you have 50% more of it in the cylinder! So the heat energy produced in the cylinder when you burn alcohol is 1.5 X 0.7 =

1.05 times as much energy from a cylinder full of alcohol-air mix as from a cylinder full of gasonline-air mix. Our theoretical "alcohol" makes 5% more power than gasoline. The actual number for ethanol is 9%.

That results in more horsepower from the alcohol fuel, at a cost of burning much more alcohol than gasoline. We are ignoring here the higher octane rating and higher overall thermal efficiency of burning alcohol. Even without considering those things, the alcohol-fueled engine makes more horsepower.

This whole exercise was based on your statement:

" /some/ race engines use ethanol. most don't. those that do use it do so because it's easier for firefighters to handle, not because it's a better fuel."

I responded because that's not really true. Alcohol is, indeed, a better fuel for racing, because it produces more horsepower. The amount of extra fuel you have to burn may or may not be an issue, depending on race rules for fuel-tank capacity, number of pit stops in a race, and the effect of dragging around the extra weight of more alcohol fuel. At Indy, those issues weigh to make alcohol the better fuel -- today, ethanol, because the race rules dictate it. But even when they didn't, the cars ran alcohol because it produced more horsepower.

Not so. It determines how much fuel is contained in each cylinder full of fuel-air mix.

This statement is too tangled to decipher. I'll leave it mostly alone.

Charge cooling is an advantage for producing more horsepower, but not, necessarily, for fuel economy. Like most engineering issues, the answer to that one is "it depends."

See above. I think you're missing the fact that the lower caloric heat content of alcohol is more than made up by the greater amount of alcohol contained in a cylinder full of fuel-air mix.

Again, that means more horsepower, but less fuel economy.

The alcohol-fueled car thus produces more horsepower, at a cost of more fuel consumption per mile. (I'll try expressing this every way I know how, in the hope that one will sink in.)

Going back to your original statement, that makes alcohol a better fuel for racing engines.

See above. In the case of the Indy engine, they decide how much horsepower they want and build an engine to produce it, with the goals of low cost (just under $1M for a year's contract -- that's cheap) and reliability (Honda's contracts require that they maintain and rebuild the engines). All Indy engines are the same and all are rev-limited to

10,300 rpm.

In the case of the F1 engine, it's Katy-bar-the-doors, balls-to-the-wall, victory-or-blow-up, whichever happens first. 18,000 rpm and stand back.

Is this still fun? d8-)

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That depends on which country you're in, what you make your liquid fuels from, and fuel taxes. In Brazil, for example, the per-mile costs of gasoline and (sugar cane-derived) ethanol are very close. So they make dual-fuel cars and switch back and forth with market prices.

In the US, the best cost/mile often is with compressed natural gas (CNG), depending on local taxes. Honda made a CNG Civic until a few years ago.