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Can Your Car Get 1,700 MPG?
Xaroth writes "Given all the hubbub over EPA mileage ratings, I'm a little surprised that this one hasn't come up earlier. SAE apparently holds a contest each year to encourage students to design single-person, fuel-efficient vehicles. This year's winner achieved 1,747.4 MPG, with the press release that tipped me off pointing out that third got a 'measly' 1,194. There are more details on the competition over at SAE's site about the competition. Now, if only they could make these street-legal..." However, even the winner has nothing on top entries we mentioned in Shell's competition a few years back.
and that's how I likes it.
(you knew this one was coming)
What kind of gas mileage will they get when they are loaded up with 1000+ pounds of DOT required safety equipment?
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Somehow I dont think a styrofoam hummer will take off..unless there is a gust of wind.
Fred Flinstone, with infinite miles to the gallon.
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My bicycle.
I win.
How about the most fuel efficient 4 door seating for 4 w/ trunk space, radio, air conditioning, that meets federal safety and crash tests?
Than watch those MPG numbers plummet. Add to that must have respectable performance numbers (ie it must not be so slow accelerating as to cause a hazard on public roads)
That's a real contest.
When I was working on a solar powered car in college there was one of those SAE cars next to our bay. I don't think they're all that plausible because they are little more than go carts. I think we should work toward some of the technologies they use, like superatomizing and mixing the fuel, and trying to get engines above their pathetic 30% efficiency, but 1500 mpg is a bit out of reach. Of course, I guess I should never say never.
So, how much energy can you get from combusting a gallon of gas? If an engine was completely efficient, how far should it push 1ooo pounds?
> Fred Flinstone, with infinite miles to the gallon.
Laugh if you will, but we'd all be a lot healthier if we followed Fred's example and ran to and from the office, instead of hit cruise control after rolling drive-thru.
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I'm not impressed. The Spanish in the 15th century in their voyages to the New World and back were getting thousands of miles per galleon.
When I can buy a car with that kind of effencieny I'll look into it, but until then, a walkin' I a' go.
Must be a bitch to take that shiny new 21 inch monitor home from the store.
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These cars typically achieve their best mileage using a 'coast and burn' strategy. They run the engine full throttle until they reach ~20mph, then cut the engine. This way the engine is always operating at peak efficiency (no throttling losses). This driving technique could be a little impractical in stop-and-go traffic...
This article makes me wonder: just how fuel-efficient can an aircraft be?
-jcr
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It's important to note that MPG has a lot to do with driving style. While my car cannot get 1700 MPG, a bit of predictive driving (i.e. know when to start slowing down, when to build up momentum) will greatly increase the MPG.
It depends on where you are, but in the US the NTHSA and the DOT would strongly disagree with you. Vehicles sold in the US have to meet certain standards of crashworthiness in order to be allowed to be sold here for street use. This has kept a lot of cars from being imported here, because they would require significant modification. It is a result of all the big old cars (and big new cars) we have on our roads, of course. In Japan, where large vehicles are relatively rare (you have delivery vehicles, and tiny vehicles, and not much in between) you can have lots of little beer can vehicles because they can't do nearly as much damage to one another, whereas here in the US you have scads of two-ton-plus vehicles, even passenger cars with that kind of weight.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
You can get 125 miles per gallon all ready with one of these little mopeds, And they're cheap and street legal too.
Your saying that your car can drive 4305564.16 Square Feet for every 52.5 gallons? First of all how do you calculate how many square feet a car drives? You would have to take the width of the car and multiply it by the length the car has driven. I will assume for the sake of easy math that your car is 10 feet wide; If you divide 10 4305564.16 by 10 you get 430556.416 feet, which converts to about 81.5 miles. That means that your car gets 1.55 miles to the gallon, which is pretty bad unless of coarse you are driving a canyonaro. :P
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Checking some classnotes there is approx 686 kcal/mol in glucose which gets converted to 219 kcal/mol of potential energy in ATP. Which means only 32% efficiency for converting glucose to the energy form used by about every cell operation inside a cell.
Now there is also inefficiency in getting glucose to those cells (and not all of it of course gets to them). Plus ATP isn't completely itself efficiently used so 10% is prolly around the correct figure for the amount of energy used of digested food.
There's one catch. Nitrogen is very stable. Almost any chemical reaction will take more energy than it releases. When it comes to engine efficiency, this is Not Good.
Ideally, what you'd want to do is separate the oxygen and nitrogen, so that the oxygen ratio in the engine is much higher. Since you're losing less energy through the nitrogen, you would (by implication) get more useful energy out.
Ok, so how to do this, without reducing the energy you're getting from the oxygen at the same time?
That's tough. However, it may be possible. Nitrogen, as mentioned, doesn't react easily. The electrons in the outer shell are tough to displace. With oxygen, the reverse is true. Oxygen reacts very easily, and electrons are displaced with considerably less effort.
You can certainly use this to separate oxygen and nitrogen. Just set up an electrically charged grid, such that the charge will convert O2 into O2+, but leave nitrogen (N2) electrically neutral. Set up a second grid, with the reverse charge. The oxygen will be attracted towards it, the nitrogen won't.
If you picture the first grid at the entrance to a y-shaped tube, and the second grid at the fork splitting off of the long section of tube, you can see how the nitrogen will travel straight on, whilst the oxygen will be diverted.
Now, here's the tricky bit. The oxygen is one electron short (it's charged), and you've got to put quite a bit of energy into a device like this to charge the grids up enough. Will you get a net gain in efficiency?
That part, I can't answer.
Would it be worth doing anyway? Maybe. Well, it'll cut out a major air pollutant. The oxides of nitrogen that you get off will react with water to produce nitric acid. Not really something I want to be breathing in, if I don't have to.
Are there better solutions? Not using a conventional piston engine. We're almost at the limits for those, given a standard air mix. A rotary engine might get you a better theoretical limit (you don't have to keep reversing mechanical devices), but they're costly to make (they develop far higher pressures) and you have to develop one that's large enough that the increased surface area to volume is no longer a factor.
For ultimate fuel efficiency, I suggest a small fusion reactor. Though you may need to wait a while for them to be approved for use in cars.
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The SAE competition in the link requires a four cylinder engine. This kind of rules out other types of power such as steam, fuel cell, and stirling engine. Although, I suppose with enough modification, the provided Briggs and Stratton engine could be converted into a steam engine (not that this is necessarily more efficient). Let's see, new camshaft, a means to adjust the valve cutoff, maybe one of those cool looking fly-ball governors... Since a steam engine can apply power in each cylinder on every revolution, this makes it equivalent to a V-8. If you seal off the crankcase into a separate compartment for each cylinder, you can use both sides of the piston and make the equivalent of a V-16. Of course, details like, how to water from condensing in the oil will have to be addressed.
Also, since the peak horsepower of a car is rarely needed except in rapid acceleration, I would think that the key to reducing engine size, and thus, improving efficiency would be to use a small engine with some kind of storage system. Since batteries are bad for the environment, maybe two flywheels rotating in opposite directions (to cancel out precession) under the floor can be used, along with an electric motor/generator to transfer power to/from them. Extra power generated by the engines, as well as from braking, can be used to accelerate the flywheels. This would also improve handling because the gyroscopic effects would keep the car perfectly level on fast turns.
Also, I would think that the car would be cheaper to engineer and produce if you could eliminate most of the mechanical parts. How about a gasoline fired generator, a flywheel battery, and an electric motor on each axle?
Unknown host pong.
Can increase the efficiency over metal based ones. The temperatures they can withstand are far higher, raising the efficiency substantially over conventional ones.
They're also much lighter, the materials don't expand/contract and can be machined to closer tolerances and they wear out much slower than metal ones.
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Some students do something cool in a contest and all most people are saying is "yeah, call me when it's really a car." Criminy. Articles on case mods get friendlier comments than this, and this is something that I would have thought geeks would have found interesting. Or nerds. Or whatever we are.
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How about comparing modern day cars, trains, busses, and planes, on a per-passenger basis?
According to Top Gear a few nights ago, trains get worse mileage than the average car, per passenger(I'm trying to find any info about the study online to see if that's based on maximum capacity of each type of vehicle or real-world average passenger counts) and a high speed train gets worse mileage than a jumbo jet! Personally I'm kind of curious about a subway train as well. Both averages(ie based on typical # of people in them) and maximum figures would be interesting for all vehicles.
When they asked the UK "Green Party" for a statement, they said "the best choice is the journey not taken". Um...okay.
Oh, and ever watched a diesel locomotive idling or at speed, belching lots of blue/black smoke? How about a city bus? Here in Boston, they're downright filthy, and in neighborhoods near the bus depots and garages, asthma rates are much higher, and studies have repeatedly shown diesel soot causes both cancer and asthma.
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See subject line. I accept your rant, and raise you a hear-hear, in general.
However, you seemed to have invoked shades of a strawman - the grandparant did _not_ make any reference to a hydrogen fuel cell. It is, in principle possible to make a fuel cell that will convert fuels other than pure hydrogen into electricty (+ wastes).
That's not to say that they exist - most 'methonal' fuel cells are reformation style, where the carbon -> CO2 converstion is not used to produce power, but just to free up the hydrogen.
In principle, however, there is no theoretical barrier to a gasoline fuel cell, with high efficency (just a huge, _huge_, long list of practical ones). There _is_ a theoretical barrier to raising the efficency of an internal combustion engine.
The PDF on the web site says the engine in question is a Briggs & Stratton Corporation (Model 091202 Type1016E1A1001). The engine is air cooled, four cycle, with a 2.61 kw (3.5 horsepower) rating at 3600 rpm.
It's a tiny 1 cylinder engine.
-ted
Oh wait.... This is Slashdot... Never mind... :-)
The race isn't always to the swift... but that's the way to bet!
There's a University competition sponsored by Ford and the DOE to build environment-friendly, fuel-efficient vehicles called FutureTruck. The catch? They have to modify Ford Explorers, not create go-cart sized vehicles, maintain existing performance, and remain fairly manufacturable. (In other words, Ford is using college teams for their R&D.)
There've been amazing results: the winning team, from University of Wisconsin Madison, built a hybrid Explorer that got somewhere over 40 mpg. (Different sources disagree as to the exact number.) For reference, stock Explorers are rated at merely 15/19 mpg for city and freeway driving. They also scored well in emissions and made a vehicle which could probably be manufactured and sold for about the same price as a stock vehicle.
So it's not 1700 mpg. It's still pretty darn impressive for an SUV!
"Science is a way of trying not to fool yourself." -Richard Feynman
If it was something like "SAE contestents achieve 1,700 MPG" then I would think that these comments would be much less.
> Vehicles sold in the US have to meet certain standards of crashworthiness ... This has kept a lot of cars from being imported here
Their are many cars that are safer than anything in the US, not legal because the US requires the cars to be crashed, wont take any computer simulations. So many of the safest (and most expensive) vehicles are precluded since it's to expensive to sacrafice a dozen cars to sell a few dozen.
Actually if you check that link, theres a bit in there that states: "Why was this design not used earlier in autos, see as it has been around since at least 1904?" So a hemi wasn't a new invention, it was just Chrysler that recognized something good and ran with it. AFAIK, Hemi's were popular in airplane engines long before they ever got their start with Chrysler in automobiles.
:)
As for your first question, well, they do! Most every engine I can think of has a hemi shaped (commonly called "pentroof" to get around the trademark) design. From what I know, virtually all automakers use a hemispherical inspired cylinder roof in their engines. They just aren't called "Hemi's" because thats Chryslers thing. And since hemispherical chambers are now commonplace because of their efficiency, no one bothers marketing the feature. Chryslers "rebirth of the Hemi" kick is just a marketing gimmick. "Hemi" has been synonymous with "power" since Chrysler popularized it. The word 'dissapeared' when the gas crisis hit, because "hemi power" used lots of gas in the minds of the public. Instead, we got smaller I4 and V6 engines with "efficient" designs that were still basically a hemi/pentroof cylinder head. Understand that Hemi's just get more power out of the same amount of displacement as other designs do. So a small hemi is "efficient" because you can make the same amount of power with less displacement (which burns less gas), and a big hemi is "powerful" because you can get more power out of it than a similarly sized engine.
Now that we're back into a modern day horsepower race, its cool to have a powerful engine again. Mix with nostalgia, and voila: the Hemi is "back" when really, it never left.