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Old 10-11-2004, 01:31 AM   #1
buickmastermind
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Question Gas mileage question.

Is it possible to, say, get 200 mpg on a standard internal combustion engine? Why do we NEED catylitic converters? Why don't cars ever run at 100% efficientcy? It seems like everywhere you look, cars eat gas like man drink beer. What is a Supercarburator? How do they work? I saw a website (or 2) (or 3) (or about 300) that talked about them, but don't know what they were talking about. Can anybody help?
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Old 10-11-2004, 02:18 AM   #2
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Re: Gas mileage question.

1. ya, if your car weighed less than 500 lbs and couldn't go faster than 30 mph, but thats hardly a car.

2. because they reduce Nitrogen Oxide and Sulfur Oxide emissions by some order of 90%+

3. No mechanical system ever runs at 100% efficiency, its called the law of conservation of energy.
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Old 10-11-2004, 02:22 AM   #3
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Re: Gas mileage question.

200 mpg? Short answer...yes. However, it would be a very small engine in a very light vehicle. Could it be built to current safety and emission standards and keep up with traffic? Doubtful. Think moped on a diet. Converters are needed because current engines emit gases that are harmful to the atmosphere, animals (us too) and ecology. The government has standards for the emissions and most cars would not pass without one. Efficiency...I assume you mean 'why don't engines run at 100% efficiency?'....because 100% of the energy in current fuels cannot be turned into useful power by current engine technology(25 to 35%). Supercarbs...well, there are a lot of stories, but little proof. Carburetors do only two things..1) convert liquid fuel to vapor fuel and 2) meter the fuel into the airstream at the correct mixture. Currently, fuel injection does a better job in both catergories. Super-mileage carb stories have been around a long time.
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Old 10-11-2004, 12:57 PM   #4
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Re: Gas mileage question.

You can't convert 100% of the energy in the fuel into mechanical work, to do that the exhaust must have the same temperature as the intake air, there may be no friction in the engine and it may not run any hotter than ambient temperature.

1 kg of nromal gasoline contains 43 MJ of energy, gasoline engines are as most 30-40% efficient. At part throttle they are even less efficient due to the large pumping losses.
To get a low fuel consumption the most important issues are a low drag, an efficient small engine which can operate at full throttle at cruise and a low weight to decrease power needed to accelerate the car.

Have you heard about for example Shell Eco-Marathon? It's a competition where you are supposed to get as long as possible with the fuel you get. The team that won last year got 9700 miles per gallon on gasoline.

Catalytic converters are "three way" catalysts, they convert:
1. NOx into N2 and O2
2. HC into H2O and CO2
3. CO into CO2
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Old 10-11-2004, 04:50 PM   #5
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Re: Gas mileage question.

HC? WTF? you mean un-burnt hydrocarbons. NOx? not following your compounds here. anyways there are gasoline/electric cars that get in excess of 300mpg. toyota is currently working one one. problem is with such a small engine not much power is avalable and the car wont be able to reach very high top speeds, meaning that they are not in production because they couldnt travel at the normal floww of traffic on roads such as expressways where the normal flow of traffic is in excess of 75mph. and going less than the normal flow of traffic is extremely dangerous (even if yo uare doing the speed limit and everyone else isnt). a gasoline negine cant work ar 100% effciency because in order for it to do so the exaust tempatures would have to be the same as intake tempatures (as sabb said, ive found out most of the time he knows what he is talking about and i only do some of the time ) this is because a gasoline negine gets its power my burning fule. when fule burns it expands causeing an increased pressure to do mechanical work while trying to get from an area of high to an area of low pressure. in order for an engine to work at high effeicency the pressure would have to become equal with ambient air pressure (14.7 PSI) by the bottom of the stroke. a stroke this long would be massive and just cant be done. since the pressure cant be lowered enough to lower the gas temp to that which it was before it was burned energy is lost and blow out the exaust. the use of a turbo harneses some of that exaust energy but not enough to raise effency to near 100%. some of the most effecient internal combustion engines are very large 2 storke diesels (as much as 65%) and airplane prop engines (as much as 50% on very high octane leaded gasoline) .
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Old 10-11-2004, 07:18 PM   #6
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Re: Gas mileage question.

NOx is a catch all for all Oxides of Nitrogen
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Old 10-11-2004, 07:23 PM   #7
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Re: Gas mileage question.

Throw this curve at ya all.
A normal 455 ci v8 (carbureted) with hood scoop and headers uses standard 87 octane unleaded gasoline to get 86 MPG and an estimated 360 hp.
Explain that with your mini engine theories...
Let me assure you, until you see one for yourself, you won't believe it possible.
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Old 10-12-2004, 12:15 AM   #8
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Re: Gas mileage question.

Quote:
Originally Posted by buickmastermind
Is it possible to, say, get 200 mpg on a standard internal combustion engine?
that was a urban legend about a secret prototype car that got 200MPG, that accidently got sold at a dealership, then was tracked down by R&D, somebody saw two guys messing with it at night, then it got 20MPG. URBAN LEGEND

however, if you use hyrdogen with a lean mixture, combo'd with a hybrid system, small car, a specially designed engine and proper aerodynamics, you could easilly get 200MPG

Quote:
Originally Posted by buickmastermind
Why don't cars ever run at 100% efficientcy?
its impossible, they knew that 150 years ago. most internal combustion engines must convert linear motion to rotory motion, the mazda rotory engine is more efficient then most others, but have zippo torque.

Quote:
Originally Posted by buickmastermind
Why do we NEED catylitic converters?
so a little kid can wrap his lips around the tail pipe (just kidding, don't try)

Quote:
Originally Posted by buickmastermind
Throw this curve at ya all.
A normal 455 ci v8 (carbureted) with hood scoop and headers uses standard 87 octane unleaded gasoline to get 86 MPG and an estimated 360 hp.
Explain that with your mini engine theories...
Let me assure you, until you see one for yourself, you won't believe it possible.
maybe if you put it in a go-kart frame and play around with the cylinder head. show us....
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Old 10-12-2004, 08:34 AM   #9
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lets add it up
that 455 can get 86 mpg ??????
okay lets lean up the a/f and drive it with minimum load at 5 miles an hour
an estimated 360 horsepower????
no dyno? did ya just guess?
first off 360 is not an impressive number when running 455 ci
whats the point of a big block if you're making less power than a mild tune small block?
and like sierrap said
wheres the proof
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Old 10-12-2004, 08:48 AM   #10
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Re: Re: Gas mileage question.

Quote:
Originally Posted by CBFryman
HC? WTF? you mean un-burnt hydrocarbons. NOx? .
if you ever got your car inspected thats what is listed(in percent) and that is what they look at to determine if youre going to pass or not.
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Old 10-12-2004, 08:57 AM   #11
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Re: Gas mileage question.

I will try and explain it a different way. Does anybody know what happens when gas evaporates? It expands, right? Any liquid that turns to a gas expands. Alot. Hint:ever noticed that on a very wet day, your cars emmisions decrease? Power increases? Do you know why?
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Old 10-12-2004, 09:01 AM   #12
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Re: Gas mileage question.

Oh, and 360 is about standard factory horsepower for that motor. There are, as you say, ones that get more, but the princlipal holds true for those as well. It doesn't matter if it has specialty racing parts or not.
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Old 10-12-2004, 09:48 AM   #13
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Please explain why emmisions decrease and power increases on a damp day.
(Higher humidity=less oxygen????)
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Old 10-12-2004, 11:04 AM   #14
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Damp/humid air has a greater density that dry air does. when it gets into the high heat of the motor, most of the water evaporates (liquid --> gas, big surface area expansion) either in the manifold or the cylinders, and you have more air in the motor than the computer knows about. Also, gasoline normally evaporates in the motor, but the amount is not significant enough for the car to run on the evaporated gasoline. When you have the wet air, the chances of a given amount of gasoline evaporating increase, and even though the computer sees a correct exhaust mixture throught the o2 sensor, you really used more air for the same amount of gas. It's advanced chemistry, and I don't expect you to understand it. You might be asking "why don't we heat the gas up enough so that we can run the motor entirely on gas vapors, then?" It is possible. When a gasoline changes to a gas from a liquid, it expands it's original surface area. That, and the gasoline molecule in its gaseous state is normally very reactive to hydrogen and oxygen, and when it reacts with hydrogen and oxygen (water-or-rain), it produces methanol and methane. The two chemicals combined produce a "percussion" explosion, rather than a heat explosion. A motor that correctly untilizes this method is the official definition of a supercarbureted system. It is like using gasoline to make propane (which is what the correct mixture smells similar to), and eliminating hazards to our environment. To visualize (not 100% to scale),
Start with this much gas vapor.
ggg
add this much water vapor.
wwwwwwwww
and you get this much methanol/methane
mmmmmmmmmmmmmmmmmmmmmmmmmmmmmm

If you did notice the increase in gas mileage and power, you noticed that it wasn't very substantial, but it was there. The reason the current vehicles don't get the huge gas mileage as this system allows is because, even though they say the gas you are buying is unleaded, it really isn't. Lead is a type of preventative. It can be used to prevent methane and methanol from forming because it takes the reactivity out of the gasoline molecule, and every oil company intentionally puts a lead additive into their oil to prevent this reaction from happening. It still happens, but not to an extent that it can be utilized without filtering out the lead. Simply spraying a fine mist of water into the air breather can help this process along, but only slightly until the lead is gone.
Don't believe me? Type in "200 MPG supercarburetor" in at google. you might have to look on a few pages before you find the websites, and there are a few, but you would be surprised.
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Old 10-12-2004, 11:07 AM   #15
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Re: Gas mileage question.

Oh, and water is made up partially of oxygen, bjdm. H2O. The hydrogen is also a crucial part of the process.
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