That’s okay…there are plenty of mechanial engineers who don’t understand how the transmission functions or why you shouldn’t overfill your oil reservoir.
Engineers are not always the most sensible people; oddly (or perhaps not so) those with the highest GPAs in school.
Stranger
Yeah attitudes like his in some engineers (I’m an ENGINEER!) is what drives some technicians to say things like:
That’s nice, Amtrack or Union Pacific?
Or
Wow that’s cool, do you wear a stripped hat and get to blow the horn?
Or
Yes sir I understand that, but this is an automobile not a train.
well, let’s look at it this way. The “correct” (stoichiometric) ratio of air:fuel for a gasoline engine is 14.7 parts of air to one part of fuel. Theoretically, this is the ratio where every bit of fuel has the correct amount of air to burn completely. Too rich (say, about 11:1) and the engine starts puffing soot out the exhaust; too lean (say, about 16-17:1) and the engine may misfire or not run at all.[1]
Now, keep in mind that the “200 mpg carburetor” story got its start in the 1930s as noted by both Cecil’s response on SD as well as the article on Snopes. Back then, cars got anywhere from 10 to 30 mpg depending on size and engine (can’t find a cite right now, if I do I’ll back this up.) In order for a carburetor to try to get the car to return 200 mpg, it would have to add such a lean air:fuel mixture that the car wouldn’t even run. Granted, later on some manufacturers put out “lean burn” systems of varying quality; Honda’s stratified-charge[2] CVCC seemed to work the best of them. But even the relatively tiny CVCC didn’t return 200 mpg. And the old, low-compression flathead engines of the 1930s-40s had no inlet/chamber design whatsoever to support a stratified-charge setup.
One more thing to consider is that many/most port fuel injection systems actually spray fuel into the intake port while the valve is still closed. When the intake valve opens, the act of the piston drawing the fuel in with the intake air evaporates the fuel. And even with wet fuel being sprayed on the intake valve, port fuel injection engines run squeaky clean. So the notion of the “200 mpg carburetor” working because it heated the fuel:air mix to vaporize it completely is bunk.
Further, now we even have high-pressure direct fuel injection for gas engines (the fuel injector sprays directly into the cylinder, not the intake port) and lo and behold, we still have to keep close to 14.7:1 air:fuel ratio, and we’re still not getting 200 mpg.
[1] In reality, modern cars don’t try to maintain a perfectly stoichiometric ratio, they oscillate between slightly rich and slightly lean to make sure the catalytic converter is working optimally. see http://ect.jmcatalysts.com/images-upload/graph-2.gif
[2] “stratified charge” means that the air:fuel mix right by the spark plug is slightly rich, while the overall air:fuel charge is lean. This way it ignites reliably.
I had a very frustrating conversation with a deluded young farm-boy who bought this crap hook line and sinker. He was seeking “investors” for his father’s attempt at creating a “franchise” of selling these things.
It’s a whole new form of pyramid scheme. Unfortunately this guy was literally the embodiment of the Dunning-Kruger theory. He was too unintelligent to understand the basic language that would have been used in proving his claims false. I know because I tried. I even tried to break it down into the most basic form, starting with a layman’s understanding of thermodynamics.
Didn’t help. It never will. So basically, the tl;dr is “Nothing to see here, move on.”
That all seem like knowledge derived from a less-than-rudimentary grasp of engine design etc. Not a rudimentary grasp of thermodynamics ( which is my point)
A rudimentary grasp of thermodynamics should permit a person to readily dismiss perpetual motion engines such as those that use their output power to split water, then be powered by burning the resulting hydrogen.
But the 200mpg carburettor thing isn’t claiming anything quite so wildly impossible - it’s just claiming to improve efficiency by a fairly modest factor. Obviously it would take a redesign of much more than.the carburettor to achieve such performance, however, I dont believe the claim is in the same category as perpetual motion.
These vehicles are produced every day, so the story must be bogus.
WRT my drive-by “urban legend” comment above, I once met an eminent retired admiral from the Royal Navy who had actually parted with money to fund such a scheme. The guy went into “hiding”.
yeah a fairly modest amount, they only added one zero to the MPG number.
That or a bit less - which is precisely my point.
Someone comes along and says “this thing runs forever on permanent magnets”, or “this thing generates its own power to split water into Hydrogen and Oxygen, to drive the process” or “this thing outputs more energy than you put in”, then you’d be quite right to dust off your rudimentary understanding of thermodynamics to refute the assertions.
But someone comes along and says “I can make this machine more efficient by not quite a single order of magnitude”, and it’s a claim that deserves much skepticism, but the laws of thermodynamics don’t instantly and obviously forbid it.
Seriously you think an order of magnitude is a modest gain?
If a car company could do this, they would have. They would then proceed to sell everyone single one they could screw together.
Of course, but that’s an argument from corporate greed, not thermodynamics.
Both the 200mpg carburetor and the OP’s “lasts 10 years and several hundred thousand miles” are stories from the 60s and 70s, when the North American automobile market was mostly locked up by Detroit’s Big Three, which make collusion of the imagined sort more plausible (or at least less implausible). In 2011 the cutthroat nature of competition between automakers is far more apparent.
My point is not that it’s believable, but that it doesn’t seem like the sort of claim that seems immediately false on the grounds that it’s violating physical law. That’s the only point I’m taking issue with in this thread - I don’t believe that a rudimentary understanding of thermodynamics provides a snap judgment against the claim of a 200MPG car.
nobody’s saying that thermodynamics claims a 200 mpg car is impossible. Where I was going is that the rumors said this “200 mpg carburetor” promised such fuel economy on the engines of the day, in the cars of the day. meaning, a low-compression, 4.0 liter (or thereabouts) flathead cast-iron lump. the claim was that this magical carburetor could take that engine and improve its fuel economy by a factor of 10 by doing nothing other than “making sure the fuel and air were completely mixed and thereby eliminating any unburnt fuel after the combustion event.” I started talking about engines and air:fuel ratios to try to show that fuel “wasted” by not being burned in the combustion chamber is already practically nil; so in order for an engine to increase its fuel economy tenfold, it would have to massively increase its thermodynamic efficiency which would pretty much blow Carnot’s theorem to smithereens.
Actually, I read a version of the 200mpg carburetor myth in Heinlein’s “Let There Be Light” from 1940.
I absolutely agree with your analysis, but I think Mangetout’s point is that this is beyond many reasonably well-educated people. Everyone with a high school science education should know that perpetual motion machines are impossible. But understanding Carnot efficiency? That’s a topic that isn’t usually covered in first-year college physics. If it is covered, it’s not in any great depth*. So the only people who are really equipped to understand why 200 mpg is impossible are people who have taken an upper-level thermodynamics course.
*for kicks, I looked up the table of contents of one of the standard intro physics texts, HRW. Thermodynamic efficiency is only addressed in five pages, tacked at the end of general thermo chapters that many classes skip.
What percentage of the American public do you think have even a “rudimentary understanding of thermodynamics”? My own guess is about one in a thousand, if that.
I don’t think that’s even the issue.
How many people know how efficiently an IC engine is working now.
It may seem perfectly reasonable that there’s room for an order-of-magnititude improvement in efficiency.
Given the outstanding technical and technological ignorance and apathy of the average American dumbass, I’d say you’re being generous.
Yes - this is exactly the point I’m trying to make. The layperson’s understanding of thermodynamics is that you can’t win, break even or quit - you can’t get out more than has been put in. That understanding doesn’t equip someone to summarily dismiss a claim of this nature.
On a slightly different note (and this is a bit of a hobby-horse for me), a rudimentary understanding of thermodynamics sometimes leads people to summarily dismiss things quite wrongly - for example, I have seen the following incorrect arguments, supposedly based on the 2LoT:
[ul]
[li]The amount of energy available from a biofuel cannot exceed the energy expended in harvesting and processing it[/li][li]The lifetime energy output of a solar cell cannot exceed the energy used in its manufacture[/li][li]An industrial process to depolymerise waste plastic into liquid oil cannot be powered by one of its own end or intermediate products[/li][li]A domestic heat pump can’t be more effective/economical than a simple resistive heater[/li][/ul]
(and that’s without even bringing the creationists on stage)
Eh. Twenty years ago, I had a car that routinely got 50 miles per gallon (actually measured by me, not based on some estimate). Nowadays automakers brag that their cars get 35 mpg. Nobody’s dominating the market with the 50 mpg car I drove (Ford Festiva) and consumers seem to have accepted that mileage that was mediocre two decades ago is the best we can hope for today.
