The following is a reprint of Chapter III from the Fish Carburetor Book by Michael H. Brown, pp. 11-12 (1982) about the carburetor myth that has been circulating since the 1950s.
III. The 100 MPG Carburetor Myth
There have been numerous books and plans written purporting to “reveal the secrets” of the famous “200 mpg carburetor,” a device supposedly built in 1935 by Charles Nelson Pogue of Winnipeg, Canada. As of this writing Mr. Pogue is in a nursing home in Winnipeg, Canada. Several of our customers have visited with him. Each came away with a slightly different story.
Mr. Pogue actually did manufacture a carburetor he titled the “Winnipeg” in the late 1930s; 317 all told. One of our customers had one and claimed it delivered 35 mpg on a Ford Mustang with considerable loss of power; however, he agreed to let us have it for testing and we are still waiting.
There are two problems with the “Pogue principle,” which is being touted in high mileage seminars and books all over the country.
The first is that the Pogue carburetor violates the first law of thermodynamics, a commonly accepted scientific postulate that has been with us since 1830.
The law is written as follows: U = q + w
Or, in simple English, if you have chemical energy in a system (U) in its expenditure, it must equal q (heat) plus work (w). That is, if you have 100,000 BTUs in a gallon of fuel in which you then burn the end products—in a system operating at 30% efficiency—you will have 30,000 BTUs of work and 70,000 BTUs of heat.
Anything you put inside the combustion chamber can do only one of two things during the ignition stroke.
Produce energy (mechanical movement) during the reaction.
Absorb energy (leave out the exhaust as heat) during the reaction.
There has been a lot written about the “unburned particulates” furnishing the extra fuel for the extra 50 mpg or so, but if you’ll check the Fish dynatune emissions levels you’ll see there aren’t enough of them to get you another 300 yards down the road.
The second problem encountered with Pogue-type devices is that—in some instances—they actually predate the carburetor.
Let’s elaborate in both cases.
Back before the carburetor as we know it came into being in the 1890s there were several novel methods of getting fuel into the engine.
One method was using a kerosene-soaked rag to drip fuel into the engine.
Another method—that became quite common—was allowing air to pass over the surface of gasoline and then to be sucked into the engine. Sometimes a valve—called a “mixing valve”—would be positioned between the fuel reservoir and the engine. The valve would pop open when the downward motion of the piston created enough suction.
This method—and variations of it—have been touted all over the United States in “100 MPG CARBURETOR” seminars sponsored by various individuals as being the “ultimate” in sophisticated fuel systems, usually with exhaust heat or radiator water added to “vaporize” the fuel much more effectively than a standard carburetor.
There are a number of things wrong with the concept of such a “100 MPG” system.
The first is that the gasolines in use during the days of the mixing valve were far more volatile than the ones in use today. Some of you may remember when you could stand ten feet away from an open pan of gasoline, light a match, and watch the gasoline immediately catch fire.
Gasolines were changed in the 1930s with the advent of the catalytic cracker now used in petroleum refining. Carburetors like the Pogue, which depend on easily vaporized gasoline, simply will not work with today’s gasolines.
The second seminar-taught error is the method of using exhaust heat or radiator water to heat the fuel to the “vapor” point to extend the mileage. Warming or preheating fuel does have some value, but it’s limited.
Consider using hot water from the radiator to vaporize the fuel first.
Today’s gasolines do not completely vaporize until they reach 450º Fahrenheit heat, while the maximum temperature of the water in today’s pressure radiators reaches only 250º Fahrenheit. You just can’t heat a substance to 450º Fahrenheit using a 250º Fahrenheit heat source.
At least, not on this planet.
Exhaust heat works a bit differently.
It is the function of an internal combustion engine to change chemical energy into heat, and then the heat into mechanical movement. If the heat is not changed into mechanical movement it simply leaves—as heat. Any time you feel heat coming off an engine you are feeling wasted energy. The exhaust ports of an engine that operated at 100% efficiency would be ice-cold to the touch since ALL the heat would have been changed into mechanical movement.
Which means that the more efficient your engine is the less exhaust heat you’re going to have.
For example, if you have 600º Fahrenheit exhaust heat produced by one gallon of gas over a 20-mile trip and you use “exhaust heat” to “vaporize” the fuel and go 60 miles, what produces the 600º Fahrenheit heat for the next 40 miles?
If you answered “two more gallons of fuel,” go to the head of the class!
Seriously, there are ways to go several times the distance on a gallon of fuel (none of them involving carburetors); it’s just that the foregoing examples aren’t two of them.
In short, Charles Nelson Pogue was a machinist with no formal training in thermodynamics and may have actually believed that what he was attempting would work.
All a carburetor can do is meter and atomize fuel in correct proportion to air.
Any further increases have to come from increasing the thermal efficiency of the engine itself (such as raising compression) or reducing rolling friction. And this last is why a diesel locomotive with steel wheels will go ten times as far on a gallon of fuel as a diesel truck of the same weight with rubber tires.
For Pogue—or any similar carburetor—to go 100 mpg on a gallon of fuel on a vehicle normally going 20 mpg, the air/fuel ratio would have to be in the neighborhood of 75 to 1 or better.
Any second-year college chemistry student knows that.
I received the following in my email:
Mike: a friend just sent me your website and I found some interesting reading.
My father was very big on the 100MPG carb. So much so that him and I built a Pogue in 1980, It didn’t work for all of the reasons you outlined in your write up. He then designed a new carb that utilized Coolant heated evaporation chambers dispearsed around a common portal that sat on top of the normal Carb on his 66 olds. He would swap a valve to change fuel flow from the main to the aux carb but use the main carb butterflys for throttle control. It got exactly the same mileage as the normal carb,15MPG but with much less performance. For all of the same reasons as you stated in your writeup.
It was interesting to note however, that because of the involvement of several vendors and machine shops in the Valley area near Reseda CA, that the word got around he was building a high mileage carb, and his car was stolen right out of his driveway. When it was returned the only thing missing was the Carb.
He thought he could do similar miracles with steam, however as a graduate of the SoCal Edison Steam Generation School, I managed to convince him that his Idea of powering an Olds Toronado with a modified Olds engine converted to run on steam, just wasn’t going to work,,,,AT ALL! For all of the same reasons in your writeup on 100MPG carbs.
There is no substitute for complete understanding of a given subject. Partial understanding is just plain dangerous.–RB