High Mileage Carburetors MPG-increasing Devices and Hyper-miling

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For decades, rumors and desktop-publishing interests have proliferated the ‘200 MPG Carburetor’ and other such gas mileage boosting devices. While virtually none of these seem to have ever made it to the consumer level, the faithful seem to contin


The Pogue Carburetor and other 200 MPG Carburetor Devices

Probably the most notable and public example was the Pogue Carburetor from the 1930s. Three different patents were issued for three different and progressively smaller and presumably more efficient models of what became known as the Pogue Carburetor. While engines today are larger, torque harder and have much more weight to move under load, the purported "200 MPG" is unlikely. But the inception of the device may be legitimate; improved combustion that turns more of the fuel's energy into work instead of expelling it as waste heat. 200 miles per gallon is unlikely.

According to cited data in the above link, engineers have built and tried designs based upon Pogue's theories and the results have been less than reported, substantially less. Allegedly (from the link and source cited above,) Canada National Research Council once made a statement to Marketplace (a consumer affairs programme) this quote:

  • "You can get fantastic mileage if you're prepared to de-rate the vehicle to a point where, for example, it might take you ten minutes to accelerate from 0 to 30 miles an hour."

I attempted to find the source of the quote at the URL given but no matching documents were returned. Still, this above statement is veritably accurate and rather insightful. On a carburetor automobile, unhooking the accelerator pump arm will greatly (!) increase your miles traveled per tankful and even miles per gallon; if one did the math on it, however the acute loss of acceleration from a standing or stopped position is deleterious to normal driving and quite objectionable.

Fuel Efficiency : MPG at any cost

One may require a minute or two to feather the gas pedal to not only make the car move forward but to prevent the car from starving and stalling for lack of fuel. Reasonable acceleration from a stopped position is required. That requires an additional injection of a metered amount of fuel, possibly amounting to a just teaspoon or so. This will of course, affect the bottom line of effective MPG.

One would be better off using another technique to effectively double mileage, called hypermiling. Little changes in driving habits applied broadly to your driving habits can greatly decrease the amount of fuel that your car uses. Removing unused bike and ski racks to reduce wind drag, keeping the windows rolled up when commuting, coasting to stops and red lights to avoid braking, shutting the engine off before the parking spot and 'coasting to a dead stop' that way, etc. Even taking roads that may be longer to drive but have less traffic affords a greater range of fuel saving driving techniques such as maintaining a more constant speed (use of cruise control is advised and highly desirable, if your vehicle has this option.) Or, another method that is also extremely effective: drive and coast.

'Drive and coast' is something that quite effectively doubles your MPG on ANY vehicle. You get the car up to a maxim speed of say, 65 miles per hour then remove your foot from the gas pedal and put the transmission into Neutral, coasting until you decelerate to around 35 miles per gallon. While still rolling and engine running, put the car back into Drive and slowly accelerate back to 65 MPG and repeat, again and again. Do this until you reach your destination. This is best employed on straight, flat paved roads with no traffic behind you.

My wife and I did this once all the way across northeastern Colorado to the Nebraska border out of sheer necessity once. We departed Fort Collins, Colorado in the north-central region of Colorado on ¾ tank of fuel. The expectation was that we would find gas stations as we traveled east across the Colorado plateau. Little did we know there are no gas or service stations along that route. Or the ones that existed were closed. For the last 350 or so miles, we did 'drive and coast.' Those last 75 or so miles to the Nebraska border (and in torrential rains, as if there were not enough stress already) were dubbed the White Knuckle Flight. We surely thought that at some point we would find ourselves stranded in the dark rainy eastern Colorado plateau, miles from help. The gas gauge was WELL below "E" on the dial. I knew that my car had a 'one gallon reserve' below the "empty" mark and we were beyond there already! We were making semi-serious jokes about who was going to be first to get out and push!

By using the Accelerate and Coast hypermiling technique, we traveled the distance on well under two gallons of remaining fuel and made it to the border where there were abundant gas stations, rest areas, restaurants and service malls. Nirvana!

But again, this is not practical for routine and day-to-day driving for most people. It remains a technique that can save you in an extreme situation however.

Another and primary hypermiling technique is similar to Accelerate-and-Coast but it involves shutting the engine off and coasting, restarting and accelerating, etc. You lose your power steering and power brakes when the engine if OFF, and this practice is not advised. Saving a gallon or two of fuel per tankful is not worth potentially being in or causing an accident.

There are hundreds of genuine fuel-saving devices that have been patented by the U.S Patent Office ranging from complex methods of carburetion and fuel delivery to preheater devices to simple devices that swirl the air-fuel mixture prior to entry to the combustion chamber.

The Famous Pogue Carburetor Patented Design

Pogue Carburetor from the U.S. Patent

Don't plan on building this yourself. Seemingly impossible, but think about it; -could you build a 'regular' carburetor yourself? This is something best lest the the engineers and manufacturing experts. Still, far simpler designs exist that CAN be made by the novice inventor.

I had experimented with several of these devices myself back in the late 70s and early 80s and had some successes. One in particular was by using a coil of copper line wrapped around a hollow steel tube that is spliced into the hot water heater core. The car starts and runs as per normal and when the water begins to heat up, it exchanges heat into the metal fuel line and therefore, pre-heats the gasoline just before delivery to the carburetor. This does increase mileage. The fuel can attain a temperature of around 150-160 F (the hot water in the heater core should be around 185-195 F, depending upon the type of thermostat the car uses. A complete heat-exchange is improbable, and also undesirable.)

Simple Fuel Pre-Heater Gas Mileage Device for Increased MPG

simple copper-coils wrapped around pipe inserted into heater-core hoses, pre-heats gasoline for higher MPG

(this is a sketch of the design I started working with, which gave increased mileage in a 1970 Oldsmobile.)

I was recording a 8-10 MPG increase in a 1970 Oldsmobile. A down factor was that upon turning the car off, the hot fuel still in the short coil of copper fuel line was hot and would gassify and escape through the carburetor's meter valve. The meter valve is a small device that works in a manner very similar to the float device in the back of your toilet except that like toilets, carburetors it is intended to meter liquid, not gases.

This vapor gasoline was passively escaping via the carburetor, forming a potentially explosive 'fuel cloud' under the hood that would dissipate within an hour or so. Escaping fuel vapor is lost fuel. While the MPG (miles per gallon) may increase, the MTpT (miles traveled per tankful) was decreased. Not a good conservation nor fuel-saving option, not to mention safety issue. A re-start of the car while still 'warm' if there are any sparks present (bad connection to battery, a spark plug boot improperly seated, etc.) and there could be potential for an explosion.

A solution might be to use an electric tank-switching device to shunt the fuel away from the preheater, bypassing it directly to the carburetor as per OEM a few minutes before reaching your destination. This way, the hot fuel in the preheater coils would be used-up and not be an issue.

A non-mechanical one-way back-flow preventer (a ball-check valve) would prevent the slightly pressurized fuel from reverse-venting the preheater back into the fuel tank.

I never got around to investigating ideas. My next car employed throttle-body injection: a early form of fuel injection. Fuel preheaters do not function well (or at all) in engines that monitor efficient operation and inject fuel based upon anticipated need and adjust the idle accordingly. The automotive industry as a whole moved to an engine design that seemingly render these mileage devices inoperable and truly obsolete, once and for all.

If you are interested in high mileage devices for automobiles, the internet is rich in pages that explain the theory and design of these devices, how they supposedly work and how & why most of them do not. Still, I believe. I have built devices that doubled or nearly tripled the mileage of my car.

Every invention had at least one or two rather serious limitations along with the obvious mileage improvement, problems for which I may have had solution had I the resources and time to investigate them. But fearing damage to my car (which was absolutely required to go to work, so I was a bit unwilling to experiment too deeply with unproven devices) I abandoned my backyard research. A good oil change, wax job, windows up and proper tire inflation and proper driving technique can do wonders for your fuel economy. And you will not be voiding your car manufacturer's warranty. Probably it is better to stay with the advice of the car manufacturer and leave the experimental high mileage design to the inventors and engineers.


Posted on Mar 13, 2013
Posted on Mar 13, 2013
Johnny Dod
Posted on Feb 23, 2010