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Techniques to Improve Gas Mileage

By Philip N. Ledoux
September 28, 2005


Here is something of current interest. Locally lowest octane gas just went through $3 per gallon. I think 'Big Oil" is telling us: Line up, grab your ankles please, and expect a surprise.

Philip N. Ledoux

One of the simplest and oldest techniques used to improve gas mileage (to our strongly accented cousins it is petrol mileage) is vaporization. Pogue, Fish and others perfected the technique in the 1930ies, probably urged on by the harsh economics of the times. The principle is to feed gas vapor into the carburetor or into the intake manifold. For those not familiar, this is the classical example used to demonstrate the differences: If you take a barrel full of gas and throw a match into it, you will have one hell of a fire, and that’s about it. Take that same barrel with 3 inches of gas in the bottom, throw a match into it, and take cover, she’s headed for the moon with a hell of a KaBoom. The nearly empty barrel was full of gas vapor which releases its energy dramatically. The same difference occurs within an engine; what is needed is some method to control the amount entering the engine.

Pogue and Fish redesigned the carburetor itself to create vapor and regulate vapor flow. Others used exhaust heat to accomplish the same thing. Let me jump ahead to post WW II days around the early 1950ies. Popular Mechanics published a simple device that never “caught on”. I learned about it from a tinkerer who had heard about my electrical ignition system and “found me”. I think I was the one who learned the most that day. But first a few precautions.

I have always been interested in increasing gas mileage since I was a teenager. During my lifetime I have almost met 4 men who designed high mileage carburetors. I knew men who personally knew these men. Every one believed in the American Dream and set out to manufacture and market their carburetors. All suddenly disappeared, never to be heard of again. It was as though they had never existed. I tried to market my invention, but I was a flop as a marketer, so with my “victory by default” I live on to talk about it. This is serious business, the business of getting better mileage. A fellow in the Boston area in the 1990ies was a refrigeration expert, contractor. He discovered that a certain refrigeration “part” would create gas vapor with little or no modification. He had success. Painted two cars bright yellow and advertised on it “This car gets 150 MPG, ask me about it”. He got to drive it 15 miles. Ended up in jail. Long before his sentence was completed, he was released. Everybody abandoned him when he again persisted in marketing his invention. He had a web site with all the info for a handyman to duplicate his efforts. Before a month passed the site no longer existed and apparently neither did he. Nobody has seen hide nor hair of him since. I am certain that this paragraph is the most important part of his discussion with “how to do it” instructions. You have to cuss me up vigorously in public, and blow me kudos in private. That is the only way you will continue to breathe when you own a high mileage vehicle.

This “invention” is really simplicity in the extreme. You do have to be somewhat of a handyman or mechanically inclined. By some means a line is attached to the intake system of a carburetor driven engine. This line connects to a small tank or “can” that has a small metal tube soldered or brazed through the top of the tank or “can”. The screw on cap, has another similar tube soldered or brazed through itself. On the inside a fish tank air stone is connected by a regular plastic tube to this cap. The cap is screwed into place. The cap is the fill point until you get exotic and fancy. Start out simple and save headaches along the way. One step at the time.

The engine is started normally, then the main fuel supply is turned off. When the carburetor reserve fuel is used up, the engine will now be sucking on the line connected to the top of the tank. The suction in turn pulls air in via the cap pipe, down through the air stone and bubble up in tiny, tiny bubbles resulting in gas vapor forming in the top of the tank or “can”. The engine will be running on gas vapor. You may have to adjust the timing because of the greater power available and other factors involved. Remember in adjusting that you still have to be able to start the vehicle. Many worry about the loss of cylinder lubrication that is done by the actual non-burned fuel in the normal mode. On a hydrogen (water) system, the follow up instructions said: operate the engine for 3 minutes before and after using the high efficiency, in the normal gas mode for lubrication. So, it appears that the fears are not that acute.

On older vehicles you make a ½ inch think “riser” under the carburetor. If you are not familiar, ask any “dirt track” racer, they will proudly give you complete instructions. The nice part about a “riser” is that it can be made of aluminum which can be worked with wood working tools. Cut the holes as accurately as you can; like a gasket it can be somewhat imperfect; strive for perfect, knowing we never really achieve it with wood working tools. Obviously two carburetor gaskets are needed for the riser. Drill one horizontal hole through this riser to the (singular or plural) main throat. Drill for the tap size of the fitting you are going to use to this auxiliary tank or “can”. Then tap the hole. From experience I find less frustration using soft copper; flared fittings are best, although ferrule fittings are OK. This line goes to the top outlet on the auxiliary tank or “can”. You are ready to fire up and test.

Let’s put some common sense into this inventiveness. If you understand the general principles and layout, have you brought along a fire extinguisher, just in case? If it isn’t 40 below outside, you should be working out doors; and for safety make that soft copper line ling enough to place the tank some distance from the vehicle just in case you need to use the extinguisher! Plan ahead for worse case scenario. Maybe I have many guardian angels looking over me (so sayeth my ma), I have never needed to use the extinguisher. You are now ready to fire the beast up. Be patient, after turning off the fuel supply (pull the fuse, or a shut off in the main line to the carburetor, it takes awhile to use up the carburetor reserve. You should be able to hear when the shift occurs. From here on out, you are on your own because all engines are different in timing, etc.

What about these new marvels that you need a shoehorn to get at anything? A carburetor expert told me: Place a “Y” in the smog line as it goes to the carburetor so that the main line is straight and the “Y” will suck (venturi effect). This “Y” connects via a tube to the top of the auxiliary tank or “can”.

There should be some kind of check valve in the operating system between carburetor and auxiliary tank or “can”. Some recommend an oxygen-acetylene check valve, I find they have too strong a spring action, and the connectors are non-standard. A low pressure domestic steam system check valve should work. Orient it physically to open easily and close quickly if the engine backfires. This prevents the auxiliary tank from becoming a rocket in a backfire condition.

There are many methods of filling this auxiliary tank or “can”. A fuel tank gage, a sight glass type device with floating magnet with external magnetic switch, etc. etc. Or you can use a larger tank that will last reasonable distances before needing refilling. The largest problem on today’s vehicles is finding a place to fit this auxiliary tank. A magician helps. I think the company managers could see this day coming and designed so that no additions could fit into the engine compartment. At worse, one could cut a hole in the hood to one side and do like the street rods used to add a scoop.

Now I’ll allow you to laugh at me. I had a 1970s small bus with a big loadstar engine in it. A racer gave me a riser that happened to fit perfectly. I welded up a tank that would withhold an explosion, did all the plumbing, tank gage, changed engine to an electric fuel pump, and an electric fuel pump to fill the tank. Switches and whistles on the dash. When I built the tank, my thinking was: this is a mighty big engine, it will need large lines. In the bottom of the tank, I had a 3/8 inch black iron pipe welded internally at one end and extending through the tank wall on the other end with lateral holes for a series of 6 individual fish tank air stones that were sealed in place with “liquid steel”. Externally this had an elbow with vertical standpipe with a small engine filter. The soft copper connector lines were 3/8 inch. The engine started OK, then it loaded down badly. Hmmmm. The old girl went from 6 miles to the gallon to 6 gallons per mile! The intake to the auxillary tank was so large with so many air stones that the engine just sucked up raw fuel. Back to the drawing board.

How many miles do I get to the gallon? Go back to paragraph #3 which states the facts about not wearing cement shoes. With a smile on my face I tell you: 6 gallons to the mile. Damned cuss who put it together must have had rocks in his head, if you’ll help me we’ll skin him alive. Do not email me or snail mail me, it will still be 6 gallons to the mile, and with the instructions given, you better get some mechanic to give you a hand, I’m not able to lead you by the hand any better than described.

Philip N. Ledoux

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All information posted on this web site is the opinion of the author and is provided for educational purposes only. It is not to be construed as medical advice. Only a licensed medical doctor can legally offer medical advice in the United States. Consult the healer of your choice for medical care and advice.