| The best candidates for fast burn conversion are | | | | the fuel tank full, so a drain in the air supply line will |
| spark ignited piston engines with adjustable spark | | | | be handy for accurately checking fuel economy. You |
| timing. Those with carburetors as original equipment | | | | add ten gallons to an empty tank and drive until a |
| do not have computers that control additional | | | | working fuel gauge goes below 1/4 tank and you |
| automotive functions besides fuel metering and spark | | | | then drain the remaining fuel from the tank into gallon |
| timing. The fast burn engine can’t use | | | | jugs. Subtract the remaining fuel from the ten gallons |
| computer management as a low cost conversion | | | | you started with. Divide the gallons used, into the |
| option. If an idle circuit similar to that of a carburetor | | | | miles driven and we will know our MPG. |
| is added to a fuel injection throttle body as a spacer | | | | We never want to fill our fuel tank to filler nozzle |
| plate, a throttle body might be able to serve as a | | | | shut off, as that would give us a minimal surface |
| basic carburetor for cold vapor fuel. Many modern | | | | area from which to vaporize our fuel and our mixture |
| fuel injected engines can be owner retrofitted with | | | | could then be too lean to run our engine. However, if |
| carburetors and aftermarket or used factory intake | | | | one wanted to build a vapor chamber and install it |
| manifolds for use with carburetors. | | | | above the top of the fuel tank and filler tube, there |
| The traditional multi circuit carburetor is not required | | | | might not be much difference when the tank is |
| for vapor fuel, but is less expensive than producing | | | | overfilled. One thing we definitely want to avoid is |
| new twin circuit carburetors designed specifically for | | | | liquid fuel in our vapor supply line. Though it is unlikely |
| vapor fuel. All carburetor air vents should be plugged | | | | the liquid fuel would reach the carburetor, the more it |
| so engine vacuum signals draw only from the | | | | wet the vapor supply line, the richer the mixture |
| unvented carburetor fuel bowl, which is connected to | | | | would be at the carburetor. |
| the fuel bubbler in the tank or racing fuel cell. The | | | | I envisioned a tri Y air bubbler on the fuel tank floor, |
| fuel float and needle valve assembly is removed. Any | | | | to evenly distribute air in the tank. The line |
| accelerator pump is removed and the enrichment | | | | connecting to the old fuel supply line, inside the tank |
| hole is plugged. In carburetors that use vacuum | | | | would split into two equal length lines of the same |
| power valves, such can be used to fine tune vapor | | | | diameter from a Y or T connector. The two lines are |
| flow according to vacuum signals. The idle circuit must | | | | then split into two more equal length tubes (fuel |
| retain adjustment from barely open to wide open. | | | | proof, of course) and porous air bubblers to make |
| Rod and jet enrichment systems such as used on | | | | small bubbles moving through the fuel. This would |
| Carter and Rochester carburetors can also be used | | | | give us a richer mixture at the fuel supply line, than a |
| to fine tune vapor mixtures. Go as lean as you can | | | | single tube with no air diffusers. I would terminate |
| without the engine stumbling under load on the | | | | my air supply lines with those bronze fuel filters many |
| power circuit and richen slightly for best throttle | | | | carburetors used just ahead of the needle and seat |
| response. If the max power metering is sufficient | | | | assembly at the end of the supply line. Short term |
| with selected main jets, which flow much more vapor | | | | tests I did several years ago showed that the |
| than liquid, we can regulate the maximum fuel supply | | | | ceramic bubbler filter for fish aquariums gave very |
| by means of an adjustable valve in the supply line. | | | | fine air bubbles and did not seriously deteriorate in |
| Start the fast burn engine with the idle mixture | | | | gasoline. They were not very expensive. |
| screw open wide and quickly close it after the engine | | | | I can only guess at supply line sizes. My guess is that |
| starts. Back the adjustment screw off one turn after | | | | the filtered air supply line need be no more than a |
| you stall the engine for lack of idle fuel. Too much | | | | quarter inch ID. The vapor supply line probably needs |
| idle fuel could melt engine parts as easily as too much | | | | to be no greater than three eighths inch ID. |
| fuel in the power circuit. If we never meter more | | | | These are the basics of a cold vapor, fast burn fuel |
| fuel than can burn in half a power stroke, we avoid | | | | system. I would expect improvements to come |
| meltdown while maximizing power and fuel economy, | | | | rapidly following road testing. When we know the |
| minimizing exhaust emissions. | | | | typical optimum spark timing and air/fuel mixtures, |
| With fast burn, we want to retard initial spark timing | | | | we can apply this knowledge to small engines with |
| to between sixty and eighty degrees after top dead | | | | fixed spark timing, like lawn mowers, snow blowers |
| center. On a V-8 we can move each wire in the | | | | and electrical power generators. |
| distributor cap forward one position on the cap in the | | | | My expectations of fast burn performance is |
| direction of rotor rotation. This will retard timing 90 | | | | between two and three horsepower per cubic inch |
| degrees from the standard initial timing. A timing light | | | | displacement, which would make fast burn conversion |
| on the number 8 cylinder will allow you to set initial | | | | the best power bang for the dollar. No other |
| timing with the stock timing marks. Setting number 8 | | | | modification can come close in dollar costs. Under |
| cylinder for ten degrees advance would have number | | | | most racing rules, fast burn would be legal for the |
| one cylinder firing at 80 degrees after top dead | | | | allowed fuel and add more power than supercharging |
| center. 20 degrees advance would have number one | | | | or nitrous oxide injection. Yet, these power boosters |
| firing at 70 degrees ATDC, etc. An aftermarket | | | | will add a lot more power to a fast burn engine than |
| timing tape, when available, is another way to | | | | to a slow burn engine. Hence, the fast burn |
| accurately set spark timing. Otherwise, one can | | | | conversion will out perform slow burn by a wide |
| remove the crankshaft dampener or pulley with | | | | margin, regardless of class allowed modifications. The |
| timing marks, measure the circumference, divide by 4 | | | | fast burn conversion can also be camouflaged to look |
| and mark at 90 degrees ATDC, 85, 80, 75, 70, 65, | | | | stock by plumbing the supply line through a non |
| and 60 degrees. Marking all the way back to 30 | | | | functional fuel pump. |
| degrees ATDC is a good idea. This is the most | | | | As to economy, Charles Pogue exceeded 200 MPG |
| advance likely practical for max fast burn power and | | | | with his hot vapor, 37 V-8 Ford, which would |
| allows one to check for total mechanical or electronic | | | | rarely yield 20 MPG in slow burn configuration. Uniform |
| spark advance. Optimum timing for best performance | | | | cold vapor might have allowed him to achieve the |
| and economy, like fuel mixture, must be worked out | | | | 300 MPG economy he was shooting for, while more |
| by road testing the converted vehicle. | | | | than doubling stock power output. When fast burn |
| Fully vaporized fuel is likely to be combustible over a | | | | conversions become common, performance and |
| wide range of air/fuel ratios. As a safety precaution it | | | | economy contests will lead to rapid improvements in |
| makes sense to install a PCV valve or something | | | | the very simple technology. |
| similar. Should a timing chain let go or an intake valve | | | | As to emissions, if we are consuming less than 10% |
| bend, we don’t want fire in the intake | | | | of the fuel per mile driven, emissions will be less than |
| manifold to find its way back to our bubbler and | | | | 10% of the slow burn equivalent. Burning 100% of |
| explode it. Better that a fuel supply line disconnect or | | | | the fuel on a shortened power stroke, will further |
| rupture under the hood from combustion back | | | | dramatically reduce emissions, probably to less than |
| pressure. | | | | 5% of slow burn engines. In addition, the much higher |
| The bubbler where our vapor is made by engine | | | | power outputs of fast burn engines allows engine |
| vacuum, is a modified fuel tank or racing fuel cell. Our | | | | downsizing. A 300 cu. in. slow burn engine can be |
| tank/cell must be vented to atmosphere. We want | | | | replaced with a 140 cu. in. fast burn engine and still |
| our air pick up filtered with something like a | | | | provide a power increase. Economy is improved, |
| lawnmower air filter and mounted higher in or outside | | | | along with emissions. Big cars and trucks Americans |
| the vehicle, than the outside of the fuel filler tube, | | | | favor, in fast burn configuration will easily exceed |
| which is the most convenient place to tap our tank | | | | hybrid electric cars in economy and reduced |
| cell for a very rich vapor. | | | | emissions, as well as power. On the other hand, a |
| On the typical fuel tank, our air vent can be easily | | | | fast burn hybrid could top 400 MPG if we want to go |
| installed where the original fuel supply line attached. | | | | that far. |
| We want another PCV valve near our air supply filter | | | | I would love to hear from any individuals or groups |
| to seal the tank from atmosphere when the vehicle | | | | already doing fast burn conversions and learn what |
| is not running and the tank/cell is pressurized by | | | | they have learned. While the piston engine has had a |
| atmospheric heat. Gas expansion in our tank now | | | | bad rap for efficiency due to the liquid fuel systems, |
| moves fuel through the carburetor into the intake | | | | the Tesla Turbine, seldom used as a combustion |
| system, where it allows instant starts, as with fuel | | | | engine, can be built as a very lightweight, compact, |
| injection. | | | | multi stage, supercharged, exhaust scavenged 30 |
| Bubbler design is guesswork. Whatever supplies the | | | | horsepower per pound, fast burn engine. The Tesla |
| most consistent air/vapor mixtures from a tank 3/4, | | | | Turbine with only one moving part is cheap and easy |
| 1/2, 1/4 and 1/8 full, is what we want. Variations in | | | | to manufacture in a small machine shop. The turbine |
| vapor from the tank will make engine tuning difficult | | | | requires no drive train except the connection to the |
| and variable. Consistent mixture from the bubbler is | | | | drive wheels. No gear reductions, instant tire spinning |
| important. If the air supply is opposite the vapor | | | | torque and instant rotational reversal for engine |
| supply line, we would expect a richer vapor than if | | | | braking. Stay tuned for more on the potential of this |
| the air supply line was near the vapor supply line. We | | | | remarkable engine, developed early in the 20th |
| want the air supply line to lie on the bottom of the | | | | Century and virtually ignored by industry ever since, |
| tank, below whatever fuel we have. We never want | | | | except for vastly superior pumps. |