The best candidates for fast burn conversion are spark ignited piston engines with adjustable spark timing. Those with carburetors as original equipment do not have computers that control additional automotive functions besides fuel metering and spark ibc탱크. The fast burn engine can’t use computer management as a low cost conversion option. If an idle circuit similar to that of a carburetor is added to a fuel injection throttle body as a spacer plate, a throttle body might be able to serve as a basic carburetor for cold vapor fuel. Many modern fuel injected engines can be owner retrofitted with carburetors and aftermarket or used factory intake manifolds for use with carburetors.
The traditional multi circuit carburetor is not required for vapor fuel, but is less expensive than producing new twin circuit carburetors designed specifically for vapor fuel. All carburetor air vents should be plugged so engine vacuum signals draw only from the unvented carburetor fuel bowl, which is connected to the fuel bubbler in the tank or racing fuel cell. The fuel float and needle valve assembly is removed. Any accelerator pump is removed and the enrichment hole is plugged. In carburetors that use vacuum power valves, such can be used to fine tune vapor flow according to vacuum signals. The idle circuit must retain adjustment from barely open to wide open.
Rod and jet enrichment systems such as used on Carter and Rochester carburetors can also be used to fine tune vapor mixtures. Go as lean as you can without the engine stumbling under load on the power circuit and richen slightly for best throttle response. If the max power metering is sufficient with selected main jets, which flow much more vapor than liquid, we can regulate the maximum fuel supply by means of an adjustable valve in the supply line. Start the fast burn engine with the idle mixture screw open wide and quickly close it after the engine starts. Back the adjustment screw off one turn after you stall the engine for lack of idle fuel. Too much idle fuel could melt engine parts as easily as too much fuel in the power circuit. If we never meter more fuel than can burn in half a power stroke, we avoid meltdown while maximizing power and fuel economy, minimizing exhaust emissions.
With fast burn, we want to retard initial spark timing to between sixty and eighty degrees after top dead center. On a V-8 we can move each wire in the distributor cap forward one position on the cap in the direction of rotor rotation. This will retard timing 90 degrees from the standard initial timing. A timing light on the number 8 cylinder will allow you to set initial timing with the stock timing marks. Setting number 8 cylinder for ten degrees advance would have number one cylinder firing at 80 degrees after top dead center. 20 degrees advance would have number one firing at 70 degrees ATDC, etc. An aftermarket timing tape, when available, is another way to accurately set spark timing. Otherwise, one can remove the crankshaft dampener or pulley with timing marks, measure the circumference, divide by 4 and mark at 90 degrees ATDC, 85, 80, 75, 70, 65, and 60 degrees. Marking all the way back to 30 degrees ATDC is a good idea. This is the most advance likely practical for max fast burn power and allows one to check for total mechanical or electronic spark advance. Optimum timing for best performance and economy, like fuel mixture, must be worked out by road testing the converted vehicle.
Fully vaporized fuel is likely to be combustible over a wide range of air/fuel ratios. As a safety precaution it makes sense to install a PCV valve or something similar. Should a timing chain let go or an intake valve bend, we don’t want fire in the intake manifold to find its way back to our bubbler and explode it. Better that a fuel supply line disconnect or rupture under the hood from combustion back pressure.
The bubbler where our vapor is made by engine vacuum, is a modified fuel tank or racing fuel cell. Our tank/cell must be vented to atmosphere. We want our air pick up filtered with something like a lawnmower air filter and mounted higher in or outside the vehicle, than the outside of the fuel filler tube, which is the most convenient place to tap our tank/cell for a very rich vapor.
