Curtis Dyna-Fog BLACKHAWK 2620, Instruction Manual

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The purpose of the Carburetor is to supply a combustible mixture of fuel and air to the Pulse
Jet Engines. The Carburetor uses four systems to create this mixture. These systems are:
1. A Venturi
2. A Metering Chamber
3. A Fuel Pump
4. A Fuel Needle
The Venturi is the air passage through the Carburetor. When air moves through a Venturi a
partial vacuum is created. The strength of the vacuum varies proportionately to the amount of air
flowing through the Venturi. When a constant volume of gasoline is connected to the Venturi, the
vacuum created by the Venturi will draw an amount of gasoline proportional to the air flow past the
Venturi and disperse the gasoline in the airflow. This arrangement allows the Carburetor to always
supply the correct ration of fuel and air to the engine.
The Metering Chamber maintains a constant volume of gasoline for the Venturi and prevents
gasoline from leaking out through the Carburetor should the machine be overturned. As gasoline
enters and begins to fill the Metering Chamber, it presses out on the Metering Diaphragm allowing
the spring under the Metering Lever to push out on the lever, closing the Inlet Needle Valve. When
the air flowing through the Venturi draws gasoline from the Metering Chamber, the Metering
Diaphragm moves in pressing in the Metering Lever and opening the Inlet Needle Valve, thereby
allowing the Metering Chamber to fill with gasoline again. When the engine is not running, vacuum
is not created in the Venturi to move the Metering Diaphragm, so the Metering Diaphragm does not
move in and out. In this condition the spring beneath the Metering Lever holds the Inlet Needle
Valve closed preventing gasoline from leaking through the Carburetor if the machine is overturned.
The purpose of the Internal Fuel Pump is to deliver the gasoline to the Carburetor and be
capable of delivering at least the maximum amount of gasoline the Pulse Jet Engine would ever
require. The Fuel Pump Diaphragm is driven by the alternating positive and negative air pressure
from the engine’s intake-explosion-discharge cycle. Movements of the Pump Diaphragm draw
gasoline through a series of check-valves and push the gasoline toward the Metering Chamber.
The Fuel Needle fine tunes the fuel-air mixture allowing for small differences in engines and
Venturis.
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