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SAFETY FIRST
Before you install the fuel components do the following to minimise the dangers.
NO SMOKING
Work out side, not in a garage.
Ensure the engine and exhaust system is cold.
Disconnect the battery.
Before cutting the fuel line, remove the fuel cap to relieve the vapor pressure built up in the fuel tank. Replace the cap as soon as you attach the new parts.
Always use metal joiners and 'T' pieces on fuel lines, not plastic. Use hose clamps.
HOW THE SYSTEM WORKS
The fuel and air is cut off at idle by the solenoids. This can be used on any cold vapor system, not just the one described here. The system is best applied to vehicles fitted with an oxygen sensor.
Remember to attach a small air filter to the air intake. This air does not come through the airflow meter.
The restrictions in the fuel and air lines determine the flow rates. You can of course use adjustable valves if you prefer. Initially set the fuel flow to a rate of about 15 - 20 ml per minute, and adjust for best operation. Too little will not give much mileage gain, and too much will cause the mixture to go rich as the computer can only compensate over a narrow range. The hose is 3/8 th or half inch ID heater hose or vacuum hose. The air restriction is an orifice of about 1/8 th inch or 3 mm. A half inch length of fuel line pressed into the hose works well. This is also determined by trial and error. The amount of air added has a great affect on the driveability of the car. Too much air will make the car play up at low throttle settings. The restriction is best at this end of the hose and not the open end because we don't want any vacuum acting on the fuel input. The vacuum varies with throttle position and driving speed, and so would cause the fuel flow rate to vary.
The fuel solenoid is any sort of fuel cutoff, or petrol solenoid such as found in LPG vehicles. see photo
The vacuum solenoid is the same as described in the water controller. The air control solenoid (valve) is a vacuum operated heater valve. It allows a much larger air flow than a vacuum solenoid would. see photo. This valve is normally open, and uses vacuum to close. It takes quite a strong vacuum to fully close the valve. Try different vacuum sources to find the strongest. When connecting the vacuum solenoid, remember to connect the common to the air valve, the normally open goes to the vacuum source, and leave the normally closed connector open. Don't block it off, because it is necessary to relieve the vacuum, not trap it in the system.
The vacuum will vary with throttle setting, so it may be necessary to include a check valve in the vacuum source line. This prevents the air valve opening if vacuum is lost or slightly reduced. A check valve is another aquarium air accessory available from pet stores. We found it necessary to fill the valve with oil to improve the seal. ( ordinary engine oil ) The direction of air flow is upwards so the oil is not lost. See photo.
ELECTRONIC PARTS LIST
Transistors 2 x TIP32 pnp high power
Transistors 4 x BC337 npn general purpose
Transistor BC327 pnp general purpose
Diodes 9 x 1N4007 or equivalent
LED's 1 each red, green, yellow 5 mm round
Capacitors electrolytic 330uF, 220uF
Resistors carbon film 1/4 watt
1 x 100K
3 x 10K
3 x 3.2K
1 x 47K
1 x 100 ohm
3 x 1K
Trimpot 100K linear carbon
This list does NOT include the optional VAPOR CONTROLLER INPUT circuit or THE SIMPLE MIXTURE DISPLAY circuit.
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THE CIRCUIT
The region shown in the dotted line is part of the water injection controller circuit. This is the main input to the circuit to operate the solenoids. If you aren't constructing the water controller then use the following additional circuitry in the input stage. This includes a delay of about 2 seconds. The idle switch when closed, holds the transistors off. When the idle switch opens, the capacitor charges until the voltage is high enough to turn on the transistors. The output is either zero volts or +12 volts.
The delay is necessary to allow the revs to rise before the air and fuel is turned on. This prevents stalling, and surging at very low throttle settings.
VAPOR SYSTEM CONTROLLER CIRCUIT DIAGRAM
Mount the LEDs in the dashboard somewhere you can see them.
All the unlabelled diodes are 1N4007 or equivalent
Mount the solenoids in the most convenient place under the hood, and attach via long leads from the controller.
When testing the circuit on the bench, it is necessary to attach the air solenoid because it forms part of the circuit, providing the discharge path for the 200u capacitor, to turn off the fuel stage.
The 220u capacitor near to Q3 base is to provide a slight delay to the fuel solenoid. This is only necessary if the air control valve opens too slowly. The capacitor is optional and can be left out if the air and fuel operate at the same time.
The output transistors are large enough to not need heat sinks.
The bottom circuitry Q5, Q6, Q7 is there to monitor the mixture. If a rich condition exists for more than a few seconds, then the output of this part of the circuit will cause the fuel to be cut off. The delay is set using the 100 K trim pot. 3 to 5 seconds is a good delay. The fuel will be enabled again as soon as the mixture goes lean. If the red LED comes on often while driving then either too much fuel is being added or too little air.
The mixture input is the 0 or 1 volt signal out of the mixture controller that we send to the computer. If you are not building the mixture controller, then you will need to build the Simple Mixture Display shown here instead. The input is from the sensor. Don't disconnect the sensor wire, it still has to go to the computer. Just splice it in somewhere near the sensor.
Connect to the top of the LED as shown in the diagram. This point should have zero volts or about 1.2 volts when the LED is on. This led should blink on/off during normal driving.
FUEL SOLENOID
AIR VALVE
VACUUM CHECK VALVE
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