Better-mileage by shuifanglj


									             Electronic Mixture Controller Manual
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The car's computer is expecting to see an oscillating signal from the oxygen
sensor which goes from zero volts to plus one volt approximately. The fuel
flow is adjusted to maintain the average voltage at close to 0.5 volts

The signal from the sensor isn't a square wave, but more like a smooth
triangular wave form. The computer doesn't care about the exact shape but
simply tries to maintain the average.

The Electronic Mixture Controller is installed in the system between the
oxygen sensor and the car's computer.

What this device does is convert the wave form into a square wave, but
more importantly it sets up a threshold voltage that is lower than 0.5 volts.
When the sensor output is above the threshold, which is set quite low, say
0.1 volts, then the device will send a high signal to the computer. When the
sensor signal drops below the threshold the device signal out will be low.
The computer adjusts the fuel flow accordingly and now is actually
maintaining the average voltage from the sensor at 0.1 Volts (100mV)
instead of 0.5 volts. (500mV)
                           From the Sensor Output graph you can see
                           that the mixture is now slightly leaner than it
                           was. The operating range is shifted to the
                           We have cut the fuel quantity by no more
                           than few percent, perhaps 5 %. This by itself
                           will produce some mileage improvement but
                           not a lot. The greatest benefit occurs when
                           applying the device in support of some other
                           high mileage system. Especially cold vapor
                           systems and water injection. The computer
                           will normally fight these systems to
                           compensate for the added exhaust oxygen.
                           This device fools the computer and enables
the maximum possible mileage improvements.

If your oxygen sensor is old and sluggish this device will also improve the
reaction time. Because it instantly tells the computer when the sensor
output is below or above the threshold, there is less overshoot. Smaller,
quicker corrections to the mixture occur rather than long slow corrections.


The heart of the circuit is the LM3914 linear LED dot/bar Driver IC, which
we operate in bar mode. This is the same IC as is in the Mixture Display
circuit. We set the sensitivity to 500mV full scale for this controller.
If you want to be able to adjust your mixture richer for more power rather
than leaner then you should adjust the sensitivity to a greater voltage,
around 700mV. It is not recommended to set the threshold too high,
because it is quite possible that your sensor output may never reach that
high. The computer will keep adding fuel expecting the signal to go high.
Remember, excess fuel will be burnt inside the catalytic converter which
could cause a meltdown. Don't risk a fire under your seat. Or it may simply
ignore the sensor and operate in open loop mode.

              Electronic Mixture Controller Circuit Diagram
WARNING This is a static sensitive device.

Handle it carefully and always use an IC socket to mount it. Don't directly
solder the IC into the printed circuit board. Install this component last.

We use this IC to sample the sensor voltage and provide outputs at various
thresholds that we can select from. The trim pot R1 sets the sensitivity and
we adjust this for 500 mV full scale. Each LED output then is 50 mV apart.
We don't actually install LED's on each output, and any unused outputs are
left open circuit. The front panel rotary switch selects which ever output we
choose. We only need 2 or 3 to choose from. You can leave out this rotary
switch and simply select one of the outputs to connect if you prefer. The
front panel on/off switch is a DPDT toggle switch. All the capacitors are
electrolytic type of about 16 volt rating. All resistors are 1/4 watt.

The input resistor/capacitor circuit provides filtering of the sensor signal.
Because the entire circuit comprises high impedance components,
including the sensor and IC input, the input line is susceptible to induced
noise. Ignition noise in particular will affect the circuit and cause incorrect
operation. If you install the LED Mixture Display as recommended, you will
see that until the sensor heats up all the LED's will be dimly lit. This is
showing that there is a lot of noise on the line. When the sensor heats up,
the signal becomes cleaner and then only the appropriate LED will be lit.
We also include a delay circuit so that after start up, the output is held low
for a few minutes to simulate a cold sensor. The sensor must be
operating correctly before we send signals to the computer. The most
common problem, if we don't have this delay, is that the output will be high
simply from the noise on the signal line. The computer will think the sensor
is working, because it is high, and will cut back the fuel to make the signal
go low. When this happens we end up with a very lean condition and very
poor acceleration.

The front panel switch is very important. It doesn't switch the power to the
device. What it does is allow the sensor signal to bypass the device
altogether. This is an essential feature. You can switch your vehicle back to
it's unmodified state instantly if you suspect that there may be a problem
with the device or if the vehicle simply isn't performing as it should.
Remember, only you know what you have done to your car and other family
members that drive the car may not be able to fix any problems that may
arise. Just show them the switch.

The front panel LED is not just to show that the device is operating, but
forms a simple voltage regulator for the output signal to the computer. In
operation the LED is lit when the output is high. So the correct state for the
LED to be in is flashing.


This is a simple test you should perform first. The oxygen sensor earth
connection is the exhaust system, which is firmly bolted to the engine. The
computer earth is the vehicle body. We have seen that 0.5 volts can make a
large difference to the mixture. If the engine is not well and truelly earthed
to the body then a voltage difference can exist between the two, and 0.5
volts would normally go unnoticed. We can't afford to have that sort of
voltage difference when trying to accurately control the mixture.

Start the engine, switch the headlights on high beam, then measure the
voltage between the engine and the body. Use an accurate digital volt
meter. Any more than 50 mV will mean you have a bad earth connection
which will need cleaning and tightening. Modern cars usually have more
than one connection so look around. If you have trouble achieving this then
use an engine earth connection for you circuit rather than a body
connection. What is most important is the signal voltage from the sensor,
since we are operating at such low voltages.


IC LM3914 linear LED dot/bar Driver IC
Transistor BC 327 pnp general purpose
Darlington Transistor MPSA14 npn high gain darlington
Diodes 2 x 1N4007 or equivalent
LED 5mm round, any color
Trimpots 2 x 10K linear carbon
Capacitors 3 x Electrolytic 10uF, 0.1uF, 2.2uF
Resistors carbon film 1/4 watt
 1 x 10M
 2 x 1M
 1 x 3.9M
 1 x 10K
 1 x 2.7K
 2 x 1K
Rotary switch single pole
Toggle switch DPDT
Printed circuit board general experimenters board about 2 x
3 inches
Case to fit


Read this through completely before beginning.

All the parts needed should be available from your local Radio Shack store.
They will also be able to show you the component orientation and which
legs are which etc.

You will require a soldering iron, a 12 volt power supply such as a small
power pack and an accurate digital volt meter for this project. No other test
equipment will be needed. The 12 volt supply should be well filtered. You
want proper DC, not simple rectified AC, which contains too much ripple.
Lastly you will require a variable voltage source that can go from 0 to 1 volt
to simulate a sensor input. It's simple enough to make this using a resistor
and a variable resistor.

The transistors are nothing special, just general purpose devices so it
should be OK to substitute where necessary. The darlington transistor
(MPSA14) is a special high gain device needed for the delay circuit. Again it
is just a general purpose darlington transistor. The printed circuit board can
be any general experimenters board approximately 2 x 3 inches. Try to
plan ahead and think where you are going to mount the device, either
behind the dash or in a small case mounted somewhere. The printed circuit
board has to fit and after the components are mounted it will be more
difficult to fit in a tight location.

Start with the IC socket, and mount it slightly in from one end. The circuit
diagram can give an indication of the general layout of the components. It
makes it easier to follow the circuit if the components are in the same
position as on the diagram.
You will have to decide for yourself where and how you mount the front
panel components, the rotary switch, the on/off switch and the LED

The IC legs are numbered 1 to 9, left to right across the bottom as seen on
the diagram, and 10 to 18, right to left across the top. The notch shows the
left end, this is standard for all IC's.

Try to plan the component positions so that you require the least amount of
additional wire to make all the connections on the board.

Don't connect the wires to the front panel rotary switch just yet, except for
one which connects to pin 10 on the IC. This is the full scale output and will
be connected to the rotary switch in the position of FULL RICH, whichever
you prefer, fully clockwise or anti-clockwise position. You are going to test
you device first on the bench, then decide which outputs you will use for the
other switch positions.

Don't install the delay capacitor C3 yet. Don't install the IC yet.
Now install all the other components and double check every single solder
connection. Check the quality of the joints and check that the circuit
complies with the circuit diagram. Before installing the IC you can apply
power to the circuit to check for any overheating components. The circuit
has been designed such that none of the components will get even slightly
warm in operation. If any parts do get excessively hot then there is a

With the IC not installed the output transistor should be off, and the output
LED off. The darlington transistor should be off because the capacitor is not


Disconnect the power before installing the IC.
You can now install the IC, the correct way round or it will be destroyed
Apply 12 V power to the device.

Set up the test voltage source to 0.5 volts and apply to the input.
Set the switch to the FULL RICH position.

Now adjust the sensitivity control trimpot VR1 so that the output LED is just
lit. Leave the trimpot alone and now adjust the test voltage lower then
higher to test the adjustment. The LED should come on at 0.5 volts, and go
off just below 0.5 volts.
You can measure the voltage on the other output legs and see when each
goes on and off. They will be zero volts when on and some very vague
voltage when off. The outputs will even sometimes go negative when they
are off. We suspect it is something to do with the high impedance outputs
rectifying the ripple on the DC supply.

All the outputs should be about 50mV apart in their threshold points.

With the output high, (LED lit) adjust now the output voltage to the computer
by adjusting the trimpot VR2. You want to set the output to 1.0 volts.

Adjust the test voltage to below the threshold to turn off the LED. The
output voltage should be zero volts.

If all the above happens as it should then your circuit is working correctly.
Next install the delay capacitor C3. Set the test voltage above 0.5 volts and
turn the power on. It should take about 30 - 120 seconds before the LED
comes on. You can adjust the delay by changing the value of the 3.9M
timing resistor and/or 2.2uF capacitor. If you find the oxygen sensor heats
up quickly then set the timer to a lesser value. Having too long a delay is
bad, since the computer could be adding extra fuel to try and make the
mixture rich.

The next task is to select which other outputs you want to use, and connect
these to the front panel rotary switch. We recommend you use 100mV or
150mV as your lowest output, depending on what other high mileage
devices you use.
If you want you can alter the sensitivity to say 400mV full scale to make
available settings like 80 or 120mV.

Thoroughly test the device on the bench to be certain it functions as it
When you first install the device in you vehicle, use a setting near to 500mV
to test the operation of the device. Your performance should be completely
normal. Drive like this for a while to prove the system is working reliably
before changing to lower settings.


You can now test the device in the car. Don't install it yet though. Lift the
hood and locate the oxygen sensor. Don't cut the sensor wire. Find a
convenient place along the wire where you can strip back some of the
insulation. You are going to cut it here later, but not yet. Connect this point
to the input of your mixture controller and attach the power leads to the
Start the car and allow the sensor to warm up. Remember there is a delay
built in so after a few minutes you should see the LED start to flash. Rev the
engine and the LED will stay on. When you release the throttle, the LED will
go out for a while. A flashing LED is what you want to see. The rate of
flashing will be somewhere between 1 and 10 times per second, most likely
around 2 per second.
Check that the LED goes out when you switch the front panel switch off.

Now comes the exciting bit, cutting the oxygen sensor wire and inserting
the controller. Cut the wire in a convenient place. You are going to use
crimp connectors to finish the installation. Use a matching set on the wire
you just cut, in case you need to reconnect it back together.
Don't drive the car yet, do this test in the driveway.
With the front panel switch off, start the car and check it runs normally.
Set the front panel rotary switch to the FULL RICH position.(the position
connected to the last LED output, 500mV) and switch the device on. The
car is now running with a modified oxygen sensor signal although the
mixture is still the same. Try the other positions in order and see how it


Fit the controller to the vehicle and finish hooking up the wiring. For the 12
volt supply find a connection which is switched with the vehicle
ignition. You don't want to have to turn it off every time you stop.
Return to the FULL RICH setting and road test the car. Drive a few miles at
each setting to see how it performs. If you have also installed the Dash
Mounted Mixture Display you can also see at which level your output LED
comes on. It is very reassuring to see the actual sensor output displayed in
real time, and to see the Electronic Mixture Controller actually make a
difference to the sensor output.


Only connect the display input to the raw sensor output, not the
controller output. The display is independant of the controller, and is
not switched off when the controller is switched off. We can at all
times see on the display what the sensor is putting out.

The controller doesn't directly change the sensor output, it fools the
computer into cutting back the fuel.

It is up to you to decide which setting you will use for normal driving. If you
have not installed any other high mileage device or water injection then you
should be conservative in your adjustment. We have installed water
injection only and are driving on a setting around 240mV. We believe it is
close to ideal at this setting.

Mileage Gain

Since installing this device and the steam injection our mileage has
improved approximately 18%. This is in a vehicle that has always been
serviced regularly and has driven over 150000 miles.(250000 kilometers)

Good luck with your project and safe motoring.

         Electronic Water Injection Controller Manual
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The water (or steam) is cut off at idle for a number of reasons.

      To save water and permit fewer refills
      To enable a higher flow rate in a simple vacuum operated system
      To prevent excess water and rough idle
      To delay the water at startup till the exhaust manifold is hot enough.

We utilise the existing idle switch which is mounted usually on the throttle
body. If you can't find on you will have to devise one yourself. The computer
                      uses this switch as yet another of it's inputs to control
                      engine operation.

                     The electronics are very simple. None of the
                     components are of critical tolerance and all should be
                     available over the counter. The whole circuit, except for
the solenoid can fit inside a 35mm film cannister as shown. The valve that
we use to control the water flow is an electric solenoid such as an idle up
solenoid. These are found in most vehicles on the fire wall and are normally
used to switch vacuum. Get this component from your local wrecking yard.
They are sometimes referred to as vacuum solenoids. They are usually
made of plastic, which is good for water, but you do have to be careful not
                      to break off the connections. It is very important to
                      connect to the water hoses correctly.The common
                      connector attaches to your water reservoir, the normally
                      closed connector goes to the engine, or boiler, and the
                      normally open connector goes no where. Block it off
                      with a cap. This configuration makes it less likely the
                      system will suck air. Mount it high so the water won't
siphon out if the cap leaks.


Transistor TIP32 pnp high power output
Transistor BC337 npn general purpose
Darlington Transistor MPSA14 high gain darlington
Diodes 4 x 1N4007 or equivalent
Capacitors Electrolytic 220uF, 2.2uF
Resistors carbon film 1/4 watt
 2 x 10M
 1 x 10K
 1 x 2K
 1 x 1K
Printed circuit board small experimenters board 1 x 1.5 inches
Vacuum solenoid

                                          The construction is straight forward
                                          and like the Mixture Controller, you
                                          should fully test the device on the
                                          bench before installing. Being so
                                          much simpler this is a good project to
                                          complete first. The printed circuid
                                          board is a small rectangular piece of
                                          general purpose board, about 1 x 1.5
                                          inches. Make it bigger if you plan on
                                          using a larger container. The output
transister TIP32 is larger than necessary so that it will operate reliably
without the need for a heat sink.The circuit includes a similar 2 minute delay
circuit as in the Mixture controller. In operation the idle switch, when closed,
turns off the BC337 transistor which in turn, turns off the TIP32 transistor,
thus stopping the water. The 220uF capacitor forms a 2 second delay with
the 10K resistor. The water will stop quickly, but will take 2 seconds to start
again. This prevents the system from surging when cruising at a throttle
setting which is right on the verge of opening the idle switch. All the
capacitors are electrolytic type of 16 volt rating. All resistors are 1/4 watt.

The water flow rate you choose will vary according to the size of your
engine and what sort of other high mileage devices you have installed.
However as an example and as a ball park figure, we have installed a
steam system as described on the main web site, and our flow rate is about
1 litre for every 75 klm. This is fairly consistant whether we do city or
highway driving. The car never pings now, but it did quite a lot before
adding water. Pinging may not stop immediately, as it may take a few
hundred miles before all the deposits are cleaned from the cylinders. Ours
took several weeks. Anywhere from 5% to 25% may be correct for your
situation. There is a limit to how much water can be boiled in a given size
boiler, so if you go too high you may have cold water entering the engine in
large drops. Start at 10% and gradually increase till you find a setting that
feels right, with no idle problems and good driveability. There are too many
variables to give an exact amount that will be correct for every situation.

         Electronic Vapor System Controller Manual
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security reasons.

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Before you install the fuel components do the following to minimise the dangers.

 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.


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.

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
DISPLAY 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.

 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

Back to

To the Mixture    Controller.
To the Water    Controller.
This material is for your personal information only and is not to be
reproduced or sold.
No liability will be accepted for the use or misuse of this information.
The purchaser accepts all risk regarding the use of this information and is
responsible for determining the legality of using this product in your
particular area, and of any possible vehicle warranty or insurance

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