Using HHO EFIE with Hydrogen Gas Saver

If you seriously thinking about MPG gain, a hydrogen on demand system alone just isn't enough. Hydrogen makes the combustion more stable and as a result less fuel per cycle is needed to operate.
in order to benefit from the HHO gas, a method to change the air / fuel ratio is needed.
The most accurate way to make this change when using a HHO device
is by connecting a device called EFIE between your oxygen sensor and the ECU (car's computer). The EFIE device changes the signal coming from the O2 sensor. As a result the ECU maintains a different, lower air/fuel ratio (instead the
original 14.7/1)
Do not try to use EFIE without Hydrogen gas saver.

ECU and the oxygen sensor: IC engines is designed to work in air/fuel ratio of 14.7/1. The oxygen sensor is used to read the oxygen value in the exhaust. Because engines work in cycles the oxygen reading is constantly changing between 0.1 to 1 Volt.
The ECU works to maintain a constant average of oxygen: if average value gets too low (too little oxygen), the ECU reduces fuel supply. If average value gets too high, the ECU orders more fuel to be injected.

The EFIE: If you add a hydrogen gas saver to your car, HHO gas is added to the combustion. As a result not all the oxygen takes place in the burning and more oxygen is emitted through the exhaust. The problem: the ECU "feels" more oxygen than usual and orders more fuel to be injected for compensation. This action ruins the gas economy gained thanks to hydrogen gas saver.
The solution: EFIE - an electronic circuit used to covert oxygen readings from the sensor to needed values and prevent unnecessary rich mixture injection.

If your car have two O2 sensors constructed on the exhaust pipe, between the engine and the catalytic converter, you need to connect both of them to an EFIE. This is a special case and special EFIE required called Double EFIE for the system to work properly. Alternatively, you can use two "regular" EFIEs, one per each sensor (this is not a straight forward option because each EFIE need to be adjusted separately).

The is an interesting alternative to EFIE device. It is possible to increase air / fuel ratio using this small metal part called "oxygen sensor spacer ".
A removal of the oxygen sensor from a direct contact with the exhaust gases to a farther place, where the oxygen reading will be reduced using the spacer.
Won't work for every car but due to very low price it's worth a try.
Read more about the "oxygen Spacer"

The spacer removes the oxygen sensor from direct contact with exhaust gases to change the reading, the ECU is affected and less fuel is injected as a result:
Read about the "oxygen Spacer" here