Basic operation of an Oxygen (O2) Sensor: The O2 Sensor is basically a device that measures the oxygen content in the combustion results (exhaust gases) of an engine. The more oxygen in the exhaust gases, the leaner the mixture and the less oxygen, the richer the mixture. The working voltage is from 0v (0mv) to 1v (1000mv); the leaner the exhaust gases (more oxygen) the lower the voltage and the richer the exhaust gases (less oxygen) the higher the voltage leaving 500mv as the perfect mixture. If a volt meter is connected at the signal wire, the changing in voltage can be seen. The Electronic Control Module (ECM) tries to keep the voltage around 400mv to 600mv (lean to rich, rich to lean) and this is going on all the time while the engine is running. If the voltage signal from the O2 sensor is below 500mv (lean, too much oxygen), the ECM compensates by sending more fuel (gasoline) to the mixture and if is above 500mv (rich, not enough oxygen), it compensates by sending less fuel to the mixture.

Now here is why we need to use an Electronic Fuel Injection Enhancer (EFIE): When we’re using an HHO generator, we’re not only adding hydrogen to the fuel mixture but also adding oxygen and by doing this the voltage on the O2 sensor signal is going to be low (lean, too much oxygen) that’s when an EFIE comes in. With a GOOD EFIE, we will add very low voltage to that signal without interfering with the voltage variation of the sensor (lean to rich, rich to lean).

How much voltage can we add? This all depends on how much HHO gas your generator produces. All we’re trying to do is keep the voltage of the O2 sensor on the rich side (above 600mv) so that the ECM does not add more fuel so normally the voltage to add will be between 200mv and 400mv. Always try to keep the total voltage below 1000mv (1v).

Why does the Check Engine Light (CEL) come on? If the voltage signal stays the same for a long time and does not change (lean to rich, rich to lean) or the voltage goes beyond 1v (1000mv).

If anyone needs more info or if I forgot something important, let me know and I’ll add the info here.