Until some enterprising engineer develops a way for the settings to be automatically calibrated, it is up to the individual user to set the EFIE voltage.
Some EFIE developers have put in dual settings - One for city driving, and when you are on the highway you switch to Highway mode.
What this does is varies the voltage that was originally produced by your Oxygen sensor and fed into your vehicle fuel computer.
As a general rule of thumb, most people set their EFIE voltage somewhere around .4v (point four of one volt) and use it for both city and highway driving. If you spend most of your time in either Highway or City driving I suggest initially setting it at .45v and monitor the economy increasing it up or down in .05v increments until you find the best voltage for your car.
In a posting on O2 sensors I have a report on voltages for the EFIE at
http://reduceyourfuelbill.com.au/forum/index.php?topic=22.0The below excerpt from this posting more than nicely explains the need for different voltages that normally are controled by the O2 sensor. Remember that when using HHO as a fuel catalyst you will be seriously increasing the Oxygen levels in your exhaust.
When the air/fuel mixture is rich and there is little O2 in the exhaust, the difference in oxygen levels across the sensing element generates a voltage through the sensor's platinum electrodes: typically 0.8 to 0.9 volts. When the air/fuel mixture is lean and there is more oxygen in the exhaust, the sensor's voltage drops to 0.1 to 0.3 volts. When the air/fuel mixture is perfectly balanced and combustion is cleanest, the sensor's output voltage is around 0.45 volts.Bit of clarification - excess Oxygen in the exhaust tells the computer to rich up the fuel supply. Obviously you don't want this to happen as you end up using more fuel and get no savings.
