Bill. Volo modules do indeed work. Not everyone understands how though. I'll share what I have learned.
The O2 sensors drop voltage to the ECU when they sense a lean mixture of exhaust gasses passing over them. This voltage drop could be .1 to .3 volts depending on the leaness of the mixture.
The Volo module is programmed with the same program as the ECU. It knows what voltage to expect from the O2 sensors at any given rpm and engine temp.
The Volo is attached to 4 wires coming from the OBD port. It has a sampling rate of 20,0000/sec. When it reads a drop in voltage from the O2 sensors, it compares that to the default settings of the ECU and adds enough voltage to the signal to match what the ECU is expecting. Otherwise the ECU will sense a lean configuration and richen the mixture thus negating any fuel savings from the hho.
The Volo has limits on how much voltage it can add to the signal going to the ECU. These limits are set by the manufacturer to comply with ECU programming parameters.
Once the Volo has reached it's limit on how much voltage it can add to keep the ECU from richening the mixture, any further voltage drop from the sensors will cause the ECU to richen the mixture despite the Volo module. This is because the further drop in voltage is now lower that what the Volo can compensate for and is passed directly to the ECU which richens the mixture and negates any mileage improvement. If more hho is added to the engine at this point mileage will continue to drop.
The trick is to add just enough hho to improve mileage but not exceed the limits of the Volo.
I have installed over 40 Volo modules in customers' cars over the past year. Our Distributors and installers have installed another 40 and all work well. We have determined how much hho with our system to add for optimal mileage improvement.
We now guarantee a minimum of 20% increase in mpg on the highway or we refund the system cost minus 15%. To date we have had no one asking for a refund.
So my experience with Volo modules is positive. You just have to keep the amount of hho in the engine to a level that doesn't exceed the limitations of the Volo module.
You can also try adding an extender to the O2 sensors to take them out of the exhaust stream but still allows them to function and send data to the ECU.
I hope this helps.
The Volo modules have limitations on how much they can attenuate the voltage to the ECU
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