This hydrolysis setup is different from other types that waste power when your vehicle needs to accelerate or stay at a speed while in gear. When you are using your brakes, you are compromising efficiency for safety. You will not have to compromise as much if you do what this instructable says. A hydrolysis will put a load on your vehicle when it does not have much of a load(you can see that with a $6 OBDII adapter). It will not be used most of the time but it will be good during traffic jams. This will not take any more gas than normal, because your rpm will not increase . I am not explaining how to make a HHO generator, because there is enough tutorials like that. Those tutorials do not usually tell you that it is a bad idea to stick your HHO generator in a hot place like the photo above shows you. more heat will produce more steam. This will add moisture to the air, and give you worse for gas milage.
What you will need
Step 1: Wiring it up
First, put the parking brake on, turn your key to accessory, then put your car in neutral. Find brake light switch. Then, connect your positive from your multimeter to the positive in a cigaret lighter. Press the brake, and find the wire that makes your voltmeter show at least 6 Volts. When you release on the brake pedal, the voltage should drop to 0 Volts. Now put tape around that wire. The last parts of this instructable are telling you how to follow the circuit schematic above. You will have to feed a wire long enough to reach into the fuse and relay box through your firewall. Solder that onto the wire you labeled earlier. Solder the other end of that wire to the coil of your relay. Solder a wire from the positive of your vehicle to the other side of the coil. Connect the positive of your vehicle to the switch part of the relay and connect the other side of the relay's switch to the hho generator. Connect the negative to the other terminal of the hho generator, and tape around the metal of the relay. Finally, put the relay in the fuse box.