Materials

• Most HHO generators built for diesel engines are housed in quart-sized containers so that they can be easily installed under the hood. To house the generator you will need a heat-resistant quart-sized container. This can be as simple as a piece of PVC pipe capped on both ends. To construct the electrodes you will need about four thin pieces of stainless steel cut to fit inside the container and some bolts and washers to assemble the plates together in tandem. The container will need to be wired to the ignition switch of the vehicle with some shielded copper wire, and you will also need plastic tubing connected to the container for the hydrogen to flow out of the canister and into the engine's intake. You should also have silicone caulk and rubber O-rings handy to seal any holes made in the canister.
  
  

Construction

• First build the electrodes. Take four or more pieces of stainless steel plates and drill 1/4-inch holes through all four corners of them. Thread a bolt through each hole of each plate, separating the plates with several washers. You will need about an 1/8 inch of space between each plate. Place a washer and a nut at the end of each bolt. Once you have the plate array assembled, figure out a way to secure the plates in place at the top of the container. How you do this will vary depending on your container, but keep in mind you want ensure that any holes you make in the container are sealed air tight afterward.
  
  Constructing the cap to the container requires two things: an output for the HHO and a way to pass electricity to the plates. The best way to design the electrical input is to have wires running from the plates to two metal terminals mounted on top of the cap. You can then connect wires from your power source to the terminals. Leave enough slack on the inside wires so that you can easily remove the cap. You will also need to cut a hole in the top of the cap for the hydrogen out-take. This hole needs to be big enough for whatever type of plastic tubing you are using to run the hydrogen to the intake. Seal all of the holes with silicone caulk around the edges to ensure they are air tight. At this point the generator is ready to be installed in the vehicle. Simply secure the canister somewhere under the hood, connect the terminals to the ignition and plug the hydrogen out-take into the ignition.