Filtering Oil

Written by TsTDI

Filtering is very important when dealing with waste vegetable oil (WVO). They call it waste oil for a reason. Waste vegetable oil is laden with free fatty acids, bacteria, dirt, debris you name it, its probably there. To get this fuel to acceptable means of burning it without damage to your injection pump, it must be filtered thoroughly. The other aspect that is important is that the WVO can not have water in it. In my experience, we have not had the need to dewater our oil because we know where the oil comes from and our suppliers are good about keeping the lid tight on the barrel that covers the WVO. To ensure that we have filtered our oil well enough, we do a number of things.

Method 1: Gravity Filtration

Gravity filtration is the cheapest and most effective method available. I mentioned above that we have the capability of stockpiling 700 gallons of WVO at a time. The WVO sits in a shed, protected from sunlight and sits in sealed containers. At any time, the WVO can sit from 1 month to an entire year. We draw the oil from the top 2/3 and let the bottom 1/3 stand indefinitely. The reason for this is the bottom third would be the dirtiest oil of the entire barrel. Allowing the oil to stand in the barrels for a long time results in great filtration of the WVO.

Method 2: Centrifugal Filtering

After our oil has had plenty of time to settle out any of the larger debris in the oil, we use our centrifuge to filter the finer dirt particles out of the oil. We bought our centrifuge from diesel craft and it works quite well in filtering the oil. The basic idea is you heat the oil up to roughly 150-160 deg and pressurize it to 80 PSI into the centrifuge where the pressure of the oil going in spins the centrifuge and the forces of gravity do the work. The centrifuge is supposed to filter down to less than a half micron. Our output (filtered oil) is piped to a funnel where it is final filtered in a 5-1 micron filter bag and then collected into a 5 gallon cubie. The bypass of the oil is sent to a 5 micron bag and will later be centrifuged with time.

This is a painless way of filtering our oil. Including the time it takes to wait for the oil to heat up, 5 gallons of oil can be filtered relatively quickly to a tune of 20 minutes. We bulk filter roughly 50 gallons of oil at a time so it takes roughly an hour and a half to 2 hours total time. Keep in mind, the only time we are present during this operation is to switch cubbies out that have already been filled up and to fill the barrel to be heated. The filtering setup itself does all the work that we don’t have to do.

The finer you filter the oil, the better for your car. 5 micron is not enough filtration in my opinion. You should at the minimum filter to 1 micron. Filter bags are made to 1 micron; however, once they plug with debris you either have to wash the dirt out or replace them with new ones. Chances are you will have to replace the bag itself which can be quite costly. This is the benefit to using a centrifuge. The rotor itself that collects the debris from the oil is simply wiped clean and ready for use again.

The above is a great video explaining the entire process. This is exactly what we do with ours.

Performance Modifications and WVO

This is an interesting topic and to be quite frank, I don’t recommend in doing so.

This is contrary to what I have done to my car because I have a lot of performance modifications on my car. The list includes a 17/22 turbo, pp520 injectors, a chip tune, Eurojet SMIC, 2.5 inch turbo back exhaust and upgraded intercooler piping.

I don’t recommend doing so because so far, I have yet to meet ANYONE with enough self-control to not use the power while on WVO. In all my driving on WVO, I have gone past half throttle maybe once in the car’s life with that kind of power on tap. You must understand that to make that much more power over stock, it required more fuel. If you have learned anything from this guide thus far, you will realize that more fuel is a problem on WVO.

However, look at it from this approach. Driving normally on a mildly tuned diesel engine results in better fuel economy because timing parameters and fueling are adjusted to a fine degree. Many people do not report increases in economy because their right foot is too heavy and they enjoy the boost in performance more so. Put a diligent driver with self-control behind the wheel and you reap the benefits of better fuel economy which means increases in combustion efficiency. This is my reasoning behind it being ok, but only if you can respect that the extra power.

From the start of my conversion, I have ran the PP520 nozzle (bigger nozzle orifices which in turn means more available power). Although these nozzles are capable of more fuel you do not have to use it. Also, bigger nozzle orifices result in less stress on the injection pump as opposed to smaller nozzle orifices. Since we are running a thicker fuel, this is an added benefit.

With all this said, I would recommend against it. This is treading down dangerous waters and most people are barely able to convert their stock cars with success on WVO.