Waste veggie oil (WVO) for fuel and how it all works.
In this long overdue write up, I’ll briefly summarise how we have managed to clock up approximately 50,000ks of driving while using under 500ltrs of diesel.
To run a vehicle (or engine) successfully on STRAIGHT WASTE VEGGIE OIL, there are really only 3 important things to address.
Firstly you must start with an older style diesel engine. Modern diesels with high pressure common rail injection systems, or complex computers involved in their operation, don’t seem to like the veggie oil. A few other factors come into play when selecting the right engine for conversion, such as direct or indirect injection (indirect is more tolerant of cold oil, such as the 2h engine soon to be fitted to Troopy, however direct injection engines make much more power, like the 12ht in Bluey) The style of injector fuel pump must also be considered, inline is the way to go as rotary pumps don’t handle very well the increased viscosity of the oil. There is a great page on an Aussie forum I’ve gleaned most of my information from, that lists all the different vehicles (and more importantly their engines) that members have successfully converted to run WVO.
Secondly, you must get the oil clean. There are a few ways this can be done, time and gravity being the easiest, and therefore the most common technique. It then must be passed through some sort of filter to get it down to fuel quality oil. This can be done either hot, melting the fats and passing them through the filter, or cold, removing the fats from finished product. We needed to build a setup that could handle any grade of dirty oil, and clean it on the fly, so we installed into Bluey a specifically designed centrifuge from a US company, WVO Designs (they are great to deal with by the way, thanks again Leon and team). This spins the oil to 6000 rpm, seperating the heavier particles out, and collects off the lovely clean oil.
Thirdly, you must overcome the viscosity. At room temperature veggie oil is just too thick. It dribbles out of the injectors rather than being sprayed, gets picked up by your piston rings, and ends up glueing them in their ring groves, ruining your engine pretty danm fast. To overcome this, you could chemically convert your oil to be runny at room temp (this is actually making biodiesel, a common misconception of what we do) blend with up to 15% petrol (illegal in Australia due to tax, and has dubious effects on engine longevity) or simply heat the oil to around 80°c, where the viscosity drops to that of diesel.
When designing and building Bluey, we had the luxury of doing a scratch build, so I was able to take the best elements of other systems and incorporate them into our dream truck, that collects, cleans and heats the oil all on board. We have built a 3 tank system, dirty, clean, and diesel, which is used for engine start up and shut down (remember, cold oil doesn’t burn well) First up in the system we have a 120 ltr holding tank for dirty oil. This sits in the central part of the ute tray, in what is otherwise hard to use storage space. We fill this tank via an integrated gear pump and hose that moves the oil at about 14ltrs per minute. This same pump is then used via a motor speed controller, in reverse, to supply the centrifuge. Bluey also has a heat exchanger between the pump and centrifuge, passing hot engine coolant through one circuit, and oil through another, swapping heat, but not allowing them to mix. This reduces the viscosityof the oil, making it more efficient to seperate the muck and also melts the solid fat content, so they too can be used for fuel, a good thing, as fats actually burn with approx 15% more power than veggi oil. From here the clean oil runs out of the centrifuge and down into our 120ltr driving tank. The centrifuge runs on 240v, 3 phase power, so we use our 1000w inverter to transform Bluey’s 12v to 240v, then step it up to 3 phase with another special unit. As this is quite a thirsty process, we make sure the truck is running and the alternator is spinning when the centrifuge is in use.
The driving tank is fitted with an internal heater, a 2m coil of pipe also running hot engine coolant. The idea here is to heat the oil while in the tank so it moves more easily up the fuel lines. However, this is currently disconnected, as we have found the addition of larger fuel lines (12mm) is sufficient to provide the engine with plenty of fuel. If using standard fuel lines (8mm) or in a cooler climate, this tank heater or an additional fuel pump to push the thick fuel up the lines will probably be needed.
From the driving tank, the clean oil makes its way up to the engine bay. Here it passes through a 30 plate, flat plate heat exchanger, then a fuel filter with a 10 micron filter element. This filter has a water separator incorporated, an essential device for diesel engines. It’s important to filter the oil hot, as it passes through the element more easily, and also as we are centrifuging hot oil, the fat particles that are often in our collected, cleaned fuel need to be liquified before filtering, as if left solid they will quickly clog the filter. After the filter, I run my oil through a second, smaller (10 plate) heat exchanger. This tops up the heat, and also heats the cold oil contained within the filter housing straight after diesel to veggie oil switch over. From here the oil passes immediately through a 3 way motorised ball valve, a small inline filter with glass housing for monitoring, through the stock lift pump, and onto the injector pump and injectors. As the oil is now nice and hot, it sprays nicely, atomises completely, mixes thoroughly with oxygen, and ignites with comparable power to regular diesel.
Just before the dirty oil gets to the centrifuge it passes through a small inline flow meter, with the display mounted in the cab. As we clean the oil while driving, I like to keep my eye on how much oil is going through the centrifuge, too fast and its not getting clean enough, too slow and and we are potentially using more oil than we are cleaning. We are aiming for approx 700ml per minute, and can adjust from the cab accordingly.
Initially we ran the truck on diesel for the first 15 minutes of each day’s driving, enough time to allow the coolant to rise to a temperature where it will effectively heat the oil. This was an agonising process, as burning diesel at a dollar forty a liter while having two tanks of free fuel on board just didn’t make sense, and it bothered me enough to do something about it. The solution to significantly reducing the diesel used on start up was to insert 3 glow plugs into the veggie oil system, one in the filter housing, and two in the second heat exchanger. We now start on diesel, turn on the glow plugs, and can swap to veg after about 3-4 minutes, turning off once full operating temp is achieved. I think the last time we filled the diesel tank was about 2 months ago, and it’s only just gone below half way.
There are also 3 thermostat temperature sensors plumbed in. One to monitor the filter temp and switch off the filter glow plug at 65°c, one just after the 2nd heat exchanger, giving output oil temp and switching the other two glow plugs off at 84°c, and one bound to my injector lines, giving oil temp at the injectors.
No matter how clean we try to get the oil, over time (currently about 4000k’s) the filter will become blocked, restricting and eventually stopping the fuel supply. As a diagnostic tool, and a pre warning for this I have a small pipe running to the dash, where it’s joined to a vacuum gauge. This pipe is plumbed in between filter and the lift pump, that sucks fuel through the system. As the filter gets more restricted, the gauge needle climbs, and I know I’m soon going to be doing a filter change, ideally at plus 5000k intervals, depending on oil cleanliness.
Another important thing to rember is to shut down the engine with fresh diesel in the injector pump and injectors. A common problem I came across when researching veggie oil conversions was forgetting to purge the oil from the system, having it cool down, and then not being able to restart the engine and risking damage. As a precaution to this, Bluey has a buzzer installed that sounds if the ingition is turned off while in veggie mode. This reminds us to flick back to diesel, and the turbo timer allows the engine to continue to run for long enough to purge the oil, automatically shutting down once completed.
Reading back over this write up, it all sounds pretty complex, but in truth it’s a very user friendly system, and works like such.
* Start the truck
* Turn on glow plug heaters
* Drive for approx 3 – 4 minutes, depending on ambient temp and prior use
* Keep eye on engine temp, once over 40°c, and coolant temp needle has just started to move, flick switch to veggie oil mode
* Flick eyes to oil output temp, it should climb quickly to 60°c and creep up from there, don’t be too heavy on the throttle untill 75°c
* Turn off glow plug heaters once engine at full temp (block at 74°c)
* Continue to periodically monitor temps and vacumme, they don’t change much, but I like to know it’s all sweet
* If the driving tank needs to be topped up with clean oil, turn on inverter, centrifuge and feed pump
* Check flow rate and if required, adjust to 6-700 ml/min
* Continue to drive to your destination for free, keeping an eye out for purveyors of fried food for potential fuel pickups
* Turn off ingition once arrived, get reminded by buzzer to change back to diesel, lock up and walk away while Bluey runs on for a few minutes, purging oil and filling with diesel for next startup.
And there you have it, Blueprints guide to free travel. If you’re interested in running waste veggie oil as fuel, keep reading and researching. Bare in mind I’m a qualified motorbike mechanic and a natural tinkerer, so our system has evolved to include many things not actually essential to a bare bones install. Just remember, older diesel engine, clean oil, hot oil, and diesel for warm up and shut down. It can be done alot simpler, and shouldn’t be out of the abilities of anyone prepared to do the research and is handy with a spanner.
Cheers heaps, thanks for reading.
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