Before I start, I'd just like to quickly summarise my views on biofuels. I don't believe we can all continue to travel the way we do on biofuels instead of oil, as the land area required to provide the fuel would simply be too great, aside from issues of fossil fuel inputs to the farming process. However, biofuels could allow essential transport systems (emergency services, public transport, tractors, etc.) to continue to operate when oil is in short supply. I hope that by people like me converting vehicles to run on biofuels now, before it is essential, it will be possible to develop the technology and infrastructure that we will need when there is less oil available.
In the long run, I intend that my wife and I will go down from two cars to one, and then to zero, but this will take time as we will need to change jobs and maybe relocate. Until this happens, I'm hoping that by running my car on a biofuel I can reduce my impact on fossil fuel use and CO2 emissions, especially as I'm burning used veg oil which would otherwise be going to landfill or incineration. (Some used oil does find it's way into biodiesel production, but with the current tax levels on biofuels, this isn't really commercially viable). I'm also finding that it makes people sit up and think - they can see I'm serious about Peak Oil and that I'm spending my own hard-earned cash in preparing for it. There's also the added advantage that as long as we're living in a situation where it's difficult to manage without a car I'll have a more secure fuel supply, as I can safely store vegetable oil at home. Hopefully this will enable me to make any essential journeys in a time of shortage, and also help out friends and family.
OK, that's the intro over, here's the technical details:
My car
VW Polo 1.4 TDi, 2001 Y-reg
Usual fuel consumption on a variety of roads: 65mpg if I drive gently, 55mpg if I drive fast
The Conversion System fitted
Smartveg, an 'intelligent' semi-automatic system produced by Regenatec. http://www.smartveg.com/
What's been added for the conversion to veg oil
- Extra fuel tank (33l) - this is in the boot, and is full of veg oil, the main tank still holding diesel.
Heat Exchanger - this uses the engine coolant to heat the incoming fuel.
Filter heater - this uses the engine coolant to heat the fuel filter, essential if you want to burn used veg oil, which contains heavier oils.
Fuel valves & temperature sensor - these monitor the fuel temperature and switch fuel supplies.
Control module - electronics to monitor temperature and switch state, control the valves and display.
In-car switch & display - switch to select fuel supply and display to show system status.
Initially the engine is cold, and the fuel system is filled with diesel. After the engine is started, and it warms the control module senses the fuel temperature and begins to mix a progressively larger proportion of veg oil into the diesel supply, until after a few minutes there is no diesel being used at all. The exact length of time to warm up depends on the ambient temperature and the design of the engine. When you are almost at the end of your journey, you instruct the system to "flush", which takes about a minute. This flushes out the veg oil from the engine's fuel system using diesel, so that when you restart the next day with a cold engine, there is no veg oil present. Of course, if you know you will only be stopping the engine for a short period, you can leave it on veg oil, as it will still be warm when you restart.
Detail on fuel and temperatures
Veg oil is thicker than diesel, and as the engine was designed to run on diesel, the veg oil needs to be heated in order to have roughly the same visocosity of diesel. Putting cold veg oil into the engine could result in poor operation and even internal damage, as oil droplets may land on the metal surfaces inside the engine and turn into a kind of "lacquer" which will wear the piston rings. This is the clever bit of the Smartveg system - it monitors the temperature of the fuel, and as it warms up it starts to mix in veg oil with the diesel in increasing proportions until the engine is fully running on veg oil. In this way, the possibility of damaging the engine in massively reduced. The Smartveg system heats the fuel by passing it through a heat exchanger, which has engine coolant flowing through it.
Why the heated fuel filter?
If you want to run on fresh veg oil, a normal fuel filter is fine. However, if you want to run on used veg oil, you need to heat the fuel filter, especially in winter. This is because the oil has been used in cooking, and although it has been filtered there are still traces of heavier animal fats dissolved in the oil. When the oil is cold, these can come out of solution, and clog up the filter. By heating the filter, it ensures that the used oil will pass through it without problems.
What the in-car display and controls do
The only control in the car is a simple switch - up for diesel and down for veg oil. You can put the switch down when you start the engine, and the system will then automatically switch to run on veg oil as soon as the fuel has warmed up sufficiently. At the end of the journey, flicking the switch up again will start the "flush" procedure. The switch has a status LED, which is off for diesel, on for veg, and flashing during flush. There is also a buzzer to tell you when the system is changing from diesel to veg, when it has completed the flush, and to warn you if you turn off the ignition without flushing (this warning can be ignored if you know you are only stopping for a short period).
In addition to the switch, I've also gone for the optional display unit. This performs several functions:
- - When the engine is cold, it shows a warm-up progress bar, at the end of which the switch to veg oil can start.
- When the engine is warmed up, it shows the fuel level in the veg oil tank (the fuel level sensor and suitable tank are also optional upgrades)
- During a flush, it shows a progress bar, at the end of which you can stop the engine
Well, it works, what more is there to say?! I've had it in there for a week now, and have driven 200 miles or so. I'll update this thread with further information on fuel consumption, performance, and answers to any questions. Oh, and photos too when I get round to it.
or a big tank with in-built heater, plumbing and fill-up nozzle, what's the real story?
However, the place selling the fuel is installing a pump shortly. It is also possible to get a second filler cap cut into the vehicle, but that was more than I wanted to do for now - at the moment the car could be returned to normal and the kit put on another vehicle.
