good idea - why didnt i think of that......
here you go....
IM doing this conversion on my Merc Vito traveliner so I can drive round for free....not strictly on a VW but this is transfereable to ANY diesel vehicle....and since some of us on here run on diesel....I thought a how to might be useful to dispel some myths and summarise all my research over the last months.
Background.....
Tax - it is now legal to use veg oil as a fuel - you used to have to register as a fuel producer and pay tax according to your declared litreage....however this has now changed and you only have to do this if you use more than 2500 litres per year....and whose counting....
There a a number of veg oil related options available to you related to veg oil....these are as follows:
Biodiesel - this is diesel refined from Vegetable oil rather than mineral oil - no conversion is necessary for this just pump it in and away you go. Its time consuming to make and only about 10p per liter cheaper to buy...one for the environmentalists really.
Blend - depending on your diesel pump (eg Bosch/ Lucas/ Cav - some dont like it) you can run a blend - this involves tipping veg oil into your tank, chucking in a bit of additive and mixing with diesel - you vary the amounts through the year as it can impair yourstarting ability - no conversion is neccesary but you still end up spending about 70p per litre on fuel.
100% veg oil - this is the option I have chosen and can use either new clean veg oil or waste veg oil (chip fat) also known as WVO. Depending on the vehicle and its pump you will find that most diesel pumps wil last a short while on 100% veg oil. HOwever two problems occur: Starting in cold weather is near impossible due to viscosity of the oil so youll need a blend, and for the same reason your diesel pump (especially if a lucas) will not like it...consequently your engine will not run. There is always someone in the pub who will tell you how they just pour it in off the shelf....but if you want reliability and longevity this is not the way. The answer is to run a 'two tank system'. The disadvantage of this apporach is you have to spend time and money converting your vehicle - but then you can run on 100% veg oil - which if you get it free (WVO) soon pays for itself.
What is a two tank system?: essentially you use your existing tank for veg oil, and add another small tank for diesel for starting. To overcome the cold starting and viscosity problems the kit does two things: 1) you start on diesel and switch over to veg 2) you preheat the oil to make it less viscous.
which kit should I use?
There are a lot of kits out there - SmartVeg, Dieselveg, etc etc and all are a variation on a theme. Obviously its up to you to offset which each kit offers you - but for me it was quality parts, good reviews, good tech help and having an auto switch over that sold me on the DieselVeg ATG kit.
The kit is as below:
the main components = switchover valves, tanks, pipes and clips, wiring loom, dash mounted switching unit, tank, and heat exchanger (not pictured), instructions.
This kit cost me £475 - if you want to save a bit on this you can for example provide your own tank etc. As I say there a a lot of much cheaper kits on the market so do your research - smartveg and dieselveg ATG are generally considered to be the top end. If you have more time then you can put together your own kit - its fairly simple and will prob cost you £150-200 - but for me the priority was to get on the road for free ASAP and with minimal teething problems.
WVO - waste veg oil
I will be using waste veg oil - sourced from take aways etc for free. There is a lot of info on the net and if filtering/ settleing isnt for you then you can buy this prefiltered at approx 45p a litre. INitially I have bought 20L of clean oil for £13 to get the system running. ONce fully functioning ill be on WVO.
It seems there are lots of options for filtering kits but I sourced mine from
Oilybits for £145 - it includes a pump, inline filters, pertol station type nozle, pipes etc (again cheaper options available if you have time to figure something out)- i will be filtering to 1 micron via a 10 micron filter and after the oil has settled for a minimum of 2 weeks. Cold Filtering to this level will allow me to remove a lot of the fats and salts from the cooking process - there is a lot of advice suggesting you filter to less - some people just use legs of jeams (sewn up) as these filter to about 10 micron....but its up to you. As im going for reliability im filtering as much as possible.
The most common question I get asked is what happens when you run out of veg oil in eg france. Well there are a few options 1) if you have space like me i will try to carry most of my fuel with me - plan ahead and stockpile filtered oil. 2) Go to any supermarket and pour in veg oil - still cheaper than diesel 3) last resort - override the system and run on diesel.
This is the fat from the chippy - its good stuff - after two weeks it has not seperated out or gone creamy suggesting low animal fat content. I reckon of the 80L of my first batch - 60L is usable. The other parts are the inline filters, nozzle and pump.
Fitting
This is the first instalment of a few - the diesel veg kit is 'suitable for a competant home mechanic and can be fitted in two days'. i started last night.....
First I read the instructions and checked kit contents...good job as one of the relays was 24v....also helped me get my head around the system and put off going out in the cold a bit longer.
First job was to identify diesel pump feed and return. I then identified the heater matrix feed and return by running the engine (heater on) and seeing which pipe got hot first. ITs important that the heat exchanger fuel and water flow in oppositie directions. I then mounted the heat exchanger in a convenient place where it could easily recieve all pipes.
I cut the fuel supply line from the original tank, put the inline filter in and connected to the H-exchanger.
Then i cut into the van heater pipes and inserted the t-pieces. ITs important that the Heat exchanger is fitted across the circuit (ie you cut into both pipes) you can just make out the blue t-pieces on the bulkehead. The gold thing is the inline temp sender which actuates the switchover relay once 60 degrees is reached - this is fitted in the return line.
next you need to find a suitable location for the supply valve...this switches between Veg oil and diesel. Then connect the fuel outlet on the heat exhcanger to port R. ITs a heavy thing so a good vibration free mounting is required.
so thats the heat exchanger in, supplied with hot water and veg oil. Now to the diesel.
The auxiliary diesel tank can be mounted anywhere and can be any size - too small and youll be filling up forever - too big - you loose space - Mine 22L - as i have a van i have fitted mine behind the front seat so it can be easily filled through the sliding door. IT should be properly secured - the ratchet strap came with my kit on 'special offer'.
as its inside (we sleep in this van) I need the tank to breath outside....so i fitted this small pipe - again this came with the kit.
Then fitted the tank in place and marked holes in the floor for the breather and fuel supply.
and thats as far as i got last night.....time so far....4 hours. More to come.
Thanks 
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