freeagent Posted January 11, 2008 Share Posted January 11, 2008 I'm planning a SVO (Veg Oil) conversion on my 300Tdi Disco, I want to keep it as simple as possible, with a second tank in the boot (for Veg oil) manual changeover switch, and a simple 3-way valve. What i have in mind is just like any other twin-fuel tank vehicle, but with a plate heat-exchanger in the supply line from the second tank, I then manually switch over when the engine is warm, then switch back just before the end of my journey to purge the injector pump with regular diesel. To keep thinks simple i thought I'd leave the returned fuel line going to the original vehicle tank (which contains the diesel) regardless of which of the two tanks the lift pump is drawing fuel from. My only concern is the amount of fuel returned to the tank.. is it just a dribble, say 5-10%? or are we looking at larger amounts (maybe upto 30%) if there is a large percentage of fuel returned i may have to look at dumping the fuel back into the Veg tank, or having a second return line. what I want to avoid is my primary Diesel tank becoming full of SVO, as this will not help with starting... I'm trying to keep this as simple as poss so it can be easily removed if I sell the disco, and doesn't require me to hack too much of the original system about, what I have in mind only cuts into the original main supply line in order to fit the changeover valve... Quote Link to comment Share on other sites More sharing options...
Peter Posted January 11, 2008 Share Posted January 11, 2008 I'm planning a SVO (Veg Oil) conversion on my 300Tdi Disco, I want to keep it as simple as possible, with a second tank in the boot (for Veg oil) manual changeover switch, and a simple 3-way valve.What i have in mind is just like any other twin-fuel tank vehicle, but with a plate heat-exchanger in the supply line from the second tank, I then manually switch over when the engine is warm, then switch back just before the end of my journey to purge the injector pump with regular diesel. To keep thinks simple i thought I'd leave the returned fuel line going to the original vehicle tank (which contains the diesel) regardless of which of the two tanks the lift pump is drawing fuel from. My only concern is the amount of fuel returned to the tank.. is it just a dribble, say 5-10%? or are we looking at larger amounts (maybe upto 30%) if there is a large percentage of fuel returned i may have to look at dumping the fuel back into the Veg tank, or having a second return line. what I want to avoid is my primary Diesel tank becoming full of SVO, as this will not help with starting... I'm trying to keep this as simple as poss so it can be easily removed if I sell the disco, and doesn't require me to hack too much of the original system about, what I have in mind only cuts into the original main supply line in order to fit the changeover valve... Was out laning on Surrey downs the other weekend with Twinaxle club, and my friends Disco had a leak from the return pipe. To get some idea of how much is pumped back down it. It was enough to drip like a house tap needing a new washer. Why not just use 25% veg oil /75% diesel - just make sure clean filters every 1000 miles. Then come the summer go 50/50. I know people who do this and have a Macro card (Cheaper oil) Personally when I do mine, I'll buy the kit - is only about £450 and will pay for itself very quickly. (As in one of the LR rags this month) Think you'd sell your Disco much quicker with it fitted BTW. Reckon we are going to see lots more of these as Diesel goes up to £1.50 a litre over the next year !! BTW it leaves a trail of mobile chip van behind you. You'll get put at the back of a laning trip, as it truly honks. Quote Link to comment Share on other sites More sharing options...
RRX Posted January 12, 2008 Share Posted January 12, 2008 running 50/50 diesel/WVO on a normal tank with inline heater and no issues. Twin glow plug heater with water heat exchanger and temp switch to turn the plugs off when the engine is up to temp. Just carry a spare filter and make sure you replace the spill lines on the injectors otherwis they will start to leak as they don't like veg in standard form Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted January 12, 2008 Share Posted January 12, 2008 In short, really quite a lot. My lift pump failed once, i got home by using a plastic cereal tub (2.5L?) strapped to the wing mirror, and a section of hose pipe to the injection pump. the injection pump took around 2.5 L every 5 minutes or so. I fed it 25L of fuel to do less than 17 miles. I got home with a brim-full tank! Quote Link to comment Share on other sites More sharing options...
GBMUD Posted January 12, 2008 Share Posted January 12, 2008 Yup, the answer is "a lot!". You will need change over valves on the return line too. Have you sourced a heat exchanger? Td5s have a nice one. Chris Quote Link to comment Share on other sites More sharing options...
freeagent Posted January 12, 2008 Author Share Posted January 12, 2008 thanks for the replies guys, I already run 25% veg in with my regular Derv, rising to 50% in the summer, but i'd like to go over to a twin tank system, so I can do a proportion of my daily commute using 100% Veg. I think i will use a second 3-way valve to switch the return line aswell, its only another £30ish... I've been looking at heat exchangers and Biotuning do a nice one for about £47... I reckon I can put together a kit to suit my needs for about £200, and fit it in a weekend. Quote Link to comment Share on other sites More sharing options...
TheRecklessEngineer Posted January 12, 2008 Share Posted January 12, 2008 You don't need a lot of heat for a TDi - just enough to help it through the filter. I made one from plumbing fittings for under £10... Quote Link to comment Share on other sites More sharing options...
green110 Posted January 12, 2008 Share Posted January 12, 2008 Sorry for the irrelevance of the information that follows. On a big (18 litre) Caterpillar engine the answer to "how much fuel is returned) is lots, probably up to ten times what the engine uses. I ran one off a 10 litre can the other day (don't ask - it was a long day and everybody ended up smelling of diesel) and it ran for less than a minute at tickover. The fuel is used to cool the ECU and then passes through a cooler on the way back to the tank. I don't really know why there is a cooler fitted as the ECU monitors the fuel temp and I would have thought could compensate for the change in volume as it warms up. Most machines using this engine would hold 1000 litres or so which would absorb a lot of heat. It may just be typical Cat overengineering. Gus Quote Link to comment Share on other sites More sharing options...
simonr Posted January 12, 2008 Share Posted January 12, 2008 I converted my 110 from NA Diesel to Tdi. The NA did not have a return to the tank, whereas the Tdi has. Rather than do it properly, I just fed the return back in to a T before the filter. This would make it hard to bleed, but the filter had it's own bleed which made it easy. Worked fine for many years. Can't see a reason why you couldn't just do the same! Si Quote Link to comment Share on other sites More sharing options...
freeagent Posted January 12, 2008 Author Share Posted January 12, 2008 Interesting replies guys many thanks. I'd like to keep the Veg system as separate as possible as it won't be used all the time (am driving to the Pyrenese for 2 weeks in the summer, and won't use it at all then, and probably won't use it when its realy cold) so I think I will just run a separate return back to the veg tank so when running on dino diesel the truck is almost as it would be if un-modified, when running on veg, both the supply and return lines go to/from the Veg tank... Quote Link to comment Share on other sites More sharing options...
ciderman Posted January 12, 2008 Share Posted January 12, 2008 I converted my 110 from NA Diesel to Tdi. The NA did not have a return to the tank, whereas the Tdi has. Rather than do it properly, I just fed the return back in to a T before the filter. This would make it hard to bleed, but the filter had it's own bleed which made it easy.Worked fine for many years. Can't see a reason why you couldn't just do the same! Si Basicly the same princible as a TD5 , only a very minute amount of fuel returns to the tank , Its sent back to the filter Quote Link to comment Share on other sites More sharing options...
streaky Posted January 13, 2008 Share Posted January 13, 2008 There is a very indepth article in LRM this month about doing this veg oil conversion. It would definatly be worth reading. There's also a rather fetching Dicovery that was photgraphed in the UAE.... Quote Link to comment Share on other sites More sharing options...
jimmy_neutron Posted January 13, 2008 Share Posted January 13, 2008 Most of the time you will be running on the veggies, so you could use the primary tank for veggie oil, and fit a small 2-3 gallon tank in the boot for diesel. Just vent the tank to outside so it doesn't stink the car out. This way you will always return any excess fuel to the veggie tank. A bit of diesel in the veggie tank is good anyway especially in winter. And you will always have pure diesel fvor starting and warming the car on which is much better for the injector pump. Quote Link to comment Share on other sites More sharing options...
bishbosh Posted January 13, 2008 Share Posted January 13, 2008 There is a very indepth article in LRM this month about doing this veg oil conversion. It would definatly be worth reading.There's also a rather fetching Dicovery that was photgraphed in the UAE.... Very true, same the pictures were marred by some ugly bloke getting in front of the waggon though!! Quote Link to comment Share on other sites More sharing options...
freeagent Posted January 13, 2008 Author Share Posted January 13, 2008 Most of the time you will be running on the veggies, so you could use the primary tank for veggie oil, and fit a small 2-3 gallon tank in the boot for diesel. Just vent the tank to outside so it doesn't stink the car out. This way you will always return any excess fuel to the veggie tank. A bit of diesel in the veggie tank is good anyway especially in winter. And you will always have pure diesel fvor starting and warming the car on which is much better for the injector pump. I have thought about that, but would like to use the internal tank for Veg for a couple of reasons; When we go to europe in the Disco we won't bother with Veg, as its no cheaper than diesel, the internal tank will be buried under all our stuff and impossible to get to. I don't like the idea of 25Litres of diesel in a plastic container sloshing around inside the vehicle, and if it was to spring a leak i'd rather it dumped veg all over the carpet than diesel. I won't use the veg system much when its really cold, as I only have shortish journey to work and i'd spend most of it warming the veg, then purging the system... i'd rather just not use the veg when its frosty.. I've drawn up a diagram of what I'm intending to do, I'll post it up here and ask for any other ideas shortly... Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.