Diesel Engines running veg oil - turbo vs. non-turbo?

[Paul the 6th]

Another camper related post (I promise I'll be back asking questions about bikes as soon as I've got a track bike of some kind).. There's a load of guys on the vwt4 & brick-yard forums who are running veg oil as an alternative to diesel. Some are running upto 70% oil to 30% diesel, but most are on around 50/50 depending on the ambient temperature..

Some say that you require a specific bosch fuel pump to deal with the slightly higher viscosity, but it's commonly accepted that the 1.9 and 2.4 non turbo engines will run fine on veg oil. The 1.9tdi and 2.5tdi engine however, are a big no-no.

I read into it, understood it (for the most part) and decided that it's not something I'd like to risk, despite the 30-40p saving per litre. I understand octane and cetane ratings, as well as knocking/detonation, but was just wondering whether the turbo/compression ratio might have something to do with the tdi engines not liking veg oil?

YC & the whacky scientists of the org, enlighten me :study:

[andrewsmith]

Paul PM Carl (Berlin)
He ran a old N/A Iveco lump. The modern common rail diesel cannot run veg oil as the injectors are too small amongst other issues.

[fizzwheel]

but was just wondering whether the turbo/compression ratio might have something to do with the tdi engines not liking veg oil?

When I looked into it, seemed to be two issues

1. Fuel pump not liking it, something to do with the veg oil knackering the seals IIRC, but I might be wrong

2. Common Rail diesel engines dont like veg oil, its not a turbo issue, as said above IIRC its to do with the injector system.

[metalangel]

I used to run my 1.9TDI on the bio diesel sold at Morrison's. Never used actual veg oil, so dunno. There was never a concrete answer as to why, though I heard it would eat through the seals and hoses which weren't designed for it, and likewise the injectors and pump would be unhappy.

[The Guru]

Injectors clog up with crud when running on veg oil.

[Paul the 6th]

thanks for the replies guys :thumbsup: found this post on pistonheads as well which mentions about the amount of back pressure which the pump has to deal with on common rail injection engines..

http://www.pistonheads.com/gassing/topic.asp?h=0&f=23&t=814111&mid=0

ta!

[maviczap]

There's a lot of chat on my Mazda Bongo forum about running on veg oil, and plenty of people do, without any problems.

My Mazda engine is fairly low tech (read tractor like) without any the the common rail gubbins, so it'll happily run on neat rape seed oil.

One guy has run his Mazda for 20,000 miles without any problems and I've seen pictures of another one with a twin tank diesel/ veg oil tank

http://www.youtube.com/watch?v=b5AwH9GdFV4

However there is another type of conversion you can use which is a combination LPG/diesel system. The cost of the conversiopn is only worthwile when you're doing reasonable milage, as you get better MPG

I don't know too much about it, but if you're worried about veg oil buggering up your fuel pump, then this might be an alternative?

http://www.google.co.uk/#hl=en&xhr=t&q=LPG/diesel+mix&cp=15&pf=p&sclient=psy&site=&source=hp&aq=f&aqi=&aql=&oq=LPG/diesel+mix+&pbx=1&fp=d75367f29cd5c777

[Paul the 6th]

well, I wasn't so bothered about mpg or trying to be more environmentally friendly - purely the £1.40 average cost of diesel compared with around £1.07'ish per litre of SVO..

I'm quite happy with the economy though - 500 miles from 70 litres of diesel for a van is brilliant. Our renault master works van (also 2.5 tdi) holds about 80 litres and gives around 380-420 miles at best!

[husky03]

http://www.vegetableoildiesel.co.uk/forum/

all questions answered here mate-i start producing my own biodiesel this weekend-gonna be costing 70p/litre in total after all production costs-diesel will hit 180 a litre this year me thinks.

[Skip]

My mate ran his 1994 Audi 1.9 TDi on veg oil on and off for about 2 years - then it developed a lumpy idle - turned out to be dirty injectors - now whether the 225,000 miles on them was the cause or the usage of veg oil - who knows! Still going strong though!

[johnnyrod]

Newer engines with comon rail systems can't use neat oil as the pressure in the common rail is high and the injectors are small, and the fuel can get very hot while it's in there waiting to be injected. Veg oil can't handle this. Good quality biodiesel is fine, to be hoonest I wouldn't make it at home, and I wouldn't use neat veg oil unless the engine's been designed to use it. Yes, the viscosity is higher than diesel so you need a stronger pump, but the combustion isn't as good so you risk a rapid build-up of nasty sludge in the lube oil which has been known on many occasions to lead to the end of your engine.

Making it at home is pretty easy but the quality can be pretty bad, and you have some nasty stuff to dispose of afterwards, so it's not very green really unless it's made in factories where it's an integrated process. I'm all for tree hugging but I'm afraid most of what you read on the internet about saving the planet with used cooking oil or whatever is just cobblers. (I know you are all talking about new oil above, you get the picture though. NEVER make biodiesel out of old oil, people are throwing it away for a good reason.)

[yorkie_chris]

Waste oil burns fine
http://backyardmetalcasting.com/oilburners/oil04_oilflame.JPG

Depends on the pump.
If it is right sort of pump, then it is fine with turbo.

DI engines can be funny with it and get gummed rings and stuff, IDI is better for burning crap. The more agricultural engines can run on anything. Read up other owners experience and apply common sense. :)

Oh and forget most of what you know about preignition/detonation when talking about diesels.

[johnnyrod]

What's that a picture of? Chris, I bow to your vastly superior mechanical knowledge but waste oil is full of grot, polymeric crap, and all manner of nasty stuff, plus it's very variable in composition. As regards combustion, there have been plenty of people who've found out the hard way e.g. the South African govt ran a test with sunflower oil in tractors on test beds, and by the end of the week they were all in the skip. If the oil doesn't burn properly (and there's a good chance of this in the short time it spends in the cylinder) then a load of crap inc. a good chunk of glycerine ends up in the sump. On the other side of the coin there are trucks (artics) in Germany running on neat rapeseed oil, but there I believe they've done work on improving the combustion so this problem doesn't happen. I've seen so much BS on this that I wouldn't want people on here to blindly stumble into things and find out later that they shouldn't believe everything they believe on the internet.

[yorkie_chris]

A furnace for melting metal. I know that's rather a more brutal act than finely expanding a working fluid with heat lol.

I'd be happy using waste oil if I took steps to dry and filter it. Then again depending on the vehicle, on the sort of £500-1000 sheds I was looking at buying it would only have to last what 3000 miles and after that it might as well eat itself, you're still in front.