Biodiesel for a PD TDI.

[horace1664]

Firstly please excuse me if this has been asked before, but I’m trying to get my head around the biodiesel thing for a PD TDI.

To be clear, I am interested in running the engine on Biodiesel 100, and I’m aware that VAG have changed their mind since 2003 as to whether this is permitted.
Since then (2003) I understand it only Biodiesel 5 is permitted (which is what Low Sulphur Diesel is any way!).

I am not talking about adding: -
Chip fat
Cooking oil from Tesco etc.
I am not considering making Biodiesel either.

Now that is out of the way my question is: -

From what I can find the problems with running Biodiesel on the VAG 1.9 TDI (and other VAG TDI lumps) are
1) The fuel breaks down under the extreme pressure of the PD injection system, which causes fuel filter blockages.
2) The regenerating particulate traps in the exhaust (This is also referred to as a cat?) are not regenerated by Bio diesel.
3) There are issues with the engine oil having a shortened life (not VAG only VAG TDIs).
4) Heating issues in cold weather.
5) A change from petroleum based Diesel to Bioodiesel is best made gradually as the solvent value of Biodiesel cleans the fuel lines, injectors etc and blocks the fuel filter.

Am I close to the mark?

James

 

[muddyboots]

Firstly please excuse me if this has been asked before, but I’m trying to get my head around the biodiesel thing for a PD TDI.

To be clear, I am interested in running the engine on Biodiesel 100, and I’m aware that VAG have changed their mind since 2003 as to whether this is permitted.
Since then (2003) I understand it only Biodiesel 5 is permitted (which is what Low Sulphur Diesel is any way!).

I am not talking about adding: -
Chip fat
Cooking oil from Tesco etc.
I am not considering making Biodiesel either.

Well done

Now that is out of the way my question is: -

From what I can find the problems with running Biodiesel on the VAG 1.9 TDI (and other VAG TDI lumps) are
1) The fuel breaks down under the extreme pressure of the PD injection system, which causes fuel filter blockages.
2) The regenerating particulate traps in the exhaust (This is also referred to as a cat?) are not regenerated by Bio diesel.
3) There are issues with the engine oil having a shortened life (not VAG only VAG TDIs).
4) Heating issues in cold weather.
5) A change from petroleum based Diesel to Bioodiesel is best made gradually as the solvent value of Biodiesel cleans the fuel lines, injectors etc and blocks the fuel filter.

Am I close to the mark?

James

1) Not sure - I thought the filter blockages were due to the same reason as point 5), you could be right though
2) Again, don't know - but only some of the latest models have particulate traps, the rest just have ordinary catalytic converters. Cats on TDIs can be removed and still pass the MOT anyway, and I think before long people will know how to remove particulate traps too....
3) and 4) Don't know
5) I believe this is true.

 

[TornadoRed]

From what I can find the problems with running Biodiesel on the VAG 1.9 TDI (and other VAG TDI lumps) are
1) The fuel breaks down under the extreme pressure of the PD injection system, which causes fuel filter blockages.

It's important to use only high-quality fuel

3) There are issues with the engine oil having a shortened life (not VAG only VAG TDIs).

This shouldn't happen, but it might.

4) Heating issues in cold weather.

Winter additives for biodiesel are not the same as for dino diesel.

5) A change from petroleum based Diesel to Bioodiesel is best made gradually as the solvent value of Biodiesel cleans the fuel lines, injectors etc and blocks the fuel filter.

Possible, but not that common.

 

[wiganlatic]

I used to tip 12 litres of ASDA's best veg oil made from rape seed into the tank with about 30 litres of normal diesel and it ran fine (my TDI FR that is). Started using biodiesel from the local garage any my car developed a flat spot at about 3000 rpm. Went back onto normal diesel and everything went ok after about a week. NOW I've got the yellow warning light on the dash with the engine symbol in it but occasionally it goes off for 5 minutes or so. Can't find any info on that light but I'm wondering if the old veggie oil might have had something to do with it???

 

[TornadoRed]

Biodiesel that meets commercial specifications is a fuel. Raw vegetable oil is not fuel. I only burn genuine fuel in my TDI.

 

[wiganlatic]

Rudolf Diesel originally designed the diesel engine to use vegetable oils as a fuel in order to help support agrarian society. Taken from Wik. Granted engine technology has come on a bit since then.

 

[ChrisGTL]

Biodiesel attracts water, and when biodiesel and water are together it promotes the growth of bacteria and mould. Similar to what boats suffer from when water is present in the fuel tanks.

The bacteria isn't so much a problem as it only really smells and doesnt effect fuel systems, the fungus is the problem as it gets thicker and thicker clogging or plugging the fuel filter thus starving the injectors.

Biocide will prevent these bacteria though, and other products are available to clear up any bacteria that has already started to multiply.

 

[wiganlatic]

ohhhhhhhhhhh
got ya.

 

[Tuscan_No27]

Biodiesel attracts water, and when biodiesel and water are together it promotes the growth of bacteria and mould. Similar to what boats suffer from when water is present in the fuel tanks.

The bacteria isn't so much a problem as it only really smells and doesnt effect fuel systems, the fungus is the problem as it gets thicker and thicker clogging or plugging the fuel filter thus starving the injectors.

Biocide will prevent these bacteria though, and other products are available to clear up any bacteria that has already started to multiply.

You would have to have stored your biodiesel for a long long time open to humid air without a lid on for this to be a significant problem - its not a problem in reality and is probably no different to dino-diesel ? Doesn't the fuel filter act as a water separator anyway - water sinks and there's a little bleed valve on the bottom to check / drain off any water ?

 

[tomn5518]

hi all.i have an 08 plate fr 170,i have read so many different views on using 100% biodiesel but i have looked inside the fuel cap and it says not to use biodiesel?
Is this because they changed there minds after 2004 or should i just not bother?

 

[CrispDust]

IMHO VAG changed there minds on biodiesel beause of the huge variation in bio diesel quality or composition/interpreation of the term. - from the Tesco veg oil to high quality branded stuff. The latter should be perfectly okay but general advice seems to be:
1. Gradual change to bio - eg 1/3 bio/2/3rds tank dino, then 1/2 to 1/2 and so on. To help ecu/engine management adapt gradually.
2. Change fuel filter after 1st or second tank - bio has a higher solvent action (higher cetane I believe) and will flush the crud and depsoits from fuel lines.
Fuel line cloging/breakage is only a problem on older cars due to material used for flexible piping.
Never rely on pure Bio during winter due to lower temp gelling - use a dino mix.
3. Biodisiel oftens takes more turns on the starter motor to fire up.
4. Bio has better lubrication so its is unlikely to cause any problems to the injectors etc.
Mine did have problems starting on bio ( I use it occasionally when i pass the garage that sells it)

 

[tolly_tdi]

I always thought that 100% biodiesel for PDs was not a good idea as the injection pressure is very very high on PDs and as biodiesel is slightly more viscous and more so at lower temperatures obviously the pump will have to work harder and so affecting the longetivity of the pump?

CrispDusts comments are very true though.

 

[Tuscan_No27]

I always thought that 100% biodiesel for PDs was not a good idea as the injection pressure is very very high on PDs and as biodiesel is slightly more viscous and more so at lower temperatures obviously the pump will have to work harder and so affecting the longetivity of the pump?

CrispDusts comments are very true though.

Urban myth - my 150PD Leon FR has been running for 14000 miles on homemade bio all the way up to 100% including through this recent cold winter without any problems.

 

[tolly_tdi]

thats very interesting tuscan. I was hoping someone with experience would add to the thread! would be good to have a biodisel subsection within this TDI froum also.

 

[CrispDust]

PD doesn't have a pump as such apart from basic tank pump - the pressure is generated by the camshaft/lobe system.

 

[Tuscan_No27]

thats very interesting tuscan. I was hoping someone with experience would add to the thread! would be good to have a biodisel subsection within this TDI froum also.

Hi Tolly, yeah I wouldn't be deterred - there's biodiesel forum (google "biodiesel infopop") with a wealth of experience to draw on. But CrispDust's comments are all valid.
I started on a small percentage and built up the percentage as I grew confident I was making good quality bio.
The filter change after your first tankful of bio is necessary because it tends to clean out the muck left by dino-diesel in the fuel tank and fuel supply lines.
It's generally recommended that you run a small % of dino in winter but to be honest UK veg oil is predominantly derived from rapeseed oil which has a low cloud point with the result that bio made from rapeseed oil also shares this advantage - I've run on 100% in freezing temps this winter without any probs. I've even had some bio leftover in a bottle outside all winter and its remained liquid even at -5degC without gelling. You do get a little more smoke on turning the ignition very cold mornings but I tend to anticipate it and give the glow plugs two heats before ignition to help reduce it. Other than that everything is the same.

Hope this helps.