Going Veggie
A Bit of Background
Vegetable oil is chemically very similar to diesel. The first Diesel engine (invented by Rudolf Diesel) was demonstrated for the first time running on peanut oil. It was meant to run on whatever oil was produced at the farm. Needless to say the oil industry got their hands on it as it ran very well on ‘heavy oil’ which was an annoying by-product of the petrol distillation process.The Problem
The major issue with running vegetable oil through a diesel engine is the viscosity. It is many times thicker than diesel, especially at low temperatures. There are many ways to overcome this. One is to change the chemical composition of the oil by transesterifying it, and producing proper bio-diesel. I won’t deal with this here, but there are many sites on the internet that detail how to do it.The Solution
The other major way is to simply heat it up. This is done most easily by attaching a heat exchanger to the coolant lines to heat up the fuel as it passes through. This is the underlying principle – every conversion kit is based on this. However, there are a few other problems you need to be aware of:Going Veggie
Lucas injection pumps are notorious for failing on vegetable oil. These are fitted to 2.25, 2.5 and 2.5 TD engines. The reason is that they rely on the fuel for lubrication, and because vegetable oil is so much thicker, it cannot seep around the rotor head and so deprives it of lubrication. Eventually it seizes and normally snaps the drive shaft or strips the timing belt. Either way, it’s expensive. The way to overcome this is to fit a second fuel tank. This way you can start or stop on diesel and using changeover valves, change to veg when the the engineand fuel is hot enough (normally when the engine is up to normal operating temperature). You can also loop the return – take the return to tank line from the injection pump and plumb it into the heated fuel line. Not only does this help the fuel stay hot enough, it also reduces the stress on the injection pump. If you are really cunning, you can fit a second heat exchanger in the loop to ensure everything stays nice and hot. In fact most DIY kits consist of a heated fuel filter from a Peugeot with the thermostat removed being used as the first heat exchanger. A second is then fitted in the return loop. Some commercial kits however use a modified glow plug arrangement to heat the fuel electrically. However – it has been shown that in a draughty engine compartment (such as your Land Rover) that they have very little effect on heating the fuel. Use a heat exchanger! For 2.25 2.5 and 2.5 TD engines, this is all you need to do. Your engine will run as before, just the exhaust will smell like a BBQ. TDi owners however, have a slightly different concern: Both the 200 and 300 TDi are fitted with the Bosch injection pump. These have proven to be very robust on vegetable oil. However, the engine itself is the problem. As they are direct injection, it is possible for the vegetable oil to not completely combust in the cylinder when cold. It can then condense onto the cylinder walls, get under the piston rings causing coking and find it’s way into the sump, where it polymerises the sump oil. Not very nice! The way around this is to use a twin tank system as outlined above. This enables the engine to heat up on diesel and then when it is warm enough you can change over to veg. Again, heat exchangers and a looped return all help. If you have a Td4 or Td5 however, a twin tank might work… I have not heard ofany Td4 or Td5 owners using vegetable oil, but a twin tank should work in theory.
Anyone fancy trying it?
Some cars (not any Land Rover) will go on vegetable oil from cold with no modification. Generally any engine with a Bosch VE injection pump, or inline injection pump that is indirect injection will be fine if you tip the fuel straight in the tank. It might go a little better if you loop the return and add a heat exchanger though.I have converted a 2.25, and 2.5 TD and a 300 TDi, and all go very well on veg.