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So you want to run your diesel engine on vegetable oil (SVO/WVO)?
Basic Principles FAQ Glossary Photo Gallery Links
VERY Basic Principles (follow the hyperlinks if you want to know more)
Petrol engines are NOT capable of running on vegetable oils or animal fats!
Many diesel engines are capable of running on a wide variety of oils, including vegetable oils and animal fats.
Diesel engines compress the air in the cylinder many times higher than petrol engines compress the air/fuel mixture. At the height of the compression cycle diesel fuel is injected into the (pre-) combustion chamber at high pressure. The injected fuel combusts without the need for a spark (plug), although glow plugs are used to get cold diesel engines firing. High compression alone doesn’t do the trick, though. To get diesel and other oils to combust properly, they must be introduced into the combustion chamber as a fine mist. This is done by compressing the fuel via the injection pump and then spraying it into the combustion chamber via the injectors.
Not all diesel engines are suitable
The major obstacle to running a modern diesel engine on vegetable oils and fats is viscosity. SVO/WVO is thicker then diesel, in some cases more than 15 times so. Animal fats may even go solid at room temperature.
The thicker the oil the harder the injection pump has to work.
Because of the high compression ratio, diesel engines have traditionally been "over engineered". In a modern manufacturing environment, over engineering is, of course, a dirty word. That is why older diesel engines are more tolerant of thicker fuels.
And that’s why it is so important to check if your engine is suitable for a WVO conversion.
Will my diesel engine be damaged when run on WVO
I do not consider Direct Injection type engines as suitable. The diesel or SVO/WVO mixture is (as the name implies) directly injected into the combustion chamber. This makes the engine vulnerable to having any improperly nebulised WVO mixture coat the cylinder walls, causing or adding to "glazing". Glazing can happen even when using diesel is can use to serious engine damage. While most DI engines have a "well" in the piston head, to avoid this problem, anecdotal evidence suggests that it does not completely eliminate it. The problem is most likely caused by cold SVO/WVO (at startup) resisting proper nebulisation.
"Common Rail" type diesel engines are also not suitable.
Even if WVO is properly heated it will still be somewhat thicker than diesel. The injection pump will have to work harder and it WILL wear out faster. Older inline injection pumps (Bosch, NipponDenso, etc) routinely last for 500,000kms or more under normal conditions. However, it stands to reason that even these "over engineered" pumps will last less long when used with WVO. Distribution type pumps are less robust and will most likely last even less long.
Acidity of certain WVO’s and high water content may further contribute to shorten the life of your pump. There are even suggestions that under certain circumstances WVO will cause piston oil ring sticking and cause engine seizure.
The point is that nobody really knows, since no scientific studies have been made that I am aware of. The Internet is full of contradictory anecdotal evidence, from diesel engines running hundreds of thousands of kilometres on WVO problem free and others that have failed in a very short time.
I cannot and will not be held responsible for any damage you may cause to your engine. Due diligence is YOUR responsibility.
I am urging any prospective WVO’er to at least ascertain what an injection pump rebuild (or a replacement from the wreckers) will cost.
The WVO Cost/Benefit Calculator
A = Fuel consumption (litres per 1 km)
A * B = Savings per kilometre
D / (A*B) = Break Even (The number of kilometres your diesel engine will have to run on WVO until it will have payed for the conversion AND a pump rebuild.
Your cars consumption is 10ltrs/100kms
A = 0.1 litre per 1 kilometre
B = $1.00 (diesel = $1.20 - WVO = $0.20)
D = $500.00 + $1500.00 = $2000.00
A * B = $0.10
2000 / 0.10 = 20,000kms
The WVO Rule of Thumb
Diesel Engine combustion technology:
Indirect injection engine =
Direct injection engine =
Common Rail Engine =
Turbo charged engine = does not effect suitability, simply see 1. 2. or 3. above
Diesel Injection Pump types:
Bosch, Nippon Denso in-line injection pumps =
Distribution type injection pump (Bosch, Zexel, etc) =
Lucas, Delphi, CAV, Stanadyne or Roto-Diesel injection pump =
The WVO’s "How brave am I" test :
1. Is the engine using "indirect injection"? (Yes =
If you smiled trice you are on your way to become a WVO’er.
My suggestion for a WVO motto:
Get it free, get it clean and get it going…
Why does it work
How difficult is it
Why heat WVO first
How to heat WVO
Why use a "two-tank system"
Why is viscosity a factor
What’s a "hose in hose" heated fuel line
Will it damage my engine
Are all vegetable oils suitable
How do I treat WVO before use
Is my local climate a factor
What about excise duty
What about storage
SVO – Straight Vegetable Oil (as in new, unused)
WVO – Waste Vegetable Oil (as used, recycled, to be disposed of)
A metal nozzle protruding into the (pre-)combustion chamber. It delivers a spray of atomised fuel at a predetermined rate and pattern.
A small electrically heated metal rod protruding into the combustion chamber. As its name implies, it glows (at very high temperature) and thus aids the combustion of diesel fuel in a cold engine.
Fuel Line Heater
I prefer hose in hose due to its simplicity and cost factor. If you are worried about water leaks, you could install an engine overheat alarm (very cheap from places like Jaycar (Australia).
I can see no real advantage in using an electric fuel line heater. You may be able to use WVO a little earlier, but not by much. Remember that only very little fuel (in terms of mass) enters the injection pump. The much larger metal mass of the pump would bring any fuel entering it very quickly to its own temperature. A cold pump receiving hot WVO would still equal cold oil, for a while at least.
The worst thing in terms of wear for an injection pump is repeated and/or sustained use of cold (thick) WVO. So my advice is to always wait until the engine has reached its operating temperature. By then you have plenty of hot (and free) radiator fluid to heat your WVO.
An electric heater would put a load on the alternator, most modern ones of which are designed with little spare capacity. Even if the alternator is capable of providing the extra power, you would use more fuel (no free lunch on this planet), albeit hopefully very cheap WVO.
Heating methods are, of course, climate driven. You may need to consider tank heating, fuel filter heating, etc if living in a colder climate.
The message is clear:
Get it free, get it clean, get it hot, and get going...
I am considering converting 1HZ engine myself.
Conversion is straight forward:
The 1HZ is an indirect injection type engine with pre-combustion chambers. This type of engine is considered to be ideal for a WVO conversion.
The injection pump is a "distributor" type pump made by ZEXEL (KIKI). It’s supposed to be a BOSCH design; again, that is considered suitable.
If you already have a two tank system (as my previous ‘95 Troopy had) you’re already halfway there. The factory two tank system already employs a Pollak 6-port fuel valve of the kind most WVO conversion sites recommend and which I am using on my BJ45.
I strongly recommend a two tank system in which you start the engine on diesel until it has reached operating temperature. Then you press the little switch on your dashboard (if you have a two tank system already) and voila you’re running on WVO. Before you reach your destination (2 or 3km’s) you switch back to diesel to empty the injection pump of any WVO.
The conversion consists mainly of a "hose in hose" fuel heating line, in which the WVO is heated to +700 Celsius to reduce viscosity.
I have a diagram on my web page – please note though: This diagram will not work for the 1HZ engine, it needs a switch return loop. I am happy to alter it for you since I am going to convert my 1HZ engine soon. (http://www.tiemann.com.au/tiemannfamily/toyota_bj42.htm)
The type of WVO and more importantly the treatment you put it trough before running it in your engine is absolutely crucial:
You need to filter it to at least 5 micron (I can advise on filter socks, etc.) – I filter mine to 1 micron!
You need to remove water as much as possible – (it will not separate from WVO as water in diesel does)
You need to reduce acidity (depending on the type of oil)
If you are still not frightened off, do yourself a very big favour and ring your local diesel pump reconditioning shop: Ask what a full reconditioning of a stuffed ZEXEL injection pump for a Toyota 1HZ engine costs. Once you have had the required hart transplant, ring local 4WD wreckers and ask if they have any second hand pumps available and how much they cost.
Once you have done all that and are still amongst the living, I am happy to send you a parts list and more detailed instructions to make up and install your own kit.
just for the record - your method of identifying injection pumps may not be
all that accurate. The "round ended" pumps are not necessarily made by Lucas.
"Round" injection pumps (injector supply lines are arranged in a circle) are
usually distributor type pumps (also called rotary). They are suitable for WVO
conversions unless they are of the Lucas brand*.
My advice on suitability and to test your intestinal fortitude for a WVO conversion: Take your Patrol to your local diesel specialist and ask these questions:
1. Is the engine using "indirect injection" (Yes - good) 2. Is the injection pump made by Delphi, Lucas, CAV, Stanadyne or Roto-Diesel. (No - good) 3. Can you afford an injection pump rebuild. (Yes - good) If you come up all "good" you are ready to go...
The Bravo I have just converted is a year 2000, 2.5ltr Turbo. It may well be the same as your Courier engine.
The Bravo diesel engine is indirectly injected and uses a ZEXEL (Bosch designed) distributor type injection pump. This pump is considered to be suitable for a two-tank conversion on SVO/WVO. However, the older, piston type BOSCH pumps are considered to be ideal.
I have no personal long term trials with Zexel type pumps, yet. Ask again in a few weeks - The chap driving the Bravo covers 6000km's a week!
My own Toyota BJ42 has now consumed almost a 1000 litres of WVO and is running just fine.
I only recommend a two-tank conversion: see a sample diagram on my websitehttp://www.tiemann.com.au/tiemannfamily/toyota_bj42.htm
Zexel pumps use a more sophisticated fuel delivery system then the older style piston type injection pumps (used in my BJ). It is crucial to use a conversion design that "loops" the return line back to the respective tank. I'll provide a revised diagram for the Bravo conversion as soon as I have finished it.
Most problems with WVO conversions appear to be related to air in the fuel lines. Air will cause fuel starvation symptoms such as loss of power, racing, etc.
Obviously, I cannot give you any guarantees, but if your engine is indeed identical to the Bravo engine, you will be able to run it on WVO.
Here's what I would do first:
Consider scenarios below and ask local diesel shop for quotes (verbal rough estimates will do):
1. Catastrophic - engine ceases, needs a total rebuild 2. Semi Catastrophic - engine ceases, needs a top end overhaul 3. Injection pump dies - needs a total overhaul
Find out if second hand engines and/or injection pumps are available from wreckers. These phone calls will not take too long and are time well spent. Do not skip this preliminary work!
It is my belief that the failures listed above are unlikely to occur in the short term. They may never eventuate, but you should expect at least the injection pump to fail a little sooner than if run exclusively on diesel.
Heated WVO is still more viscous than diesel - the thicker the oil the harder the injection pump has to work. There's also the higher acid content of WVO to consider. This acid may accelerate corrosion of finely machined parts in the pump. Again, this is not going to happen in weeks or month, but it may be a factor nonetheless. For this reason, I personally would not convert a new vehicle to SVO/WVO, even if the engine type is suitable.
Older diesel engines are cheaper to replace or repair since more second had parts are likely to be available.
I hope I haven't scared you too much. But I feel I would do you a disservice if I didn't point out these things.
Now to the fun part: If you decide to go ahead, I am happy to provide a diagram, a parts list, help with sourcing parts, etc. I actually have a few components here, like hard to come by Pollak 6-port fuel valves, etc. I also have a diagram for automating the use of the two-tank system. I am currently adding a turbo timer to my electrical diagram. My website will show these developments soon.