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T'sTDI January 12th, 2010 12:08

Comprehensive/Technical Approach to Burning WVO Successfully
I am writing this guide on behalf of the WVO community as a primary means of searching for relevant, experienced information regarding the use of WVO in diesel engines (specifically the TDI VE rotary engine).

This is a guide and by no means a guarantee. There is nothing guaranteed with the use of experimental fuels (Please see Experimental and Alternative Fuels: an overview). This guide is written on behalf of me and my experiences thus far with the use of WVO. My experiences include the use of burning WVO in three different vehicles, two of which are converted with the Greasecar kit. I will discuss each of these further in detail later in this guide.
This guide is written to ensure the most long term success burning WVO with the information we currently have available. I cannot guarantee you will go out and run your car for over 100k on WVO, nor can I guarantee that you will switch to WVO and explode your engine in 5000 miles. These are unchartered waters and using a non ASTM Spec fuel in an engine that requires it, will always run some kind of risk. However, my research/experiences have provided success in three different vehicles and enough confidence in my program to write my own guide regarding the use of WVO.
I like to use this analogy. Having experiences with auditing financial statements at public accounting firms, an auditor provides assurance to the public (or any user of the financial statements) that the financials are in accordance with generally accepted accounting principles. This means, an auditor provides assurance, not a garuntee that the financials are not materially misrepresented. Through an audit, we can only confidently assure that there were no instances of fraud, but we can not guarantee there were no instances of fraud.
Back to WVO, I can only provide you the assurance that to the best of my knowledge this is an effective way of burning WVO the safest and most efficient way possible. I can not guarantee anything regarding your use of my directions/ insight and one must take full responsibility for their own actions regarding their use of WVO, whether it is the right or the wrong way. If you blow your engine up, it is your own doing, not mine.
I urge you to read this guide and understand it thoroughly. Although the information provided in this guide is my own thoughts and reasoning, this guide is sourced from countless of hours of research (searching wide varieties of forum threads) on the internet and personal experience. Hopefully I encompassed this topic well enough for you to believe in what I am saying. If I did not, read my opinion, read another, read twenty more, and then form your own opinion regarding the topic. This guide took a long time to write and I hope you enjoy it as much as I did writing it.

T'sTDI January 12th, 2010 12:09

The Basics
The Basics:

VO/WVO is a much riskier endeavor then that of its popular counterpart biodiesel. Although derived from the same source, these are completely different fuels. “Biodiesel is made from vegetable oil or animal fat (triglycerides) reacted with methanol or ethanol and a catalyst (lye), yielding biodiesel (fatty acid methyl or ethyl esters) and glycerin as a by-product.” (
VO/WVO is the same stuff that you cook with and eat your greasy fast food fries from. VO (vegetable oil) becomes WVO (waste vegetable oil) as soon as it is heated to a high temperature (typically fryers run at a consistent 350 deg F), and used for cooking and eventually disposed of at a restaurant. At this temperature, the oil actually burns (signaled by the small amounts of smoke rising from the deep fryer) which is cause for the darker tint that WVO typically has.

T'sTDI January 12th, 2010 12:10

Before the Conversion
Before the Conversion

There is a lot to consider before thinking about converting your vehicle with a recommended WVO burning kit. Some things to consider are as follows:

Source of Oil
Consistent Source of Oil
Initial Fixed Costs (time, cost of conversion, filtration, and storage)
Time needed to pick up Oil
Relationships with Oil Sources Management
The “Mess” Factor

Source of Oil-
Obviously for any of this to be possible you need a source of oil. Not only do you need a source of oil, you need a consistent source of oil. It would be very unfortunate to purchase a kit and learn that your supply source has chosen another means of disposal or in many cases, someone else stealing the oil from you. One must understand that burning WVO or creating biodiesel (both need sources of oil) is not a revolutionary idea and if your considering starting now, your probably already behind. People have already established their suppliers and they are VERY good about making sure pick up’s are timely and clean.

Initial Fixed Costs-
There is a decent amount of money that will be invested in your “WVO burning program.” My experiences have three cars burning WVO on a consistent basis so it was much easier for both my dad and I to invest a bit beings the demand for three cars was there. If you only have one car that you plan burning WVO in, you may be more conservative in your purchases for filtration, storage, and maybe even a kit; however, one must not cheap out at this stage of the process. It is very important that you invest enough money to create an acceptable means of filtration and storage. With WVO, you get what you put into it. A poor effort = poor results.

If you live in a condo or don’t have a backyard, I would sincerely recommend you to not pursue WVO. This operation needs space and lots of it. Gravity filtration is the cheapest and most effective filtration methods out there and if you do not have the space to allow this to happen, you’re severely limited to what you can do in regards to effective filtering. I recommend a shed or a garage with 30 or 50 gallon barrels of WVO oil (pre filtered) to sit and stand. We have roughly ten 30 gallon barrels, six 50 gallon barrels and one that holds over 100 gallons of oil. So in theory we can stockpile in excess of 700 gallons of oil at a time. Obviously, for the needs of a TDI, this is insane. However, burning WVO in three different vehicles, we can burn anywhere from a couple gallon during a week to close to 16-20 in a single week (our Powerstroke).

Time Needed to Pick Up Oil-
You must be aware that there is time that needs to be allocated in picking up oil, typically once a week. This must be done on a consistent basis to keep your source. If you are an unreliable pick up, management won’t deal with you and kindly ask you not to pick up their oil from their store. There is definitely a responsibility factor on your part to keep in mind that people are relying on you to get rid of their waste.

Relationships with Management-
We are friends with everyone we pick up oil from. Long time ago I worked fast food and made friends with management at a couple different stores in the hopes of being allowed to pick up their waste oil. One must kindle relationships with GM. Remember, they have a means of disposal already, they don’t need the help but you do.

The “Mess” Factor-
You’re required to pick up disposal of the oil in the cleanest and most efficient way possible. Remember that restaurant chains are trying to run a store and customers will complain over the stupidest things. If you are a slob, you will lose your source quick. You must pick up with care and have a means of clean up because spills will occur.
You will spill oil everywhere at one point or another. We are very clean and neat and even we have spilled on our garage floor more than once. Expect it to be messy and dirty. If you’re the type to not want to get your hands dirty, I would recommend against burning WVO. I will say this though, even though WVO is a messy operation, that does not mean the final product going into the final tank needs to be messy. We are very careful pouring oil in our WVO tanks in our cars (use of an oil funnel). Our trunks are spotless and free from smells of oil. Have some pride…
As I said above, our trunks are spotless on our nicer vehicles. My 2001 TDI and dads 2000 Powerstroke are kept always in immaculate condition. Our beater 86 VW IDI is a different story. Although kept in good shape, we have spilled oil in the trunk many of times. It is the car we take to pickup oil with. I would recommend designating a particular car for pick up’s because it’s hard to keep clean. Our trunk of that car will forever smell like WVO. We do have towels in the trunk but it doesn’t help much. Bottom line, be smart and understand messes will occur but that does not mean you have to be a slob. If a second car is not available, one must understand that this scenario could occur on a nicer vehicle. This is obviously a personal choice, some people could careless about their cars and some people are anal retentive like myself. Understand messes will occur at one point.

T'sTDI January 12th, 2010 12:11

Ok Now What?
Ok now what?
You’re far from converting your car yet. I feel this is a much overlooked step of the process. One must start with a well maintained vehicle that is in perfect working condition. The car must run like a clock for you to be successful with WVO from the start. If your car is a POS, expect it to be an even bigger POS after the conversion. If the car is in perfect working order (timing belt, glow plugs, filters, routine maintenance, oil changes, water pump, all the amenities…. etc… etc.. etc…) one’s chances of successfully burning WVO are greatly increased. Other than doing obvious maintenance, ones car should not smoke excessively on startup, should not burn any oil, and one should address any CEL (check engine lights). A great idea would go to a person who knows TDI’s well and ask them to go over the car and see if they can find any problems. Do not take your car to a dealership and ask this, they will only up-sell you. Of the above things, the most important factor is making sure engine timing is correctly set (would correlate most with your timing belt install). In the TDI timing graph, your engine timing should be set above the middle (blue) line, preferably in the middle between the blue and green (upper) line. This website below shows a great example of this.
The basic premise of this graph is advanced or retarded timing. Where the two lines meet on this graph would be an example of advanced timing. If the lines met below the blue line and more closer towards the red line, this would be an example of retarded timing. A detailed explanation of why this is important will be discussed further. Explanations and details aside, advanced timing is where engine timing should be; especially on a car burning WVO. This graph is a great example of where your cars engine timing should be.
One cannot expect to start burning WVO with a car on borrowed time and be successful. One also cannot blame WVO on the destruction of an engine that was already hurting from the start. I will mention “the idiot factor” many times in this guide. This is where it applies greatly. Do yourselves the favor and start off at an advantage with a perfectly running, well maintained vehicle. Do not blame WVO as a reason for YOUR IDIOCY.
Other than the obvious benefits of starting off with a fine running vehicle, you are able to make comparisons. If you pay attention to your engine you can prevent catastrophic engine damage. For example, if your car was not smoking prior to a vegetable oil conversion and it is now, you should expect either a coked up intake manifold (engine not breathing properly) or coked up injectors (compromised injector spray pattern and atomization). Another example of this case would be burning oil or smelling oil on startup. If this was not the case prior to conversion, one should understand that something had happened while burning WVO to cause this. Probable causes is coking of the oil piston rings. Be smart, be cautious and always pay attention! This is critical to long term success. Understand that if any problem is left unfixed, burning WVO will exacerbate this problem and accelerate it to an engines almost certain demise. It is a slippery slope…. know this and respect it!

T'sTDI January 12th, 2010 12:13

Congrats Your Ready for the Conversion
Congrats your ready for the Conversion

At this point, you are chomping at the bit to start burning WVO and doing so successfully. There are many options out there to decide from, so many that will make your head swim. I will discuss the three approved kits. They are kits that come with all the parts and assemblies for you to install it on your car. Note: I said YOU install on your car. I will stick to Greasecar, Frybrid and Elsbett. I will discuss the advantages/ disadvantages of all three. My experience has only been with the Greasecar kit; however, I know enough to comment on all three and understand the most important aspects of a kit.

Two tank conversion kits include Greasecar and Frybrid, let’s look at the mandatory requirements of a two tank conversion.

2 Three Port Switchover Valves-
Two three port valves ensure very little to no cross contamination occurring between fuels (WVO and diesel). This is the art of the two tank kit. Having 2 three port valves keeps the WVO out of the main diesel tank. Now a little bit of cross contamination will occur, but it is negligible at best if you follow purging requirements. The art of a two tank is to start on 100% diesel and to stop on 100% diesel. Keep it that way, purge correctly and for enough time. You should also drive on diesel long enough to purge not only the WVO supply line, but the injection pump, injector lines, injectors and the combustion chamber. Let that TDI rip, they are fun to drive, USE IT. The six port Pollack valve that was used on some kits is not on the approved list for a two tank kit. The six port Pollack, although simplifies fuel line hose routing, has been known to fail and has no means of preventing cross contamination. STAY AWAY from it… remembering that the art of a two tank is to start on 100% diesel and to stop on 100% diesel. The six port Pollock was commonly found on Golden Fuel systems and Greasel conversions. Plantdrive also offers a six port Pollock available on their website for sale. A six port Pollock valve means almost certain death to any diesel engine if it is used… (Two- Three Port Valves Mounted)

Heated Fuel Filter-
The filter must be heated because this is the first source of supply WVO when switchover occurs. The idea is to keep everything heated and to not send cold WVO (molasses) to your pump when you switch to WVO. This should be the last stop for your WVO before it hits the injection pump. A lot of people like to put a vegtherm in between the heated filter and the injection pump because this part of the hose is not heated. I like the idea based on that fact; however, I do not like the idea that electric heat is unregulated. Since electric heat is unregulated and the vegtherm itself is a metal piece, polymerization of the oil could possibly build up in this spot over time (through continued heating of the WVO and consequential cooling through use of purging with diesel fuel). This theory has not been proven; however, if this was to occur, this would allow unfiltered polymerized pieces of WVO to be sent to your injection pump. I know if a filter is the last stop before hitting the injection pump, I don’t have to worry about this. Lucky for us, there is a more effective way of heating the oil that avoids this completely. Injection line heaters… this will be explained later.

HIH vs. HOH-
Both of these kits offer HIH (hose in hose). Let me explain what that means. HIH (hose in hose) means the supply WVO line from the tank in your trunk is submerged in a coolant line that goes back to the tank for the heat exchanger coil. As the car warms up, the entire supply line (usually PEX) sits in heated coolant, thus providing a great heat exchanger. HOH (hose on hose) means the coolant that goes to the tank for the heat exchanger coil in the tank sits on top of, or as close as possible to the WVO supply line, thus not a very good heat exchanger. The advantages of this are you will never run into cross contamination of coolant into your fuel. However, in my research, it is extremely rare to hear of PEX line breaking down to where coolant contamination of the fuel would occur. If this was to happen, chances are the PEX line was kinked during the install and therefore weakened. HIH is the best way to go because this is one of the best heat exchangers available. Using HIH and a FPHE, my oil is ready to be injected when the engine reaches operating temperature even in the winter. You can’t ask for anything better than this.

Fuel Level Gauge-
This is pretty obvious. You always want to know how much WVO you have in the secondary tank. (WVO Gauges) (Another View)

FPHE (flat plate heat exchanger) is another effective means of final heating the WVO before injection. Unfortunately for Greasecar, it is an optional item, but should be standardized and is highly recommended on the TDI. Frybrid makes this a standard part of their kit. Not only will a FPHE heat the oil extremely well, it will regulate it at that temperature. With a FPHE, unless your in the extreme dead of winter (20 deg and below), typically once you reach operating temperature your very close to being able to inject the oil and start burning it. and Heated Filter)

Heated Tank-
Both kits come with a 13-15 gallon secondary tank that replaces your spare wheel in your tank (can also opt for a square tank if you don’t want to remove your spare). The 13-15 gallon tank comes equipped with a coolant exchanger (typically a copper coil). Some people say this can get the oil too hot and can cause polymerization of the coil and the oil. Polymerization is caused by oil being exposed to extreme heat and air/ agitation. I can not comment on this so far as we checked our coil on our Powerstroke after 22k WVO miles and it was spotless. People have reported problems with excessive polymerization at or around 100k of WVO use. Signs of this would be changing the WVO filter more frequently then what is expected. The basic idea behind a heated tank is to heat the oil enough to flow, not to heat to injection temperature. People have looked into a third valve that cuts coolant supply off to the WVO tank to prevent excessive heating and therefore consequential polymerization. Although a great idea, I have not done this myself. What I do try to do is to keep my tank over half full at all times. This limits the amount of air available in the tank and therefore room for the WVO to move. Also keeping the tank half way filled up will prevent the coil from being exposed to air and thus, avoiding this problem entirely.

These are the basics of the kit that are mandatory. Frybrid and Greasecar also supply all the fittings and valves to make this all work. Both of these kits have what I like to call “flashy items.” Frybrid offers an LED panel that shows what fuel you’re on. Greasecar supplies an optional handheld computer device that purges for you at the push of a button and also tells your coolant temperature. In my opinion, all this does is make the kit complicated. I have a simple switch that I flip and I always know that if the switch is flipped a certain way; I am on a certain fuel. Computers are much more prone to fail. These kits have a fail safe to default to diesel fuel if anything goes wrong; however, I abide by the KISS method (keep it simple stupid). Also, you are much less conspicuous with just a switch on your dash. If you get pulled over or have friends in the car, be prepared to explain that you burn WVO. Enjoy explaining that to the cops! (WVO/Diesel Switch)

With only a kit installed on your car, you’re accepting a bare minimum means of injecting WVO in your TDI with little or no modifications made to the car to do so properly. (Greasecar Kit Installed Properly) (Close Up) (Entire Engine Bay)

T'sTDI January 12th, 2010 12:15

Fallacy and Elsbett Conversion
The kits provided above do not provide the means of burning WVO for the long term. Modifications are a MUST to a TDI engine to ensure the utmost confidence in long term success. This information is not released to you, they run a business, they sell a kit, and it works, but not for the long term.

There are people on this forum and other forums that have burned WVO successfully for over 100k with just a bare minimum kit that I described above. I am amazed by this personally. My thought process on this was as follows, “If I can do more than the minimum that is only giving me a better opportunity at success.” I will leave that choice to you, a bare minimum kit and the above directions will get you a car that runs WVO. Personally if I was to go that route, I would have NO confidence in the long term.

This guide is written as a means to go “above the call of duty.” That’s what I did and that’s what I am writing this guide to describe. The choice all rests with you.

The Fallacy stated above flows into the next manufactures kit, Elsbett. Elsbett is a German company who designs VO kits with much success. Take note that I said VO and VO only. Even though people burn WVO with an Elsbett kit, Elsbett only warranties the kit for use with pure, virgin oil. Good luck with honoring the warranty if anything goes wrong, I’m just stating the facts. Elsbett’s design is unique in two different ways compared to the above other kits:
1. Elsbett is a single tank conversion (pour in your main tank)
2. Elsbett addresses more than just a kit, they address atomization and combustion

The components of an Elsbett kit include the following:
Injector Nozzles ß address atomization and combustion
Glow plugs ß address atomization and combustion
Coolant heat Exchanger (similar to a FPHE)
Electric Filter heater
Fuel Lines and Fittings
Oil Temp Sender

As far as I know, the injectors are supplied with a different nozzle that has a different spray pattern compared to the ordinary TDI nozzle. I have to take their word on this as there is very little scholarship regarding the nozzle. Obviously, this seems to be a trade secret so they would hide this pretty well. The second step is they increase the popping pressures of the nozzles by roughly 10 bar. The popping pressures in injectors have to do with how much pressure is needed to “pop” the injectors and allow them to spray into the combustion chamber. This would increase stress on the injection pump, but would cause better atomization of a thicker fuel due to higher pressures.

For what it’s worth, injector nozzles should be pop tested roughly every 100k even on diesel fuel. It is not too common because diesel fuel is very thin and you can get away with a nozzle not popping adequately; however, on WVO this is a different story. Popping pressures need to be the same across all four nozzles to ensure adequate atomization for combustion and burning properties.

Since the Elsbett kit is a single tank conversion, you pour the oil directly into your main tank. The advantage of this is you never have to wait to flip a switch, you are always burning VO. As much as this is an advantage, this is a huge disadvantage. Because you are always burning VO, you are also burning VO on startup when the engine has yet to reach operating temperature. Piston rings have not expanded, the combustion chamber is cold and the VO is not heated at all. Good luck to you trying to atomize this properly. People have reported that the extended glow plug length time will help this. To make this as simple as possible, if your car is not smoking out the exhaust pipe on startup, you are acquiring a complete burn (or as complete as the engine design will allow). However, this does not change the fact that you are starting on cold oil on a cold engine. This scenario is what causes piston ring coking, injector nozzle coking, contamination of engine oil and stress on every fuel system component. Cold oil is like molasses and your injection pump is forced to pressurize molasses to be injected into the tiny orifices of the nozzles. CAN YOU SAY STRESS???

Other aspect of the Elsbett system is you need to blend different fuels (diesel, kerosene) when the weather gets cold. On the contrary, when the weather is hot, it is much more possible to run close to 100% VO. You have to pay close attention to combustion and smoking. If this is occurring, your percentage blend of VO to diesel is too high.

Interestingly enough, Elsbett has had great success over the years they have been in business and have been in business for the longest.

No kit in America addresses combustion related issues in the direct injected diesel engine. Elsbett, a German company, is the only company to address issues related to combustion. Coincidentally, they are the one manufacture with the most amount of long term success….

Hmmm…. Can you put two and two together???

T'sTDI January 12th, 2010 12:15

Why Do I Recommend the Two-Tank Conversion?
Why do I still recommend the two tank conversion?
Even though the “Americanized Two Tank conversion” does not address issues of combusting and atomizing a thicker fuel, its benefits are numerous. The greatest benefit is you get to control when and where you want to burn WVO. This is an advantage as well as a disadvantage. I use it to my advantage in strictly keeping my WVO burning to the highway only. Not only that, if traffic conditions become undesirable, I can purge and get back on diesel fuel. This is a disadvantage because the “idiot factor” comes into play. The “idiot factor” is the elements that only the user can control. There is a certain amount of greed and freedom that comes into play when having a “free fuel switch” at your hands at all times. The very first instance in which you push the limits of WVO burning theory (more on this later) you are pushing the envelope into what is considered relatively safe WVO burning. For example, not waiting till operating temperature, not waiting until WVO temperature, not purging long enough or not driving long enough on diesel before you reach your desired location are all aspects of greedy WVO use. This can be eliminated, and created with a two tank conversion, be careful…

The other advantages with the two tank conversion is if you run the kit properly and adhere to the directions of running a kit, you will consistently start and stop on 100% diesel. Starting and stopping on 100% diesel eliminates the undesirable effects of incomplete combustion of WVO/VO. Thus, you eliminate piston ring coking (cylinder wall scaring), injector nozzle coking, and motor oil contamination which are most prevalent at startup.

It is entirely possible for us to replicate the desired combustion effects with Elsbett and the desired aspects of a two tank conversion. We can achieve the best of both worlds. To understand how to do this, one must understand that not all diesels are similar.

T'sTDI January 12th, 2010 12:16

Everything below gets complicated if you don’t understand a TDI engine or engines in general; however, it is all VERY important and MUST be understood.

T'sTDI January 12th, 2010 12:17

Not all Diesels are Similar...
Not all diesels are similar…

Diesel engines have different means of injection and injection pressures that make them widely different from engine to engine. You must understand that IDI engines are less prone to failure compared to DI engines and the reasons why. So whats IDI and DI? IDI stands for indirect injection in which fuel is delivered into a pre-chamber before it reaches the main combustion chamber. Combustion starts in this pre-chamber and eventually reaches the main combustion event. This is beneficial to those who burn WVO because it allows more time for atomization and therefore a better opportunity at a complete burn for a fuel that is slower burning then diesel. IDI engines are based on a fuel/air mixture based off of fast moving air, slow moving fuel in an engine. Thus, the injectors are not as complicated as a TDI’s and can run lower fuel pressures.

IDI’s are a very good engine of choice for burning WVO for the above reasons. Longer time for combustion is great advantage. Less fuel pressure means less stress on the injection pump and because the pressures are less, IDI injection pumps are not built to as tight tolerances as a TDI pump. IDI’s drawbacks are obviously an old technology found in an older car. If you’re a person of comfort or want to look good in a car, chances are an 86 VW or an 80’s model Mercedes isn’t the most attractive option. Having airbags and anti-lock brakes are also nice amenities to have.

DI stands for direct injection, which is also where the TDI derives its name from (turbo direct injection). DI engines are based on slow moving air and fast moving fuel. Direct injection means the fuel is sprayed directly in the main combustion chamber; there is no pre-chamber, unlike an IDI engine. Fuel pressures are much greater and design tolerances are stricter. Injection pumps are built to tight tolerances and standards in which there is very little leeway for error. The injectors of a TDI engine have two stages of injection in which two spring pressures must be met before the injector “pops” or injects fuel. The first injection is called the “pilot injection” in which a small quantity amount of fuel is injected to raise cylinder pressure. The increase of cylinder pressure allows for a more complete burn when the main combustion event occurs. Pilot injection occurs when the first spring pressure has been met of roughly 190-220 bar. The second injection is called “main injection” in which the second spring pressure of roughly 300 bar is met and the injector needle is lifted that much further to allow fuel to be injected. In a DI engine, the most sophisticated part of the engine is its fuel system and in the case of WVO, is what we are trying to risk the most.

This website shows the basic combustion event of a DI diesel engine. Understand how it works to get a better understanding of what I will be explaining further into this guide.

DI engines can achieve adequate burn without the use of a pre-chamber through extremely high fuel pressures. In comparison to an IDI engine which runs fuel pressures anywhere from 1400 to 1700 psi (threshold pressure to “pop” the injectors) a DI engine runs fuel pressures in excess of 23,000 psi. Remember the IDI vs. DI principle is entirely different. IDI principles are based on fast moving air and slow moving fuel. DI principles are based on slow moving air and fast moving fuel. It is clearly evident that 1700 psi vs. 23,000 psi of fuel pressure is a tremendous difference worth being noted.

Since we are using WVO as a fuel, we are risking the most important aspect of the TDI engine, the intricacies of the fuel system. Since the TDI engine is entirely based on the principles of the DI engine above, if this principle (slow moving air, fast moving fuel) is not met, the engine will not run at its designed capability. If the fuel is not being atomized properly by standards of which the DI engine calls for, incomplete combustion will occur. Understand these differences. Fast moving fuel means atomized properly for combustion and timed in the correct fashion for optimal combustion efficiency. If either of these is not met, problems will occur. The TDI engine gives us problems with both of these factors.
This website further explains the differences between IDI and DI and has pictures describing both. This website is a great reference on vegetable oil burning theory.

T'sTDI January 12th, 2010 12:18

Let the Problem Discussion Begin...
Let the Problem Discussion Begin…

EGR- Exhaust Gas Recirculation- EGR has been a popular emissions device on gasoline engines for a long time but arguably has been a disaster on the diesel engine. Problems caused with EGR equipped on diesels are intake clogging with soot and clogged turbochargers. This results in poor performance and poor fuel economy. The reason why intake clogging occurs is because diesel engines were manufactured from the factory with EGR’s before the introduction of ULSD (ultra low sulfur diesel). Sulfur laden diesel fuel that for the longest time was considered to be a lubricant for a diesels fuel system, causes particulate matter emissions. The easiest way to eliminate this was to take the sulfur out of diesel. Even with the reduction of sulfur in diesel fuel, it still seems that intake clogging continues to be a problem with diesel engines due to particulate matter accumulating over time. Even with ULSD, diesels equipped with EGR’s tend to still have the above listed problems.

So why does this apply to us?
Running a fully functional EGR system on a car that runs on WVO is asking for clogged intakes. The problem with WVO is polymerization. Polymerization of WVO basically turns into a hard carbon. If you are familiar with deep fryers or own one currently, the hard carbon deposits on the rim and the outside of a fryer is the result of polymerization. Polymerization is a result of hot oil coming into contact with cool surface temperatures.

T'sTDI January 12th, 2010 12:18

In-depth look into Polymerzation
In-depth look into Polymerization

The easiest way to explain this is the hot pan analogy. If you were to take a pan with a small amount of oil in it and set the stove to high you will be able to observe this process. The oil heats up with the pan but there are cold spots present around the lip of the frying pan. Once the pan reaches 300-350 degrees Fahrenheit, the oil itself will start to smoke (designation of burning). Applying more heat and allowing this process to continue, the oil will eventually burn to the pan in the form of carbon or splatter to relative cold spots and polymerize. This is easy to see at any fast food restaurant. In fact, I have cleaned my fair share of clumpy, moldy, oil laden fryer baskets and hard carbonized fryer filters. It is a result of hot oil coming into contact with relative cold spots, or oil that is continually heated to the object in which it eventually will burn to. Have you ever observed the underneath of a fryer station where they filter the oil on a daily basis? Have you observed the waste oil barrel at fast food restaurants? The moldy clumps and hard carbon deposits are a result of polymerization. This is what occurs in your intake manifold with a fully functional EGR while burning WVO.
Now, take that same hot pan, do not introduce oil to the pan, and heat the pan surface to 600-650 deg. (who knows if you can actually do this, I don’t expect this experiment to be done its just for explanation purposes). There are two points of interest here, the flash point and fire point. “Oil reaches its flash point at about 600°F when tiny wisps of fire begin to leap from its surface. If the oil is heated to its fire point 700° F, for most oils, its surface will start vaporizing and spontaneously ignite, surging up and out almost instantly.” Reaching these temperatures results in no opportunity for polymerization because the oil reaches its fire point, or for our purposes, the combustion point.

T'sTDI January 12th, 2010 12:19

The Basic Vegetable Oil Burning Theory
The Basic Vegetable Oil Burning Theory

Reaching this temperature results in no polymerization, just ignition of the oil (fuel) itself. This is the basic theory on why burning vegetable oils is possible. Although these fuel temperatures can’t be achieved through the use of a WVO kit, it can be achieved in the combustion event thanks to diesel compression ratio, boost pressures and cylinder pressures. All of these factors combine to raise the temperature beyond the ignition temperature of vegetable oil.
The only scientific data with thorough analysis of vegetable oil burning properties is the ACREVO study (advanced combustion research for energy from vegetable oils). In this study, pure rapeseed oil (virgin VO) was used, unlike WVO. The objective of the study was to observe the burning characteristics of vegetable oil droplets under high temperature and pressures. The complete study can be found here:

According to this study, “Atomization tests showed that at 150°C the performance of the rapeseed oil are comparable with that of the diesel oil.”
150°C equates to 302°F which is impossible to achieve through heat derived from a WVO kit alone. However, there are two parts to this equation and further reading results in the following information.
The overall combustion performance of the rapeseed oil is very satisfactory in comparison with the diesel fuel while the rapeseed oil produces almost 40 % less soot than diesel fuel. The different volatility of this fuel respect to the diesel fuel is responsible of the different behavior of the sampled gas concentrations in the base of the flames while at the end of the flames, both attain almost the same values. It has been established that an addition of 9 % of ethyl alcohol (95 %) bring a great benefit regarding the pre-heating oil temperature. In fact, the presence of alcohol allows a reduction in the inlet oil temperature from 150 °C to 80 °C. Moreover, the combustion of the emulsion produces less soot and, at the exhaust, the amount is almost one half less than that produced by the combustion of rapeseed oil.”
Amazingly a small amount of ethyl alcohol (ethanol) of 9% by volume of vegetable oil resulted in a required pre- inlet combustion temperature from 150°C to 80°C or 176°F. 176°F represents the typical fuel temperature achieved through heat of the WVO kit. Using a Greasecar kit, a 9% volume amount would equate to 1.17 gallons of ethanol to 11.83 gallons of WVO for a total of 13 gallons.
I DO NOT recommend adding ethanol to your VO mix but understand the chemistry of what is occurring. Ethanol is measured by octane, not cetane. Octane and diesel engines DO NOT MIX and should never be attempted. If you have ever mixed gasoline in your diesel tank, you would know this… Quite frankly, I doubt anyone who “splash mixes” fuels is doing much more than hoping for the best. However, understand the chemistry that caused the tremendous drop in pre-inlet temperature of the fuel before combustion. An inherently thin fuel that is much more volatile than vegetable was to be mixed with a thicker fuel oil. When introduced to the combustion chamber, the ethanol in small particle amounts is the first to ignite which becomes a catalyst for the entire mixture of vegetable oil to ignite more thoroughly. This causes the pre-inlet temperature to be much lower than if we were running 100% rapeseed oil.

Two things of interest here:
Pure virgin vegetable oil is thicker than waste vegetable oil and therefore will require more heat to achieve the adequate viscosity for combustion than waste vegetable oil.

In a two tank setup, small quantities of diesel fuel are sent back to the WVO tank in the purge cycle which is achieving the above scenario (thinner fuel mixed with a thicker fuel).

Diesel fuel is not as volatile as ethanol is; however, you’re achieving the same principle behind introducing other fuels to thin the WVO mixture out. Therefore, there is a less need for extreme amounts of heat to achieve the same viscosity of diesel fuel.
I do not blend fuels with my two tank setup, although I have greatly considered it. My recommendation if you feel you’re not getting your oil up to temperature (even with the FPHE and heated injection lines) would be to splash mix a gallon of kerosene or diesel in your WVO tank. Kerosene is known for its extreme thinning properties and would be an effective way of lowering the viscosity requirements of WVO for combustion.
My experience has shown this is not required as I have always had plenty of power and similar fuel economy compared to diesel fuel. However, the science behind it proves me wrong. Let it be known, there have been diligent people who have operated their WVO kit in the correct fashion and have had plenty of long term success.

T'sTDI January 12th, 2010 12:20

Your Worst Enemy, EGR
Your worst enemy, EGR

So the most important part to take away from this lesson is hot oil that has not reached its flash/fire point that comes into contact with relatively cool surfaces will start to form carbon (polymerization). EGR is your worst enemy!!! Exhaust gas recirculation involves combustion gases that did not combust (un-combusted tiny WVO particle matter) to be re-circulated through the intake tract (relatively cool surface of the engine) and then to be combusted again. So in the process of this emissions device, the tiny molecules of WVO are being subject to the cooler surface temperatures of the intake manifold and intake valves. Intake temperatures on an engine that has reached operating temperature range anywhere from 120 to 200 deg. None of these temperatures are close to the flash point of vegetable oil and thus, creates the perfect environment for coking, polymerization, clogged up intake manifolds and intake valves. Go back to the example, hot oil on cool surfaces… recipe for disaster.
An interesting theory to note, older IDI engines are more prone to success. None of these are equipped with EGR systems.
EGR is the culprit to many WVO engine failures. It becomes a slippery slope. The more clogged your intake becomes, the less power you have available and the less fresh air you have coming into the combustion chamber. Air flow and boost pressures operate primarily on MAF input and load only. Intake restrictions cannot be compensated for with less fueling. It will continue to burn the same amount of fuel in which the fuel map specifies for (requested/actual injected quantity). So look at the scenario we have. We have a clogging intake which is more susceptible to more clogging due to the process already being started and we have continued decreases in combustion efficiency. The engine is receiving less and less air (being choked) and is still injecting the same amount of fuel. This will eventually cause decreases in performance, fuel economy and excessive smoking. All of which will exacerbate the intake clogging problem.

Primary problem #1 Coking of intake manifolds, and intake valves with polymerized vegetable oil.

Primary Solve- Reduce the EGR duty cycle through use of VAG COM or eliminate it all together (my recommendation). EGR causes way too many problems on a diesel engine that burns vegetable oil. Elimination of the EGR will cause a check engine light; however, I think it is very evident to see that the benefits of eliminating the EGR exceed the drawbacks of a yellow light. A CEL can also be eliminated through tuning.

Primary considerations- If you delete your EGR, your check engine light will be on all the time and will not go away unless you get your car chipped. Also if your state requires emission testing for diesels, there may be a problem in eliminating the system all together. Your best bet would be to reduce the EGR duty cycle to its minimum and then change it back to stock before testing. I do not have to worry about this as Maryland does not require emission testing for diesels. If you reduce the duty cycle and do not eliminate it all together, you probably should check your intake every so often, maybe every year to year and a half. This is why eliminating it all together makes everything much simpler and easier.

Here is an example of EGR at its best while running WVO. This is what will happen if combustion efficiency is poor and EGR is fully functional.

Scrolling down to picture 4, 5, and 6, you see the signs of a car with poor combustion efficiency while running on WVO and having EGR fully functional. Observe the buildup behind the intake valves (valve stem). Remember the thread about polymerization and relatively cool surfaces?

Observe the polymerization on the bottom of the exhaust valve (the flat surface, not the stem). The exhaust valve is the one without the polymerization buildup on the stem of the valve. Un-combusted WVO gases were coming into contact with relative cool surface temperatures in the combustion chamber. Also note, any type of carbon deposit in the form of polymerization on an exhaust valve is proof that combustion efficiency was quite poor to say the least. If that isn’t enough proof, the intake valve stems show exactly what happens when polymerization occurs in a diesel engine due to burning WVO with EGR.

So if you want to run your EGR while burning WVO, you better be absolutely certain that combustion efficiency is at its peak in all instances. If you’re cars air to fuel ratio while burning WVO is leaning towards rich, this is what very well can occur. I did myself the favor and avoided this in its entirety.

T'sTDI January 12th, 2010 12:21

The Next Problem: Fuel Temperature and Engine Timing
The next problem: Fuel Temperature and Engine Timing

The next friendly adversary on the TDI engine is the fact that engine timing is mapped with fuel temperature. The reason why the TDI engine is so efficient is due to the intricacies of the fuel system. The one component of interest is the fuel temperature sensor. For explanation reasons, let’s assume we are talking strictly of diesel in the next two paragraphs.
Timing is adjusted with hotter and cooler fuels. Upon startup, which should be 100% diesel fuel, the fuel is cold and therefore quite dense. Density will change for liquids under two scenarios, temperature and pressure. The ECU senses the cold fuel, injects less fuel and advances the timing to compensate (you can actually hear this upon startup with slightly higher pitched ticking initially until it goes away). The reason why the ECU injects less fuel is there is a preset injected quantity amount the ECU abides by. To achieve the same mass of fuel to meet actual vs. requested injected quantity, the ECU must inject less. The reason for the advanced timing is because the fuel is denser (cold) and therefore has more mass. A denser fuel is less prone to combust. To combat this lower cetane, (not readily wanting to combust) advancing timing will help combust an inherently denser fuel by allowing more time for the fuel to atomize in the combustion chamber before it is compressed.

The exact opposite is the case for hotter fuels. When the fuel is hot (operating temperature) the fuel is less dense (hot) and therefore the ECU will compensate for a less dense fuel by injecting more. The ECU injects more fuel to match the actual vs. requested injected quantity. The reason for retarded timing is hotter diesel fuel has a higher cetane value. Higher cetane means the fuel is easily ready to combust. Therefore, the fuel does not require as long in the combustion chamber to combust fully; therefore, advancing timing is unnecessary strain. A less dense fuel is more prone to combust and therefore will combust and atomize much easier.

Understand that even though more or less fuel is injected depending on temperature, the mass of the fuel injected is the same in all circumstances.

What does that mean to the VO community?
It means we have a problem!!! Not only do we have a fuel (WVO) that is not readily to combust (low cetane, high dense fuel) we have a HOT fuel that is still WAY TOO DENSE!!!

According to the graph that Frybrid developed that charts fuel viscosity vs. temperature, even at 160 deg, the WVO is anywhere from 10-15 centistokes more viscous than diesel at that of 0 deg C.

So what does the ECU do? The ECU senses the hotter fuel and retards timing because it thinks we are burning diesel fuel; however, we are burning WVO. So the ECU sees the hotter fuel (WVO) and retards timing even though the WVO is still denser then diesel at that temperature (185 deg). Remember the ECU’s only means of measuring mass is that of temperature of the fuel, it has no way of knowing that even at 160-180 deg, WVO is still thicker than diesel fuel because it has no way of knowing we are burning WVO. Logical sense tells us that engine timing can not be retarded with WVO because the thicker fuel needs more time in the combustion chamber to combust fully due to its lower cetane.
This originally was the one reason why I wouldn’t convert my vehicle because I thought there was no way around this. Until I found the fuel temp resistor modification that another TDIclub member introduced to me. This modification calls for the use of a resistor to be placed inline of the fuel temperature sender signal wire to fool the ECU’s reading of fuel temperature being sent from the sensor to the ECU. Fuel Resistor Modification
This modification causes your ECU to read fuel temperatures on WVO to read no higher than 20 deg C. On a cold engine, my fuel temps read 15 deg and on an engine that is at operating temperature, it read 20 deg C. These readings were taken during the summer time. This caused my fuel temp readings to drop from the true 85 deg C (185 deg F) to 20 deg C (68 deg F). Observations on WVO through VAG COM (see thread)

T'sTDI January 12th, 2010 12:21

What Have We Accomplished?
What have we accomplished??

We have fooled the ECU by eliminating the process of retarding timing for a higher temperature fuel (less dense but in the case of WVO untrue) and at the same time, we are injecting 185 degree WVO at a timing degree amount of diesel fuel at 68 degrees. We accomplished the best case scenario for burning vegetable oil in a TDI. Without this modification, your ECU views the fuel your burning (WVO) as a fuel with very little density (thin) and therefore to compensate, retards timing. WVO even heated is still more dense then diesel fuel and would require advanced timing to achieve adequate combustion efficiency.

Retarded timing causes less time for the WVO (an inherently thicker fuel of lower cetane value which is not prone to combust easily) to combust. Combustion efficiency would be sacrificed due to this and therefore, a complete burn would not be possible. Incomplete burn = tiny molecules of WVO that love to polymerize and coke on relative cool spots in the combustion chamber. You guessed it, a major problem. Relative cool spots in the combustion chamber include tips of the injector nozzle’s and glow plugs. This is why people say to pull your glow plugs and observe the tips for any WVO residue. If there is WVO residue present, chances are you got a problem due to incomplete combustion of WVO. If polymerization is occurring on injector nozzle tips, this is a major problem. Coking of nozzle orifices (the holes in the nozzle) results in poor atomization. Remember, WVO has a low cetane value and therefore, not readily to combust. Injector nozzle orifices that are compromised would result in poorer atomization and therefore the opportunity for even less combustion efficiency. The worst case scenario would be coking to the point of injector streaming. Basically the injector would not be doing its job of atomizing the fuel and it would be dribbling fuel on a constant basis. This would cause the fuel to not combust fully and eventually would accumulate enough into burning a hole in the top of a piston.
And what if you were running an EGR while this was happening? The poor atomization would cause more WVO molecules being re-circulated through the intake tract and therefore more intake clogging. This would lead to less air available for combustion but fueling would stay the same. This means even less combustion efficiency and eventually, blowing up your engine. Understand what I mean when I say, the WVO burning process can be a very slippery slope; however, we can prevent this from happening.
This whole scenario above is strictly unique to the VW rotary TDI. I know for absolute certain is applies to the 99.5-03 TDI, any early ones or the PD engine, I am unsure of. My guess it would be different for the PD because it’s an entirely new fuel system and that the earlier TDI would have a similar process of injecting fuel beings it uses similar nozzles.

The resistor caused a CEL on my car that went away when I deleted it with a scanner. Much like the EGR argument made above, the benefits of the fuel resistor modification exceed the drawbacks of a CEL. I have deleted the CEL and it has never come back so it is not a reoccurring code like the EGR code is.

How this was discovered?

I figured this out using probably the best indicators of combustion efficiency out there, an EGT gauge (exhaust gas temperature). For those that don’t know, an EGT gauge measures the temperature of exhaust gases. Basically this is a measurement of the temperature of the byproducts of combustion. Incomplete combustion results in higher EGTs because more molecules of fuel are not being used as energy for combustion. More complete combustion results in lower EGT’s because all molecules of the fuel are being used strictly as energy for combustion. This can be applied to the power enhancement section of any diesel. The goal of a diesel tuner is to achieve a “grey haze” when a diesel is at WOT (wide open throttle). This means that the ratio of fuel to air is near perfect and thus, the most amount of power your car will make without further air modifications. A “black cloud” means over fueling, high EGT’s and poor combustion efficiency.
So lets apply this theory to that of burning WVO. Prior to the fuel temp resistor mod, I noticed that my EGT’s were running 50-100 deg hotter in situations where I would expect them to be much lower. I also noticed my car to not have as much “pep” when I got into the throttle (designation of retarded timing and not as complete of combustion). After the fuel temp resistor mod, my power came back and my EGT’s are the same.
I cannot stress the importance of the fuel temperature resistor modification enough. Burning WVO comes down to two things, atomization and combustion. These are two easy words to say, but hard to achieve when there are tons of variables that affect it. Timing is a direct related factor of combustion. Bottom line, retarded timing = a bad thing. Low cetane fuels (WVO) are less prone to combust and therefore need advanced timing to compensate, we just learned this above. The fuel temp resistor modification prevents the unwanted affects of retarded timing and returns timing to what a car would operate at 68 degree diesel fuel temps. Timing changes on a continual basis; however, my highway log of timing (requested vs. actual) never registered anything below 0 deg (ATDC after top dead center). The typical range was anywhere from .5 deg – 2.5 deg (BTDC before top dead center) through use of cruise control. This is what we want to achieve.

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