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Things you can do to get maximum engine life from a VO converted diesel.
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Originally posted by DCS:

quote:
I still more than ever believe coking is a greatly over hyped problem but I have found an example of it first hand. ( finally!!)
It was on a very well converted merc and I helped change the engine and saw the damage to the old one. I conversation with the owner, he felt the cause was changing over to oil too early, before the engine had fully warmed up.


A "well converted Merc", or any other vehicle, should have enough temp sensors to indicate proper safe switchover. Likely may have been the only gadget missing, but one of the most important ones.
 
Registered: September 26, 2005Reply With QuoteReport This Post
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enough temp sensors to indicate proper safe switchover

But the operator may choose to switch over at a lower indicated temperature. I've witnessed this attitude - "I do't need to wait for X degrees becasue it runs just fine when I switch over at Y degrees". The coking process doesn't change the way the engine sounds or runs, until it's progressed too far to do anything about. If in doubt, wait a bit longer before switching over.
 
Location: Moses Lake, WA, USA | Registered: August 15, 2001Reply With QuoteReport This Post
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Coking can be a problem.

I think it can be avoided with a suitable engine modifications, fuel quality, operating and maintenance regimes.

Scientific Papers which record coking -

Study 1

Study 2

Study 3

Study 4

Full Study Paper

Ive posted a lot of other information about using vegetable oil as a fuel - links to research studies and other information over at obed.org.uk




www.obed.org.uk Open Biofuel Engine Development - Collaborative biofuel engine tuning.
 
Location: UK | Registered: March 25, 2003Reply With QuoteReport This Post
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quote:
But the operator may choose to switch over at a lower indicated temperature.



Sure, but there's no substitute for knowledge & wisdom is there?
 
Registered: September 26, 2005Reply With QuoteReport This Post
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quote:
Originally posted by vegburner.co.uk:
Coking can be a problem.

I think it can be avoided with a suitable engine modifications, fuel quality, operating and maintenance regimes.

Scientific Papers which record coking -


Excellent post of research papers. The takeaway from reading the summaries of all the studies is that the one-liner proclamations spouted on forum pages ranging from the one extreme "don't worry just dump in the veggie, drive and be happy" to the other extreme "coking is inevitable, you're destroying your car and the rapture is nigh" are worthless.

There are just too many factors including but not limited to: type of veg fuel, quality of veg fuel, if blending with what and how much, engine design, design and use of engine modifications, engine condition (compression), fuel pump design, operating ambient temps, driving style - granny or maniac, car use -mostly city or highway, maintenance regimen and rigour.


83, 85 sd
 
Location: SoFlo | Registered: May 01, 2008Reply With QuoteReport This Post
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quote:
There are just too many factors including but not limited to: type of veg fuel, quality of veg fuel, if blending with what and how much, engine design, design and use of engine modifications, engine condition (compression), fuel pump design, operating ambient temps, driving style - granny or maniac, car use -mostly city or highway, maintenance regimen and rigour.

EXACTLY!!! Unfortunately most everyone wants cheap quick fixes and simple answers to complex problems. VO fuels are NOT for dummies.



 
Location: coldest N.America | Registered: May 03, 2005Reply With QuoteReport This Post



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Agreed..but even running a car on diesel is not for "dummies".

We have learned enough over the past decade however to allow nearly anyone with an average IQ and moderate mechanical skills to decide if VO fuel fits thier needs and situation, choose a vehicle that is a good conversion candidate, compute if a conversion is economically viable, and extract the maximum number of miles from a converted diesel engine.
The general rules to do each of the above are freely available and relativly simple to put into practice.



quote:
Originally posted by john galt:
quote:
There are just too many factors including but not limited to: type of veg fuel, quality of veg fuel, if blending with what and how much, engine design, design and use of engine modifications, engine condition (compression), fuel pump design, operating ambient temps, driving style - granny or maniac, car use -mostly city or highway, maintenance regimen and rigour.

EXACTLY!!! Unfortunately most everyone wants cheap quick fixes and simple answers to complex problems. VO fuels are NOT for dummies.
 
Location: Central MN..Brrrrrr! | Registered: November 06, 2001Reply With QuoteReport This Post
<DCS>
posted
quote:
Originally posted by welder:
Originally posted by DCS:

A "well converted Merc", or any other vehicle, should have enough temp sensors to indicate proper safe switchover. Likely may have been the only gadget missing, but one of the most important ones.


I have also said that I didn't think coolant temprature was the best or most accurate indicator of when an engine is fully and properly up to operating temp.

If I start my merc from cold, in a few minutes the HE becomes too hot to leave my hand on. The block itself however barely has become lukewarm.
Clearly the coolant in the head becomes hotter a lot faster than the block itself and most likely the oil as well.

People have argued with me that the combustion chambers come up to temp faster than anything else and are much hotter than the heat they dissipate out the other side into the water jacket and therefore once the coolant is hot, the engine is warm enough for safe change over.

I have had my reservations over this and as my friend was changing over when the temp gauge was at normal operating temp and he still suffered problems despite running a 20 and a 30 plate HE, my reservations have not been pacified.

I have always said I thought it was poor practice to be in any hurry change over and a few extra miles to allow the engine to heat sink properly was the best practice.
I have also come to believe that a W123 type Merc needs no conversion other than a change over valve to run WVO *-PROVIDING-* Changeover does not occur till the entire engine is fully and completely warmed to proper operating temp.

I have no doubts coking can occur, it's just that the actual examples do not warrant what used to be the endless and over the top incessant "It's about to fall on you like a ton of bricks at any second" Fear mongering warnings there used to be about it.
 
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I wouldn't run a Merc W123 without at least a heat exchanger.

It's not just the cylinders you have to worry about, it's the injection pump too. If it is getting cold oil, I don't think it's going to last long. It is a mechanical pump and has very tight tolerances and is not designed to pump thick viscous stuff like vegetable oil.

I've read that oil at 160F is about the same viscosity as diesel, so that is a good figure to aim for entering your IP.


Paul

1983 Mercedes 240D Single tank WVO - FPHE, Injector Line heaters, aux fuel pump. Water/Methanol Injection. Frantz bypass oil filter. - North Florida
 
Location: Fernandina Beach, Florida | Registered: March 29, 2006Reply With QuoteReport This Post
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quote:
People have argued with me that the combustion chambers come up to temp faster than anything else and are much hotter than the heat they dissipate out the other side into the water jacket and therefore once the coolant is hot, the engine is warm enough for safe change over.

I have had my reservations over this and as my friend was changing over when the temp gauge was at normal operating temp and he still suffered problems despite running a 20 and a 30 plate HE, my reservations have not been pacified.


I may have been one of those that argued this point with you...though I DO agree that being too quick to switch to VO is probably unwise. However there are several contributing factors to ring/land/groove coking other than Engine and VO temp that may have been responsible for your fiends ring/land/groove coking experience.

Formost among those contributing factors is injector condition and injection timing. If injection timing is significnatly off the fuel charge may not combust fully even in a fully warmed engine. Similarly if the injectors are not operting within spec uncombusted or partially combusted VO will be present in undesirable concentrations. While this is especially true for DI diesels it is also significant for IDI diesels like the MB your friend has.

Worn rings are also a significant factor in ring/land/groove coking since the safe switchover temp is actually when the pistons are warm enough to allow the compression rings to fully seal and contain the products of combustion above the upper rings. This occurrs some time before the coolant in the head reaches operating temp IMO but I would not argue against allowing the engine to warm a bit at full operating temp as I try to err on the side of caution when I have a choice.

quote:
I have also come to believe that a W123 type Merc needs no conversion other than a change over valve to run WVO *-PROVIDING-* Changeover does not occur till the entire engine is fully and completely warmed to proper operating temp.
This is something I would not agree with you on except in very specific and rare situations.

quote:
I have no doubts coking can occur, it's just that the actual examples do not warrant what used to be the endless and over the top incessant "It's about to fall on you like a ton of bricks at any second" Fear mongering warnings there used to be about it.


I do not recall ANYONE ever actually arguing this point. But I suppose it depends on ones POV. I DO recall some folks arguing that ring/land/groove coking was something no one had to worry about..ever. My POV is that if ones goal is to run VO as fuel yet not shorten the life of a diesel engine (compared to simply using petrodiesel) there are several considerations that must be given high priority and avoiding ring/land/groove coking is one of them.

Some of the erliest researchers in VO fuel use discovered that ring/land/groove and valve coking COULD occur very quickly if one simply subsituted VO for petrodiesel. The goal of the second wave of VO fuel researchers became eliminating this most obvious roadblock to practical use of VO fuel. It did not take long before we realized that simply heating the VO fuel to lower its viscosity was the single most generally effective way to lengthen the number of engine hours that could be accumulated before ring/land/groove coking became a significant problem in most applications.

However we also learned that this was not the ONLY factor and it was when these other factos began to be discussed that the perception of "fear mongering" became a side issue raised by some of the participants that changed an otherwise productive discussion into an eventually unproductive public argument. Perhaps we can agree that as long as the basic concepts of reducing viscosity via heating and allowing ones engine to fully warm are followed many useful miles can be obtained on VO fuel before significant coking damage of any kind will occur.

This message has been edited. Last edited by: danalinscott,
 
Location: Central MN..Brrrrrr! | Registered: November 06, 2001Reply With QuoteReport This Post
<DCS>
posted
quote:
Originally posted by danalinscott:
Perhaps we can agree that as long as the basic concepts of reducing viscosity via heating and allowing ones engine to fully warm are followed many useful miles can be obtained on VO fuel before significant coking damage of any kind will occur.


You use the Term " Will" occur.
You state it as a foregone conclusion that it is inevitable, which I do not agree with at all.

It is this sort of statement that pushes a single minded view with no possibility of any other outcome that is the basis for exactly what I was talking about.

When I think of it, there really only was one person pushing the Coking version of " the sky is falling" and their absence from these fori happened to co-incide with the hiatus of the coking warnings as well. I note that in that time, no one else seems to have had any troubles with this issue apart from the single case I cited.

Guess those of us that haven't been doing this over 2 decades or 6 years (whichever sounds more impressive or we want to deny at the time) just haven't had a chance to see the hundreds of examples ( none of which happened to be documented on the net) that those with more "Experience", real or imaginary, have. Roll Eyes

Exactly how long will the rest of us have to hang around to see enough of this happening so we too can form the same narrow opinions and forego any possibility of Veg used in the right manner may NOT cause engine damage??
 
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quote:
You use the Term " Will" occur.
You state it as a foregone conclusion that it is inevitable, which I do not agree with at all.


Actually that was not what I intended to convey and I don't think that most folks reading that would have chosen to believe I did.

However since you raise the issue I DO believe that most engines run on VO WILL EVENTUALLY be taken out of service due to ring coking or secondary damage caused by piston ring/land/groove coking. Please do not interpret this to mean that I think that fatal ring coking is "just around the next corner" for every VO fueled diesel. This is most definitely not what I believe. If you wish to offer counter opinion or rational argument please feel free to. It is discussions by those with opposing POVs that result in greater understanding of any subject.

quote:
Guess those of us that haven't been doing this over 2 decades or 6 years (whichever sounds more impressive or we want to deny at the time) just haven't had a chance to see the hundreds of examples ( none of which happened to be documented on the net) that those with more "Experience", real or imaginary, have.


I don't see how ad hominem attacks like this strengthen your argument that ring/land/groove coking is an extremely very rare ocurrence. But that has been the pattern whenever I have held a position in a discussion which is different than yours. In fact choosing to mount a personal attack rather than sticking to the subject at hand usually has the effect of weakening ones position.

quote:
Exactly how long will the rest of us have to hang around to see enough of this happening so we too can form the same narrow opinions and forego any possibility of Veg used in the right manner may NOT cause engine damage??


I guess that it doesn't really matter how long one "has been hanging around" if one is not activly LOOKING for evidence of this potential problem with VO fuel use. Anyone that devotes the time, effort, and funds to actually look for "ring coking" will find some evidence of it in most diesel engines with over 50K of VO fuel use. This should not be interpreted to mean that I believe that ANY engine with over 50K of VO fuel use is in imminent danger of catastrophic failure. Nor should it be interpreted to mean I believe that ANY diesel engine no matter how sloppy the conversion, operation, or maintenance can expect 50K before ring coking becomes a significant problem.

This is because:
The better the conversion and the the better the operation and maintenance regimen the more engine hours one can wring from any diesel engine run on VO fuel.
 
Location: Central MN..Brrrrrr! | Registered: November 06, 2001Reply With QuoteReport This Post



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http://resources.metapress.com/pdf-preview.axd?code=h43...714xu668&size=larger

Engine Test to Measure Injector Fouling with VO - Diesel blends

This message has been edited. Last edited by: john galt,



 
Location: coldest N.America | Registered: May 03, 2005Reply With QuoteReport This Post
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Like to add my cents.

Running a MB 240D manual on soybean WVO that is settled and centrifuged. Two tank system with electronic induction injector line heaters controlled at 105 celcius ( 210F)just before the injector. I use full throttle water injection as DCS (thanks DCS) has described it and the car has gotten noticeable more responsive.
After 5000 miles I heard some pinging and pulled the injectors and noticed 1/64" thick hard deposits that had to be scraped away. The center hole was clogged and spray pattern was not good.
The pintle moved freely and had no scratches or visible damage
The car still started fine but is seems to be wise to check the injectors once in a while.
I will make pictures and do a compression test to get some data.

Dana, do you have any lab test where the oil is preheated?

Everybody , this is all very good and help full info.

Later


240D, 300TD, pwrstroke, niva diesel, 73 vette, DS20, 77XJS,
 
Registered: May 03, 2008Reply With QuoteReport This Post
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After 5000 miles I heard some pinging and pulled the injectors and noticed 1/64" thick hard deposits that had to be scraped away. The center hole was clogged and spray pattern was not good.

How do you know the oil doesn't contain water?



 
Location: coldest N.America | Registered: May 03, 2005Reply With QuoteReport This Post
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Hi John

I do a crackle test. The oil comes directly from the fryer to me. Also this home build centrifuge is similar to the simple centrifuge design. Water is heavier then oil and it stays inside the centrifuge untill I have to clean it out.
It separates the waxy contents very well.


Here is a photo of a listeroid DI valve on WVO after 40 Hours. The WVO is heated before injector to 215 F

Later


240D, 300TD, pwrstroke, niva diesel, 73 vette, DS20, 77XJS,


ImageIMG_1267_1_1.JPG (45 Kb, 34 downloads) lister DI valve
 
Registered: May 03, 2008Reply With QuoteReport This Post
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quote:
Originally posted by joeblack5:
Hi John

I do a crackle test. The oil comes directly from the fryer to me. Also this home build centrifuge is similar to the simple centrifuge design. Water is heavier then oil and it stays inside the centrifuge untill I have to clean it out.




I suggest substituting the to Pan Test for the crackle test unless you have the lab equipment to actually DO the CT correctly. Depending on what type of centrifuge you are using, how it is operated, and how laden the oil is with suspended water it may or may do an adequate job of removing it.

quote:
Dana, do you have any lab test where the oil is preheated?


I don't understand the question. Can you be a bit more specific?

quote:
Here is a photo of a listeroid DI valve on WVO after 40 Hours. The WVO is heated before injector to 215 F


From the looks of that carbon accretion I suspect that you need to heat the WVO closer to 300F and/or change the injection timing a bit. You may also need to do something to raise the coolant temp a bit as well. DI diesels tend to be a lot more succeptible to coking generally than IDI diesels and therfore need a bit more tweaking to wring the maximum engine hours out of them without carbon/coking related problems.

Are you starting and warming the Listeroid on petro diesel prior to switching to VO?
 
Location: Central MN..Brrrrrr! | Registered: November 06, 2001Reply With QuoteReport This Post
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Dana,

I am sorry,

crackle test should be pan test, I thought it was the same but no.

The rapid engine test a couple of post earlier to support the carbon deposits showed several " cold" oils in a hot engine. Is there a similar "lab" test with those several oils that are pre-heated to several temperatures and show differences in carbon deposits.

These pictures were taken with cold engine start directly on soybean oil. So not good.
I am running ow on pure diesel to compare after 40 Hours of run time.
The image was more for readers who liked to see actual documentation of carbon build up on valves and injector with an incorrect conversion.

Later


240D, 300TD, pwrstroke, niva diesel, 73 vette, DS20, 77XJS,
 
Registered: May 03, 2008Reply With QuoteReport This Post



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here two more images of same lister DI with a second try and tear down after 30 H

Please let me know if I am of topic.

Later


240D, 300TD, pwrstroke, niva diesel, 73 vette, DS20, 77XJS,


ImageIMG_1309text_1_1.jpg (46 Kb, 35 downloads)
 
Registered: May 03, 2008Reply With QuoteReport This Post
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Sorry the other side did not came through.

Later


240D, 300TD, pwrstroke, niva diesel, 73 vette, DS20, 77XJS,


ImageIMG_1305text_1_1.jpg (45 Kb, 35 downloads)
 
Registered: May 03, 2008Reply With QuoteReport This Post
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