Causes of coking

Single Tank WVO systems and blending SVO WVO to thin it.

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Causes of coking

Postby denson » Sat Jun 07, 2008 5:32 pm

Do fats or PHO's cause coking? Any more or less than fresh VO?
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Postby 240Volvo » Sat Jun 07, 2008 8:47 pm

Any incompletely combusted fuel (including petro-diesel) can cause coking. Elements that contribute to coking include improper atomization of fuel, leaky injectors, low compression, and improper injection timing.

As Sunwizard has mentioned, animal fats have higher BTUs (more energy) than pure VO (andd similar viscosity issues with PHO). What is needed to avoid coking when using such fuels is heating them so that the are fluid enough to flow through the IP and be properly injected at the right time.
1984 Volvo 240 diesel with a single tank Elsbett conversion: electric fuel filter heater, FPHE, glow plugs, and injectors. Also injector line heaters and block heater, running 20%kero/80%WVO winter blend.
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Postby coachgeo » Sat Jun 07, 2008 10:21 pm

Everything 240Volvo says is true as far as I know. (Which is not saying much)

Other things to consider is when is a normal engine most likely to produce the potential to build up a little coking.

Cold start of the engine from what I have read is the number one.

Thus one has to consider that unless your engine is precicely tuned for WVO fuels etc. then this cold start point will produce even more coking than if the engine was running diesel as designed.

What are other times a diesel engine is more liable to coke up?

Some I've read about are

Low to No load operating (idle) engine
Constant RPM


Any others?
Last edited by coachgeo on Mon Jun 09, 2008 8:15 am, edited 1 time in total.
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Postby David » Mon Jun 09, 2008 7:52 am

I have Said it before ( many times) and I'll keep on saying it till someone can prove me wrong with real and creditable evidence....

The warnings about coking far outweigh the actual evidence of it happening in real world WVO use in Vehicles.

And before anyone starts in on me over that statement, please read it properly for what it says and not twist it with your interpretations is and don't bother quoting old lab tests on stationary engines or the forum posts about some idiot amateur mechanics that coked up a TDI and ruined a new turbo in a week because they were morons, not because of anything to do with WVO.

Coking can occur but the reality is, despite a lengthy argument I had with the know it all god of coking gloom and doom, no one has yet been able to show or tell me of one single first hand evidence of coking in a vehicle engine caused by WVO.

There are many things that can cause coking and the established WVO fuel practices should not be ignored however the fear and warnings of coking caused by running WVO is in no way supported by any evidence of it actually happening.

I have no idea why coking is so endlessly warned of and worried about when the reality of it is that evidence of it actually happening is virtually impossible to find.
It also seems that water injection hugely reduces the likelihood of coking occouring and I believe there is a very strong chance that it can remove and reverse the effects on engines that may already have it.

I suggest that before anyone loose sleep over the biggest worry in veg oil use that they try to put it into perspective by going and looking up instances where it has happened in real life every day vehicle use and then base their concerns based on the facts they find rather than just the endless and for the greatest part, unsubstantiated, warnings about coking.
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Until then, it's just more endless gloom and doom Veg folk law.
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Postby John Galt » Mon Jun 09, 2008 12:31 pm

You'll love this discussion
http://www.frybrid.com/forum/showthread.php?t=10914
Reminds me of the recently converted reciting scriptures while rocking back and forth, hoping that Father Chris will notice and bless them.
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Postby denson » Mon Jun 09, 2008 4:12 pm

John, nice thread, very funny. I think 240volvo hit it on the first take. I have now come to the conclusion that since I am running with no heat or any other mods. for that matter. I should stay away from burning fats and PHO's.
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Postby John Galt » Mon Jun 09, 2008 5:37 pm

A heated system is necessary for burning fats and PHO; they will clog an unheated system if not removed by processing.
That's why I separate the fats and PHO and don't use them in my truck's stock unheated fuel system.
Water will bond with fats and PHO rather with VO; if the fats are removed most of the water goes too.
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Postby 240Volvo » Mon Jun 09, 2008 6:09 pm

Oh, Brother John, such blasphemy!

I love it when people use "research" that is based on papers that were written 22 years ago and more by people with no experience or background in the use of the fuel they were testing, and says of those conclusions that it "indicates" not indicated, a particular conclusion. The fact that the conclusions made in those studies are not applicable to engines that are properly tested for their basic functions (compression, etc.) before undertaking the use of oils, blended or not, makes any conclusion reached in them useless. There was no apparent modification of any of the engines in question for the proper timing of injection, either.

Then Craig has the gall to misrepresent Elsbett's work (there is a big difference between designing an optimal multi-fuel engine, and optimizing a diesel engine to burn seed oil for instance), and using this misrepresentation as evidence to support the trashing of a competitor's system that has been in use for decades. He ignores the fact that Elsbett only sells single tank systems for particular vehicles, a fact that is consistent with Elsbett's approach, but inconsistent with Craig's opinion of Elsbett, or his own "theory."

Garbage in, garbage out.
1984 Volvo 240 diesel with a single tank Elsbett conversion: electric fuel filter heater, FPHE, glow plugs, and injectors. Also injector line heaters and block heater, running 20%kero/80%WVO winter blend.
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Postby denson » Mon Jun 09, 2008 7:39 pm

Ok, I know diesel is a dirty fuel and causes coking on it's own in different situations, even gasoline leaves behind carbon buildup. With gasoline the higher the octane the cleaner the fuel burns. Can the same thing be said about cetene levels and diesel or VO for that matter?
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Postby John Galt » Mon Jun 09, 2008 8:18 pm

Cold engine starts, with cold fuel causes partially burned fuel that leaks into the crankcase and leaves deposits in the combustion chamber. Smokey exhaust is a sign of unburned fuel and deposits forming. Preheating the engine and adding solvents to VO can significantly reduce 'dirty' starts. VO solvents I'm experimenting with are pump diesel, kerosene and naphtha.

Alter the VO with solvents that reduce the viscosity and improve it's ignition characteristics, and the need for two tank conversions becomes questionable.
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Postby denson » Tue Jun 10, 2008 8:36 am

Alter the VO with solvents that reduce the viscosity and improve it's ignition characteristics, and the need for two tank conversions becomes questionable.[/quote] This is the 1000lb gorilla in the room that not to many people want to talk about. Where do you get your naptha from?
Last edited by denson on Tue Jun 10, 2008 6:21 pm, edited 1 time in total.
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Naphtha

Postby John Galt » Tue Jun 10, 2008 12:14 pm

I get naphtha in stale JetB helicopter fuel. JetB is 50-50 kero-naphtha.
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Postby rtarh2o » Tue Jun 10, 2008 4:25 pm

What exactly is naptha and what does it do?
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Postby John Galt » Tue Jun 10, 2008 5:33 pm

naphtha a.k.a. 'white gas', campstove fuel, closely related to gasoline. It thins the VO and the fast burn characteristics of the naphtha balances the slow burn characteristics of the VO.
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Postby rtarh2o » Tue Jun 10, 2008 8:58 pm

So will this help reduce the coking? If so how much should I add to my blend, or does RUG accomplish the same thing?
Rusty
1994 Mercedes G350DT
94 6.2 Diesel Toyota Land Cruiser 7,000 miles on blend (sold)
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