Causes of coking

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

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Postby John Galt » Tue Jun 10, 2008 9:16 pm

Observe the exhaust on a cold engine start; smoke = coking.
Adjust the blend to eliminate smoky starts.
Stale RUG is close to naphtha.

More information on Mixed fuels
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Postby rtarh2o » Thu Jun 12, 2008 4:35 pm

So how would you recommend adjusting the fuel to reduce coking? I do have some smoke at start-up for about 10 seconds but it seems like it did the same with diesel. Will the naptha reduce this or should I add something else? I am currently using about 75wvo/15diesel/10rug. I am going to get some kerosene to replace the diesel but that is the current blend.
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1994 Mercedes G350DT
94 6.2 Diesel Toyota Land Cruiser 7,000 miles on blend (sold)
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Postby John Galt » Thu Jun 12, 2008 4:54 pm

I suspect the RUG will act the same as naphtha to balance the VO combustion. Note any changes in cold start exhaust smoke with different blends.
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Postby 240Volvo » Thu Jun 12, 2008 5:21 pm

Odd that David's water mist injection hasn't entered this discussion. The injection at WOT removes coking deposits. It seems that a small amount of coking that is regularly removed should not be a problem. Other issues (lube oil contamination) would still need to be monitored.
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 » Thu Jun 12, 2008 7:45 pm

240Volvo wrote:....water mist injection hasn't entered this discussion. The injection at WOT removes coking deposits. ....
That is a rather blanket statement that is very debatable.

While from what I've read antidotal evidence of folk who did tear downs on their engines have said that water injection does seem to leave very clean piston tops and heads. BUTtt there is little to no mention of (good or bad) about if it cleans ring lands, rings, etc. And that is where coking causes the most problems. (if coking is happening at a fast enough rate for it to fail instead of having your vehicle to rot away around the engine.
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Postby Burbarian » Thu Jun 12, 2008 10:04 pm

Coking of the piston rings and lands is caused by incompletely combusted fuel that coats the inner surface of the cylinder liners. These are then swept up by the piston rings and can build up and even jam the grooves. This typically happens on cold engine start when fuel droplets reach cold cylinder walls, and is aggravated by worn or leaky injector tips producing bigger droplets.

Since fuel is still sprayed while the piston is on its downward stroke, incomplete combustion of the fuel will coat more of the liner surface, and hence get swept up by the rings on the upward stroke. On cold start, some of that fuel also makes it past the rings as blow-by, and as the engine gradually warms up the piston rings expand and form a better seal. But in the time it takes while still warming up, some amount of unburned fuel has accumulated between the rings, and remains there trapped between the rings to char in an oxygen-poor environment when the engine finally reaches operating temperature.

Preheating the engine makes 'cold' starting considerably easier. It might also be argued that using light highly combustible starting fuel, and being light on the throttle on startup also help.

A worn IP that puts out insufficient pressure, and worn injector tips that produce an insufficiently fine spray pattern aggravate coking.

Water injection helps clean piston tops, cylinder heads, valve seats and stems, and the exhaust manifold somewhat, but would have minimal or no effect on prechamber, swirl type IDI and piston rings. Also, using a highly enriched (methanol, isopropyl, etc) injection could lead to premature detonation as it might get ignited by an active glow plug. Straight water injection on startup is also a bad idea as it would contaminate the crankcase oil with water. Among other nasty things, this might also accelerate polymerization. Hence water injection seems best applied only when the engine has already warmed up, and therefore will not be of any benefit during the critical startup and warm-up period.

I use water/methanol injection myself, and have found it to be useful. But it is not a magic bullet against all forms of coking.
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1985 Merc 300TD
1968 CAT D4D 3304 dozer
1971 Waldon 4100 loader
1981 IHI 30F excavator
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Postby David » Fri Jun 13, 2008 1:04 am

240Volvo wrote:Odd that David's water mist injection hasn't entered this discussion. The injection at WOT removes coking deposits. It seems that a small amount of coking that is regularly removed should not be a problem. Other issues (lube oil contamination) would still need to be monitored.


240Volvo I didn't bother mentioning the water Injection because I am really tired of all the endless carry on about coking when I'm still yet to find a scrap of creditable evidence of it happening. There are endless warnings and theories espoused over and over and over again yet how many times do we actually see anyone say they stripped an engine and this is what they found?

I haven't seen it once despite many and lengthy arguments with people over this. If anyone thinks coking is such a threat to an engine, then don't use veg and fer Christs sake stop whining and posting the same old boring and unsubstantiated crap about it all the time when there is nothing to suggest it is any where near the concern it is made out to be.

If there was any evidence to support the warnings of coking actually happening with everyday Vehicle use, there wouldn't be a vehicle on the road that had run veg for more than 1000 miles.
While evidence of coking is impossible to find, there are many instances of people actually running straight, pure veg in completely unmodified vehicles and having done it for good long times. The " Pro Coking" fraternity convinently overlooks this sort of creditable evidence as it undermines their pet position of gloom and coking Doom. :roll:

I believe that in some point in time, people will see that rather than being the single looney that questioned and doubted the frequency of it actually occouring, coking will be realized to be the Y2K of veg oil use. I spose then everyone will say they always doubted it and it was others who fell for the unfounded beliefs, not them.

I believe that water does remove coking and deposits from all parts of an engine including the rings over time. Judgeing the performance of my own vehicle that was run on Dino before I got it, My suspicions are that it was coked up before I got it and it is now significantly improved in condition much closer to the way it ought to be. I break a lot of the veg rules with my car yet I have Never seen a decline in performance. But of course you have to do compression checks and other convinent things no one ever practically does to pick up on engine damage don't you? Like engines that are failing always run with no outward signs of power loss or any other trouble right? They run perfectly then just stop just like that! :roll:

I also do not believe that smoke is an automatic signal of engine damage.
Last weekend I visited an Uncle in the country who showed me his 1950 Vintage D7? Bulldozer. This thing has a small " Pony" petrol motor you start and engage a clutch to turn over the diesel motor and get it going...eventually!
The thing sits there for about 2 minutes in the cold weather churning away with significant amounts of white smoke issuing out of the main engine until it finally catches. They all do the same thing and have all done it since day 1.
As this engine worked 6 days a week for the first 20+ years of its life without a rebuild and hasn't had one since, if smoking is engine damage, it sure as hell can't be too significant! This engine was also fed it's own engine oil after being passed through an old felt hat to clean it and never had coking problems of any kind thanks to other sound operating practices despite smoking like a chimney for many minutes after start up.

I also noted a number of other Diesel stationary engines that were used around my uncles farm for water pumping and other chores all started with impressive clouds of smoke that lasted up to a minute and the most recent one of those to be rebuilt was also 22 years ago but I'll bet the naysayers have some excuse as to why these engines are lasting so long but any other that smokes is being damaged.

My own merc I suspect has dodgy injectors because it smokes quite plentifully at the lights on veg but runs clean when cruising and when idling on B100. It has been like this for the 18 months I have had it but since fitting the WI, the performance has become remarkably better. This dosen't support the smoke = damage theroy either but at the end of the day, people are free to be brainwashed all the gloom and doom f they so wish or they can think things through logically and practically. I know which most people will believe and what most people will choose to carry on about. As much as I don't want it to, I will be keen to tear the thing apart when it does die and will put my position on the line and document the internals to see if and where there is any coking in the engine anywhere.

It seems to me that there are some complete myths about Veg that will live for a very long time as simply some people are compelled to have something to harp on about even if it is completely unsubstantiated and there is no creditable evidence to support it. If the problems were put into real and balanced perspective, some people would simply be lost if they didn't have anything to done on about and what would they do to fill their obviously plentiful time in with then. I am not directing this at anyone specifically because there are a whole mess of people that do this and it applies to.

Some people go on about wanting to be safe and not ruin their engines and all that but if that is the real case, then why the hell are they playing with alternative fuels in the first place?? If you want guarantees, stick to dino.
Oh, wait, there isn't any guarantee that will be perfect either is there?

Me, rather than believe everything I read, I go out and try things for myself and so far I can say with complete and utter surety, that the number of Veg rules and beliefs I have discovered are not right far exceeds the things I have found to be accurate.

I'll sit back now and wait for all the dooms dayers to give me the usual excuse's, propaganda and insults as to how coking threatens the very lives of every vehicle and person driving them that runs Veg and I'll go on my happy way waiting for my engine to finally die and prove them right. I think it's going to be a verrrry looong wait! :lol:
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Until then, it's just more endless gloom and doom Veg folk law.
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Postby zoochy » Fri Jun 13, 2008 4:14 am

Burbarian great info, David great rant, thanks! As always the readers challenge is in deciding what to believe.

I choose to ere on the side of caution by using clean burning fuel at start up. I switch over to my veg blend as soon as it idles nice and drive easy until she’s warm. I know this is the single tank/blending section of the forum, I’m sorry, but the same “start gently” strategy is key to any system.

Once your engine is hot, drive it hard and avoid long idling. The only time my van ever smoked like the farm equipment David described was after shutting down immediately after an unavoidable 45min idle. Belching smoke cannot be a good thing but if you run it hot for hours after starting, I imagine what happened at start-up is largely irrelevant...?
Last edited by zoochy on Sat Jun 14, 2008 2:10 am, edited 1 time in total.
91 Toyota Hiace 3L engine w/ a 300W ½” heated fuel line, lift pump, additional 10um fuel filter, and a 2nd diesel tank for starting.
>160,000 km on:
88% canola WVO
11% old gasoline
.6% turpentine
.3% acetone
.1% eye of newt
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Postby David » Fri Jun 13, 2008 9:33 am

What you say Zoochy is good advise.
I have nothing against being careful and doing things properly, its people who constantly take things too far and create fears which have no substantiation that get me annoyed.

Like everything, there are right and wrong ways of using veg.
Used correctly, a person has no need to worry about coking or all the fear mongering that is constantly raved on about it.
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I don't give a damn about what might or could happen until a significant group of people can tell me it HAS happened to them.
Until then, it's just more endless gloom and doom Veg folk law.
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Postby denson » Fri Jun 13, 2008 12:17 pm

Coking happens in every combustion engine. I'm not afaid of it, but would like to get the longest life possible out of my engine. WI is a good idea, but it is also a modification. I don't want any mods. Has anyone tried crankcase oil with linkite in it. Propeller driven aircraft use it. and I was wondering if it could help to combat coking
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Postby zoochy » Fri Jun 13, 2008 6:50 pm

linkite is just another snake oil. Don't go there. Or... better yet, you try it and report back. I never trust any product that advertises on late night info-commercials.

Yes there are right and wrong ways to use veg but keep in mind that there is more than one right way to do everything.
91 Toyota Hiace 3L engine w/ a 300W ½” heated fuel line, lift pump, additional 10um fuel filter, and a 2nd diesel tank for starting.
>160,000 km on:
88% canola WVO
11% old gasoline
.6% turpentine
.3% acetone
.1% eye of newt
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Postby denson » Fri Jun 13, 2008 7:28 pm

Snake oil, that is FAA approved.
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Postby denson » Fri Jun 13, 2008 7:32 pm

Yes there are right and wrong ways to use veg but keep in mind that there is more than one right way to do everything.[/quote] Amen to that!
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Postby jburke » Fri Jun 27, 2008 7:03 am

"There are endless warnings and theories espoused over and over and over again yet how many times do we actually see anyone say they stripped an engine and this is what they found? "

I am by no means a nay-sayer. However I have read of three VW TDI's that suffered high oil consumption and blowby. Coking was confirmed iirc in one possibly two.

Also read of oneIDI's an M-B and know aVW that coked on unheated blend. Th eVW wasn't torn down, but blowby was sufficiently bad to launch the dipstick when starting.

And given the recent explosion in interest, and the shocking lack of knowledge about how to do WVO safely, I think the warnings are usefull.
I bet half of new WVO'res spend less than 20 hours reading about proper WVO design and filtering.
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Postby David » Sat Jun 28, 2008 1:09 am

jburke wrote:
I am by no means a nay-sayer. However I have read of three VW TDI's that suffered high oil consumption and blowby. Coking was confirmed iirc in one possibly two.


AS far as I am concerned, TDI's dont count.
There are plenty of reports of these things coking on Diesel behind the inlet valve thanks to faulty EGR valves. If the things coke on Diesel, its hardly fair to point to veg and say something to the effect of " Veg coked my engine" when the bloody things have the self same trouble on the fuel they were designed for!

I am aware of a W123 Merc that coked up on veg on a very through 2 tank conversion and was used with suitable care. I have found out that the thermostat on this Vehicle was know to be faulty for some time so it would seem that not only the Oil wasn't up to temp, but it is also likely the entire engine was running cold.

And given the recent explosion in interest, and the shocking lack of knowledge about how to do WVO safely, I think the warnings are usefull.
I bet half of new WVO'res spend less than 20 hours reading about proper WVO design and filtering.


I agree completely.

I have noticed on many forums lately a rash of questions that could nly be described as idiotic. Sure, No one starts as an expert but anyone that is half serious and has quarter of a brain tries to educate themselves somewhat in the hope of avoiding embarrassing themselves as complete and clueless noobs!
Many it seems don't have any worries about this and try to take the shortcuts right from the start by getting people to do the basics for them.

I used to get a bit annoyed when I saw veg being rubbished and given a bad name, now I see an upside to it. If veg gets a bad name and people shy away from it, Good for me and the rest of the people that have trouble getting oil. If the lazy bludgers can't be bothered to do their homework to make veg a success, I certainly can! :D
_____________________

I don't give a damn about what might or could happen until a significant group of people can tell me it HAS happened to them.
Until then, it's just more endless gloom and doom Veg folk law.
David
 
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Joined: Thu Mar 06, 2008 4:12 am
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