I have a few ideas on Coking based on experience and first had observations of other peoples engines. Many go against the parroted mantra of Veg oil use but I base my beliefs on First hand experience and testing where I get my hands dirty, Not just parroting the same old ( and demonstrably Flawed) theories.
* Overfueling is a no no. If you see excessive smoke you need to wind the fuel back.
I have had vehicles that smoked a bit at Idle, particularly noticeable at night in the headlights and that dosen't seem to be any cause for concern. Belching black smoke is leaving Deposits of tar like crap in the engine which will Sure as sunrise build up on the rings and kill the engine no matter how healthy it was previously.
* Water injection is Fantastic at preventing Coking.
I have broken a lot of the rules for a long time and got away with it. I put that down soley to running a simple water injection system which removes any build-up before it causes trouble.
Water injection seems great at preventing Coking/ Gumming, I believe it also slowly will help remove builtd up that is already there but the effect is slow and the WI needs to be at a high level of what the engine will take and activated readily. I am of the opinion that Methanol or methylated spirits helps considerably with the cleaning effect mixed in with the water at 50% or less.
It can also add a noticeable amount of power which I have confirmed many times over with a stopwatch.
The First mod I do to any Vehicle I get running on WVO is to fit a WI system and I wouldn't run one without it. Lots of people do however so having it there can only ensure the longevity of the engine. The slight performance boost is not unwelcome either.
* Long Idling and traffic is a WVO engine Killer.
I have a coked up engine in my backyard that had a very through heated 2 tank system on it but had a short highway drive at the beginning and end of each days Journey with a long crawl in the traffic in the middle. The owner was fastidious about the set up of the oil heating system and the way the oil was prepared but still the thing coked up. ( W123)
When I have been stuck in traffic for long periods I have noticed a fall off in performance and drive ability till the car can be got up to highway speeds and loaded up and in my case, the WI can be used. WVO is best suited as a Highway Driving fuel not a City traffic one. For regular city Driving, WVO is best used as a Fuel extender rather than a Primary Fuel. For regular City Driving a person would be far away better off making even low conversion Bio if they wanted to make sure the vehicle engine did not suffer an early demise.
* Blending, particularly with 5-10% ULP is also very helpful in preventing coking and Gumming.
It is MHO that the ULP offsets the change in ignition timing that occurs when using SVO in an engine timed for Diesel. Because ULP will light off at much lower compression ratios than WVO or Diesel, I believe it starts the ignition process earlier in the compression cycle at a point closer to ideal where WVO alone will effectively be retarded in the Cycle.
I think this gives the WVO a chance to more fully combust and consumes all the oil leaving only ash which is easily blown out the exhaust. Anything that may remain is taken care of by the Water injection and the steaming effect removes it before it can settle and build up on the rings.
I have run accelaration tests on 3 Different Vehicles, Turbo and NA, and all showed performance gains ( Small but repeatable) with the addition of 5% ULP in the SVO. 5 to 10% ULP also greatly enhances the cold weather start performance of SVO and I believe also the Combustion for the first few minutes of engine warm up therefore reducing deposits in the engine.
Any thinning of the oil with Kerosene, turps or other lighter than diesel fractions is beneficial. Diesel less so as you are really just making thick diesel rather than thin SVO.
* Heating the oil to coolant temp or above BEFORE the IP to aid combustion in the Cylinders is a flawed notion.
As long as the WVO is warm enough to melt any fats in the filters, the final determination of how the oil sprays in the engine is controlled by the heat it picks up from the injectors. Heating previous to the injectors is irrelevant to how the oil is atomised into the engine.
You can have the oil at boiling point but if it hits a Cold IP it will be cold coming out and even if it is at boiling point in the injector lines and the minuscule amount administered on every cycle hits a cold injector and all the passageways and surface are contained within, the oil will
Heating the oil may be beneficial for some of the more fragile IP's to lower Viscosity but on inline and VE type pumps, one only has to examine the way they work to see that the viscosity of the oil is largely irrelevant to them.
When you say this, I guess I don't know what an engine that is 'coked up' means. Are you referring to the engine as irreparable? I've driven on WVO for over five years in Atlanta (25 MPH morning commute at best, a parking lot at its worst) and haven't had a problem. Assumed with rounds of diesel purge and a good fast run, there was nothing these big engines couldn't shake loose. But now concerned that there's a whole element having to do with WVO that I need to be aware of.
I had a hard look at the work I have done so far on the FPHE install and I have some issues I need to clear up. As stated earlier I returned the coolant line out of the FPHE *AFTER* the water pump. I want to fix this, but the only hose I could see going into my water pump was a large (1.5"?) radiator type hose. Is this the one I should tee into with my 3/4" FPHE coolant out line?
Also I need to move the FPHE before the filters, I am currently after the fuel filters. I should be able to figure that one out. Hee hee.
The rings on this engine are " cemented" in place with hard carbon deposits. The rings stopped moving freely and therefore compression was lost to the point the Vehicle would no longer start.
It's the 2nd W123 I have personally seen like this.
I helped a mate pull another engine from his Benz that was the same. The amazing part was we found bits of piston ring on TOP of the piston. The bores were unscathed and the pistons showed only light scuffing in the carbon deposits that ran all the way down the piston skirts.
To me that defies Physics how pieces of ring could get between the Piston and bore in the first place let alone without chopping everything up in the process.
There were several small pieces in I think 3 cylinders from memory.
Surprisingly the valves and ports all looked in pretty good shape with no overly thick deposits despite some obvious time with the engine combusting poorly.
I think either of the engines I saw would have been repairable with the engine stripped down, the carbon wire brushed out of the ring lands and the skirts cleaned up and new rings fitted.
The thing is, On these old cars the price of an engine rebuild even like this is more than the car is worth if you were paying a mechanic for it and even a set of rings and gaskets makes it a questionable proposition if you are doing it yourself.
OF course while you are there you would do the bearings and if you do that you'd do the timing chain and so it goes on.
I have been going to do the one in my yard for a few years but never got around to it.
I have another good runner so I might put the stuffed one up for sale for parts or just strip a few of the alloy parts off it and junk it for scrap.
I don't know what you are doing as far as any blending, changeover etc so can't comment on your success so far other than to say keep doing whatever you are doing. My friends car coked up in about 18 months so if you have been running your for 5 years, the Diesel purges and whatever else must be working.
After replacing his engine, my friend used to give the engine a lot more warm up time. He tested what I said about the coolant coming up to temp before the engine and was shocked to find what I said about every thing else being cold was spot on. He started making bio as a warm up/ shutdown fuel and installed an after market temp gauge to measure oil temp. It took a LOT longer for that to come up to temp than the coolant.
He had the car about another year with no problems but then it got written off when someone came through a stop sign and he collected them. The benz was a bit sad in the front, the Mitsubishi van he hit was about a foot narrower. The benz could have been repaired, The Van was structurally ruined.
After that he got a W124 and ran that on about 50-50 Bio/ wvo and used to make sure on the highway run to hold it in gear and give it a good run with the revs well up.
I can say that I'm TOTALLY sold on biodiesel B100 mixed 50-50 with WVO on my wife's W124 (1992) diesel with nothing converted whatsoever.
The old adage, 'like dissolves like' seems to hold true in that case. Sometimes the B100 I'm buying is actually cheaper than diesel (about half the time, it seems).
Find where the coolant hose comes out of the block and goes to the cab heater. Insert a 'T' there to feed the FPHE. Follow the cab heater hoses and find where the ~5/8-3/4" coolant hose comes back from the cab heater on it's way to the pump. Insert a 'T' in that coolant line [close to the pump] to return flow from the FPHE.