can I prevent coking with WMO?

[fields_mj]

Just subscribing to this thread. I've been running 80/20 WVO this summer. The 20% is half K1 and half RUG. I've got a 100 watt filter heater from WVOdesigns. Other than that everything is stock. I'd like to add water injection, but with a NA engine, I haven't seen a good way of controlling the WI that I like. I passed up on WMO earlier this year because I was focused on trying to get my WVO set up running. Of course now that winter has come along, I can't find any WMO to work with... That's okay though, I'll get some over the course of the following year for next winter. I'm bag filtering my oil down to 5 microns now, but I hope to get a fuge from simplecentrifuge. This is a good thread. Looking forward to seeing/hearing the results of what you guys are working on.

 

[mudslut350]

I just started wmo in my 97 7.3l runs great with mixing 10 gal wmo and about 5 gal #2 per tank. I have never heard of coking problem with wmo untill this thread. it makes sense as i am a jet engine mechanic we see it on our engines from the jp-8 and more so with ts-1. Does anyone have before and after pics of injecters run without water injection and some with? i dont believe that it would make that much difference being that water injection is used to cool intake air i would think it would cause even less of a complete burn with lower cylinder temps. kerosene or jp-8 added to the fuel makes more sense because that is even what we use to clean jet engine fuel nozzles and is the only thing we do for it, cleaning once a year. Also running at hotter temps will help coking burn off. before shutdown we are required to run the engine at a low speed ground idle for an amount of time which increases turbine inlet temperature burning off built up carbon in the combustion chamber and on the fuel nozzles themselves. Propane seems like it would be more of a logicle solution. anyway just my .02

 

[The_Master]

Hi all,
I have been watching this site for awhile but I just registered and thought that maybe you could give me a hand (or a few pointers).

I have been working on running WMO for a little while, mostly I was trying to get my filtration setup down.

I have now started WMO85% / RUG15%
After about 600 miles I start to have some smoke at idle/cold and after ~1500miles it smokes pretty good (white smoke) at idle, but it runs great once you get the heat up on the freeway, uphill, etc.

About 2 weeks ago (1500miles) I pulled the injectors and they were all coked up. I cleaned them, reinstalled and once-again idle was smokeless. I installed a water injection system (I had parts lying around). I started using a 4GPH injector set to come on after 10PSI, but some 600miles later I start seeing some light smoke at idle and I changed the injector to a 10GPH injector.
I am now about 1500 miles out again from the last time that I cleaned the injectors and I have consistent white smoke at idle, but performance under load is great. I am pretty sure the injectors are coked up again. I have tried some WOT runs (2200RPM, 1100DegF, 25PSI) with the water injection, and it just doesn't seem to be giving the cleaning that some people are taking about.

I am about to pull the injectors for the second time to clean them. Anyone have any thoughts on keeping this from happening? I really thought the water injection was going to take care of this.

As a side note, the truck runs great on D2 and starts right up every time, regardless of temperature. I have not done a compression test, but I have no reason to think that anything is less than great with this motor.


Here is a picture of my injector (worst one) that I pulled to clean.

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[Brad S.]

Not sure if you are doing this, but it might help to have a 2 tank system.
Starting up on D2 then when things have warmed switch to wmo...???

 

[79jasper]

And have the system engage at a lower boost psi.


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[The FNG]

Not sure if you are doing this, but it might help to have a 2 tank system.
Starting up on D2 then when things have warmed switch to wmo...???

This is what I've been doing for the last 2k miles or so and it has been much better. Everything goes smoother.

 

[AcIdBuRn02ZTS]

^^
A warm engine certainly helps when running waste oil. I'm also experimenting with a fphc and water/****.

Also, a slight bump in timing also helps as oil has a slower burn rate. Pre heating the oil should help this as well.

Sent from a pay phone... using Tapatalk v2.0

 

[The_Master]

One the the big reasons that I chose WMO over WVO was that I didn't need to heat or run a two-tank system... I was under the impression that blending (RUG, etc) would solve the viscosity issues and it could be run successfully on a stock truck in very high percentages..

As a followup, I pulled my injectors again, cleaned them and reinstalled and all the smoke has gone away. I have switched to a 50% D2 / 50% (85%WMO/15%RUG) mixture. I am going to run that for a little while to see how it fairs, but I would really like to push the WMO Mixture back up...

I am guessing that I am getting most of the coking on cold/startup or long downhill coasts (I have a long decent out of the mountains that I drive once or twice a day (about 10 min coasting downhill). This is after the motor is at full operating temperature, but I see EGT's around 150Deg (even on straight D2) after a long coast.

Is a two-tank system the only way?

 

[AcIdBuRn02ZTS]

I don't know what it is about the Cummins platform, but some have great luck while others have terrible luck running wmo. Clean oil is huge.

How do you process your oil?

Would a second fuel system help... not sure. I'm in the process of building mine as I discovered that short trips to and from work (less 2 miles) would coke my injectors in my 4bt in a weeks time even running 25% w80. I have since bumped timing and I have a flat plate heat exchanger to install... and a 2nd fuel tank so that I can run straight d2 in the main tank for start/shutdown/short trips.

What I don't get is why the water injection system isn't taking care of the coking. How badly coked were the injectors this time? Is your timing advanced?

The only difference I can see between an IDI and the Cummins platform is the temperature of the fuel by the time it hits the combustion chamber which is what lead me to believe that preheating would greatly help. The research I've done has also pointed towards this. Something else that has been done and worked well is propane fogging which according to some, all but eliminates coking issues.

With your combustion temps dropping like a rock, I'd say that's when the majority of your coking is taking place and would lean towards a 2nd tank (which is cheaper/easier to do then most would think) would greatly help.

-Chris

 

[Brad S.]

One the the big reasons that I chose WMO over WVO was that I didn't need to heat or run a two-tank system... I was under the impression that blending (RUG, etc) would solve the viscosity issues and it could be run successfully on a stock truck in very high percentages..

Years ago I thought the same thing with regards to wmo & wvo, but after doing a lot of reading little more heat in the fuel.
You guys that run Cummins, can you advance the timing just a little, maybe that would help...??? IIRC wmo burns little slower...

 

[AcIdBuRn02ZTS]

I bumped my timing 1/8" at the pump... very simple to do on the cummins and yes it helped prolong it a bit, however my main issue was the short/cold drives.

I cant wait to get my 2nd tank installed.

-Chris

 

[The_Master]

The worst injector was not quite as coked as last time, but over all they were just as bad or worse.

 

[AcIdBuRn02ZTS]

Odd that the water **** did nothing for it. What are EGTs running when the water **** is engaged? I'm curious if its cooling things down too much?

 

[G. Mann]

Coking is the result of incomplete combustion, which means one or more of the following is happening:

1. Fuel not atomized correctly, droplets to large to burn completely enough to be exhausted as vapor.

2. Combustion chamber temperature is below the flash point of the fuel being used, so complete combustion does not occur.

3. Some combination of the above that results in unburned fuel being turned to carbon and sticking to component of the combustion chamber.

Hard pull increases combustion temps so it "burns off carbon" ie. Italian tuneup.. or.. pre-heating fuel/oil reduces viscosity so it atomizes to smaller droplets, which support combustion flame path for more complete burn.. or.. thinning fuel with additional #2 / RUG mix thins fuel to do the same effect..

Result should be less coking.. IMHO.. WMO without thinning or heating won't atomize small enough droplets and coking will always result.. how much depends on the above and your particular driving habits..

 

[AcIdBuRn02ZTS]

Does heating also help by bringing the fuel closer to its combustion temp?

-Chris