Are you driving short distances on your blend?
I had issues when I first started blending my own fuel and I think I narrowed it down to short distance drives and only running one tank.
My truck is in my sig... 4bt powered tahoe. My last tank that had any wmo in it was about 75/25 - w80/d2
We took a fairly long trip and the truck did great... but as soon as I got back home and started driving back and forth to work, it coked the injectors.
Ive now got a 2nd tank in place... a 30 plate FPHE installed and plumbed to the cooling system... and I have all the plumbing to get the tank plumbed... just havnt had time.
Plans are to run straight pump diesel in the main tank and only switch to waste oil when up to operating temp. I will also shut down and start on the main tank.
For giggles, you may look into some injector line heaters or a flat plate heat exchanger to preheat the fuel before it hits the chambers and see if that helps clean up the burn a bit.
-Chris
I would assume that by short distances, you mean not getting up to operating temp? If so, then no. I drive 21.7 miles to work everyday rolling hills with two good climbing hills. Also there is 3 miles of Interstate. I always let my truck warm up 5-10 minutes before I drive. Engine gets to operating temp only a few miles into my commute. Temp always runs 195-210 degrees.
I have been thinking about this WMO thing quite a lot. A couple of years ago, I learned about cetane. Then I forgot. Yesterday I remembered it and looked it up again.
Taken from Wikipedia:
"Cetane number or CN is an inverse function of a fuel's ignition delay, the time period between the start of injection and the first identifiable pressure increase during combustion of the fuel. In a particular diesel engine, higher cetane fuels will have shorter ignition delay periods than lower Cetane fuels. "
I think the lack of cetane is the main problem with my fuel and the coking issue. ULSD has a cetane number (CN) of 40-55 points on average. I assume WMO has 0?? This explains why my timing had to be raised so much. Too much ignition delay due to lack of cetane.
Also, I must point out that in the beginning, my fuel was something like W85 mixed about 50/50 with FF. Now, I'm not using FF, and have been only using W85. That's right, no additives, no cutting with regular diesel, just W85. Had I been mixing every batch 50/50 with ULSD, and adding PS or another cetane booster, I don't think I would have had any problems with timing adjustment or coking.
With that said, this morning the truck had about 1/4 tank full, which is about 8.75 gallons, just for reference. I mixed up 10 gallons of W85 cut with about 2 gallons of ULSD, and about 24 ounces of Power Service's Diesel Clean w/ Cetane booster.
I really don't know how much cetane booster to add. If W85 has 0, that means I need to add about 40 to it. Recommended mixture 1:400 and will add CN of 6. Mulitply by 7 to get inside the range for diesel. So for my 10 gallons, I should have added 32 ounces. But I wanted to start lower and gradually add more to find the best point. Maybe I can find the perfect amount to add so that I can drop my timing back to normal diesel burning advance, and can switch back and forth without issue.
BTW: Diesel Clean was $10.96 out the door. Adding 24 oz of that, and 2 gallons of pump diesel to 10 gallons means that it raises my cost per gallon to $1.24. That's quite the jump from $0.338 per gallon.
But that's still cheaper than $3.65 at the pump today.....
