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what damage is being done when the engine first starts and is cold? Likewise, what about the fuel left behind when the engine is turned off?
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WARNING: LONG-WINDED POST:
I am the dumb one in the family. I have two younger brothers that are chemical engineers, and I have talked at length with them about my blending and converting to WVO.
If you go to
Frybrid, you will find an explanation of the "frying pan" test to demonstrate the issue of coking.
Don't try this at home. This is for mental illustration only. (I know you won't, I just feel better having said that).
In short, the test goes something like this:
Take two frying pans. In the first frying pan, put a drop or two of WVO in the middle. Heat the frying pan to 500*. As the pan heats up, you will notice that the oil gets hot and starts to smoke. Finally, all the oil burns away, leaving a crusty residue on the pan. That crusty stuff (supposedly) is the result of coking.
Now...take the second frying pan... heat it up DRY to 500*, then put a drop of WVO in the middle of it. It will explode, taking with it your eyebrows and stove... and leaving no residue.
That demonstration/analogy is supposed to show you why you can't burn "cold" WVO.
I ran that scenario past one of my brothers, and his reply was "sure, that's the case... but I wouldn't draw the same conclusions from the experiment". The reason? Do the same experiment with a drop of #2 diesel. If you slowly heat the #2 diesel, you are doing nothing more than BOILING away materials... leaving whatever impurities were in the fuel behind on the pan.
Heat up any material hot enough and fast enough, it will ignite/explode/burn. This little frying pan experiment is just showing you the difference between evaporation vs. ignition.
I then asked my brother another question... "with the exception of water (which seems to break every rule anyway), does a liquid tend to hold a constant viscosity right down the the freezing point?"
Surprisingly, his answer was NO. In fact, with the exception of some pretty oddball and rare stuff, liquids tend to follow the SAME viscosity curve, with only the freezing/boiling points being different.
He checked a viscosity reference graph in one of his official "smart guy" manuals, and said that it looked like a typical liquid will increase its viscosity as much as 8% from its "midpoint" (halfway between freezing/boiling) to the freezing point.
8%. WOW. That means that my diesel engine is running a fuel that is 8% "thicker" at 20.1* than on a sunny summer day.
Translation (in my mind): If I blend my fuel, I am doing nothing more than "simulating" the viscosity of colder #2 dino-diesel.
So... how do I figure out what blend % falls in that range?
Well... infopop says to do the "Dr. Pepper" test. In short, you take a pop can, and poke a pin-hole in the bottom. Pour in a measured quantity of a liquid, and measure how long it takes for it to drip out the bottom. (Jeff Foxworthy ain't got nothin' on me... "if you ever poured diesel fuel into a Dr. Pepper can, you might be a red-neck").
My first test was of raw #2 diesel. My measured quantity of #2 fuel dripped out in 2:50 (2 min 50 seconds).
My second test was a blend of 10/90 (WVO to #2). This took 2:53 to drip through. (About a 2% increase).
My third test was a blend of 20/80... which resulted in a time of 2:57 (about a 4% increase).
My fourth test was a blend of 25/75... which resulted in a time of 3:00 (or just over a 5% increase).
All of my tests were done at a temp of 70*F... and I stopped there.
If I would have been thinking, or had less beer to drink that day, I would have tossed a measured quantity of #2 diesel in the freezer to make sure that the viscosity increased at the lower temps...
BUT...I learned that a 25% blend resulted in a fuel mixture that was 5% "thicker"... well within my 8% threshold.
So... why is viscosity important? It's because of the atomization/splatter pattern of the fuel through the injectors. Today's diesel engines have a very tight tolerance for the spray patterns through the injectors.
You ever had to lube a squeaky bolt... and you grab a can of WD-40... but the straw thingy isn't in all the way? You press the nozzle, and the lube goes all over your hands, as well as your new jeans. Doesn't mean that the lube is BAD, it's just that it didn't wind up going where it was supposed to. Since WD-40 stains denim... you can consider your jeans "coked".
Same thing with the fuel. If the viscosity of the fuel changes too much, your splatter pattern will also change, resulting in fuel going where it's not supposed to....like on your cylinder walls, (or worse) left in your injectors. When that flashpoint hits, you have fuel igniting in places it wasn't supposed to.
How will your mileage vary in these experiments? Again, my temp was 70*... if you live in HELL, then the higher ambient temperatures will allow you to run a higher blend of WVO/#2 without altering the viscosity outside that 8% threshold.
So... how will starting your engine COLD in the morning damage your engine if you have a WVO blend? If the viscosity of your fuel hasn't changed, then my answer is "none". But let's just say that a freak ice storm came in the middle of August, and dropped your fuel temp to the point where it DID affect it. Then, the answer might be "some".
Now... I am sure that there are folks here on this forum that are smarter than me that will say that all my data is flawed because I didn't do some experiment when the moon was in phase, and the ocean was in high-tide. Certainly all of my knowledge here is the result of standing on the shoulders of giants. I'm just piecing together what I have found. I always defer to folks that have more experience than I do.... and bow down willingly.
But... that's my .02, and it's what I have come the the conclusion of to explain what's going on 'under the hood'.
Hope that helps.
Halitosis
