If it was not meant for motor oils, why is there even a specific test for them? And it does replicate sliding friction, albeit at a higher stress level. Basically, when the test starts, there is virtually zero contact area, resulting in oil film failure and rapid wear. As the wear progresses, a wear scar appears, and the resultant pressure decreases until it matches the film strength. When measurements are taken of the wear scar size, they are a valid comparison of film strength. I know there is more to engine oil than film strength, but acting as though it is irrelevant is simply wrong.
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I have not insulted you since. But I still can make cogent scientific statements based on my education and experience.
My entire career has been on application of engineering. I am a practitioner, not a researcher.
I don't mean to belittle a man's entire career, and I'm sure the things you post about here only cover a small percentage of what you have experience in.
I'm not a saw or small engine guy either, I make my money with a computer and a phone. I definitely know that those fields don't cross over, though.
Do you really think it replicates sliding friction as found with a piston ring and cylinder wall? For starters piston rings have very low tension and are lightly loaded. An EP 4 ball test us the exact opposite.
Testing for film strength is basicly irrelevant.
And you have zero knowledge of IC motors..
You also don't seem to be able to understand them either. Which is odd given you're an engineer.
How about for the lower rod and crank side case bearings?
You haven't made a valid statement since.
No.
Enlighten me. If the fuel/oil ratio is the same, why would retuning be needed?
Sorry. You do not have the knowledge of fluid dynamics or thermodynamics to make that statement. If you wish to dispute that, what is your degree in and what is your current job description?
Actually, I do know how engines work. I merely said I am no expert. I don't know all the nitty gritty about each part in the assembly. Back in my college days and shortly thereafter, I had no money to pay a mechanic, so I had to do my own vehicle repair. In addition to changing oil and replacing spark plugs, I repaired starters, replaced head gaskets, replaced carburetors, adjusted valve tappets, installed headers and a few other things. I did not like doing it, so as my career advanced, I was able to pay others to do it. I still have to change oil on my ZTR, and I had to do oil changes and an exhaust manifold job on a Kubota tractor. These days I don't even do that on my Mahindra tractor, as my neck hurts from working under a tractor. I don't do any work on breaking down my chainsaw engines. I expect my MS500i will outlast me at this point, so all I need to do is sharpen the chain as needed and replace it when worn out.
Fuel mix is metered by volume. Different density of fuel and oil in the mix = need to retune.
Tune for what you're running. Most people would be far better served by learning to tune than by worrying about what two stroke oil they're running.
Is it not true that the canned fuel at a given ratio is also metered by volume? So the net result should be the same. A bigger difference would be if the home mix uses E-10 fuel, as ethanol has a bit of oxygen in its molecule, thereby requiring a slightly richer mixture. I tuned my earlier saws (Stihl 038 magnum and MS441C) only once after purchase, as all my fuel was oil mixed with E10. On my 500i, I cannot tell any difference in performance between canned fuel, my own mix with E10 and my own mix with 95 octane ethanol free gas. I guess its microprocessor control really works!
Both of those statements are false.
Do I think it replicates the conditions exactly? No. I already said that. But I disagree that film strength is irrelevant. Obviously, I won't convince you and you won't convince me. But how about another thing PF measures: power draw of the motor running his Timken test setup. Various oils require different wattage on his machine. Would not lower wattage be a benefit, indicating less friction?
Exactly what I said. Different fuel densities have a different BTU value for a given volume, and will require a retune.
Thanks. I appreciate what you say. But fluid dynamics crosses over to any field that involves movement of fluids. There is a subset of that called tribology, which is basically the study of friction, lubrication and wear. I would love to have a tribologist weigh in on this forum. However, most of them work for oil companies, so I am not sure how objective they might be.
If you mix straight gas at, say, 50:1, how is that different from a canned fuel such as TruFuel at 50:1?
Looks like 100LL avgas(only akylate fuel I was able to find info on quickly) is ~116k btu's per gallon, and regular unleaded pump gas is ~120k btu's per gallon, 3.4% difference. I doubt that's enough leaning out to burn down an engine unless it was tuned dangerously close to the edge already, but it's definitely enough to require a retune.
Tune for what you're running, then it doesn't matter. Universal rule, tune for what you're running.
