XJet
Posts: 3174
Joined: 3/31/2003
From: Tokoroa, NEW ZEALAND
Status: offline
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quote:
ORIGINAL: pe reivers
In my tests on small MVVS engines (8cc and smaller), I also tested Aerosave and Aerosynth, along with other synthetics. The first runs with the synthetic, the engines run like with the devil on their heels, wit a lot more power. Then slowly, power tapered off until the engine would barely run like at half throttle settings, whilst needle adjustments became nearly impossible. Restoring the engine to castor mix, also restored power within a tankful of fuel. I am not alone in these observations.
This is *very* strange. Perhaps (as you suggest) it's behaviour peculiar to MVVS engines. I've found that after witching to a good synth/cator blend my engines "run like with the devil on their heels" but just keep on going.
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As far as I know, it is only MVVS that responds this way to synthetic oils, but it goes to show that castor oil has no lubrication limits.
Not strictly true. If it were true then you could *never* seize or damage an engine running a fuel with castor for oil. The reality is that you can damage engines even when running castor-based fuels.
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It becomes thicker at temperatures at which other oils fail. This cannot be said in favor of synthetic oils.
That is true. Although castor does reduce in viscosity as it gets warmer, it does polymerize rather than vaporize, thus creating a solid layer that acts to limit metal-to-metal contact -- but this is kind of like saying "you should fly over water or snow because crashing in the ground may damage your motor" because...
The reality is that if you tune your engine properly, modern synthetics will operate well-within the temperature range at which they protect and lubricate well. There are legions of folks who have run nothing but synthetic oil (and some of them even run rather poor PGA-based synthetic oils) but have never had a lubrication-related failure.
The best way to avoid heat-related engine damage is to tune your engines properly and ensure adequate cooling.
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I too abhor the castor mess, but that is no reason to downgrade the lubrication properties of 20th century castor, which still is way ahead of the synthetics that will blend with methanol.
Define "ahead" :-)
It should be remembered that different folks have different priorities in respect to what an oil should do. In the areas of extracting better fuel-economy and performance, the synthetics are *better* than castor. In extremely cold conditions, synthetics outperform castor simply because they don't suffer such a drop in viscosity. In the area of mixing with high amounts of nitromethane the synthetics win again because it becomes very hard to keep castor in solution with high nitro percentages.
True, castor will provide additional "last chance" protection against a lean run -- but if you're the kind of modeller who knows how to tune their engine and who recognizes the symptoms of a lean engine (thus landing immediately), this may be of lesser importance than the benefits you get from a synthetic oil.
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Fuchs succeeded in develloping additives to improve the base stock. These additives are not compatible with castor. Other synthetic oil manufacturers went to castor oil blends (compounded oil) to achieve at least some of the castor benefits.
I've not used Fuch's oil but it might pay to try a different brand of castor just to make sure it's not additives in the castor that are causing the problem. Some companies (such as Klotz and Morgan) claim to add "friction modifiers" and other chemicals to their castor. These may have caused the gelling you speak of.
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In standard lubrication history (not for methanol) Compounding mineral oil with castor up to 10% improved the dino oil quality above both the stock oil and the castor. This worked well until the advance of the synthetics, which can be engineered to exactly the purpose they are needed for. Too bad, these syntitics (none of them) will mix with methanol, so they are of no use to us.
The most common synthetic bases used for automotive engines are PAOs (polyalpha Olifens) and Esters. The first will not mix with alcohol but I gather the second will. Some synthetic motor oils seem to be almost entirely PAO, others Esters. Another group seems to run a blend of both.
The fact that Motul and a few of the other advanced model synthetics are also ester-based indicates that our better model lubes are every bit as good as the automotive ones these days.
In the meantime, I'll keep running a synth/castor blend and get the best of both worlds. Great performance, excellent protection and minumum mess :-)
Note: I'm not a chemist or an oil expert but I'm learning as much as I can as fast as I can ;-)
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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> RC Fuels >> Oil 30% is like ... 5% nitro, how about that ? 
Oil 30% is like ... 5% nitro, how about that ? - 
