Originally Posted by MassiveMods

excellent info Brian thank you . We tested both scenarios for front bearing engine seal as one brand in particular is notorious for seal leakage, the manufacturer of the bearing asked us to come up with a solution, part of our research was outlined in the following experiement as we were presented with the theory that castor based fuels will seal better by the manufacturer, we had to confirm or disconfirm this theory before looking at the bearing design. the experimentation is a lot more involved than what i describe here but to condense it, we ran an all synthetic through , one tank , and put a seal on the exhaust then pumped 3 psi into the case via the hsn nipple at wot. , we then measured the resistance with a Sphygmomanometer which was in line with the compressor , this measures minute back pressure varyants. we flushed the engine and ran with a fuel mix with a 4% castor component and measured , again one tank. we compared the hydraulic comp lock figures ( back pressure ) and found them to be virtually the same.

we then roated the crank while reading the back pressure and found no seal varyants between the two fuel samples.

This was using an all synthetic which was designed to have the same charachteristics as Castor but its cst value is lower by about 40%.

The wear with this all synthetic from our research and feedback from clients is doubled engine life.

So yes it very much hangs on which ester synthetic you choose. a Good one will have excellent wear properties and this goes hand in hand with hydraulic seal properties as well. In our research better wear properties than castor. And i think in defense of Castor, this is my hypothesis. When castor is used in an engine application such as Micro Engine fuels, you must take into account within Scientific testing the factor if i . This is a scientific term that caters for the interaction within an enviroment being tested. namely human interaction.

What typically happens with eMicro engines is they ar tuned in correctly , this problem has lead fuel manufacturers to use a heavy duty protectant IE Castor. Traditionally castor has always been cheap to buy so its popular in micro engine fuels. Now typically when an engine is tuned from the HSN first , which is the case in most instantces, the engine under goes a " cycling " within the run of every tank.

If the HSN is lean , which it will be if its the first needle tuned, because it has to compensate for rich LSN setings typically. What will happen is when the engine reaches full RPM towards the end of a straight the heat range rises as fuel supply reduces dis proportional to air intake , this raised the heat internally to spike higher than it should be, indicative by blackened piston tops. Where a castor oil is great is it will not burn off as much during this process compared to poly or glycol based synthetics , but where it causes a problem is it will attach to the hot spot, some think this is a good thing , normally on the back of the piston skirt on the exhaust port.

i have a different take on this.

Castor Carbon deposits is like a varnish that almost impossible to get off with solvents. But the problem then is you have a piston that is out of round. only by a few microns but its sill getting fresh layers of varnish on only one side of the piston putting your piston out of round every tank. Now the problem lies in that once the varnish is cooked onto the piston it can then become harder than the chromium lining the sleeve. The sleeve typically gets worn back more so on the exhaust port side as a result of an out of round piston. Once you have enough repetitions of this situation the engine will start to get blow by on the exhaust port side and Flame out.

This is not nessesarily a castor fault but more a fault in tuning process. This wear can also happen with cheaper glycol based synthetics as they just cant stand the heat, they burn off at 140 to 170 c and thats way too cool when the exhaust temps are almost double.

Esters can be designed to withstand extremely high heat, the good ones will not burn off before 500 c which is perfect for this application. Mind you these esters are expensive and would not be economically viable in model fuel unless the manufacturer designs the fuel for quality and performance as opposed to cost.

Thank you again for the info , this thread has been an excellent read



Regards

Mark