I had a chance to do some more testing with the olive oil lubricant today.
To recap... engine is a PAW 2.49, control line model with no silencer.
Fuel is 2parts of kerosene to 1 part of modified olive oil. This is then used to dilute a 30% ether mix down to 10%. There is 2.5% 0f "ignition improver" added. The ignition improver is based on 2-ethylhexyl nitrate and is available as a fuel additive for diesel cars.
First job was to run the engine on ordinary commercial 30% ether diesel fuel. I needed to do this to establish the compression and needle settings with "normal" fuel. I have run this engine on fuel with olive oil as a lubricant but not on normal diesel fuel since I originally bought it off E*ay.
When the settings were established and the tank run out I filled with my olive oil fuel mix as described above. The engine started easily with just a quick choke to get fuel to the carb and then a quick spin with the starter. The engine runs well on this mix although it revs up and down for 2 or 3 seconds until the temperature comes up, it then settles down to a steady run.
After changing to the olive oil mix I found the compression needed to be about a 1/4 turn more than with the 30% ether mix, the needle was not far from the same place, maybe a touch out. After a minute the compression could be backed off a bit more.
Next.... using the same olive oil fuel but with some more ignition improver added, this was a guess I just put a bit more in and didn't measure it. Would it make any difference ?
Yes it did... the compression could be backed off to just a bit more than when using the 30% ether mix.... looking good !
Last run of the day... I tipped a bit more ignition improver into the tank and crossed my fingers !
The engine again ran well and this time the compression was similar or very close to when using 30% ether
So where am I now ? Well, the engine is still intact and shows no discernible wear and is quiet when running... if you can call a PAW running flat out with no silencer quiet !!!
The ignition improver, which uses 2-ethylhexyl nitrate is definitely working and is offsetting the lower level of ether. I need to do it more scientifically now and measure the amount I add, I am thinking in terms of 10% initially.
PAW on their website state that 2-ethylhexyl nitrate can be used as a substitute for the isopropyl nitrate normally used in UK model diesel fuel.... so it is a recognised additive that is known to work. All you have to do is find the automotive diesel fuel additive that is based on it...[
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What have I achieved so far....
I have got a fuel with only 10% ether and using mostly olive oil as a lubricant running at nearly the same settings as a normal 30% ether mix. This would turn my 1 gallon of expensive commercial fuel into 3 gallons of a lot cheaper fuel. With the 10% ether content it should be no problem to use castor oil instead of olive oil and enjoy the bigger safety margin of using castor.
The engine emits plenty of oil but is far cleaner, no black exhaust deposits and easy to wash down.
I finally managed to trackdown some castor today after trying 2 pharmacies. I was surprised how viscous the stuff is, far more so than I expected. I can finally see what the stuff is like
Reg