Hi all,
Some great posts again. I am glad to see a bit of explanation about modified veggie oil. Please give us more info if you have it... me, I am a chemistry virgin [
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Regarding the comments about the modified veggie oil being similar to biodiesel.....
When the oil is allowed to settle overnight, or longer ( I have some which was produced days ago) there is no seperation into different layers. All that happens is there will be a bit of "crud" on the bottom of the container. Once the oil is filtered off into a clean container then there is no further deposit of any sort.
When heating and stirring the oil it will be seen, late on in the process, that there is a very thin layer of deposit on the bottom of the pan. The washing up liquid I used is green in colour. Towards the end of the process the oil is yellowish and there is a seperate, small cloud of green in there. It stays seperate from the mix and eventually dissapears, I assumed it is some sort of colouring tha is applied to the washing up liquid and it gets thrown out as non-essential gunge by the process of modifying the oil.
When the modified veggie oil is mixed with paraffin (kerosene) then it stays mixed... there is no seperation of any sort. I have some in a clear container that was made days ago and looks just the same as when I made it. It has been subjected to widely varying temperatures in my shed, fairly hot during the day and a lot colder of a night.... unless we get down somewhere near freezing (heaven forbid for a few months yet) then temperature variation doesn't seem to have any effect.... very cold temps may not make any difference apart from increasing the viscousity of the mix a bit... time will tell [X(]
I don't think, from observation, that the modified veggie oil is acting as a fuel in anyway. The exhaust is VERY oily, but pretty clean. From the amount of oil being thrown out of the exhaust it doesn't seem likely that the veggie oil is burning in the engine.I cleaned my engines down after using the veggie oil fuel and checking them days later they are not "sticky" like when they have been used with castor lubrication. When using a power pod with normal castor based glow or diesel fuel it will be sticky to pick up even though the wood and the engine were well washed down after use.... the veggie oil doesn't seem to leave behind this sticky deposit.
I think the reason for the modified veggie oil and parrafin mix is the viscosity of the two combined, the fuel is thin enough to act exactly like the normal commercial ether mix and the compression and combustion process is very similar with either fuel. It only takes a 1/4 turn increase in compression to get good running with either a 10% ether mix or the full blown entirely etherless mix. A 1/4 turn increase is very little and is no doubt due to the slightly higher temperature needed for combustion of the paraffin. There is only a tiny difference in compression with 10% ether compared to no ether at all.If the engine is set up to run properly with a normal 30% ether and castor type mix then it is only 1/4 turn on the compression screw to run an entirely non-ether and veggie oil mix. The needle needs turning in about 1/2 turn from ether to non-ether.
I wonder...... 2 stroke oils will probably be a bit thicker than the modified veggie oil, does that increase in viscosity affect the compression and combustion cycle ?
It would be interesting if chevy tried his mix, using diesel oil and cetane booster with modified veggie oil instead of weed-wacker oil. Alternatively if he used kerosene instead of diesel oil he may find a difference. I would hazard a guess that the compression could be backed off (the 1/2 turn increase he is using sounds a lot) and the exhaust will be cleaner.
I also wonder....
If there is white smoke being thrown out with the diesel oil mix that chevy is trying... something is not burning correctly ? White smoke idicates incomplete combustion ???
Whe I set up my PAW 2.49 RC for best running conditions with the entirely etherless/veggie oil mix then there was just a light haze of blue colour coming from the exhaust... does this indicate much better combustion, the exhaust was still nice and oily so I wasn't cooking chips in there
I wonder if bio diesel is going to effect things the same way... viscosity too high ?
Didn't someone try BBQ starter or naptha and find it wouldn't run properly when mixed into the fuel they were trying ?
Like chevy I think it is great to finally run a model diesel engine on something close to normal diesel fuel. What sort of diesel uses ether ??? Nah, it's an abomination !
The weather is preventing any testing at the moment, I might just get chance to try another PAW tomorrow but won't get chance to fly the etherless mix until next week, assuming the weather will be better next week.
Reg