Good afternoon all,

Got the yard work done and managed to spend some time running a diesel.

All tests done with my "test" engine, a 40 year old re-built PAW 2.49 DS engine with a Kavan 9x5 prop.

Ambient conditions where Temperatur 22.6 degrees C, 42% relative humidty, and 1017 mb pressure.

Test #1

10% ether 10% castor 10% Amsoil INTERCEPTOR synthetic oil 2.5% Amsoil Cetane Boost and 67.5% kerosene.

Only prime was finger over venturi and 3 flips of the prop. Needed compression set 1/4 turn higher from running postion in order to start. Ran pretty much like the 20% mix but compression setting was bit more sensitive. Consitent rpm about 9000 and head temperature between 185 and 200 degress F . My last test results showed the engine running much cooler on 20%, 130 - 160 degrees F. I now believe it did run cooler on the 20% but not that much cooler. Those lower measurements I belive are in error and attributable to my inexperience using my new remote thermometer; I am much more consistent with postion when taking readings now so temperature readings should get more reliable.

Test #2

5% ether 10% castor 10% Amsoil INTERCEPTOR synthetic oil 2.5% Amsoil Cetane boost and 72.5% kerosene.

Only prime was finger over ventrui and 3 flips of the prop; engine was left to cool after first test runs. Also needed compression set 1/4 turn higher from running position to start. Ran pretty much like the 10% mix but compression and needle setting was a bit more sensitive. Gained about 100 rpm over the 10% mix about 9100 rpm and head temperature up a bit at between 200 to 220 degrees F.
Compression could be adjusted from too little to too much in one honest half turn of the compression screw. Since the compression screw this amounts to a movement of contra piston of approximately 1/64" (.0156" ). That's a change in combustion volume of approx .004 cubic inches if my math is right (cylinder bore is .595"). How that relates to change of compression ratio I couldn't say at the moment. I will have to do a bit more reading and figure that one out too.

Going from 30% to 5% ether, compression setting became more touchy as did needle valve setting but not unreasonably so. The temperature of the engine also increased but again not unreasonably so. Also, running the 5% ether mix sure didn't smell the same as the 20%+ mixes.

There is nothing new in these observations as Andy has already shown the same basic pattern in his test reports. This excercise was very educational and I think I now have a better understanding of these wee diesel (compression ignition) engines but there is still much to learn.

I am beginning to wonder if high ether was always used in the old mixes to account for evaporation over time by giving a good bit extra to ensure the fuel would stay good for a long time.

And oil content. As you can see I am now using 20% total oil and it looks like the engine is not having any issues that. My next set of tests will be to use 15% total oil 5% castor 10% Amsoil INTERCEPTOR synthetic and go through 20%, 10% and 5% ether. After that will be changing the amount of Amsoil Cetane boost. Too many combinations and permutations to think about!

I am also a convert to using starters with diesels. I truly believed the old wives tales. These old tales do speak the wisdom of being careful and thoughtful of what you are doing. I think if continue to approach these engines with thought and care then I should never have a problem with breaking parts with the starter. I will be sure to let you know if I do.

This has all been a very interesting thread and I hope I have been able to add to it's overall value.

cheers, Graham in Embrun near Ottawa Canada