franchi

Hello All:

I attempted to fly one of my ST G20/.15D engines yesterday and I found that the compression adjustment was very critical! It was difficult to adjust the needle valve and compression to obtain a good setting.

I made no adjustments to the engine or fuel since the last time that the engine had been flown. What gives? I am running an 7x6 wooden prop. Perhaps I need to place a larger load on the engine?

Tia,

Frank McCune

1QwkSport2.5r

Whenever I have problems starting the engine or setting the needle or compression, I switch to a new can of fuel. If it starts and runs differently (better), then I go on to assume that some of the ether has gassed off from the fuel. A small squirt of ether in the old can makes it run much better.

Can you smell ether coming coming from your fuel cans when tightly capped?

franchi

Hi:

Thanks for the prompt reply!
No, there is no smell emitting from my fuel bottle. This fuel works very well In my other Diesels. The engine starts very easily but the compression adjustment is very sensitive to a point where I have a difficult time going from over compressed to under compressed very quickly. I am planning to use a larger heavier prop the next time I run the engine. I think that more load there is on the engine, the less critical the compression is to adjust for best results. I will keep you posted.

Be well,

Frank McCune

franchi

Hi:

Thanks for the prompt reply!
No, there is no smell emitting from my fuel bottle. This fuel works very well In my other Diesels. The engine starts very easily but the compression adjustment is very sensitive to a point where I have a difficult time going from over compressed to under compressed very quickly. I am planning to use a larger heavier prop the next time I run the engine. I think that more load there is on the engine, the less critical the compression is to adjust for best results. I will keep you posted.

Be well,

Frank McCune

franchi

How do I delete a double post?

1QwkSport2.5r

Indeed a larger prop will make the compression setting easier to get and less fussy. Too small a prop can be problematic, however if the fuel itself is of the wrong mixture, you may find yourself in the same boat. By his I mean perhaps the engine needs more ether? Ignition improver?

qazimoto

My Feedback: (1)

... or less ignition improver. Too small a prop can be a problem, but a ST G20/15D was designed for a 7x6 prop. Perhaps a fresh batch of fuel might help. Check all the gaskets and screws. Could there be an air leak around the NVA?

Maybe it's just clapped out.

1QwkSport2.5r

As with many things, too much or too little of a good thing isn't all that good. I am not familiar with the ST G20/15D - is it an ABC construction? Ferrous? I'd assume it's not ringed..

qazimoto

My Feedback: (1)

It's a lapped Iron Piston in a Steel Liner twin ball race racing engine that originally came out in the early 1960's. Makes a nice control line sports engine. They were still available over the counter in the 1980's. Still some of 'em will be pushing sixty years old, so they might be a bit tired.

qazimoto

My Feedback: (1)

Frank, I've just checked the weather for Blain PA, for this week. Mid 80's Degrees F and about 80% Humidity. That may be a cause of your tuning problems as well. Some days diesels just don't want to run.

:-)

1QwkSport2.5r

Well and truly understood. I suspected ferrous technology. Hopefully the OPs fuel has a healthy dose of castor oil in it.

franchi

Hi All:

Today I had Diesel engine problems all day! The weather was 83 F and I had a problem with my .40 going lean. A friend of mine from the Ukraine suggested that it was just too hot to run a Diesel. I had three other Diesel Experts from around the world helping me but we could not get in a full flight. The engine was set a bit rich and with the compression just advanced enough to where the engine was mo longer misfiring due to insufficient compression. After about two minutes of flying, the engine would really start turning a high speed. It was soon after this, the engine became so over compressed that I had to dump it on the grass to prevent engine damage. This happened each flight.

If I launch when the engine is misfiring due to low compression, it never speeds up enough to a point where it runs without misfiring, under compressed.

Today is the first time that I flew this engine in hot weather. I never had to adjust it when flying in the Spring and Fall so temperature must be to blame. My ST G 20 /15D also ran poorly with the same symptoms. Both engines started very easily so the fuel must be fine. It is the same fuel that I have been using for awhile. I will mix some new fuel and see if my problems disappear!

The .40 engine is an OS FP with a DDD conversion head. The fuel is a good mix with plenty of castor oil.

Due to the fact that Diesel fuel is so very expensive to mix and the .40 drinks it like a fiend, I think that I will install the original glow head and save the Diesel mix for the .15 engines. Lol

Thoughts and/or comments?

Tia,

Frank McCune

fiery

My Feedback: (2)

What percentage of DII and what type?

franchi

Hello All:

I am using 2% Amsoil ignitions improver.

Thanks for the replies.

Cheers,

franchi

fiery

My Feedback: (2)

Try cutting the DII to 1% and upping the ether / reducing the kerosene or AVTUR content of your fuel.

gmeyers

I found when I was a kid of about 13 (1954) that diesels run best with a heavier load than glow or gas - they don't necessarily produce more power but they seem to always run steadier with no misfires or blurps. I only have three 1/2A diesels now and it's still the same. I did chuck up a head in the lathe and make a change in the head for a friend of my to bump up compression just a mite and it worked for my friends Davis conversion on his OS-40. What I always did was take a prop that was 2 or 3 sizes too large then cut off the tips to improve the flywheel effect and that works great too. .