Reg,

Something new to try.

About etherless mixes. I've found that even straight vegetable oil will run and run reasonably well. Starting is the issue and with heat, lots of ether prime and initial, tight compression along with an electric starter, they CAN be made to run. Lots of fuels never even considered before, will run. And if WOT is your thing, then it's just a matter of finding the oil/fuel/whatever that suits your purposes.

But as you say, throttling is a BIG issue with many of us.

I finally got my .15 re-built with a new, beam style, bushed rod. I also managed to install brass bushing in the crankcase on both ends. ZERO slop in the system.

Ran it yesterday on glow to limber it up and find settings.

Today, I ran it as diesel and tried out my stock, 40/40/20 mix. A hunch told me to leave out the Cetane booster. The result was a start with no need to alter the compression setting once warmed up. Idle was solid and the top end strong. Transition was good.

Then I added the 2% Amsoil, cetane booster. The result was a start at the last setting but a minute later, the gnarly sound of overcompression became evident and the CP had to be backed out a quarter turn. Hmmm. And now, the idle went crappy because the CP was turned out from the optimum setting for idle. Hmmm.

So I went to a mix of 70% kero, 20% castor and only 10% ether and no booster. This time, the CP had to be turned in a quarter turn from the normal start position. And it didn't need adjusting once warmed up. It DID take three or four prime runs to get it going. The high ether fuel, booster or no, started easily with just the initial prime. Idle and throttling became touchy though, I wasn't able to adjust the idle mixture to my satisfaction.

There's something here. I think there may be a chemical solution to the dilema of getting a good idle along with not needing to adjust the compression between a cold start and a normally run when hot. Likely a chemical solution along with a static, mechanical one.

The carb was also given the brass treatment in the way of a new barrel with a reduced bore. This is the carb off of the Norvel .25. The original barrel had a 5mm bore and the new one was given a 4.5mm bore. Not a lot of difference but to compare the two, it does look like a substantially reduce bore. The only result was a reduction in RPMs at the top. Throttling didn't get better on any of the fuels tried. In any case, I'll be sticking with this arrangement only because it IS more like the original .15 throttle and it should make the experiment more pure.

It was cold, about 60F and damp. As it got dark, I had to use a flashlight to get tach readings. As I did so, the flashlight beam highlighted something that I had suspected for a while. As the engine ran at full throttle, there was a substantial spray of fuel droplets pouring out of the carb throat. I was amazed at how much fuel was being ejected out the carb. A screen has been installed and more runs will be done tomorrow. The screen will serve to prevent the fuel from being ejected and allow it to be pulled back into the engine. This may or may not make a difference, as the smaller .06 has a screen as a stock feature and with or without, the engine runs and throttles the same.


Chevy,

Sorry that you busted up your plane. Yes, a SPAD would be a good idea. I'm considering that for my .15. I see that on YOUR mix, the cetane booster helped. My mix, this time, on this engine, didn't like it. Next time, I'm going to use the 50 weight Aviation oil instead of the Benol castor. If that takes me in the opposite direction, I may try a blend.