This engine is driving me nuts!
My Toucan ( former name: SIG Fazer) was finally flying well after the tank change to Sullivan 6 fl.oz.
The same RPM in normal and inverted flight, good pull everywhere and lap time around 5 seconds.
The tank has been mounted on the inside facing side of the fuselage as there was not enough space to fit it on the outside.
After the plane flew so well, I have decided to shorten the fuel line. It was in three pieces connected by the copper tube epoxied to the top of the fuselage and short stiffener (see the attachment).
I routed the fuel line through the hole drilled in the bottom front part of the fuselage.
The Sullivan tank was and is set in the uniflow mode.
First flight after change: launch RPM 10,000 on 11x7 APC prop. but when the plane was launched, the RPM immediately dropped to the level barely maintaining the level flight. After boring 6 minutes landed safely.
Second flight after change: launch RPM 10,300 - the same behavior. It looked like the engine in the air started running extremely rich.
I changed the routing of the fuel line and reverted to the old configuration but without the copper tube connection to the fuselage that was removed.
Launch RPM ~10,200. In flight RPM dropped again but not that much as before. There was not enough tension though so I managed only a couple of lazy loops.
The uniflow tube was and is exposed to ram pressure. The fuel was and is the same. The tank was not moved.
Why was the engine loosing RPM in the air by running too rich when before shortening the fuel line it was dead stable?
I went back to the exact fuel line configuration as before hoping to get stable and predictable RPM in the air and will try flying this Sunday.
Please see the attachment - this is the current configuration of the tank and fuel line.
Thanks,
Matt