Lean of peak operations

[kwmoore]

I moved this post to this forum at Rod's (C-GOEM) request.

I have been running Lean Of Peak for some time now and am extremely pleased with the engine performance, smoothness and temperatures. Things seem to run great at about 2450 RPM, 25"/WOT, 50 degrees LOP resulting in about 12.6 gph. CHTs are quite even in the 350 degree range with oil at about 170 degrees. The engine has GAMI injectors and I monitor it with a JPI 700 and 450 Fuel Flow.

In the last twenty hours the fuel flow has become increasily erratic while running LOP. The oscillations of up to 0.8 gph are severe enough to make the plane surge and even backfire on occasion. Oscillations of about 0.4 gph occur running ROP with about 0.2 gph occuring at take off power and idle power settings. Both the analog fuel flow gauge and the digital fuel flow are showing the same problem.

Has anyone else experienced this problem or know what might cause it? I have checked all lines/vents/screens, the flow divider and fuel supply. The engine driven pump/regulator/vapor ejector was sent to Continental. They said it was defective and sent back a new pump. The problem did not go away. I have removed the fuel flow transducer from the system and the problem persists. Running with the electric pump on (and re-leaning the mixture) does not help.

Hope someone out there has some ideas I may have missed.

Thanks, Rod

[Todd Peterson]

Bellancas have had an occansional problem with erratic fuel flows due to small and often hard to find loose fuel connections that allow a little air into the system. These include all the fittings from the fuel tank to the engine.

With a gravity fed fuel system you just get a little leak. With the fuel injected engines that loose fitting allows air into the system which in turn creates an erratic fuel flow.

You might also want to look at the one way check valves in the fuel return system to make sure they are functioning properly.