Scott,
A very nice summary of your troubleshooting. Glad you were able to find and fix
the problem!
As to your last question, I have set up my system (IV-P with
TSIO-550E) to flow 43 GPH on takeoff at 2700 RPM and 38.5” MP--using the engine-driven
fuel pump only. My rationale was/is that if the engine is set up to flow 43 GPH
with both pumps running, it will run very lean--and may stall--if either pump
fails. By depending upon the engine-driven pump only for normal operation, I
can quickly turn on the boost pump should I need it. I have not experienced a
failure, nor tested this on takeoff, but have simulated this at altitude during
flight test and am comfortable it will work in an emergency.
A couple of notes/comments: Several experienced Lancair
builder/flyers do not agree with this concept, and you should also consider
their views in deciding what is right for you. Secondly, the 43 GPH fuel flow I’m
using was the Continental recommendation for several years, but they have
reduced the fuel flow spec to 38-39 GPH in the latest setup instruction. I re-set
mine back to 43 GPH after trying the lower flow and experiencing cylinder and
TIT over-temps during climb through the teens. The return to 43 GPH solved
these issues, BUT there are some considerations. Selecting high boost at full
throttle on takeoff will definitely flood/stall the engine with my current set
up. It stalls at anything above about 47 GPH at full throttle, and both pumps
working at full throttle generates at least 50 GPH in my airplane. I plan
to use the mixture control as part of my power management in an emergency
situation. Also, I have twice had the engine roll back (my wife is pretty sure
this is a technical term for quitting L) during climb out after takeoff
when the plane was heat-soaked (100+ degrees on the ramp). This occurred passing
12-13,000’ when I failed to turn the electric pump to low boost at 10,000’
as recommended in the Lancair flight manual for my airplane. I am more careful
to get the low boost on earlier on hot days, and actually turned it on before
TO from Las Vegas earlier this week when the surface temp was 113 degrees. I watched
the fuel flow carefully but no problems at all in the climb to 16,500 for a VFR
flight to Inyokern, CA with the electric pump on low boost for the duration of
flight.
Hope this helps…
Bob
From: Lancair Mailing
List [mailto:lml@lancaironline.net] On Behalf Of Scott Keighan
Sent: Monday, August 24, 2009 10:25 PM
To: lml@lancaironline.net
Subject: [LML] Fuel Flow Issue Solved
I
just thought I would update everyone on my Fuel Flow issue.
About
a month back I asked for advise about a sudden lack of fuel flow.
Where
I used to get 20-21gph on Take off I has suddenly getting 12-14gph.
All
run ups were normal but when applying full power for takeoff I would not
get
enough flow. When initiating the Electric fuel pump everything turned to
Well
this problem turned into quit the hunt to find the issue.
To
make a long story short I had disassembled and reassembled the majority of
the
fuel system from the:
What
did it come down to??
A
broken O-ring on the inlet side of the Electric Fuel pump fitting.
Air
was being sucked into the system. I finally discovered it by putting a
vaccum
on
the fuel lines from the engine to the tanks. When a vaccum could not be
held
I
traced it to the O-ring.
Four weeks
of down time and about 80hrs of work to find the .50 cent problem.
Of
course I had to reset all my flows of which I now get 24gph and 22psi on
Takeoff.
Now
I am still not using my Electric Boost for Take Off. Should I or should I
not???
What
is the concensis of people in the know.
Thanks
to everyone whom gave me some input.