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
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.