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.