I think the book number is 41 GPH (check to be sure). In my IV-P
I had fuel flows similar to yours at takeoff and had cooling problems in climb.
Increasing the fuel flow to the book number gave a richer mixture in climb and
the CHTs started to stay below 400 in a 31 inch MP extended climb.
We were not able to set this accurately at the shop (couldn’t
hold the plane back safely). We had to set it and then and takeoff to fine tune
it. We discovered that increasing the Fuel Flow beyond the book numbers causes
the engine to die when full power is applied at takeoff.
I cannot speak to the high altitude airport issues. I would like
to understand how that would be different than climb through those altitudes.
From: John C. Bohn
[mailto:JohnB@agcheattransfer.com]
Sent: Wednesday, October 15, 2008 1:39 AM
To: lml@lancaironline.net
Subject: RE: [LML] IO-550N take off fuel flow
I’m getting 36-38 GPH take off flow on my TSIO-550E. I
was told this is too low but I don’t believe it. If its higher than
38 it may cause a problem during take off at some higher altitude airports or
when changing from LOP during landing….just my opinion.
John C. Bohn
N28487 4P
Direct (Cell)- 503-887-2933
From: Lancair Mailing List
[mailto:lml@lancaironline.net] On Behalf Of Fred Moreno
Sent: Sunday, October 12, 2008 7:49 PM
To: lml@lancaironline.net
Subject: [LML] IO-550N take off fuel flow
I
found an article for Cirrus SR-22 owners suggesting that the
take off fuel flows on the IO-550N are set too low at the factory.
As
I recall the Continental fuel injection document calls for about 26 GPH full
rich full throttle, 2700 RPM.
The
Cirrus article recommended a minimum of 28 GPH to help lower peak cylinder
temperatures and pressures. Climb full rich, and then do the "big
pull" with the mixture knob all the way into LOP territory. The
table below shows how far to pull as a function of power setting.
Lean of peak for the IO-550 N (8.5 compression ratio)
horsepower is 15 times fuel flow in gallons per hour. This was the basis
of the LOP flow rates in the table above. I figure that with 10:1
compression which produces about 4-5% more horsepower, the number is about 15.6
horsepower per gallon per hour.
In
my correspondence with a GAMI rep, the suggestion was a take off fuel flow of
32 GPH when using 10:1 pistons.
What
are you IO-550 operators getting for take off fuel flow?? What
recommendations have you heard or seen?
Lancair
IV, IO-550, awaiting a new Hartzell prop