Fred,
I fly a TNIO 550B in a Bonanza. Not exactly what you are asking about but
similar. The turbo relief pressure is set at just under 30 inHg.
Takeoff fuel is 33.5 to 34 gph. I live in Phoenix and climb out temps are
not a problem and stay around 340 degF. Once established in cruise I pull
the mixture to 75 deg LOP which is 16.5 to 17 gph with the prop at 2500
rpm. I never pull the throttle. Cylinder head temps stay around 350-370.
A while back I was cruising at 16.5K ft and 52 degF outside temp and the hottest
cylinder head temp got up to 380. Leaning to 80 LOP fixed that. All of
these exhaust numbers are TIT.
I
would think 26 gph at sea level would be pretty lean on a IO-550N and 32 gph
with 10:1 CR would be a about right to a little low. The 550N is a non-cross
flow head so I would expect the 550N to need more fuel than the 550B at take
off due to lower manifold air temp.
Craig
Berland
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