The myths of leaning
I have been reading on the forum about leaning and find that Lycomings suggestion that it is cheaper to replace cyclinders than the amount of fuel you save by leaning to be rather an unsafe statement.
I fly a non turbo Lance in Australia and cruise at 23/2300. That produces around 65% power and then lean to between 46 - 50 litres/hr.(12/13 gal). My speed is around TAS 140 kts. My cyl temps are between 320-360. Egt's are between 1480-1550. I don't fly over 8000' much so the manifold pressure doesn't go below 23. I have an engine monitor installed to monitor everything.
It seems strange to me that in the POH Lycomings max cyl temps are 500 considering that the wear rate of metal doubles once the temps get over 400.
My mechanics have said I am mad but physics tells me I'm right.
The leaning technic is simple. Get to cruising altitude and set 23/2300 then bring mixture back until engine runs rough then increase until it runs smooth. And presto 48/50 litres /hr and an engine that has over 2200 hr on it since last overhauled and burns about 1 litre of oil per 8 hrs. It's not rocket science like some like to believe.
Thats what I do anyway.
Cheers
I fly a non turbo Lance in Australia and cruise at 23/2300. That produces around 65% power and then lean to between 46 - 50 litres/hr.(12/13 gal). My speed is around TAS 140 kts. My cyl temps are between 320-360. Egt's are between 1480-1550. I don't fly over 8000' much so the manifold pressure doesn't go below 23. I have an engine monitor installed to monitor everything.
It seems strange to me that in the POH Lycomings max cyl temps are 500 considering that the wear rate of metal doubles once the temps get over 400.
My mechanics have said I am mad but physics tells me I'm right.
The leaning technic is simple. Get to cruising altitude and set 23/2300 then bring mixture back until engine runs rough then increase until it runs smooth. And presto 48/50 litres /hr and an engine that has over 2200 hr on it since last overhauled and burns about 1 litre of oil per 8 hrs. It's not rocket science like some like to believe.
Thats what I do anyway.
Cheers
Comments
The 500°F max is a "never, ever exceed" temperature. Lycoming's advice, from the O-540 Operator's Manual, is "For maximum service life, cylinder head temperatures should be maintained below 435°F during high performance cruise operation and below 400°F for economy cruise powers."
In practice I never let a CHT get above 400. The only time that's a challenge is climbing on a hot summer day - and the answer is to lower the nose and increase airspeed.
Pefect!