Steve,

I have seen some hard data that pretty convincingly demonstrates that the temperature of the exhaust valve guide is very closely correlated with engine oil temperature.

Since a significant portion of the heat transfer from the exhaust valve passes up the stem and out through the valve guide - - keeping that temperature low helps to manage the exhaust valve temperature.

If you get the oil temperature hot enough so that the water boils off - - that is hot enough.    At altitude,  water boils well below 212 d F.    And further,  the oil temperature going through the various hot spots in the engine will be well above the average oil temperature reported by the  engine monitor.    It does make some difference where you get the oil temperature pick up.

If you start to see evidence of water condensation on the dip stick - - then clearly the oil temperature at cruise is too low. 

My personal preference is to see the oil temperature go up to around 200d F sometime during the climb and then to settle off in the 180-190dF range at cruise.

Regards,  George

Valin & Allyson,

You will need to adjust the oil cooler door all year, on almost every flight, to keep oil temps high enough.  Typically we reset the door at cruise and on descent (and now in climb.)  Prior to Neal George’s Continental Forum at Greenville, we used 175 degrees as the target.  Neal recommends 200 degrees as the preferred setting.  The door cable has enough load to require a locking button, see:  A-700 BUTTON LOCK DASH CONTROL http://www.aircraftspruce.com/catalog/appages/a700.php?clickkey=276832   An additional benefit is reduced cooling drag.

Neal also said 320 degrees is the minimum Cylinder Head Temp and the mid 200’s a lot of us have at cruise is too low. 

Steve and Claudette Colwell  Legacy RG 550

Hey LML gang,

Working on our IO-550N engine installation…  Already have baffling done and flapper door in front of oil cooler.  We’ve heard mixed reports of whether it is needed or not.  We need to decide if we really need to have cockpit control of the door or not.  We’ve heard some people just remove the door or wire it open or closed depending on the season.

Would appreciate hearing about your flight experience with the Legacy with an IO-550N engine and the usefulness or not of control of the oil cooler door…

Thanks!

Valin & Allyson Thorn

Legacy Project

Boulder, Colorado