REFLECTOR: Franklin Oil temp. (Hold the Wedding!)

[Laurence Coen]

To all Franklin drivers,

The misinformation is getting way too deep for me to remain silent.  Lycoming engines have "Vernatherms", Franklins do NOT.  A vernatherm works somewhat like a thermostat in an auto only backwards. In an auto the thermostat is closed when cold and opens on temperature rise.  The vernatherm is open when cold allowing oil to bypass the oil cooler and go directly to the oil galley. When the oil gets hot it closes the bypass forcing the oil to flow through the oil cooler.  The Franklin works on a different principal.  The external oil hoses are connected to an oil control housing on the copilot side of the engine.  This housing contains two spring loaded valves.  The one that faces away from the prop is the oil pressure regulator valve and comes set at 80 psi.  The second valve facing toward the prop is the oil cooler bypass valve that is set to open at 15 psi.  When the oil is cold it is viscous (thick) which causes a large pressure drop in the oil cooler loop forcing the bypass valve to open and allowing oil to flow directly into the oil galley.  Hot oil flows more easily allowing the bypass to close.  The Franklin in Velocity problem is the length of the oil lines to the nose cooler causing an excessive pressure drop that in turn limits flow through the cooler.  Mike did the two things that solve this problem.  Bigger lines and a stouter spring on the bypass valve.  Oil pressure and temperature are both measured where the oil enters the galley, after the oil cooler.  That applies to Lycoming too.  The oil pressure will always read less than 80 psi because of the pressure drop in the external loop so 60 psi is a good number.

Larry Coen
N136LC
SE/RG Franklin-IVO


From: Michael Watson 
Sent: Wednesday, January 28, 2009 1:47 PM
To: Reflector 
Subject: REFLECTOR: Franklin Oil temp.


Jerry,

I've been flying a standard elite RG with a Franklin engine for
10 yrs +.

I have one nose oil cooler and in Florida, I can takeoff and climb 
straight to 6000ft without the oil temp going over 210F.

In New York during the winter, It would take 10 to 15 minutes 
for the oil temp. to reach 104F.

As recommended by Franklin some years ago, I replaced the spring 
in the vernatherm valve and replaced the oil lines with 5/8 aluminum
lines. The temperature sending unit must be installed just before 
the oil re-enters the engine (Front connector closes to the prop. )
I also split the single plenum into two separate plenums, this
drastically reduced CHT temps, which also reduced oil temps, 
Takeoff should not be started until the Temp. reads 104F. 

I would suggest that you put the sending unit in a pan of water
with a oven temperature gauge, and check that it is giving you
the correct temperature reading.
 
-- 
Mike W.
1997 Velocity Elite RG
Franklin /IVO Electric CS
Dual GRT EFIS Synthetic Vision



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