REFLECTOR: vernatherm

Fri Nov 18 11:10:34 CST 2011

Grover,

A vernatherm is a component part of a Lycoming engine and not something you can add to a Franklin engine.  The bypass on the Franklin performs the same function as the vernatherm on a Lycoming.  I have a SE/RG Franklin/IVO and I can climb to 10,000 ft. at 110knts, in the summer, with a maximum CHT of 360F and oil temperature of 220F.  You haven't said but I suspect you have NACA engine cooling inlets.  They don't work very well and require vortex generators in most cases to get marginal cooling.  I have slightly modified arm pit scoops which work too well at times (CHT close to 200F in cruise).  I have the standard factory supplied oil cooler with 1/2" lines.  I added vortex generators in front of the oil cooler air inlet.  I also extended the belly scoop down 1" to increase air flow over the engine sump to aid in oil cooling.  I also have the stiffer bypass spring to compensate for the very long oil lines.  That's what worked for me but are not the only solutions to your temperature problems.  If you do have NACA's I would recommend vortex generators to bring down your CHT's which are a root cause of the high oil temp.

Larry Coen
N136LC
SE/RG Franklin/IVO

From: Grover McNair 
Sent: Thursday, November 17, 2011 10:28 AM
To: 'Velocity Aircraft Owners and Builders list' 
Subject: Re: REFLECTOR: vernatherm

Brian,

The CHTs are higher than I would like. On climb out I cannot run full power very long at all. I barely get to 1000" agl before the CHTs get up to 390F. If I level off and keep the rpm around 2500, these temps will stabilize.  The oil temp continues to rise though. 

My engine has a mag for the top plugs and a Lightspeed ignition for the bottom plugs. The mag is timed at 28 degrees. With the light speed system I am not sure about the amount of advance. After speaking with Lightspeed they recommended putting a timing light on the engine to determine where it is firing. I don't know how to do this safely. Any ideas? 

The Franklin bypass valve looks very restrictive internally. My thought was to modify it to make all of the oil flow to the oil cooler all of the time and have a vernatherm control the flow returning to the engine. Regardless I would like to try a stiffer spring. 

I am changing the flexible lines from the engine to the firewall from ½ to 5/8. The lines though the fuselage and to the cooler are 5/8.

For oil temp, there is an adapter in the line that runs from the bypass valve to the rear engine casing.

Thanks for giving this some thought. I look forward to hearing more.

Grover  

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From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On Behalf Of Brian Michalk
Sent: Wednesday, November 16, 2011 4:31 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: vernatherm

Do you have high CHTs as well?
If you are aggressive on your timing, retard it to 28BTDC, and see if your temps go down.

I don't think adding a vernatherm is going to help you.  The Franklin has a pressure bypass, and with hot oil, all of it should be going through the cooler.  You can try a stiffer spring on the bypass if you are not getting max oil through the cooler.  I think I still have some, if you want one.

Most everyone I know is running 5/8" lines to the cooler(s).  What size are yours?  Also, where are you measuring your oil temps?  245F is too high, and it means that in some portion of your system it's hotter.

On 11/16/2011 2:32 PM, Grover McNair wrote: 

The franklin engine I have in my 173LW  is running high oil temp, 245+. Having read recent posts, I am planning to install a larger oil cooler with a vernatherm. I would appreciate comments from those who have done this. Is there a modification necessary for the factory oil bypass valve? 

Grover McNair

N832AB

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