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Author Topic: Un-Cowled 1/2 VW Cold WX Ops.  (Read 1099 times)

Offline Aaron

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Un-Cowled 1/2 VW Cold WX Ops.
« on: November 15, 2022, 01:51:42 PM »
This is exclusive to all the other LE pilots who are as enthusiastic (aka stupid) as I am and fly their legal eagle in cold weather, for me that is Northern Michigan in November. This is the first winter I have decided to bundle up and fly her under 40 degrees. Contrary to expectations, I have been experiencing poor climbout performance in cold weather. When I say poor, I have better performance on a 85 degree day, which is grossly opposite to what it should be! My theory is that since my oil temp is barely getting over 100 with the uncowled 1/2 vw getting blasted with frigid air, I am not getting warm enough to expand and get a sufficient head to cylinder seal, therefore having low compression. Note I do not have a copper head gasket/shim, I lapped the head into the cylinder per original VW design, therefore it really needs that expansion to create a good seal.

Next time I am in the hangar I planned on doing a compression test cold vs warmed up (if I can even achieve that), and that should be a good tell if that is the culprit or not. Has anyone with an uncowled 1/2VW ever experienced this in cold weather operations? If so did you have a remedy? If you fly in the cold and don't have this issue do you have a copper head gasket/shim installed? I was thinking about installing one and removing a steel under barrel shim when I go to double check the head stud torques.

Anybody have any other theories? Thought it would be interesting to open this topic up and hear everyone's experiences. Note I don't really see any rpm loss, 10-20rpm maybe?? Only thing I notice is oil temp is barely over 100 F even after a mind numbing LE climb to 3000'.

Offline Theodore

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Re: Un-Cowled 1/2 VW Cold WX Ops.
« Reply #1 on: November 16, 2022, 05:17:09 AM »
...and i thought diesel cars were bad  VW air cooled needs to run over 200deg
240 is good
DOH
 thinking of my cccold diesel car, yes metals esp aluminum need to expand to tighten-up. Air cool cars 411, ghia and bug temps less than 1.9 diesels. i run engine 3K just to get more heat in cab.
Peace
""Take care of your wish""

Offline lake_harley

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Re: Un-Cowled 1/2 VW Cold WX Ops.
« Reply #2 on: November 16, 2022, 08:53:38 AM »
Having only a 20-ish RPM loss doesn't suggest an engine problem to me. What's the weight of everything you're "bundling up" with?

Offline Aaron

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Re: Un-Cowled 1/2 VW Cold WX Ops.
« Reply #3 on: November 16, 2022, 02:49:48 PM »
lake_harley - Not enough weight to produce less climb performance with 40 degrees less. Maybe 10 pounds at the most. Important info you didn't know, I only had 3 gallons on board at this instant. I don't think my coat, gloves, scarf and goggles will defeat the impressive effects of air density. I have flown heavier in 80deg. weather with better climb performance...

Theodore - I have never seen more than 180 even low on oil on a hot day, not sure why or what to do about that other than raise compression ratio. Back in initial break in of the engine, I didn't believe the gauge, so I verified the gauge and tried multiple locations in seek of the hottest oil, including drilling and tapping right below a pushrod tube, which is where it is now, in theory getting bathed in the oil fall of the hottest oil off the heads...

 

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