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which side to block?
If you know the actual flow direction of the oil, and when, is there a best way to raise the oil temp?
My plane came with a plate that bolted to the back of the oil cooler. with a few washers, you could allow perhaps 15% flow, or flush with the rear, almost nothing. I think a possible benefit might be that the front gets some warm air off the top of the cylinder fins, so when the vernatherm lets some oil thru, in theory, the cooler isn't a brick of cold thick oil. This question arises every year for me; if the engine is cold, why would the vernatherm let ANY oil thru to to cooler, until it really NEEDED to be cooled? why do we block it off? ( not unlike the rad in your car, there's no flow until cooling is needed.) Now I totally see the need to limit airflow into the COWL........but very few guys do that, first anyway. ( me included) cause it's a bit harder to do. Someone please educate me? |
Vlad, I'll try it!
Just for base numbers, I flew for 45 minutes Friday with an outside air temp of about 20 and my oil temp actually hit 138, once! Mostly closer to 125. Heading to HD Aviation to see what kind of tape I can find. Will work on a better fix later but the tape will give me a good idea of how much to block off. Other base data: WOT 3500 to 5500 feet altitude Prop pulled to 2350 rpm 50 degrees LOP Hottest EGT 1320, about 30 degree spread Hottest CHT 312, coldest CHT 289 7.8 gph 168k TAS Thanks |
Quote:
The vernatherm is an oil cooler bypass. It is in parallel to the cooler. The vernatherm valve is open when cold. This means the oil has two paths it can take, through the cooler or through the vernatherm and on to the rest of the oil system. When temperature rises, the vernatherm closes and shuts off the bypass path. All oil is forced through the cooler at that point. So the valve changes the oil flow through to cooler from some to all, not from none to all. If the flow of oil through the cooler (with vernatherm open for max bypass) is still too much and your oil temperature is too low, then the cooling fins need to be blocked. |
Even when a vernatherm is "open" some amount of oil still flows thru the cooler. I've found that even when both the front and back sides of the oil cooler are blocked off in my O-320 RV-6 in very cold weather, that I still have difficulty getting the oil temps up to 180 but blocking off the front side is more effective than blocking off the rear.
I've built a flapper door to cover the rear and it's hooked up to a push pull cable I can control from the cockpit, but when the weather gets really cold, I also have a piece of flat aluminum sheet that I put over the front of the cooler and tape it into place with Gorilla tape. |
rzbill,
Thanks for that explanation on the vernatherm. That has also puzzled me , I thought it worked like a coolant thermostat. I must have a very efficient cooling system since my IO 360 rarely rises above 165 in the summer and gets progressively cooler in the winter months. I am going to verify my temperature is accurate and then start restricting the airflow through my cooler. I would really like to see it get in the 180-195 range to burn off the condensation in the motor. I looked all over for a diagram or explanation on the oil system and vernatherm operation; do you have any official references on this system? |
Dave,
You are welcome. I understand the 180 hp Lycomings commonly have cool oil temperatures when installed well per Vans plans. Mine does too. I need 1/3 to 1/2 coverage in the summer to get 170 to 180F temp indication. Even more in the winter. DanH has posted some good oil systems diagrams here. Search his Id and the word vernatherm in the advanced search area and you will find them. |
I installed the oil cooler shutter from Van's, with an in-cockpit push-pull cable and it works *great*. I've never had high oil temps even in summer, and I can precisely control it when needed to bring it up above 180 when it's cold (in fact, I can change the temp by just a degree or two with fine movements of the cable if I want).
No speed tape, no need to decowl and fuss around with adding or removing it, etc. Highly recommend it. |
Van's oil shutter
Paul, I have a Van's oil shutter that i took off my plane. It has the pull cable and the longer AN bolts that you need. Email me if your interested.
Matt m.tucciarone@hotmail.com |
Aluminum tape
I found this:
Nashua Aluminum Waterproofing Repair Foil Tape, 11 mil Thick, 10 m Length, 48 mm Width at Amazon. It is much thicker than the tape used to repair ducts. |
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