Min oil temp?

Discussion in 'Lycoming & Continental' started by Dana, Nov 4, 2018.

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  1. Nov 4, 2018 #1

    Dana

    Dana

    Dana

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    Maybe a stupid question, but I haven't seen the answer anywhere, at least nowhere unambiguous. My engine is an O-290-D, how warm does it need to be before I take off? I've been waiting until the needle at lest starts moving off the peg, which is 90°F. No big deal in the summer, but the past few times I've flown it's quite awhile that I'm sitting in the runup area. In flight the oil temp seems to run around 100-110° over ambient, so today (55F) it was running a bit over 150. Too cold? Should I block off part of the oil cooler? Most of what I've read about "cold weather operations" talks about far lower temperatures (10-20F) than I'll ever be willing to fly in with an open cockpit.
     
  2. Nov 5, 2018 #2

    PittsDriver68

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    All of the experts advise that you want your oil temp to run 180F so as to boil out moisture and acids that get mixed into the oil. You can block off the airflow into your cooler in increments until you see 180F. Aluminum tape works.

    The factory Pitts start the oil temp green arc at 100F.

    Best of luck,

    Wes
     
  3. Nov 5, 2018 #3

    TFF1

    TFF1

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    I have a friend who blocks his oil cooler in the winter. His runs too cold. The engine clearances are set for warm oil. Constant running cold oil is hard on rings and bearings. It's probably better on the cam though. Net bad.
     
  4. Nov 5, 2018 #4

    ndlakesdreamer

    ndlakesdreamer

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    All the Lycoming operation manuals I've read say the engine needs to be warm enough to accept full throttle without hesitation. If you are waiting for the oil temp to come off the bottom peg I'd say you are good. As for in flight temps I agree with the 180*F above.
    Dale
     
  5. Nov 5, 2018 #5

    Larry Lyons

    Larry Lyons

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    My mentor and my IA both who have tens of thousands of hours GA, says in most cases by the time you get ready to launch the engine is warm enough to go.
     
  6. Nov 5, 2018 #6

    EAABipe40FF

    EAABipe40FF

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    My O290 runs cold even with cooler blocked off on even a 40F day. I try to wait until I get to the peg(100F) but I noticed CHT might become a concern if you wait to long. Of coarse an with an E-AB with CHT only on 1 cylinder it's a guess anyway?
     
  7. Nov 5, 2018 #7

    Dana

    Dana

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    Hmmm, I don't have a CHT even on one cylinder. Still, time to look at an oil cooler block, anyway.

    When I emptied the puke can on the breather yesterday it was somewhat watery, so at least some moisture is cooking out.
     
  8. Nov 5, 2018 #8

    TFF1

    TFF1

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    Cyl 3&4 are the hot cylinders. I find 3 the hottest I think it comes from prop rotation direction. Most baffles try and shield the 1&2 from direct air blast so they are not too cool. If 1&2 are hotter, there is something going on.
     
  9. Nov 5, 2018 #9

    Walter Atkinson

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    FWIW, I spent five years doing detailed baffle research. We had a 36 probe CHT monitor on six cylinders so we could see the true effects of our changes. The OP question indicates to me that there could be a measurement error. I would check the accuracy of the Inst. reading before doing anything else.

    There are only two factors in CHT: heat IN and heat OUT. Unbalanced fuel:air ratios result in different heat INTO the various cylinders. The design of the metal parts of the baffles are the biggest factor in the heat OUT part. The rubber seals are far less important than most assume. Sealing up every tiny leak is far less important than getting the little air used for cooling to go where you want it to go.

    There is much, much more air going into the cowl than can be used for cooling. Most of the air going into the cowl goes out of the cowl behind the spinner and over the windshield. That’s why you get oil on it when you have an oil leak.

    The rotation of the prop has little to no effect on cooling left vs. right. If one gets the f:a ratios balanced, the left-right difference almost always disappears and you have the difference only related to the air going where you need it on individual cylinders.

    There is so much more about this topic that can’t be posted with this bandwidth but almost everything I learned in A&P school about baffling and cooling turned out to be wrong. The “logic” of what goes on under a cowl is blown to bits by the data.
     
  10. Nov 5, 2018 #10

    Walter Atkinson

    Walter Atkinson

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    The reason #1&2 get shields is that they run seriously out of round without them. There is a better solution. We created better cooling in the lower-forward fins. Cooler cylinders produce more power and even Lycoming says that min CHT is 150dF. Cooler cylinders are stronger.

    The reason #3 is the hottest is the poor design of the aft baffle on it. Very little air gets past it and the lower aft fins get little to no air. There is a fix.

    The enemies of metal are heat and pressure. Keep them controlled and you will be rewarded with good service and longevity.
     
    Last edited: Nov 5, 2018
  11. Nov 5, 2018 #11

    Walter Atkinson

    Walter Atkinson

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    While there is ample data to support that optimal oil temp. is 180-190dF, the oil gets much hotter than that as it hits the under sides of the hot cylinders. Hot enough to vaporize the water.

    There is data that shows that to get most of the water vapor out of the crankcase, not only does it take adequate oil temp. To get the water out of the oil, it takes a minimum of one hour flying to get the water vapor out of the crankcase. Our many short hops in our biplanes are not getting the water vapor out of the crankcase.

    Fly longer!
     
    Last edited: Nov 5, 2018
  12. Nov 5, 2018 #12

    TFF1

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    Modern baffling has the prop shield that keeps back flow from happening. A Hatz with its at best Super Cub cowl setup is going to be subject to all you talked about in some form or fashion. Most are not building a new baffle set like someone building a Lancair.
     
  13. Nov 5, 2018 #13

    EAABipe40FF

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    Alas, above is probably spot on. My Spezio seems to have PA22 baffles but w/oil cooler in front of #2 cylinder. The AD2 with IO320B1A had the Piper PA30 FWF baffles and exhaust with slight modifications. Even if not exact it was still operating much slower so who knows. I put CHT on #4 which was already there. Maybe #4 was hotter because oil cooler was right there although intake air was was taken from behind #4.....? I played with exit to get "right" combo of oil temp and CHT. It's not correct for both summer and winter. Of coarse the PA30 has cowl flaps I think?

    As I said in my first post, most E-AB's are probably a guess and as Tom suggests if copied off a vintage design probably iffy to begin with. I got advice from a Rick ? on the Cub forum when I had issues with the Spezio. I had copied the exit off the EAA biplane(no CHT) I pulled the FWF off of and it ran way, WAY too cold. I hate to think how many E-AB engines are running, their pilots flying along fat, dumb and happy.... OTOH many current builders will do far better with modern engine data.

    I also understand that short hops are not best. I try to get oil temp. above 180F for 10-20 min. at least once a week. It's partly logistics-hauling gas in cans etc., it would be a huge effort not to mention $ to fly enough so as they say, pay now or pay later.....

    Jack
     
    Last edited: Nov 5, 2018
  14. Nov 5, 2018 #14

    mjk51

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  15. Nov 5, 2018 #15

    Dana

    Dana

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    I was thinking about making something like that... but for the price it's probably not worth the effort of making myself...
     

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