winter baffles & CHT Temps
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- Lou
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Re: winter baffles & CHT Temps
Here’s some comparative numbers from last week with baffles in. -8C on the ground (2300’ ASL). -12C at 6500’. My usual warm up to 95 degrees and climbing. At 1000’ AGL oil temp had climbed to 120. Of course I forgot to write down the oil temp in cruise and the data card is at the airport, but it was lower than I thought, I recall 145 or so. At 2200 squared 75 ROP CHTs range from 310 to 355. 139 kts TAS. If I fly LOP in this weather the CHTs drop below 300, which I think is too cold.
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Re: winter baffles & CHT Temps
Yes. I never have overheating problems with baffles as long as it’s below zero. If there’s an inversion - common where we are - and the upper layer is warm (above zero) I have to manage it more carefully. Anything above about 380F CHTs I begin to watch. Running LOP is the easiest way to bring it down.
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Re: winter baffles & CHT Temps
I tried my baffle again today after making several trips in the cold and oil temp never breaking 170. OAT on the ground was about 50 F, and in the air about 40 F to the altitude I climbed. As I recall happening many years ago when I tried it as well, the CHT's got hot very quickly on climb and cruise unless I ran very rich. The oil temp did, however, easily get to the 180- 195 range. As I understand it, the goal of oil temp above 180 F is to promote moisture evaporation from the oil to diminish corrosion, so my question is... which is more important, oil temps in the range, or cooler CHT's. Without the baffle, my oil temp seems to hover around 170 F in cruise around freezing temps. As others have stated, something that blocks just the oil cooler would be ideal, but the baffle as designed blocks the whole right side inlet, and taping the actual cooling intermittently for me just is not practical.
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Re: winter baffles & CHT Temps
While it's a delicate balance, if I was pushing the high end of CHT's with the baffle, I would definitely pull the baffle in favor of lowering CHT's. Mike Bush has some excellent analysis on how much metal weakens as engine CHT's rise - it's an exponential curve with potential for catastrophic results.
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Re: winter baffles & CHT Temps
That has always been my inclination as well David. How about shoving a cork or equivalent in the oil cooler hose inlet from the outside. While I do not recall definitively how far back it is, I think it is reachable. Or even perhaps just fabricating a cork equivalent hooked to an arm that attaches to the baffle camloc insertion.
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Re: winter baffles & CHT Temps
The oil cooler duct is a rather large oblong cross-section channel molded into the inside of the lower cowl. Fashioning a removable gizmo to insert into the front aperture to partially obstruct airflow would seem to be feasible.smoss wrote: ↑Mon Jan 30, 2023 12:50 am That has always been my inclination as well David. How about shoving a cork or equivalent in the oil cooler hose inlet from the outside. While I do not recall definitively how far back it is, I think it is reachable. Or even perhaps just fabricating a cork equivalent hooked to an arm that attaches to the baffle camloc insertion.
To be clear, it is not part of that circular adapter that one must fight with when removing/installing the lower cowl. This latter supplies air for cabin heat/defrost, and cooling airflow to the alternator and battery compartment.
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Re: winter baffles & CHT Temps
Ahh, thanks Rich. I was thinking it was one of the 2 small hoses you describe, which are in fact to the alternator and battery.
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Re: winter baffles & CHT Temps
I live in MN and install the baffle (usually) when it gets below 15F. No problem with the CHTs at those temps but above that I have to watch the CHTs on the climbs, and above 30F I can’t use it. It is sort of a pain to install and remove. The baffle doesn’t seem to help the oil temp much in my plane which usually runs low. I am considering putting tape on the oil cooler but I haven’t done that yet. The oil analysis never show water in oil but maybe it evaporates by the time it gets to the lab.