Oil cooler placement

J

JOhnH

Ejection Handle Pulled
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My 172n with a 180hp engine has about a 4 inch round opening in the metal panel behind the engine (behind #3 cylinder) with about 2 feet of duct diverting air to the oil cooler, which is mounted low down on the firewall. I have always had issues with high CHTs. Even running lean of peak (in "Henning mode"), I am still pushing the low 400s on a warm day in level cruise. I am thinking that too much air is being diverted from engine cooling to oil cooling.

The other day I was looking at a 172p (with a 180) that had the oil cooler flush mounted to the panel behind #3. No ductwork. This looks much more efficient as far as not diverting air away from the engine while still supplying air to the oil cooler. My A&P is going to see if there is an STC for the 'n model to move the oil cooler.

Does anyone have any comments or suggestions regarding this theory (assuming I explained it sufficiently)?
 
Wouldn't the air be passing through the oil cooler cooling fins, therefore still being diverted away from the cylinders for cooking? Possibly a tad more air will pass over cylinders, but I don't believe it will be a noticeable change.
 
How would it really help? The same amount of air will staill pass through the oil cooler.

Check baffle seals and CHT probe accuracy.
 
I think you're still worrying about a non existent problem.
 
I'm not sure of the solution, but CHT's in the low 400's in cruise are too darn hot with a Lyc O-360-A like the OP has. This really should be addressed, or you're going to have valve guide problems in the foreseeable -- well before this engine should need overhaul.
 
Please cite the engineering and metalurgical reasons along with actual evidence of CHTs as indicated under 430*F, the absolute hottest I could get them on a hot day down loan making full power as registered by an uncalibrated system are reason for concern? At the rate of wasting money looking for a solution to a non existent problem, he can change the one warm jug every few hundred hours and be money ahead. There is nothing wrong with his plane that a chill pill won't cure.
 
Henning said:
Please cite the engineering and metalurgical reasons along with actual evidence of CHTs as indicated under 430*F, the absolute hottest I could get them on a hot day down loan making full power as registered by an uncalibrated system are reason for concern? At the rate of wasting money looking for a solution to a non existent problem, he can change the one warm jug every few hundred hours and be money ahead. There is nothing wrong with his plane that a chill pill won't cure.
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Henning's advice may cost you a catastrophic engine failure, or at least an early overhaul. There are plenty of data ranging from Lycoming factory tests to the experience of engine overhaul shops to show the deleterious effects of CHT's that high on this series of engines, especially on the valve guides. I'm not going to argue with him, just point out the risks you take running the engine that hot. Y'all make your own decisions.
 
In other words, you have no data except OWTs and your own fears, thank you and please just say that. Heat does not = stress or damage, ICP does. You don't understand the relationship so just leave it alone. 410 is far below redline besides which his system is not indicating the temps in the AFM because the probes are different and read hotter than the factory ones.
 
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Henning said:
In other words, you have no data except OWTs and your own fears, thank you and please just say that.
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No, I have the considered, educated opinions of the engineers at Lycoming and those of several people who repair engines for a living, along my own experience as a degreed engineer in the aviation industry (albeit not in engine development). OTOH, we have Henning's personal opinions which are not, to my knowledge, supported by anyone who knows anything about piston engine design, engineering, development, or maintenace. I choose those with the training, knowledge, and experience. Others may choose Henning. Your choice, folks, but I'm not going to debate this further with Henning.

:bye:
 
Ron Levy said:
No, I have the considered, educated opinions of the engineers at Lycoming and those of several people who repair engines for a living, along my own experience as a degreed engineer in the aviation industry (albeit not in engine development). OTOH, we have Henning's personal opinions which are not, to my knowledge, supported by anyone who knows anything about piston engine design, engineering, development, or maintenace. I choose those with the training, knowledge, and experience. Others may choose Henning. Your choice, folks, but I'm not going to debate this further with Henning.

:bye:
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You have no written statement from an engineer at Lycoming that says operating a cylinder at 410 on an O 360 is destructive.
 
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