Constant Preheat?

Henning said:
Isn't the breather out the top of the case? That is the only crank case ventilation I am familiar with.
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Not in most models of Lycoming, the 0-235 & 0-540 is as close to top of case as you get.

The rest it seems to be as required by aircraft application.
 
Crankcase breathers are designed to vent pressure while the engine is running, not moisture while the engine is static. Most breathers have a significant down leg. That's a pretty effective restriction to the passage of warm air in a cool environment (the constant preheat scenario for most of us). A dipstick tube isn't much better given it's location low in the case. A TCM oil filler cap being left off might be the best for creating stack effect but it won't do anything to air out the cylinders. Lack of positive pressure and return air is the problem. With that in mind the engine dehydrators might make some sense. If the ambient temps are consistently below freezing I think doing nothing makes better sense. That's my regionally biased, outdoor parking, subjective attitude. Just more stuff to think about.
 
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Stewartb said:
Crankcase breathers are designed to vent pressure while the engine is running, not moisture while the engine is static. Most breathers have a significant down leg. That's a pretty effective restriction to the passage of warm air in a cool environment (the constant preheat scenario for most of us). A dipstick tube isn't much better given it's location low in the case. A TCM oil filler cap being left off might be the best for creating stack effect but it won't do anything to air out the cylinders. Just more stuff to think about.
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Correct, there is nothing designed into the system to handle the issue.

However as to setting up a convective current, you do not need a straight shot bottom to top to create a draft, you can actually use some pretty convoluted routings with not a lot of loss as long as the ends are correctly placed and sized. We deal with this in dead spaces of double hulled vessels to manage similar corrosion issues, and there are some really convoluted paths there, but it seems to be effective.
 
Tom-D said:
How would you vent past the lifter?
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You are venting from the rocker box side.... As you reminded me the return lines go back into the crankcase so airflow will use that as a path... The tubes are the highest point on a Lyc..... Well except for the top of the rocker covers but alot of cowling are so tight it might cause interference...
 
N801BH said:
You are venting from the rocker box side.... As you reminded me the return lines go back into the crankcase so airflow will use that as a path... The tubes are the highest point on a Lyc..... Well except for the top of the rocker covers but alot of cowling are so tight it might cause interference...
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I don't think the volume of flow through that path is going to be significant enough to create a measurable effect. Those return hoses are small, besides, you need to collect from the top of the crank case, not bottom. You want to introduce cold air at the bottom.
 
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Henning said:
I don't think the volume of flow through that path is going to be significant enough to create a measurable effect. Those return hoses are small, besides, you need to collect from the top of the crank case, not bottom. You want to introduce cold air at the bottom.
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I agree.... I am just brainstorming an idea for all you certified Lyc drivers and owners...... My Ford works perfectly for breathing.....;)..

And.. I am still not convinced there in NOT a few drainback holes up high where the pushrod tubes mate to the case....

Any one got close up pics of that area???
 
I started removing my filler cap after a flight, and you can see vapor's escaping. Quite a bit actually. Just remember to put it back!

The little trap door being on top of the cowl let's a lot of heat out too. Air moves up from the cowl flaps through it carrying heat with it.

Am I doing anything that helps the longevity of my engine? I don't know, but it can't hurt ....
 
txflyer said:
I started removing my filler cap after a flight, and you can see vapor's escaping. Quite a bit actually. Just remember to put it back!

The little trap door being on top of the cowl let's a lot of heat out too. Air moves up from the cowl flaps through it carrying heat with it.

Am I doing anything that helps the longevity of my engine? I don't know, but it can't hurt ....
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You have a Continental, better design in that aspect as the filler provides an excellent vent.
 
txflyer said:
I started removing my filler cap after a flight, and you can see vapor's escaping. Quite a bit actually. Just remember to put it back!

The little trap door being on top of the cowl let's a lot of heat out too. Air moves up from the cowl flaps through it carrying heat with it.

Am I doing anything that helps the longevity of my engine? I don't know, but it can't hurt ....
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Where does the make-up air come from? It can't breathe without new air to replace the old.
 
txflyer said:
I started removing my filler cap after a flight, and you can see vapor's escaping. Quite a bit actually. Just remember to put it back!

The little trap door being on top of the cowl let's a lot of heat out too. Air moves up from the cowl flaps through it carrying heat with it.

Am I doing anything that helps the longevity of my engine? I don't know, but it can't hurt ....
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FWIW, I see the same in my O-320. There's a whole lot of vapor that vents.
 
jesse said:
I leave the rental 172 plugged in 24x7 all winter. That said, it does fly almost every day.
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The school I do my training at does this as well. All of their planes fly pretty regularly. At the minimum, they get flown once a week
 
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