it seems the preheat cycles increased the relative humidity. nice recording.
if the engine is kept dry by a dehydrator, would it be possible to increase the interval between the normal 50 hr oil change if the oil is clean?
Lycoming put a vent on the engine to remove moisture and relieve pressure in the crankcase. Why do you need to open up another hole? If you have moisture in the crankcase after flying, you didn't fly long enough to fully atomize the moisture. Fly more!
I’m with you Ron. I’m wondering if this discussion would be happening if we weren’t laying low because of corona virus. Can’t fly (well, some of us can, and do), and we’re bored. It was a nice day yesterday here in OH and I flew twice yesterday - no moisture from the tube either time.
I am no expert, and please feel free to correct me if I am talking rubbish, but I think that:
You get about 1 litre of water generated for every 1 litre of fuel you burn. Most of this is expelled in the exhaust, but some will get into the crankcase as blow-by. Oil tends to absorb water, so there will be a tendency for the oil to retain some of the moisture, and because the crankcase is a semi sealed vessel with no air movement inside, as the dew point fluctuates with daily temperature changes, the water will evaporate and then condense inside the crankcase causing the dreaded corrosion. Combustion byproducts in the presence of water in the oil and crankcase will also form acids that will also contribute to engine damage.
I am thinking of doing an experiment the next time I do an oil change. My plan is to weigh the old oil on a digital scale, then heat it up to boil the water off on a stove and then re weighing to see the difference after the water is removed.
Warm desiccated air flow is ideal, but even basic pressurised air flow into the crankcase using a cheap aquarium pump will eventually equalise the moisture content of the oil in the crankcase with the outside environment. Thats ok and an easy low tech and very cheap solution if your outside humidity is relatively low.
Thanks for the data Bill, based on your description, I'm invisioning your doing the following.
Are you using a 120 volt blower?
I have used Duck Bill valves in the past and they may work well in this application as check valves.
Another thought, somewhat outside the box.... buy a second oil cap that seals 100%, and plumb it with a fitting and hose to a vacuum compressor pump. Run the vacuum pump trying to suck down the remaining pressure in your engine and crankcase. Lower pressure lowers the boiling point of water. The water will evaporate right out with the vacuum pump running.
This is how we purge all air conditions and refrigeration units before adding more freon. The whole plumbing system has to be completely moisture free.
Small problem with that theory is that an a/c system in sealed while an engine isn't. You're just sucking moist ambient air into the engine through, for example the exhaust pipes, crankcase breather tube, etc, to replace the air you're sucking out through the oil filler tube.
Yes, but if the total pressure pulled out is less than the outside atmospheric pressure, wouldn't you still be pulling moisture out of the system?
Other option is to fly at very high elevations, which lowers the boiling point of water.
You must be punking us. If you remove any moisture it means you're removing air volume which has to be replaced because the engine isn't sealed.
Regarding flying higher, just to keep this simple, you eventually have to descend and land and cool down the engine.
So I can’t find any thoughts on an open oil filler cap to let engine moisture escape from a hot engine ??
So after a nice one hour plus flight today , after a fresh oil change, on a 300 hour well maintained engine (oil temp running at 185F). I pulled the aircraft is back in hanger .. I pulled the dip stick and again saw the milky white oily mixture on the filler cap / filler neck (clearly water in the oil) and watch the vapors pour out..
Fair question on the Rotax. Are we sure they don't have cam/follower issues? We know the cam location is under the crank, and possibly they have a cam/follower design contact stress design that allows use of materials more tolerant of condensation. The entire valve train is a "system"Maybe then, someone can explain to me, then, why I'm not reading about the Rotax 912 ULS in my RV-12 having corrosion problems in the engine.
Why do they promote it as a sealed crankcase system, with a dry sump that relies on blow by from the engine to pump the oil in the crankcase back in to the sump tank on the firewall?
I've never seen any white goo or condensation in my motor oil or on the cap. Matter of fact, have to remove that sealed oil cap and turn the prop by hand numerous times until the compression blow by "burps" all the oil back into the dry sump container, so that you can check the oil level in the sump tank.
It's plenty humid here, I don't live that far away from the pacific ocean here in Los Angeles, see the onshore fog regularly, plus Baja Hurricane season in the summer too makes the heat and air nice and unbearably humid.
Yes I understand it's not a Lycoming or a Conti... but still, it's an internal combustion engine burning gasoline making water as a by product, and the motor has and relies upon combustion blowby to get the oil back into the sump tank.