Aircraft engines and corrosion: In the beginning, automobile engines and most others shared the same crank case ventilation system as an aircraft engine have today and they suffered the same corrosion problems, a simple road draft tube, on some vents were added to the valve cover to facilitate air movement through the engine while the car was moving, some engines had lymph pumps to evacuate blow by gasses that contained moisture, oxides of nitrogen and sulfur that were damaging engines. In the early 1960’s the PVC valves were introduced as a method of re burning blow by and reducing pollution, a phenomena occurred, automobile engines started running much longer, breaking the 100,000mi mark, of course better oil, machine technology also played into this, but the PVC valve was the largest contributor, moisture, oxides of nitrogen and sulfur were now being scavenged and were no longer able to dissolve into the oil, dramatically increasing the life of the oil and eliminating corrosion and ware of the internal engine parts. So, it’s now 2015 and we (aircraft owners) still have the same crankcase ventilation as a model T Ford. ??????
As for me, I’m using an oil recovery system that uses some of the vacuum system discharge air to evacuate the recovery tank, I return the oil and vacuum discharge air to a forward valve cover, thus circulating fresh air through the engine and discharging the contaminated air out the breather tube, my oil no longer smells sour and on an oil change there are no longer droplets of water in the drained waste oil. Only time will tell.
PS. my franklin has a floating oil pick up and does not pick up oil from the bottom of the sump.

Can I make a correction? I'm sorry, this may be kinda mean spirited but it's meant in good humor. Really.

The acronym is PCV. Positive Crankcase Ventilation. PVC alway seems to slip out because it's a more common acronym. PVC is Polyvinyl Chloride. Just a small point. I think you may be on to something though about our engines benefiting from PCV though. I wonder if a guy could use a venturi? Oil all down the side of the airplane I suppose. Put it on the bottom where the oil already runs? I dunno.

There are two places you can burn crankcase blow-by. One is in the engine via the intake system, and one is in the exhaust.

If you introduce it into the intake system it has to be done after the carburetor or throttle body. Introducing water and acid and oil into an engine without understanding the ramifications, including how it affects the air/fuel mixture, will have unpleasant consequences.

However, introducing it into the exhaust (properly) has no ill effects, and as a bonus keeps oil off the belly. You want to create a draw so the vapors are scavenged out of the crankcase. Here is what you use and where you use it.





Experimental only of course.

Just remember to clean it every 50 hours or so. Otherwise the opening will coke over and you'll spring oil leaks everywhere (don't ask how I know), and you won't become a millionaire.

Mister701 wrote:Can I make a correction? I'm sorry, this may be kinda mean spirited but it's meant in good humor. Really.

The acronym is PCV. Positive Crankcase Ventilation. PVC alway seems to slip out because it's a more common acronym. PVC is Polyvinyl Chloride. Just a small point. I think you may be on to something though about our engines benefiting from PCV though. I wonder if a guy could use a venturi? Oil all down the side of the airplane I suppose. Put it on the bottom where the oil already runs? I dunno.

I can't belive that I did that,,, here is my best Homer Simson,,, DDddOOoooo, not mean spirited, I laid an egg!

I have heard of breather systems on experimental aircraft going terribly wrong, introduced into the air box and icing up, you can imagine the rest, the benefit here is not from burning the waste gases, but from moving fresh air through the crank case, absorbing gasses, moisture and discharging them before they can dissolve into the oil. I have been trying not to sell any one’s product, however the AW oil recovery system is STCed and works in the manner I described, I did modify the installation a bit by moving the return to the far end of the engine. Scavenging into the exhaust is an ideal place to put them, however to get the full benefit fresh air must be introduced on the opposite end of the engine, a small portion of the clean dry vacuum pump discharge is ideal.

Another point that I would like to bring forward, oil air separators that do not have air flowing through them have a tendency to condense and return byproducts to the crankcase, yes they are catching oil vapor but they are also catching and returning the very stuff you don’t want in your engine. In my opinion that is not a good thing. God, I still can’t believe that I did the PVC thing.

172heavy wrote:..... I return the oil and vacuum discharge air to a forward valve cover.......

Fresh air aside, aren't you returning the very stuff that you say is bad right to the engine?
I would think that blowing it out the breather or into the exhaust would be better.

hotrod180 wrote:

172heavy wrote:..... I return the oil and vacuum discharge air to a forward valve cover.......

Fresh air aside, aren't you returning the very stuff that you say is bad right to the engine?
I would think that blowing it out the breather or into the exhaust would be better.

No, I don’t think so, The AW oil air separator is unique in the respect that it scrubs the return with the vacuum air discharge, all the vacuum air discharge flows through the oil air separator keeping the bad stuff in suspension and discharges it, seems to work, my oil smells better and no more small droplets of water in my waste oil. Other systems return everything. Would I like to dump it into my exhaust, perhaps.

Barnstormer wrote:
If you introduce it into the intake system it has to be done after the carburetor or throttle body.

Why?

AEROPOD wrote:

Barnstormer wrote:
If you introduce it into the intake system it has to be done after the carburetor or throttle body.

Why?

Icing, you don't want a big blob of ice forming forward of the carb do you? Combustion byproducts contain moisture, I read an account of an experimental that located the breather in the air box and caused loss of power due to icing , Cessna has an extra hole in there breather tube inside the engine cowl to ensure that the breather does not freeze up, this came about when one iced up causing sufficient back pressure to blow out the front seal and dump all of the oil.