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  #21  
Old 05-05-2014, 08:24 AM
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If you have before-and-after oil analysis to contribute, please email me.

Here are the first two contributions.

Subject #1; no water contamination. Separator with reed valve evacuator to the exhaust, negative pressure system. A small increase in silicon (dirt) is notable, but the owner reports finding a gap leaking air after the intake filter. Next oil report should tell the tale.



Subject #2; no water contamination. Record is less complete, and the previous report was from a different oil analysis firm. I've inserted the previous values, which were recorded prior to the installation of a separator. No evacuator reed valve on this one, so the crankcase and separator system was operating at positive pressure.

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  #22  
Old 05-05-2014, 10:47 PM
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A good discussion here. I thought I would point out a few things I learned working in an auto shop and from research. Condensation is a reality with or without separators. It is all about the cycle of condensation and burning it off.

The crankcase is always filled with combustion by-products, including H2O. When you shut down your engine, it cools from ~200* to ambient. In the process, the water vapor condenses to liquid and gravity takes it to the oil. If the next run spends a certain amount of time above the critical temps for burning off the moisture (I believe it is speculated to be 160-170 degrees), the moisture is purged from the oil. Granted, the separator will increase the load of water added back, but I bet it is minimal. Think about how little oil is returned to the case. People here are reporting one quart of oil over 25-50 hours.

I remember pulling valve covers off cars that were driven by housewives that only ran short errands. You would routinely find large clumps of white goo, that was a gell of oil and water. Those engines simply weren't run long enough at operating temp to burn off the moisture that collected each time a hot-cold cycle took place. These were cars from the 70's and 80's and they did not have air oil separators.

Condensation is a reality we all should think about and understand to ensure that our running patterns will purge it from our oil. However, with the proper cycles, you have nothing to worry about. Most all of the BMW's and many German cars use air oil separators and all return the oil to the case. When routinely taken to operating temps, these engines can easily surpass 200,000K without corrosion or other damaging issues attributed to moisture in the oil.

Larry
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  #23  
Old 05-17-2014, 06:10 PM
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A point of contention... If you install a crankcase evacuation system on the engine ( one way valve on the exhaust connected to the breather hose ), what would be the purpose of the separator? All the moister and blowby goes into the exhaust and burns off so there's nothing on the belly anyway.. Maybe a few drops of oil would get returned to the engine but other byproducts you might not want also returns.
Race engine builders have been using crankcase evacuation systems for as long as I can remember. I've used them on cars, boats and motorcycles and they work. They are cheap and easy to install. Mr. Gasket and Moroso sell a pair for less then $50 with all the parts for two planes. I use one on my IO-360.
The added advantage is negative crankcase pressure that stops oil weeps and also the theory it increases HP by removing pressure on the piston down strokes.
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  #24  
Old 05-17-2014, 10:24 PM
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What are the failure modes of a crankcase evacuator reed valve?

If the reed fails, it seems like there is a chance that your crankcase could be directly connected to the elevated pressure inside the exhaust manifold.

Always wondered about that.

David
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  #25  
Old 05-18-2014, 12:25 PM
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Quote:
Originally Posted by digidocs View Post
If the reed fails, it seems like there is a chance that your crankcase could be directly connected to the elevated pressure inside the exhaust manifold.
You mean the significant and substantial rapidly alternating pressure in an individual headpipe on a 4-into-1 system (below), or the lesser, but still alternating pressures in a 2-into-1 tailpipe, or the (supposed) relatively even and moderate negative pressure at the center of a collector?

Point is that the location of the tap and the type of system is another variable.

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  #26  
Old 05-18-2014, 07:10 PM
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Quote:
Originally Posted by digidocs View Post
What are the failure modes of a crankcase evacuator reed valve?

If the reed fails, it seems like there is a chance that your crankcase could be directly connected to the elevated pressure inside the exhaust manifold.

Always wondered about that.

David
There is no pressure going back to the crankcase. The tube welded into the exhaust pipe is positioned at an angle as to cause a vacuum from the passing exhaust. Even if you have no one way valve it still pulls the blowby out. The one way valve creates the negative pressure in the crankcase from the piston pulses. I've never seen one fail.
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  #27  
Old 05-18-2014, 08:03 PM
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Quote:
Originally Posted by FasGlas View Post
There is no pressure going back to the crankcase. The tube welded into the exhaust pipe is positioned at an angle as to cause a vacuum from the passing exhaust. Even if you have no one way valve it still pulls the blowby out. The one way valve creates the negative pressure in the crankcase from the piston pulses. I've never seen one fail.
Whether or not you have seen it, they are mechanical devices and they do in fact fail. My A&P had one stick closed in this exact application and blow the front crankcase seal out. It can happen, which is why AntiSplat recommends an inspection/cleaning.

Against my guru's emphatic objection, I installed one anyway....but I'm keeping a close eye on it.
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  #28  
Old 05-19-2014, 11:23 AM
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Quote:
Originally Posted by FasGlas View Post
A point of contention... If you install a crankcase evacuation system on the engine ( one way valve on the exhaust connected to the breather hose ), what would be the purpose of the separator? All the moister and blowby goes into the exhaust and burns off so there's nothing on the belly anyway.. Maybe a few drops of oil would get returned to the engine but other byproducts you might not want also returns.
Race engine builders have been using crankcase evacuation systems for as long as I can remember. I've used them on cars, boats and motorcycles and they work. They are cheap and easy to install. Mr. Gasket and Moroso sell a pair for less then $50 with all the parts for two planes. I use one on my IO-360.
The added advantage is negative crankcase pressure that stops oil weeps and also the theory it increases HP by removing pressure on the piston down strokes.
... The purpose of the separator for our application on a typical Lycoming engine for instance, in not exactly what is commonly perceived. This devise is not intended to, and doe's not capture blow-by fumes, gassed off moisture etc and return them to the oil. These byproducts of combustion are still passed overboard and are eliminated just as before, actually more efficiently if a vacuum evacuation system is in place. On our airplanes, the separators serve to eliminate the problems associated with a very poorly designed, 1930's style inadequate breather system. The main problem being, these engines literally throw out pure clean oil that is carried up to the top of the accessory case via the cam, mag, oil pump, vacuum pump and idler gears. This is perfect oil that is mainly lost because of poor or rather no baffling. This is why the oil consumption problem becomes worse when you put in the true recommended amount of oil for your engine, rather than running it a quart or so low. The lower gears in the accessory case are running in the oil and simply carry it to the top where it is thrown out of the engine. This amounts to nothing more than a leak of pure oil if not properly addressed. This is not blow-by, nor is the engine consuming or burning oil, it is in reality simply leaking it out. The separator remedies this issue and there in no down side of any kind to its use. Thank, Allan..
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  #29  
Old 06-09-2014, 12:02 PM
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There have been a few reports of failed check valves and blocked evacuator exhaust pipe ports. I previously suggested a second reed valve arranged to open if breather system pressure became positive. I've now installed that experiment, and will report back in due course. In the meantime, here's a photo of the installation in case anyone wishes to do the same:



I've added a red stripe to the breather outlet lines in the photo, just to make them obvious. The reed valve is the familiar NAPA 2-29000; it's just hanging from the end of the hose. The T-fitting was welded up using some 4130 tube from the scrap bin.

BTW, the blue firesleeve nicely insulates the line between the accessory case and separator, raising the separator outlet temperature to about 175F. For more in that area, kindly see the October issue of Kitplanes.
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  #30  
Old 06-09-2014, 12:25 PM
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What's the failure mode, do they get carboned up? I have two on my Rocket, one on each exhaust pipe. I assume its pretty unlikely for both to fail at the same time if inspected regularly.

I also relocated the breather ports and incorporated them into mag hole covers, since I don't have magnetos. No separators, just straight into the PCV valves from the breathers.
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