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  #131  
Old 07-12-2014, 05:26 AM
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DanH DanH is offline
 
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Quote:
Originally Posted by jchang10 View Post
Excellent photo Jae. Good illustration of what seems to be the common problem.

Can you tell us the installed position?
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  #132  
Old 07-12-2014, 09:51 AM
jchang10 jchang10 is offline
 
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Location: San Francisco, CA
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I updated with the position. It is the same as others, installed just after the heat muff/muffler.

Notice how the buildup is all INSIDE the tube. There is nothing outside in the direct exhaust stream itself. Also, all the buildup is near the end of the tube in a precise area around the saddle area. As you go up towards the valve, the buildup lessens for a bit for about an inch only. Further up the tube towards the valve, it is perfectly clean.

Thus, somehow it is the end of this tube that has the right combination of oil pooling up and the shielded exhaust gas creating THE perfect environment.
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  #133  
Old 07-12-2014, 10:16 AM
N427EF N427EF is offline
 
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Default Same exact position for me

Jae,
that looks like it is almost closed up, glad you found it in time.

The build up of crud in mine was exactly at around the weld and none on the stub inside the exhaust or further up.

I am installing a second reed valve.
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  #134  
Old 07-12-2014, 09:11 PM
douglassmt douglassmt is offline
 
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Location: Missoula, MT
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Default Data point

I worked on the plane again today and sent the borescope up the poop chute again to look at the oil separator discharge. It looks the same as my last picture - clean as a whistle. I had the top cowl off so I disconnected the drain hose at the separator and blew/sucked on it, it worked fine. I could stick my finger down the hose and found a thin film of oil so I'm getting oil out of the separator but absolutely no coke on the discharge tube after about 50 hours since installation. I was planning to install the second check valve today but I figured since all looks fine I'll wait a bit longer. I will be flying 10 hours or so in the next couple days so I'll check it again after that. I'll install it eventually but will mind it closely until then.

Also, I put one of those max-recording temp stickers on the air/oil separator and it looks like the max temp of the separator itself was 160 deg F.


The outlet is mounted where ASA tells you to, after the heater muff just fwd of the firewall and the bend in the tail pipe.

I run my oil between 7-9 quarts, mostly between 7-8. I wonder if running my oil a little lower than others have reported might account for difference. Still haven't assessed oil consumption since install but I will.

One other thought was weather. Today was the first really hot day, about 90+ OAT. Before today it has been 60s and 70s, and we have typically have low humidity here. It will be interesting to see if the advent of hotter weather results in any cokeage (is that a word?).
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  #135  
Old 07-13-2014, 10:07 AM
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Snowflake Snowflake is offline
 
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Quote:
Originally Posted by N427EF View Post
The valve is the only path to the atmosphere.
The oil return leads to the crankcase. (same chamber as the one where the breather tube comes from)
If the valve stays closed the crankcase pressurizes to the point of blowing the front seal, the weakest tight spot in the system.
Can someone explain this... If the breather hose (through the valve) is the only path to the atmosphere, how does more air get *in* to the crankcase if you plug it? Aren't you then dealing with a closed volume, and the pressure fluctuating between two points?
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  #136  
Old 07-13-2014, 10:30 AM
BillL BillL is offline
 
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Quote:
Originally Posted by Snowflake View Post
Can someone explain this... If the breather hose (through the valve) is the only path to the atmosphere, how does more air get *in* to the crankcase if you plug it? Aren't you then dealing with a closed volume, and the pressure fluctuating between two points?
Simple: combustion gasses leaking past piston rings - blowby.
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  #137  
Old 07-13-2014, 03:04 PM
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Tim 8-A Tim 8-A is offline
 
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Thread is a little confusing but I only skimmed the pages. Here are my results not sure if its relevant.
Prior to the install of the oil separator I was using a qt every 6 to 7 hours.
After install maybe a qt every 12 to 15 main advantage for me is no oil on the belly after install.
Here are the results after 121 hours of flight.
I removed the check valve and no issues very clean.
Using a inspection camera here are two short video's of what build up I had around the connection point between the welded tube and exhaust pipe and after cleaning.
Before cleaning

After cleaning

What was removed.
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  #138  
Old 07-13-2014, 03:32 PM
Wayne Gillispie Wayne Gillispie is offline
 
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Location: USA
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Thanks to all of you for testing this. I am still adding a qt every 8 hrs(every other month) and washing the plane about every 4 months. A creeper makes the oily belly easy enough to clean. I wax the bottom everytime and the entire plane once a year. Oil and dirt film are always thin and barely visible from the creeper. We'll continue with our stock setup for now.
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Last edited by Wayne Gillispie : 07-21-2014 at 03:49 PM.
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  #139  
Old 07-13-2014, 11:46 PM
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Snowflake Snowflake is offline
 
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Quote:
Originally Posted by BillL View Post
Simple: combustion gasses leaking past piston rings - blowby.
Of course, silly me. I knew I was missing something. Thanks!
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  #140  
Old 07-14-2014, 05:07 AM
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DanH DanH is offline
 
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Curiouser and curiouser....

Regular readers know my separator/evacuator installation is home-built, and the exhaust tap is not located on a tailpipe, but rather on the #4 headpipe, about 18" down from the cylinder flange. It was installed approximately 20 months and 140 hours ago. I've been keeping a regular eye on it; last look inside the exhaust tap was when Vic and I were comparing notes after S&F.

I have about 18 hours of flying later this month, so yesterday the cowl was off for a quick general inspection. Removed the reed valve of course. This is the deposit found in the tube. Not a lot, but it's there, a small annular ring of buildup:



What is really interesting is the location. It's about halfway along the tube length, not near the weld to the exhaust header. There's nothing closer to the valve end, nor any deposit closer to the exhaust header end. It's a ring. There is either a specific temperature at that point, or it has something to do with wave mechanics.



The material itself is interesting. First, it's not the color of burnt oil, but quite gray, like lead sludge. It also has a soft and sticky component. You can see how it adheres to the scraper. One onlooker commented that it seemed like gray anti-seize mixed with soft grit. It could be smeared between the thumb and index finger.



This is an engineering/design problem, and when we finally figure out the mechanics we'll probably laugh about it. In the meantime, pull your valve and take a look in the tube.
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