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  #181  
Old 07-22-2014, 06:50 AM
vic syracuse vic syracuse is offline
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Default Two types

I have used both Aeroshell 100W+ and Philips 20W50, both with cam guard. Just a data point.

Vic
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  #182  
Old 07-22-2014, 02:21 PM
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Bill.Peyton Bill.Peyton is offline
 
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I have decided to abandon the exhaust port system. After just 8 hours I can start to see a build up again, this after reducing the exposed area of the spigot in the exhaust pipe. I am leaving the AO sep installed and dumping the vent overboard next to the exhaust pipe.
Until a proven solution is discovered, this is just too risky for me, even with a safety check valve.
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  #183  
Old 07-25-2014, 11:24 PM
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CharlieWaffles CharlieWaffles is offline
 
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I was thinking about this today when I came across a copy of an old Cessna AD - 82-07-02 that addressed ice blockage of the breather tube. The solution prescribed was to cut an alternate air outlet in the tube as a precaution. A simple solution to prevent a head gasket from blowing.

In our case, it's the coaking/tar issue, but if the valve was to become blocked, at there there would be an alternate air vent. Same principle as the second check valve, but cheaper/easier.

The hole that is cut isnt that large, so there would be some back pressure, but better than blowing the engine.




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  #184  
Old 07-25-2014, 11:42 PM
alpinelakespilot2000 alpinelakespilot2000 is offline
 
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Yes, would an ASA setup with a whistle slot/hole in the breather line address the potential negative side effect of the stock ASA installation?
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  #185  
Old 07-26-2014, 04:09 AM
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C-FAH Q C-FAH Q is offline
 
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Default Whistle slot

I had cut a whistle slot in the rubber tube going to the reed valve. It did not work.
Gary
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  #186  
Old 07-26-2014, 08:04 AM
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Toobuilder Toobuilder is offline
 
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Remember that part of the benefit of the check valve- to-exhaust configuration is the negative pressure delivered to the crankcase. Cutting a hole in the tube eliminates that possibility.
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  #187  
Old 07-26-2014, 08:09 AM
N427EF N427EF is offline
 
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You cannot open even a small whistle slot and retain the negative pressure resulting from the installation of a Reed valve. The only way to keep the system working as it was intended without the risk of coking up the breather stub is to install a second reed valve.
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  #188  
Old 07-29-2014, 07:25 AM
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Low Pass Low Pass is offline
 
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Here's a pirep for the ASA oil separator. IO-360 blowing 1 qt every 3-4 hrs out the vent. Installed the ASA system (without the tailpipe connection). Flew to Oshkosh (after 1-2 hr lcl test), and it works just as advertised.

As for connection to the tailpipe, my time working in petrochem mfg tell me the coking issue is not going to be solved without elaborate cooling, purge or a flush stream. FWIW, that makes this option too complex/unreliable for me personally. You want negative crankcase pressure, route the effluent through a vacuum pump!

Bryan

Houston
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  #189  
Old 08-03-2014, 03:38 PM
bpattonsoa bpattonsoa is offline
 
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Location: Indepenence, Oregon
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Default Temperaturee data for RV-10 coking issue


Ok, here is a major correction of my post #177 in this thread. (Edited with a correction)

I strapped my engine compartment thermocouple to the outside of the pipe right about where the coke formed. When I took the cowl off to put in the relief valve, the thermocouple was not on the pipe. I used a tie wrap to hold it on and it was melted! Suspect it was reading local air temps near the exhaust pipe after reaching its high temp.

Installed thermocouple with a clamp. Flew up to a wedding yesterday and temps were much higher the entire flight. The above graph is the temperature on the outside of the pipe at the weld to its mounting plate.

The temperature on the inside of the pipe that the oil mist sees is most likely somewhat higher. This is obviously conductive heat from the pipe and perhaps some heating from the exhaust impingement on the small piece that is in the exhaust flow. The drop in temperature near the end was during a descent from 8.5K to 4.5K at full throttle, engine leaned to peak plus .5 GPH.

I would like Alan to get some data on the temperature of his inner pipe for the pipe in a pipe solution. The inner pipe will be subjected to much less conductive heating, but still will see the exhaust gas.

I do love the clean belly and the lack of small leaks that all Lycs seem to have. But despite the addition of a relief valve, the coking issue has me looking a eliminating the vacuum idea and just exhausting it onto the exhaust pipe.

When I added the relief valve after just about 1.0 hours from completely cleaning the coke off the inside of the pipe, there was a very small buildup starting.
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  #190  
Old 08-04-2014, 11:51 AM
jchang10 jchang10 is offline
 
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Thus we have this graph from BillL's post with Bruce's graph. The coking curves start at 200C or approx 400F. Hitting 400F+ inside the tube seems highly plausible to me.

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