What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Eng Oil Separater Thoughts

Pounder

Pounder

Well Known Member
Sponsor
My new engine install is well underway.

The engine builder- who is way way smarter then me regarding all things Lycoming- says consider installing engine breather without separator. He is of the opinion that a new, well operating engine won’t vent much oil.

I am installing as recommended (without seperator) but may retro fit in the future.

Any opinions, experiences to report, particularly with new engine?
 
I have used simple, air/oil separators on all the projects. On the current RV-8 (IO-360-M1B), at 440 hours I’m using a quart every 20-30 hours. I have an old Brasso Can mounted with Adel clamps on the engine mount that I use to collect what comes out of the separator. I drain the can once a year.

Note - I never return the oil to the engine.

This is the air/oil separator I use. I have it mounted high on the firewall:
https://www.aircraftspruce.com/catalog/eppages/hboilbreather.php?clickkey=9808

This is the amount of oil I collect over a year (~5oz):
20230302-150840.jpg


Not much oil, but enough to make a mess on the bottom fuselage.

The crankcase output from then separator is directed to an exhaust pipe (traditional way to install). There is some residue on the pipe from the crankcase fumes out of the separator (as in the separator is not 100% effective but the majority of the oil makes it to the collection can).

Carl
 
I have owned 5 aerobatic planes with the Christen inverted system, which includes a air/oil separator that returns oil to the engine. The separator is a necessity because the breather line becomes the oil supply line during inverted flight and vise versa for the normal oil pick up line. These 2 hoses hold a significantly large enough volume of oil that it is a good idea to return it to the engine to keep it off the belly and to not have to replenish the sump level after every few flights.

This system works quite well. All of my planes used very little oil and very little oil was vented overboard.

I have seen may of these aerobatic engines apart at overhaul and can say with confidence; no harm with returning the separated oil back to the engine was observed.
 
I don’t have a separator. I may install one some day. My engine pukes out anything over five quarts, leaving me to manage a lower margin. While my oil burn is normal, long trips require adding oil to keep above 4 quarts.
Standard Lycoming set up and many have reported similar performance.
I am confident with a separator you would not have to manage oil level as often although it isn’t that big of a deal.
The Bucker has the Christen system and it works very well, similar to the above post.
 
I only have about 70 hrs on an IO-320 from Aerosport. No separator (breather routed to drip on the exhaust). Nothing on the belly of the plane, really very little on the exhaust. I fill to 6 quarts after an oil change, then add a quart when down to 5 (as suggested to me by someone very knowledgeable on the subject). This seems to work well, and by well, I mean I don't seem to be losing any oil anywhere, none on the belly of the plane, and easy to manage between 5 and 6 quarts with a buffer below 5 if needed. So far, I drop from 5 to 6 quarts an average of about 15 hrs following an oil change, maybe a tad less. From what I've read on threads, this is pretty average and I'm fine with it. I feel pretty good if I only need to add a quart once between oil changes. So far, I've been changing oil every 25 hrs. I might go to 50 at some point. I'll have to do some thinking on that.

Just a data point for comparison.
 
Anti-Splat

What is the current consensus on the Anti-Splat separator? In the past I heard some concern about it pressurizing the crankcase. Has that issue been resolved?
 
At the risk of supplying second hand information partly inaccurately, our local A&P mechanic, with 40+ years of experience and who supported aircraft racing teams was negative to neutral on oil recovery for a couple reasons. Primary issue was corrosion, at least with inverted systems/oil separators collecting sludge/water. Secondary issue was partly philosophical of returning dirty oil/water back to engine, increasing corrosion in engine on margin. Overall, he definitely preferred venting blow by and adding fresh oil more often.

Personal opinion is that once we go to unleaded, these concerns would likely be mitigated.

Not that it matters as its just an opinion for one person...myself,... but I think I'm in no rush to add oil separator / 1/2 raven, or full inverted (for my likely lengths of stay inverted). I'll just try to plan space on firewall for eventual 1/2 raven if/when we go unleaded.

2 cents for what its worth (and likely that perhaps)...
 
I’m not a fan of separators, no need on a good running engine and one less thing to worry about. Cleaning the belly occasionally won’t kill anyone.
 
Carl Froehlich said:
I have used simple, air/oil separators on all the projects. On the current RV-8 (IO-360-M1B), at 440 hours I’m using a quart every 20-30 hours. I have an old Brasso Can mounted with Adel clamps on the engine mount that I use to collect what comes out of the separator. I drain the can once a year.

Note - I never return the oil to the engine.

This is the air/oil separator I use. I have it mounted high on the firewall:
https://www.aircraftspruce.com/catalog/eppages/hboilbreather.php?clickkey=9808

This is the amount of oil I collect over a year (~5oz):
20230302-150840.jpg


Not much oil, but enough to make a mess on the bottom fuselage.

The crankcase output from then separator is directed to an exhaust pipe (traditional way to install). There is some residue on the pipe from the crankcase fumes out of the separator (as in the separator is not 100% effective but the majority of the oil makes it to the collection can).

Carl
Click to expand...

Love the Brasso can. Had to be a Navy guy...:)
 
Walt said:
I’m not a fan of separators, no need on a good running engine and one less thing to worry about. Cleaning the belly occasionally won’t kill anyone.
Click to expand...

I’ve been cleaning the belly of my reliant (R-680 on the nose) since about 1966 or so when my dad got it airworthy.

And I am still cleaning it. Still alive.
 
Same here

ge9a said:
I fill to 6 quarts after an oil change, then add a quart when down to 5 (as suggested to me by someone very knowledgeable on the subject). This seems to work well, and by well, I mean I don't seem to be losing any oil anywhere, none on the belly of the plane, and easy to manage between 5 and 6 quarts with a buffer below 5 if needed. So far, I drop from 5 to 6 quarts an average of about 15 hrs following an oil change, maybe a tad less.
Click to expand...

I was also told to do this by a very knowledgeable source, and it was good advice! I was running my O-320 with way too much oil. “Fill to 6, add at 5” works perfectly, and no more oil on the belly of the plane.

Apparently an O-320 holds 8 quarts in order to accommodate full fuel flight times at Lycoming’s max allowable oil consumption. So 8 quarts is big time overkill for most O-320s.
 
On my IO390 I found that if I did an aggressive turn left, an awful lot of oil ended up under the plane. Worse if I was in some G left, then eased the G off while still banked. Enough to drip off the antenna. It took me a while to figure out what maneuvers made the mess because so often I just Cadillac around and keep it pretty flat. I eyeballed every part of my engine looking for that leak and found one at my oil cooler (now replaced), but even after that the major leak was maneuvering and oil out the breather.

I got the anti-splat separator and plumbed the oil return to the engine, and vented it to the original vent tubing, because I did not want to drill a hole in the exhaust or need to clean out an exhaust port.

I never ever have oil on the belly now. Whatever condensate goes out the vent line drips on the exhaust and burns away. After a lot of flying I will get a thin grime layer on the belly that needs cleaning.
 
Just a data point, anecdote not evidence, and I certainly have no clinical expertise regarding oil separators. The previous owner of my airplane (factory new Lycoming IO320 with 440 tach hours) installed an Anti-Splat separator about 200 hours ago. My engine self-selects 5.5 qts no matter how much more I put in. In the 150 hours I've flown that airplane over the last 3 years, I haven't had to add any oil at all. I've changed the oil about 4 times since I've owned it, each oil change included a sample to Blackstone labs. No alarming trends, just a slight improvement according to them. I washed the belly of the airplane for the first time a couple of weeks ago. There was a modest film of oil behind the exhaust--hard to know if that's from the engine or due to the smoke system. The airplane is on a dehydrator 24/7 while in the hangar.

I have no other experience with separators and don't know much about them, other than the fact that neither I nor my A&P, nor Blackstone can see any negatives thus far.
 
Walt said:
I’m not a fan of separators, no need on a good running engine and one less thing to worry about. Cleaning the belly occasionally won’t kill anyone.
Click to expand...

Thanks walt. You are echoing my builders words.

Do you do any acro?

Bryan
 
Acro

I’m not doing acro yet but will be soon, and at that point, the breathing hose will be coming from my Christen inverted system. For now, straight from the breather fitting on the accessory case and seems to work great. If you have a really smart exhaust guy too -like Clinton Anderson at Custom Aircraft Parts- you can do something similar. ( bottom center of pic, blue silicone hose )
 

Attachments

  • 24728856-D1D5-49B5-B0C1-496BBCF038C0.jpg
    24728856-D1D5-49B5-B0C1-496BBCF038C0.jpg
    362 KB · Views: 155
Over 75TT hours ago, I connected the discharge of my AntiSplat Air-Oil Separator to the exhaust system on my RV-10. I used the kit that included the safety relief valve that opens if there is positive crankcase pressure. That would occur if the PCV valve connection to the exhaust became plugged or severely restricted. I have checked that port in the exhaust 3 times expecting to have to remove some coking. It has been perfectly clean so far. Nothing to clean.

Many builders make that connection to the exhaust using the AntiSplat Aero clamp-on port. Many RV-10's have it connected to the exhaust downstream of the right muffler on a curved section of the exhaust pipe. AntiSplat's clamp-on connector is not designed to fit a curved tube. I did it differently.

I consulted with Dan Horton about where to connect to the exhaust. He suggested connecting to a single pipe before the collector, where exhaust gas temperatures are higher. The premise was to have the PCV valve see more pronounced negative pressure pulses and better incineration of the separator discharge products. Mine is connected to a straight section of the #1 exhaust pipe using the AntiSplat clamp-on port as shown in the photos. It has worked well so far.
 

Attachments

  • IMG_6640.jpg
    IMG_6640.jpg
    539.8 KB · Views: 162
  • IMG_6641.jpg
    IMG_6641.jpg
    1,020.3 KB · Views: 173
Just another data point, a few days ago it was 26 years from first flight of my RV-6. As I type this, there is over 3,500 hours on the airplane.

I have always had an air oil separator on my airplane. I used the cheap at the time what was call the Homebuilders Oil Breather / Separator and I ran the drain back into the engine. In thirty years time, it has doubled in price instead of quadrupled like most other aviation items.

I have not had issues with my setup. Your results may vary as this is only one data point.
 
anti splat aero oil separator

I have had the Anti Splat Aero oil separator on my IO360 for a year now.
No more adding oil and not a drop on the belly.
This is a great product.
 
I have the Antisplat oil separator and just few days ago I did an oil change and I saw that same water trace inside my oil filter when it dumped out. I am thinking of putting the return line to a catch can instead of back in the engine to see if that’s the issue. Any words on that from anyone?
 
RicoB said:
I have the Antisplat oil separator and just few days ago I did an oil change and I saw that same water trace inside my oil filter when it dumped out. I am thinking of putting the return line to a catch can instead of back in the engine to see if that’s the issue. Any words on that from anyone?
Click to expand...

I've never seen that, but I keep my engine on a dehydrator 24/7 when home in my hangar. YMMV.
 
RicoB said:
I have the Antisplat oil separator and just few days ago I did an oil change and I saw that same water trace inside my oil filter when it dumped out. I am thinking of putting the return line to a catch can instead of back in the engine to see if that’s the issue. Any words on that from anyone?
Click to expand...

If it's putting water back into the crankcase, you're operating a condenser, not a separator. It's not hot enough.
 
The water vapor that occurs in the engine as part of the combustion process will condense as the engine cools down to a temp below the dew point after shutdown.
 
MacCool said:
The water vapor that occurs in the engine as part of the combustion process will condense as the engine cools down to a temp below the dew point after shutdown.
Click to expand...

Correct, and it will do so regardless, separator or open breather.

The interesting activity is at next flight.

At initial startup, the separator system is cold, and will operate as a condenser. The crankcase is also cold, so the breather gas will contain aerosol liquid water from the last shutdown in addition to water in vapor phase from fresh combustion blowby. So, initially condensing vapor phase and liquid phase water will be sent to the crankcase return or catch can. This will happen following every cold start.

Catch can believers will note water in the can and offer it as evidence of ugly things. However, given a separator system which ultimately warms to a temperature higher than the dew points of water and acids, the "evidence" is merely a collection of temporary cold start product.

A separator with a crankcase return will also initially return water, but that water will subsequently be heated to vapor as the engine comes up to operating temperature. It will again go out the breather...but this time, given a hot separator, it will remain in vapor phase and be ejected.

I am absolutely sure some of you are running separators which result in high crankcase water content. It's not a reason to condemn separators. It just means they were installed with no thought as to how they work.

Below, separator outflow temperature measurement.
.
 

Attachments

  • Separator Air Outlet Temperature Sensor.jpg
    Separator Air Outlet Temperature Sensor.jpg
    86.2 KB · Views: 129
Yes very well explained. I am wondering why I got that moisture trace. My oil gets to 215 on a climb out on any warm day.
 
Don't know what Mr Nimmo is supplying, but a NAPA 229000 has been successful.
 
DanH said:
Don't know what Mr Nimmo is supplying, but a NAPA 229000 has been successful.
Click to expand...
Thanks,,

Got me pointed in the right direction.
But that specific P/N has the wrong size threaded fitting.
Looks like p/n 229005 works with my setup with 3/4” x 14 threads.
 
I have a new IO360 M1B with the stock vent in an RV8. I see very little liquid oil on the bottom of the plane. I fly 3 times a week and with a lot of power cycles and 0-3G flight.
 
You must log in or register to reply here.
Back
Top