Oil Consumption and Breather Tube

[Bill.Peyton]

Dan,
Good point. Kinda like a mini oil sep. BTW, how is your air/oil sep working for you, do you have enough time to tell yet?

[DanH]

Originally Posted by Bill.Peyton

BTW, how is your air/oil sep working for you, do you have enough time to tell yet?

Definite reduction in oil usage, and no belly oil mess....zip. Be aware my original breather was a "short rise" version (as in the sketch), so it's not hard to do better in both areas.

I'm now due an oil change. The plan is to track oil added over the next 50 hours, more accurate than a short term eyeballing of the stick.

A surprise is always possible, but going in my only concerns were (1) the structural reliability of the weld area at the header tap, (2) the long-term temperature resistance of the reed valve and hose end. It may take a while to be sure of either point.

It's a sump return system. I've not seen any visual signs of water; cloudy or milky oil, fill cap condensation, whatever. However, that doesn't mean there is none. For insurance I'm swapping to 20-50 Phillips and CamGuard. The non-synthetic base should suspend water better. The CamGuard is intended as prophylactic against returned acids, etc. The combination costs only a little more than a case of AS 15-50.

[N427EF]

Dan,
Like most others I have been considering an Air/Oil sep as well as a Reed valve.
If heat is a concern, why can't the reed valve be placed further away from the exhaust between 2 pieces of hose?
Having the breather hose go up as much as possible makes good sense for the reason you mentioned. Stuffing steel wool into the hose far enough to fill the riser portion of that hose would capture most of the oil mist and drip it back into the case, wouldn't it? Just an idea to maybe get away with the reed valve only.
Like most I have a drip or two after shut down not a big deal but a little annoying.
Without an oil separator would the reed valve capture a drop or two while the aircraft is sitting on the ground?
Could the hose be routed horizontal into the exhaust to have those few drops
pool inside the hose and be blown out and burned once the engine is running?
My oil consumption is 11 hours per quart, it's a good average but an air/oil sep
would probably keep the belly dry.

[zav6a]

There is a common theme that combustion water is being returned to the sump by air oil separation systems. Given the water is in vapor form, we just need to keep the temp of the stream up through the separator to prevent water condensation, keep it as a vapor and dump it overboard. Some form of insulation on the inlet line and canister would go a long ways towards keeping it hot.

With the check valve and negative pressure in the crankcase, the flow is probably high enough to keep the inlet line and separator canister hot if insulated.

Rubber inlet hose like Dan's would seem to do the job for the inlet. I am sure there is some sort of thin spray-on material that could be used for the separator.

Not saying it is a real concern but it it is, there is an easy solution.

[DanH]

Originally Posted by N427EF

If heat is a concern, why can't the reed valve be placed further away from the exhaust between 2 pieces of hose?

It can. It may be a little less effective vacuum-wise; the hose section between the header and the reed would act as an accumulator. You would still need to be sure the hose itself can stand the heat where it connects to the header pipe.

Stuffing steel wool into the hose far enough to fill the riser portion of that hose would capture most of the oil mist and drip it back into the case, wouldn't it?

Not a good idea. Result would probably be rusty, broken shards of steel wool working back to the breather fitting and accessory case.

Without an oil separator would the reed valve capture a drop or two while the aircraft is sitting on the ground?

I dunno. It may or may not get past the reed and run out the pipe end.

Originally Posted by zav6a

Given the water is in vapor form, we just need to keep the temp of the stream up through the separator to prevent water condensation, keep it as a vapor and dump it overboard.

Agree. We're running fairly high engine compartment temperatures anyway.

[SHIPCHIEF]

I'm wondering what the service life of the NAPA #2-29000 check valve might be?
I think the FAA would want on-going maintenance instructions on the form 337 if you were installing this on a certified plane?
A periodic test, inspection or replacement schedule? (NAPA 3 year 35,000 mile warrantee)
Dan, I know you are very method driven, so you must have considered this, including failure mode analysis.

[DanH]

Originally Posted by SHIPCHIEF

I'm wondering what the service life of the NAPA #2-29000 check valve might be?

Don't know. Hopefully users will report failures here. Most installs will be similar.

[DanH]

Quick data point.

I previously mentioned operating temperature of the NAPA 2-29000 check valve was an item of interest, given its mounting on a stub welded to a hot header pipe.

I have a pair of thermistors on long cables which I can position anywhere under the cowl. For this question I simply strapped one to the backside of the check valve flange (red, see below) with the tip against the flange, buried in heat sink grease.

Yesterday the check valve thermistor was showing around 150F. OAT was low for south Alabama, high 30's in flight. I'd expect more like 200F and maybe higher when we return to summertime. For now I'm satisfied that the valve is operating at temperatures which should not compromise its lifespan.

Do note I installed this check valve with a heat sink/radiant heat shield....the steel disk welded to the mounting nipple. As I've only measured this particular arrangement, I can't absolutely promise the same result for one without a shield. I can tell you how to check.

[N427EF]

I installed an Antisplat air/oil separator and so far so good.
I have flown about 8 hours since and one thing is obvious, no oil anywhere
and no drip after shut down. The breather tube simply sticks out between the exhaust pipes about 3 " past the fire wall.
I now have the muffler removed to have the stub welded in.
While doing all this work at the hangar I am catching quite a bit of flak
from locals about reducing the size of the breather tube from 1 " down to 1/2" at the exhaust pipe. I am being admonished about crank case pressure and blowing a crank shaft seal if for some reason this set up won't work.
I am not concerned but the seeds of doubt have sprouted in my mind.
How many have installed the set up with the reed valve on an IO 540?

[Bill.Peyton]

Ernst,
I also have installed the same. I have not flown yet. I have not installed the check valve yet. It would be very easy to measure if there is an issue by hooking up an airspeed indicator or vacuum gauge through the oil dipstick tube and measure the crankcase pressure. Measure it without anything connected to the breather port. Normal pressure is around 1.5" of water, or around 30 mph. Then attach the separator and check again. I intend to do this when I get a chance. I wonder if Alan has done this for the IO540
I am glad to hear that it is working well for you thus far.