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Oil Consumption and Breather Tube

Oil eating engine

My engine was leaking oil and using it until I re-routed my breather tubes to another location which seems to have more negitive pressure. Since then my oil leak stopped and my engine is using less oil, about 15 hours per quart.
You may have problems with too much crank case pressure which I'm sure was my problem.
 
Mine

Saw this thread and wondered how my air/oil separator is doing with regard to plugging. Got out the borescope and looked up the exhaust. These are poor quality pix but I don't see any fouling or coke-like deposits. As I understand it, the deposits were accumulating on the outlet of the beveled tube? I have about 50 hours since installing the air/oil separator from Anti Splat. Not enough data to compare oil consumption, but the recently cleaned belly is still clean. Will remove drain tube from exhaust pipe fitting at next oil change to check entire area, might install the extra reed valve per Dan H.
201407021_zpsf92b76ae.jpg

201407022_zps23bd13ec.jpg
 
Bryan,
That is clean. I originally had mine protruding out 1". That could be some of the issue. I have corrected that and it looks just like yours now. BTW, what brand and type oil are you using?
 
Oil

Bill -

I'm using Phillips X/C 20/50.

Was I correct that the plugging you found was on the very end of the tube where it extends into the exhaust stream?
 
safety valve recommended

I would encourage everyone to put the safety valve in the breather circuit. I reinstalled the valve on the exhaust hoping to keep the belly clean on the way to Alaska. I have now put about 30 hours on it and when we landed in Anchorage there was oil on the belly coming out from the safety valve. I took it apart today and it was coked completely shut again. I have now just put the breather tube directly overboard, and when I get home I am going to reinstall the airwolf oil separator, as I never had any oil on the belly when using it.
This is on my RV-10. In the 30 hours mentioned I added 3 qts of oil. I put in 9 qts at the oil change plus 1 can of camguard. So, I don't know if I should let it run lower than 6 qts. Kind of hesitant to go that low with all of the exposed flying up here in Alaska. We were actually solid IMC with approaches to minimums coming up the coast yesterday and the day before (Ketchikan and Yakutat).
I will add more later....


Vic
 
Continued...

Ok, sorry, had to go to dinner.

Here's the positive. I think we have proven that Dan Horton's recommendation for the safety valve in case of blockage actually does work. That's nice! The last time mine coked up I had oil blowing out from every seam on the engine and luckily didn't blow the nose seal.
The last time I had it installed with the Anti-Splat air/oil separator. This time it was the straight breather tube.
I think we need to figure out why it is coking up. I believe it might have to do with location, but don't know for sure. Mine is installed right in the bend of the tail pipe aft of the mufflers/heat muffs on the RV-10. IO-540 with Vetterman exhaust.
The compressions are all in the mid 70's or better. I measured crank case pressure and Dan and I agree that it seems normal, so I am not thinking I have excessive blow-by. The engine burns about a quart of oil every 7 hours or so, and the oil analysis from Blackstone says everything is great. Perhaps I am running the oil level too high, but it is interesting to me that it also coked up when running the separator.
Again, I would certainly recommend that anyone going on long trips should have a safety valve setup.

Vic
 
Has anyone looked at putting the valve right at the engine? As long as the hose (or pipe) connecting it to the exhaust has a stiff enough wall, there still should be a strong vacuum pulse. That should solve the problem of valve coking.

I was considering adding my second (safety) valve right to a fitting on my vacant vacuum pump cover plate rather than routing it to a corner of the cowl somewhere.
 
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After talking to Bart at Aerosport (now Titan), I add 9 qts at oil/filter change, which becomes a little less on the stick after the filter fills up. Then I add a quart at 7-7.5 qts. Before the ASA separator I was still getting oil on the belly but was adding about a quart every 12 hours. The oil on the belly wasn't bad but added up over time. After the ASA separator I have no oil on the belly but haven't had enough time to get a new oil use rate. I also don't have any coking in my exhaust pipe at the separator discharge, but it's only been 50 hours or so. I will monitor it but I suspect it may be due to the oil levels that I run.
 
Mike,
It's not the valve that's coking up, it's the outlet of the spigot at the exhaust. I suspect that Dan is correct, for the rv10 we must have the outlet location placed where the exhaust temp is perfect for coking. I was burning around. A quart every 10 hours or so, so that's a little less than Vic. This could be the reason it took over 100 hours for mine to start to clog up. I suspect I am going to have to relocate the A/O sep outlet upstream to a hotter area, or just dump the outlet overboard directly.
 
Mike,
It's not the valve that's coking up, it's the outlet of the spigot at the exhaust...


OK, I get the coking of the pipe - I thought Vic was seeing the valve itself clogging...

The point remains however, these valves don't see much temperature for the automotive AIR system they are used on/designed for - at least compared to hours of glowing red aircraft pipes we have. I wonder if relocating them to the engine end of the hose would be of benefit?
 
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Are we satisfied that all coked taps were installed in a tailpipe? No coked tap was installed in a headpipe, or in a collector?

Vic, can you confirm yours was in a tailpipe, downstream of a muffler? Anybody else with mufflers?

Get some temperatures. Nobody can do it but the folks with the problem.

The point remains however, these valves don't see much temperature for the automotive AIR system they are used on/designed for - at least compared to hours of glowing red aircraft pipes we have. I wonder if relocating them to the engine end of the hose would be of benefit?

Let's not confuse the issue. Don't think anybody has failed a reed valve, at least not a good reed valve.
 
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Strong Opinion and advisory

OK, I've been thinking about his all day and have done some research, so I am going to express a much stronger opinion, and I understand that some may not be comfortable with it. I'm OK with that and I'll tell you why.

I believe very much in all of the Experimental aviation we do. However, sometimes there becomes enough data that points to a potential safety problem. I have spent the last year chasing down everything I could thing of that could be wrong with my engine, because others on this board, and even certain suppliers, stated that no one else is having this problem, so it must be me. I had occasion today to get some advice from "old-timers" who claim that this setup was tried 30 years ago by a number of them and they had nothing but coking problems, so they all removed them.

Looking back, I think one of the differences is not with my "setup" but the fact that I fly it A LOT. I fly 200-300 hours per year, and take long trips like this current trip to Alaska, where we will put 50+ hours on it. I believe I am seeing things that ALL of you with this setup are eventually going to experience, and that is coking within 30-50 hours. There are already a few of you in this thread who have reported it.

It is true that we are experimenters, and I also believe the axiom that "we stand on the shoulders of giants." It has become clear to me today that some of the giants have already had bad experiences with this setup.

Here's my concern for those of you running this setup, especially without a safety valve. With a lot of local flying, 1-2 hours at a time, maybe 20-30 hours per years, you won't see this issue rear it's ugly head until you decide to take that long cross-country to OSH, to the Bahama's, or to Alaska, where you will very quickly add the 20-50 hours where the coking WILL show up. Without the safety valve, the odds are you could have a very serious problem before you catch it, including a blown nose seal and the commensurate loss of oil pressure.

No, there is nothing wrong with the valves. There is most likely nothing wrong with the air/oil separator (I don't even have it installed this time. I have duplicated the problem with and without the separator). This is a problem with attaching the output of the breather tube to the exhaust system. And yes, Dan, mine is aft of the muffler on the RV-10.

Against my best judgment I made this change again before a long trip to Alaska. I broke my own rule of no changes at the last minute, but at least Dan's safety valve worked. Someone must be looking out for me. So I feel obligated to pass along the experience and the warning. Please heed them. :)

Vic
 
I'm with Vic, when it comes to aircraft I'm pretty conservative and will "NEVER' be one of the early adopters of untested accessories/components that may effect the operation of the airframe or powerplant.

Just to add an extra 2c here, this mod has been done by many just to keep a little oil off the belly, hardly worth the risk IMO (get a rag and some mineral spirits and clean the belly for petesake, it won't kill you) :eek:
 
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It's probably done by most airplane people to keep the belly clean, yes, but the drag racing guys use it for power. So the concept is valid - the execution may be suspect.
 
...Let's not confuse the issue. Don't think anybody has failed a reed valve, at least not a good reed valve.

I never liked the idea of attaching a valve to a 1000 degree exhaust pipe, but I was willing to run with it until I saw Vic's post about the "coked up valve". Perhaps I took the reference to literally, but do you see any harm in locating the valve in a more favorable operating environment anyway? Certainly we can discuss without "confusing" anyone.
 
...do you see any harm in locating the valve in a more favorable operating environment anyway?

Well, ok....

I have run one in a remote location. It was 1985. Works fine, with a caveat....the trick is attaching the hose to the exhaust pipe. The large diameter spigot allows hot exhaust gas to pulse into the hose, as the hose volume acts like an accumulator. The hose gets hot. Go ahead, give it a try.

Or we can just measure the temperature of the reed valve.....

http://www.vansairforce.com/community/showpost.php?p=729808&postcount=38
 
Let's not confuse the issue. Don't think anybody has failed a reed valve, at least not a good reed valve.

My A&P put this setup on his RV4 a long time back (he and Vetterman were experimenting)....valve stuck and blew his front seal out. Wasn't coking in the tube, it was a stuck valve. He couldn't have been more emphatic in his objection to the Antisplat system I have installed (though clearly I didn't listen...it is an experiment I wanted to run). I'll keep a close eye on it.
 
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This is dangerous

I don't know how much clearer I can be here. This is a dangerous configuration that will eventually bite you. I've clearly demonstrated it twice. Which is exactly 2 more times than I would have liked.

I would not recommend you fly your airplane home without first disconnecting the attachment to the exhaust system.

It could be a valve, but it more likely is the coking. Don't waste your money on another valve unless you are going to put it in the system as a safety valve. It is a very risky proposition otherwise.

I am going back to the Airwolf separator. I have used it on multiple airplanes with never a problem and no oil on the belly. Yes, I know it is more expensive. But it works.

Vic
 
Double hit

I have had one valve fail, luckily it failed in an open position. I have also had my spigot coke over, which then produced leaks all over the place. I have since disconnected it and will not be hooking it back up. I like the idea of the valve, it just needs to be made fail safe but not sure how that would be done. I think Rocket bob has used a wet vacuum pump to pull a vacuum on the case, that maybe the answer?
 
I have had one valve fail, luckily it failed in an open position. I have also had my spigot coke over, which then produced leaks all over the place. I have since disconnected it and will not be hooking it back up. I like the idea of the valve, it just needs to be made fail safe but not sure how that would be done. I think Rocket bob has used a wet vacuum pump to pull a vacuum on the case, that maybe the answer?

How many hours did it take to coke over? How many did the valve last? Where were you tapped into the exhaust?
 
How many hours did it take to coke over? How many did the valve last? Where were you tapped into the exhaust?

The valve was attached 6" behind the ball joint where the two pipes join and 16" from the end of the exhaust pipe. It lasted about 20 hours and ASA shipped me a new one no charge. Time to coke over was about 40 hours.
 
OK, I've been thinking about his all day and have done some research, so I am going to express a much stronger opinion, and I understand that some may not be comfortable with it. I'm OK with that and I'll tell you why.

I believe very much in all of the Experimental aviation we do. However, sometimes there becomes enough data that points to a potential safety problem. I have spent the last year chasing down everything I could thing of that could be wrong with my engine, because others on this board, and even certain suppliers, stated that no one else is having this problem, so it must be me. I had occasion today to get some advice from "old-timers" who claim that this setup was tried 30 years ago by a number of them and they had nothing but coking problems, so they all removed them.

Looking back, I think one of the differences is not with my "setup" but the fact that I fly it A LOT. I fly 200-300 hours per year, and take long trips like this current trip to Alaska, where we will put 50+ hours on it. I believe I am seeing things that ALL of you with this setup are eventually going to experience, and that is coking within 30-50 hours. There are already a few of you in this thread who have reported it.

It is true that we are experimenters, and I also believe the axiom that "we stand on the shoulders of giants." It has become clear to me today that some of the giants have already had bad experiences with this setup.

Here's my concern for those of you running this setup, especially without a safety valve. With a lot of local flying, 1-2 hours at a time, maybe 20-30 hours per years, you won't see this issue rear it's ugly head until you decide to take that long cross-country to OSH, to the Bahama's, or to Alaska, where you will very quickly add the 20-50 hours where the coking WILL show up. Without the safety valve, the odds are you could have a very serious problem before you catch it, including a blown nose seal and the commensurate loss of oil pressure.

No, there is nothing wrong with the valves. There is most likely nothing wrong with the air/oil separator (I don't even have it installed this time. I have duplicated the problem with and without the separator). This is a problem with attaching the output of the breather tube to the exhaust system. And yes, Dan, mine is aft of the muffler on the RV-10.

Against my best judgment I made this change again before a long trip to Alaska. I broke my own rule of no changes at the last minute, but at least Dan's safety valve worked. Someone must be looking out for me. So I feel obligated to pass along the experience and the warning. Please heed them. :)

Vic

Bingo - - Oil going from a crankcase temps in a metal tube to exhaust temps will pass a coking temperature point somewhere. Period.

Knowing this and having it as a maintenance point or design a pressure relief can avoid trouble.

I investigated oil breather separators 30 years ago when working at Conti. My friend and super engineering guru there said most of these just don't work . . . I was challenged.

I found that in theory and practice it takes surface area to truly coalesce the aerosols to a liquid and allow them to drip down. Higher blowby will drive the oil out, then a larger container is needed. Our Lycs don't typically have a lot of blowby. Here is the interior of the Airwolf, see the expanded metal for surface area?

ExplodedAirOilSep.jpg


Now, in the experimental arena, we have options. All of which are valid based on the requirements of the builder for under cowl space, cost, belly cleanliness, maintenance (safety), and oil retention.

Your Coefficients WILL Vary (YCWV) in how you weight the relative importance.

Everyone can be right, but should be fully aware of all the ramifications of the "configuration" they choose.

Full disclosure - I will be using the standard draft tube until my coefficients change, with some attention to a back flow angle ad DanH has illustrated previously. Sharing results with others helps us all understand and act accordingly.

FYI - The original Allison 1710 in the P51 had to drain, strain, and replenish the coolant every 10 hours. The engine TBO was 300 hrs. All according the the maintenance manual from the day.
 
I don't understand the idea that if a valve fails in a closed position, it could lead to blown seals.

Wouldn't the pressure of a closed valve be relieved through the oil return line to the engine?
 
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.
 
This whole thread got me to worrying about my installation so off to the hanger I went. I installed my anti splat vent system about 30 hours ago on my 160 hp rV9. Most of my flying was local with two trips. One to sun & fun about 1050 miles each way and another to north Texas about 500 miles each way. My valve and tube are located in the left exhaust tailpipe just in front of the firewall and about 12" from the end of the pipe. What I found was that there was already a small buildup or material deposit that was forming. The deposit was not inside the vent tube. It was however was forming immediately downstream of the vent pipe where it exits into the tailpipe. The deposit was somewhat pyrimidal in shape and about 1/4" high. I knocked it right off with a ling screwdriver and it would easily crumble when compressed by the fingers. While there was no buildup in the breather pipe itself there certainly were deposits forming in the tailpipe which is somewhat concerning. I'm taking dans approach tomorrow and installing a second vent line and check valve just in case. It appears there is enough evidence to support the additional precaution. I will also check the system now at each oil change for further obstruction and if found remove them. This system has been great in keeping my engine dry and belly clean. I don't want to give that up and a few minutes extra work at oil change time is a small price to pay. The secondary vent is there as a just in case so I should never suffer from a blocked vent. Just another point of data and my thoughts.
 
This whole thread got me to worrying about my installation so off to the hanger I went...................... .

Thanks for your input. So, any noticeable performance increase with this mod?

I wish others would chime in. Im particularly interested in those who have had no issues. I will monitor mine, i have the hose clamp version so it can be removed and reinstalled in about two minutes.

So, if you remove the reed valve from the tailpipe, where is a good spot to route the breather too then, AND how do you patch the big hole in the tailpipe
 
I just checked mine, too. Similar finding. Black carbon build up on the end of the pipe near the exhaust. I would estimate about 40 to 50% blockage with about 150 to 200 hours? I will certainly be checking it after each oil change from now on.

Area all around the valve itself is super clean. Installed in the exhaust pipe on the bend after the heat muff/muffler.

IMG_20140711_164946424.jpg
 
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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.
 
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.
 
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.
photo2_zps6fecfe1f.jpg


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?).
 
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?
 
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.
 
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.
 
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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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:

29lhgg2.jpg


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.

2whlaat.jpg


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.

23h6agk.jpg


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.
 
<snip>
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.

Yes indeed it is. But we will have no hair and not laugh . . . .

This is an age old challenge. Think about a hydro carbon that is introduced into a hot flowing gas. The location of coking is a heat transfer and chemistry problem. First lets look at the coking media. In our, case oil. I could only find a synthetic but the curves will be similar just offset to a lower temp. 40-50F maybe?
oil%2520coking.jpg


The basic problem is illustrated below. The coking temperature point WILL BE PASSED somewhere along the flow line of the blowby. The tube is conducting heat from the hot exhaust pipe and transferring that heat to the mass flow of the blowby gasses. Some oil droplets (no matter how small) will touch the wall and at the right temperature stick there and continue to evaporate the light ends and combine with oxygen.

This is the same challenge of any liquid hydrocarbon fuel introduced into a hot gas. Diesel injection, or turbine fuel in a combustor. To absolutely prevent coking, the point at which the temp reaches the coke temp must remain in the air stream and the drops can never touch the walls.
Slide1.jpg


The flow velocities, oil droplet volume and size, cooling rates under cowl, plus frequency and oscillating flow in the tube etc will change the point of coking but won't eliminate it.

Any problem can be mitigated by maintenance, and ensuring that less oil is entrained in the blowby gasses. Plumb a relief, and check regularly.
 
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Good stuff Bill.


Question...in the case of a diesel fuel injector, coking of the tip is prevented by ensuring that the injector body, including the tip, is held below coking temperature? Key is proximity to relatively cool head material?
 
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Good stuff Bill.

Question...in the case of a diesel fuel injector, coking of the tip is prevented by ensuring that the injector body, including the tip, is held below coking temperature? Key is proximity to relatively cool head material?

Yes, Dan, the bodies or stems come through the head surrounded by the water jacket. The check that controls/stops the flow is in the tip itself. There is a volume in the tip beyond the check on some injectors, but many now have what is called VCO, valve closed orifice. The nozzles themselves are kept clean by the natural cavitation action during injection 30ksi doesn't hurt either), although this is also a fuel additive solution area. If the cavitation action is too aggressive then it will erode the nozzle. This is controlled by flowing an abrasive fluid through the nozzles (kinda like silly putty) during manufacture to radius the inlets and avoid cavitation from that source. The tips are made from 52100 (ball bearing) steel and heat treated pretty hard.

One additional benefit of the diesel is that a full loads where the combustion temps are higher, there is more fuel flow and when the loads are low then all the temperatures drop pretty low compared to an otto cycle engine running at stoic.
 
Curiouser and curiouser....

Snip

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.

Snip

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.

Well, how about a tube within a tube? The inner tube would be quite a bit cooler...

Carry on!
Mark
 
We were all saying the same thing but not quite so perfectly presented as BillL!!!

I was thinking along the same lines:
1. tube within a tube.
2. maybe teflon coated inside so that the coke/oil does not stick to the tube walls so well.
3. a gasket for my clampon version to minimize heat transfer from exhaust to tube. however, the end of the tube is still in the exhaust stream still creating a temperature gradient and probably a ring of coke there somewhere.

of course, we can abandon tying into the exhaust. however, i ran with the air oil separator without the valve, and it cut down on the oily belly by only 50% or so. it is really nice not seeing any oil on the belly at all. ;)
 
Further data

In conversations with Larry Vetterman (and permission to quote) He emphatically tells me two things:
They tried this 30 years ago and had the same problem.
He has spent a lot of money over the years designing and TUNING exhaust systems, and this modification has an unknown impact upon the tuning.

The stuff that I saw in ine was the same texture as described by Dan.

The prior poster said he would add checking it to the oil change. I submit that if your oil changes are at 50 hours it is too long.

Vic
 
Might be too early to report this, but here it goes anyway:

Since I have one of the Moroso crankcase evacuation systems left over from my drag race days, I was planning on using the check valve in the exhaust like the subject of this thread. But in light of the troubles reported here, I went a different direction.

First, I welded up a 45 degree pipe fitting for the accessory case, which allows the pipe to angle up and back, rather than out the side. My thinking is to get as much vertical distance possible before going downhill and overboard. To this stub pipe I attached the Moroso crankcase (valve cover) breather from the aforementioned evacuation kit. This breather is essentially a little oil separator with a vent out the top. To this vent I simply ran the vent hose up against the top of the cowl and down to the cowl exit. I welded up a simple stub tube with a little leg with hose clamps to the exhaust pipe. This is simply to ensure the oil drips on the outside of the exhaust and burns off - there's no venturi action.

A 30 minute flight tonight which included a high power climb to 7500, cruise, and some fooling around at low altitude would normally have produced a wet pipe and some drops on the hangar floor... Instead, I found ZERO evidence of any oil going overboard. Not even on the inside of the breather tube. Obviously, this is very preliminary, but promising. I have some X country work to do this weekend, so let's see if this holds.

Update: just returned from a Vegas weekend (1 hour each way), and there is only the slightest hint of oil in my new breather tube. Not enough to show any burn off on the pipe, and hardly enough to show on the inside of the pipe. It appears my engine has gone from a slobbering mess to completely tight overnight. I don't see the need to mess with the exhaust tap at this point.
 
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Continue with an evacuator or not? All users will need to make their own decision. If you elect to keep the exhaust tap, I'd suggest this approach:

(a) 25 hr inspection intervals if operated as delivered from Anti-Splat.

(b) 25 hr inspection intervals if operating an experimental system or component of your own design.

(c) In either case, install the second reed valve as an automatic positive pressure relief. (install photo in post 98)

I like the benefits of negative case pressure, so I will continue to experiment, following (b) and (c). The goal is a non-coking tap.

Special request: please report ANY problem with a relief valve installation immediately. So far, it worked just as intended for Vic (provided a positive pressure relief after exhaust tap blockage), but that's just one case. If there is an unknown issue with the relief valve installation, everyone should be made aware ASAP.
 
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