CharlieWaffles
Well Known Member
Considering these are used for several different models - should this thread be moved to the General forum for greater awareness across the different models? Thinking from a safety and possible awareness effort.
Van's Air Force
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Oil Consumption and Breather Tube
- Thread starter Bill.Peyton
- Start date
I would like to install the second reed valve but do not have the means to fabricate a T connector. I have been unsuccessful in locating a metal connector. Has anyone found a good source?
PerfTech
Well Known Member
... I agree with everything Dan has suggested here, and think this should be followed to the letter, especially with an RV-10 installations. We have stopped sales of the vacuum system parts for install on the 10s until we can assure this problem is corrected. We are trying to address the issue and do appreciate any and all input from outside sources. If someone can show a design change (say on the saddle mount for instance) that can help prevent this we would be happy to produce them and replace all the RV-10 units sold at no cost. Also we want to make anyone with an issue of any type involving an ASA product aware of our return policy. Just send it back for a full, prompt, no hassle refund. Thanks, Allan...
PerfTech
Well Known Member
... If you show us what you need we can make one for you. Thanks, Allan..
This is available from Mc. Master Carr and will most likely fill your need; 5/8" 91355K53 $8.40
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Mike S
Senior Curmudgeon
Good idea, will do so.
Toobuilder
Well Known Member
Newer diesel powered light trucks have exhaust tip augmentors that draw in fresh air to dilute the particulates. Any reason the same concept could not be applied to an aircraft engine? Exhaust flow combined with cowl exit airflow should be able to generate negative pressure in this venturi. Benefits include no need for the reed check valve, and the temperature of the stub pipe will be well below the coking temperature.
Might not have quite the "sucking power" of the reed valve tapped into the primary tube, but should still pull some, and keep the belly clean.
alpinelakespilot2000
Well Known Member
I'm trying to visualize this:
So we install the Antisplat per instructions, with the main breather line going to the NAPA-type valve first then terminating in the saddle penetrating the exhaust.
The "safety" line coming off the T, on the other hand, is simply an open tube like that of the Van's stock setup and it can be routed wherever we want, perhaps over the other exhaust pipe. Is this basically correct?
What's to keep the oil from going out the open safety tube rather than to the valve and exhaust saddle? The suction created by the exhaust does this?
Does the above suggest I'm understanding this correctly?
So we install the Antisplat per instructions, with the main breather line going to the NAPA-type valve first then terminating in the saddle penetrating the exhaust.
The "safety" line coming off the T, on the other hand, is simply an open tube like that of the Van's stock setup and it can be routed wherever we want, perhaps over the other exhaust pipe. Is this basically correct?
What's to keep the oil from going out the open safety tube rather than to the valve and exhaust saddle? The suction created by the exhaust does this?
Does the above suggest I'm understanding this correctly?
ColoRv
Well Known Member
I don't believe so. The safety line being open would simply dump the crankcase out the end of it. At the end of the safety line is supposed to be another NAPA 2-29000....allowing any positive pressure to dump overboard. Point being if the antisplat system fails as it appears prone to do, either by coking over or valve sticks....no positive pressure builds in the case.
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BillL
Well Known Member
The reason for the augmenters is to cool the exhaust during regeneration of the particulate trap. The trap is a ceramic filter that collects the carbon particulates and then uses 740 C to burn them off. This must be done at high mass flows out the exhaust or the trap will overheat during the burn off. They can get over 1000 if over loaded. In the early testing of this system the exhaust burn off paint of nearby objects and the temperatures ignited fence posts and other combustable materials nearby (pants legs). That is what the augmenter is for, temperature dilution.
Almost nothing is free, tapping pulse energy with a check valve is. Higher velocity ( to operate a venturi) comes at a price of exhaust back pressure. AND, it won't help the more frequent issue of carbon collection. Non-starter I think.
Toobuilder
Well Known Member
If the exhaust augmentor (venturi) is not a smaller OD than the exhaust pipe, it won't create any back pressure. You are simply are introducing high velocity, expanding gasses into the back end of a diffuser, which will create low pressure at the front and draw in air. This is how exhaust augmentors work for engine cooling.
douglassmt
Well Known Member
Little coke
I flew about 10 hours Sunday/Monday which brought me to about 75 hours since installing the ASA separator. I had checked the discharge tube in the exhaust with a borescope a couple times and saw nothing - absolutely nothing.
After the flights I checked it again with borescope and could just see a tiny bit of the black stuff but it was farther up the tube - slightly above where it penetrates the exhaust pipe - so I couldn't get a real good angle with the borescope. So I removed the top cowl, disconnected the discharge hose from the separator and blew/sucked on it - fine, no noticeable restriction.
I then removed the reed valve from the exhaust pipe so I could look down into the tube welded to the exhaust. There was the slightest amount of the black stuff accumulated around the inside of the tube so I cleaned it out with a screwdriver the right size but there wasn't even enough for me to see when I looked up the exhaust pipe.
I bought the second reed valve and will be installing it anyway. And, I'll be checking the exhaust discharge every 10-20 hours until I see a pattern.
I flew about 10 hours Sunday/Monday which brought me to about 75 hours since installing the ASA separator. I had checked the discharge tube in the exhaust with a borescope a couple times and saw nothing - absolutely nothing.
After the flights I checked it again with borescope and could just see a tiny bit of the black stuff but it was farther up the tube - slightly above where it penetrates the exhaust pipe - so I couldn't get a real good angle with the borescope. So I removed the top cowl, disconnected the discharge hose from the separator and blew/sucked on it - fine, no noticeable restriction.
I then removed the reed valve from the exhaust pipe so I could look down into the tube welded to the exhaust. There was the slightest amount of the black stuff accumulated around the inside of the tube so I cleaned it out with a screwdriver the right size but there wasn't even enough for me to see when I looked up the exhaust pipe.
I bought the second reed valve and will be installing it anyway. And, I'll be checking the exhaust discharge every 10-20 hours until I see a pattern.
bpattonsoa
Well Known Member
Yes, Allen has a coke problem
Just checked my -10 for coke. Was almost identical to JCHANG10 photo, a little more than Dan H. My photo turned out bad or it would be posted. Perhaps 50% blocked about 1/2" up the tube. My bracket is upon the right exhaust on the 45 just behind the heater. Total time since new is 50.8 hours with the first 40.5 using mineral oil and Aeroshell 100 since. (Engine was slow to break in)
I strapped my engine compartment thermocouple to the outside of the pipe right about where the coke formed. Unfortunately it was too late for a flight, but will try to get up tomorrow before some visitors arrive. If not, it could be a few days.
Just checked my -10 for coke. Was almost identical to JCHANG10 photo, a little more than Dan H. My photo turned out bad or it would be posted. Perhaps 50% blocked about 1/2" up the tube. My bracket is upon the right exhaust on the 45 just behind the heater. Total time since new is 50.8 hours with the first 40.5 using mineral oil and Aeroshell 100 since. (Engine was slow to break in)
I strapped my engine compartment thermocouple to the outside of the pipe right about where the coke formed. Unfortunately it was too late for a flight, but will try to get up tomorrow before some visitors arrive. If not, it could be a few days.
Second Reed installed
Installed a second Reed valve today.
Like Dan Horton, I do like the idea of negative pressure in the crankcase and I am not quite ready to do away with the idea of the crankcase breather line plumbed into the exhaust. However, there is enough evidence at this time that stubs welded into the exhaust tubes will coke up and create a potential for a crankshaft gasket to blow out.
Here is my install, I pointed the valve up so as not to have an oil drip after shut down.
Installed a second Reed valve today.
Like Dan Horton, I do like the idea of negative pressure in the crankcase and I am not quite ready to do away with the idea of the crankcase breather line plumbed into the exhaust. However, there is enough evidence at this time that stubs welded into the exhaust tubes will coke up and create a potential for a crankshaft gasket to blow out.
Here is my install, I pointed the valve up so as not to have an oil drip after shut down.
CharlieWaffles
Well Known Member
As a result of the other posts, I made a point to check my exhaust stem during my annual inspection today. I too have coke in my stem, and a good deal of it. The separator and valve were added prior to the first flight and the Hobbs currently shows about 91 hours.
I have decided to remove the valve and stem. I am going to keep the separator and will run the line to drip on the exhaust like the stock setup, so I will still benefit from having the separator and clean belly.
I used Mineral oil for the first 20/25 hours and then Aeroshell 15W-50 since.
I have decided to remove the valve and stem. I am going to keep the separator and will run the line to drip on the exhaust like the stock setup, so I will still benefit from having the separator and clean belly.
I used Mineral oil for the first 20/25 hours and then Aeroshell 15W-50 since.
I ran this way for a while until the saddle version became available. I say it cut down on the oily belly maybe 50% at best. I still had an oily belly, oily engine mount, oily firewall, etc.
Brantel
Well Known Member
A friend of mine had his stock vent line done this way for his first year flying his RV6A. It caused tons of black crud to form on everything firewall fwd.
He then moved his vent line away from the exhaust and now cleans the oil off the belly.
I agree!
Ernest, I don't know how much clearer some of us can be. This is a dangerous configuration, and someone is going to have a serious problem. Over a year ago I was told I was the ONLY one having this problem. There is now overwhelming evidence that it is the configuration. And as I stated before, others tried this 30 years ago and had the same problems.
Vic
Ernest, I don't know how much clearer some of us can be. This is a dangerous configuration, and someone is going to have a serious problem. Over a year ago I was told I was the ONLY one having this problem. There is now overwhelming evidence that it is the configuration. And as I stated before, others tried this 30 years ago and had the same problems.
Vic
PerfTech
Well Known Member
... Yes, The vacuum system definitely stops the oil seepage and small leaks that goo up the belly, engine and firewall. That is one of its advantages. Thanks, Allan...
[email protected]
Well Known Member
pretty good buildup after 350 hours...
I pulled the lower section of pipe and removed the valve... after about 350 hours over a year and a half there was a good build up irising closed. I cleaned it out and ran a bore brush back and forth a bit. Will now pull and inspect with each oil change.
I pulled the lower section of pipe and removed the valve... after about 350 hours over a year and a half there was a good build up irising closed. I cleaned it out and ran a bore brush back and forth a bit. Will now pull and inspect with each oil change.
ColoRv
Well Known Member
We hear you Vic. You can't be any clearer. With that said, you're engine, installation, oil etc aren't necessarily the same as the rest of ours. We continue to experiment, and keep an eye on it. Dangerous is relative of course. In your plane with the temps the valve sees where you located it and the amount of oil running through that valve...you are experiencing significant coking and that is dangerous.
As another data point, I have approx 65hrs on my setup. Angle valve 360, valve placed in the header pipe much further upstream than I think is typical. Two 7hr cross countries and my pipe has no coking and the valve is fine. I'm keeping a close eye on it of course. It's easy to check with the hose clamped version.
Installation, amount of oil passing through and how the engine is operated all affect a system like this. We just aren't sure how yet, as the manufacturer hasn't done any real testing. We the Test Pilots....
PerfTech
Well Known Member
... I agree with Vic on this issue on the RV-10s and have stopped selling the vacuum system for the 10s until we can assure the problem is solved. ASA has only released or sold 31 total evacuation systems for the RV-10s (six of these were given at no charge for testing and evaluation). We request that all RV-10 owners that purchased or were given the evacuation systems install the extra valve as a safety measure or disconnect the exhaust mounted valve and run the line overboard. We will be happy to help with some parts to these owners, just give us a call. This plugging up solid has been only reported on the a few 10s, and has not been an issue or reported to us on other models with several thousands in use. Some small amount of buildup is normal but has never been a problem on these other installations. This buildup is very simple to check and remove at oil change time and should be on your maintenance check lists (photo below is the worst we have seen and is soft).
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The accumulation on this tube as shown above is isolated at the weld and offers up proof as Dan suggested to me that there is a critical temperature that promotes this build up occurring. The photos below are of our double walled saddle mount that is currently being tested. This should eliminate this heat transfer completely. The inner tube that carries the blow-by products is welded only at the cooler top fitting and has .025" clearance all around. This insulates it from the hotter outer tube that is perpetuating the buildup or coking.
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It also seems that any major hard buildup is on systems that the exhaust valve mounting tube was welded into the exhaust pipes and not on the saddle mounts. We are and have been working and testing many different designed parts to eliminate the possibility of this happening and have several in use now, building time. We will report the results when they have accumulated viable, credible information at 20, 40, 60, etc hours and when available. Thanks, Allan
bpattonsoa
Well Known Member
Data on temperatures at the coking area
I flew this morning. My extra thermocouple was strapped to the outside of the pipe on the Antisplat aero RV-10 saddle mount about 1/4" above the base plate. This was where my coking appeared that was reported yesterday. The saddle is on the 45 just behind the right heat muff.
From engine start to runup was about 6 minutes. The pipe went to 239 degrees F. On run up it rapidly climbed to 291. While waiting to takeoff it went down to 280. On takeoff it climbed to the peak of 321 and then rapidly cooled down to 204. For most of the flight it remained between 196 and 210. (I was showing the aircraft to another RV pilot, so we never went into a constant cruise. I did lean it out to slightly lean of peak) In the descent it cooled to 177 and then started rising again when in the pattern.
From the above, it is obvious that the pipe is cooling a lot from the airflow out of the cowl despite being behindthe heat muff.
Since the temperatures I saw after takeoff were all below 210, I would assume that the coking is not occurring during cruise flight.
The temperature was above 280 for 2minutes and 15 seconds, from the start of run up to right after takeoff. I suspect that is the time the coke is forming, at least in my installation. Others have reported forming rapidly in cruise. I had 40 hours on mineral oil and 10 on Aeroshell 100 so it is just a guess as to when my coking was formed, the critical temperature is most likely different for the two oils. If the coking was formed with the Aeroshell 100, a 50 hour inspection interval is too long.
I do know that a relief valve is going in the line next weekend for sure!
EDIT
When I took the cowl off to put in the relief the thermocouple was not on the pipe. I used a tie wrap to hold it in 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. I will download the new data when I get home and put in a new post.
I flew this morning. My extra thermocouple was strapped to the outside of the pipe on the Antisplat aero RV-10 saddle mount about 1/4" above the base plate. This was where my coking appeared that was reported yesterday. The saddle is on the 45 just behind the right heat muff.
From engine start to runup was about 6 minutes. The pipe went to 239 degrees F. On run up it rapidly climbed to 291. While waiting to takeoff it went down to 280. On takeoff it climbed to the peak of 321 and then rapidly cooled down to 204. For most of the flight it remained between 196 and 210. (I was showing the aircraft to another RV pilot, so we never went into a constant cruise. I did lean it out to slightly lean of peak) In the descent it cooled to 177 and then started rising again when in the pattern.
From the above, it is obvious that the pipe is cooling a lot from the airflow out of the cowl despite being behindthe heat muff.
Since the temperatures I saw after takeoff were all below 210, I would assume that the coking is not occurring during cruise flight.
The temperature was above 280 for 2minutes and 15 seconds, from the start of run up to right after takeoff. I suspect that is the time the coke is forming, at least in my installation. Others have reported forming rapidly in cruise. I had 40 hours on mineral oil and 10 on Aeroshell 100 so it is just a guess as to when my coking was formed, the critical temperature is most likely different for the two oils. If the coking was formed with the Aeroshell 100, a 50 hour inspection interval is too long.
I do know that a relief valve is going in the line next weekend for sure!
EDIT
When I took the cowl off to put in the relief the thermocouple was not on the pipe. I used a tie wrap to hold it in 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. I will download the new data when I get home and put in a new post.
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Toobuilder
Well Known Member
Aside from the temperature, location and other issues discussed here, there does seem to be some substantial variation (between aircraft) in the amount of oil going overboard in the first place. For example, I went from a slobbering mess to essentially dry with only the addition of a small breather chamber and routing the exit hose as high as possible. I'm wondering if the people with the more severe coking issues are messier than those who are not? Perhaps the exhaust tap just masks the fact that some breather installations are worse than others?
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RVG8tor
Well Known Member
Clear
I have been keeping track of this thread. I have almost 40 hours on mine and no clogs or hint of any. I can get an inspection mirror up the pipe to check but also plan to check each oil change
I wonder if there is a correlation with the type of oil used. I use Phillips 20-W50 with nothing added. I was considering using CamGuard, could an additive help or hinder this buildup. Must be some smart chemist on the forum.
Cheers
I have been keeping track of this thread. I have almost 40 hours on mine and no clogs or hint of any. I can get an inspection mirror up the pipe to check but also plan to check each oil change
I wonder if there is a correlation with the type of oil used. I use Phillips 20-W50 with nothing added. I was considering using CamGuard, could an additive help or hinder this buildup. Must be some smart chemist on the forum.
Cheers
Two types
I have used both Aeroshell 100W+ and Philips 20W50, both with cam guard. Just a data point.
Vic
I have used both Aeroshell 100W+ and Philips 20W50, both with cam guard. Just a data point.
Vic
Bill.Peyton
Well Known Member
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.
Until a proven solution is discovered, this is just too risky for me, even with a safety check valve.
CharlieWaffles
Well Known Member
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.
http://rgl.faa.gov/Regulatory_and_G...89D2E182A363570F862569B9004D3EDE?OpenDocument
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.
http://rgl.faa.gov/Regulatory_and_G...89D2E182A363570F862569B9004D3EDE?OpenDocument
alpinelakespilot2000
Well Known Member
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?
Toobuilder
Well Known Member
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.
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
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
bpattonsoa
Well Known Member
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.
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.
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.
http://www.vansairforce.com/community/showpost.php?p=897381&postcount=141
http://www.vansairforce.com/community/showpost.php?p=897381&postcount=141
Can I talk someone (with a clamp-on exhaust tap) into an easy experiment?
Install a small tee fitting in the accessory-case-to-separator hose in order to connect a manometer. Get a baseline vacuum reading at some selected power setting.
Now pull the clamp-on exhaust pipe tap, file off the small angled protrusion that sticks out into the exhaust stream, re-clamp, and fly again with the manometer. What is the difference in vacuum reading?
Worry not...if you don't like the result, send the clamp-on tap to me and I'll weld the protrusion back into place.
It certainly seems like the RV-10 tap location puts temperature pretty close to the middle of the coking zone....say 200C to 300C on Bill's chart. It would be nice to find a similar chart for our motor oils. What search terms might find it?
F1Boss
Well Known Member
SERIOUS trouble waiting for you there!
Bennair; Dunnatt. Used an Airwolf wet pump. Worked great & made power, until I sold the plane to another, and he had the nerve to turn it upside down. Large blob of oil tried to get thru the pump, and snapped the shaft. Stopped pump rotation, and outlet flow. With no aux outlet, it let the engine force oil out of the nose case. BIG mess; no damage.
SO!! This *might* work if a very reliable separator was installed between the pump inlet and the case....along with a reed valve sort of emergency outlet in the case to pump line, but this active pump system will not tolerate a slug of oil getting into the pump. No sir!
Carry on!
Mark
Bennair; Dunnatt. Used an Airwolf wet pump. Worked great & made power, until I sold the plane to another, and he had the nerve to turn it upside down. Large blob of oil tried to get thru the pump, and snapped the shaft. Stopped pump rotation, and outlet flow. With no aux outlet, it let the engine force oil out of the nose case. BIG mess; no damage.
SO!! This *might* work if a very reliable separator was installed between the pump inlet and the case....along with a reed valve sort of emergency outlet in the case to pump line, but this active pump system will not tolerate a slug of oil getting into the pump. No sir!
Carry on!
Mark
rocketbob
Well Known Member
I had a wet vac pump pulling on the breather on my RV-6. I put a flapper-door check valve with one side vented to ambient on the intake side of the pump so that in the event of the pump failure the breather functioned normally. The limiting factor to the system was the fuel pump. Since it is vented to the crankcase, the pump would quit if a high vacuum was pulled. It worked well but I had to dial back the vacuum, using a simple orifice at the inlet of the pump.
F1Boss
Well Known Member
Another gotcha!
A fuel pump that actually flows fuel is important - I did not run into the problem: I had the rotary pump from the turbo setup on the engine with the pump, so crankcase vacuum didn't really matter to it. That flapper door check valve sounds like a good item of the current exhaust systems to have - even if the coking problem is solved. How about supplying a drawing, or a vendor?
Carry on!
Mark
A fuel pump that actually flows fuel is important - I did not run into the problem: I had the rotary pump from the turbo setup on the engine with the pump, so crankcase vacuum didn't really matter to it. That flapper door check valve sounds like a good item of the current exhaust systems to have - even if the coking problem is solved. How about supplying a drawing, or a vendor?
Carry on!
Mark
My O-360 will throw out anything over 5.5.
As for the breather hose, I blew out the prop seal on a real humid, 50-60 temp day running full out, I looked into causes for that. Found a ton of stuff from the canard guys. Learned most oil breather slop is about 95% water.
Most likely cause, icing in the hose. But furthermore...
I deduced my breather hose should NOT be cut facing forward - WHICH CREATES POSITIVE PRESSURE, but instead turned around so the 45 degree cut faces rearward, giving NEG case pressure, better performance, and no blown prop seals. With neg pressure, even if you find your prop seal pushed out of the engine, you won't find you are blowing oil out there. So I turned it facing backward, and got a performance boost.
Just think fuel vent: to pressurize tanks, 45degree goes forward.
Since then I installed anti-splat. 1) Don't test to see what it will do if you overfill your engine... just don't overfill, and 2) every oil change inspect the tube going into your exhaust and scrape out the coke deposits you are forming... if that totally cokes up, your going to get a backup.
YMMV
As for the breather hose, I blew out the prop seal on a real humid, 50-60 temp day running full out, I looked into causes for that. Found a ton of stuff from the canard guys. Learned most oil breather slop is about 95% water.
Most likely cause, icing in the hose. But furthermore...
I deduced my breather hose should NOT be cut facing forward - WHICH CREATES POSITIVE PRESSURE, but instead turned around so the 45 degree cut faces rearward, giving NEG case pressure, better performance, and no blown prop seals. With neg pressure, even if you find your prop seal pushed out of the engine, you won't find you are blowing oil out there. So I turned it facing backward, and got a performance boost.
Just think fuel vent: to pressurize tanks, 45degree goes forward.
Since then I installed anti-splat. 1) Don't test to see what it will do if you overfill your engine... just don't overfill, and 2) every oil change inspect the tube going into your exhaust and scrape out the coke deposits you are forming... if that totally cokes up, your going to get a backup.
YMMV
...The photos below are of our double walled saddle mount that is currently being tested. This should eliminate this heat transfer completely. The inner tube that carries the blow-by products is welded only at the cooler top fitting and has .025" clearance all around. This insulates it from the hotter outer tube that is perpetuating the buildup or coking.
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It also seems that any major hard buildup is on systems that the exhaust valve mounting tube was welded into the exhaust pipes and not on the saddle mounts. We are and have been working and testing many different designed parts to eliminate the possibility of this happening and have several in use now, building time. We will report the results when they have accumulated viable, credible information at 20, 40, 60, etc hours and when available. Thanks, Allan
Allan posted the above just before OSH, so it's time to start hearing field reports (coking or no coking) about the double wall tap.
I welded one into my homebrew tap 10~15 hours ago. Had the cowl off last weekend for an oil change and could detect nothing in the tube but a film of the same gray/beige dry deposit seen in the tailpipe. More reporting as the hobbs rolls forward.
BillL
Well Known Member
Here is a little background on motor oil testing. I think the test we would be interested in is weight loss vs temp, or boiling point fraction. The type of oil used can make a significant difference in shifting a curve.
http://www.upmpg.com/motor_oil/motor_oil_testing.htm
I looked around for coking temps of motor oils and did not find anything definitive. 225C coking temp was found for standard oils, but synthetics are higher. Coking takes place in turbos, and in ring grooves. The petroleum vs synthetics coking temps may only be 30-50C apart (guessing) for what we can buy off the shelf. If we have any RVers that work at SwRI in San Antonio, they would have access to some proprietary data (and certainly public) that we would have to pay for. They certainly have data on many oils as they do the qualification testing on single cylinder engines for piston deposits etc. They NEVER would publish, or post, definitive brand data, but might give us a delta for petroleum vs full synthetic temps. A simple toaster oven test would (could) provide some useful data if really needed.
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Wow, blast from the past. Yeah, throughout the late '80s- early '90s the facility at SwRI ran large labs of engines 24x7 for years doing oil analysis. The nuclear physicist that ran those labs was my best friend / mentor / guru, for whom I am forever grateful for his teachings.
