Great Planes Adjustable Oil Pressure Regulator

Discussion in 'Half VW' started by N8053H, Aug 27, 2014.

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  1. Oct 20, 2014 #61

    Hot Wings

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    This sounds a bit odd. There should be no direct correlation between oil pressure loss and engine roughness for momentary occurrences. Even a new VW engine will run a considerable amount of time with zero oil pressure before there is enough internal damage to cause rough running. That I know this fact is embarrassing enough - I'd prefer not to divulge the details of the experience. :emb:

    I'm guessing there is some other factor causing both symptoms.
     
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  2. Oct 20, 2014 #62

    N8053H

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    I am sharing this just maybe someone else will learn something and NOT repeat my stupid mistakes.

    Anytime my airplane comes out of the shop for reasons as this, I do a fly off of so many hrs. It must perform without any flaws or problems in this time. If it don't, she gets worked on again and the time starts all over. I would like to see 5 one hr flights without any issues before I stray from my home field. Then I am only going around 7 miles. I will fly to a friends place. Maybe land maybe not, but I am above another airstrip.

    Once I get about 30 hrs of trouble free flying doing this I will leave the area and do a x-country of around 45-50 miles. Its not happened yet, not in this airplane. I was hoping for this year, but this year has been ate up with oil pressure issues. Until this gets worked out this airplane is not leaving its home field, unless its on a trailer.

    Tony
     
  3. Oct 21, 2014 #63

    N8053H

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    Does increasing the pressure on this spring cause the oil pressure to rise?
     
    Last edited: Oct 21, 2014
  4. Oct 21, 2014 #64

    N8053H

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    Or does increasing the pressure on this spring reduce the oil pressure? I am trying to set up my adjustable pressure relief. Right now without any shims I am seeing 80 lbs of oil pressure. If I increase the pressure on the spring will it reduce the oil pressure or increase it?
     
  5. Oct 21, 2014 #65

    Hot Wings

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    Yes, increasing the spring tension (more shims) will increase the oil pressure as long as the oil isn't bypassing the bearings, the oil pump gears internally to the pump, or at some other point in the oil system beyond the ability of the pump to supply oil. The idle oil pressure is often limited by the viscosity of the hot oil, the bearing clearances, and the oil pump volume. The oil pressure spring in these conditions only limits the oil pressure above idle.

    The thickness of shims needed can be figured out mathematically using the spring constant (how far the spring compresses per unit of force) and the diameter/area of the piston. The links to the Samba site should have the complete "how to" and formulas.

    Some weird things can happen with motors. The guy I learned VW's from a had a 1300cc intake manifold he dissected nailed to his shop wall. The motor it came from was an engine he rebuilt at a dealership under warranty. It had a knock and ran rough. After a rebuild that found little out of normal it still ran the same way. He tore it down 3 times trying to figure out where he made the mistake. Turns out he hadn't made any. The intake manifold had a small (3mm) hole in it and when the aluminum was cast around it and the heat riser some went inside the 3/4 side and solidified in place. It apparently had come loose and was the source of the noise and fluctuating manifold vacuum. It was too long to just shake out, or even to see when looking in the manifold.

    VW didn't pay for his time under warranty. :cry:

    Point is that sometimes the problem is a one in a thousand, or less, occurrence and just never gets considered.
     
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  6. Oct 21, 2014 #66

    N8053H

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    Sounds like I am stuck with what I have. The oil did not get to operating temp but just started to rise. This was after about 10 mins of running at around 1900 rpm's. The oil pressure at idle at this temp was around 40 lbs and at 1900 rpm's was around 80 lbs. It did not seem to rise anymore if the throttle was increased. Maybe at 160 degree's the oil pressure will decrease some.

    This sounds like really high oil pressure to me though. I could remove a couple coils from the spring. Not sure what to do but I believe if I run her like this I will have oil coming out of every little place and maybe even blow some seals like in the mag, or crank seals.

    To much oil pressure is just as bad as not enough oil pressure.
     
  7. Oct 21, 2014 #67

    Dana

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    What grade oil are you using? My engine is a Mosler, and no GP regulator. I haven't flown it yet but the notes from the builder say, "The oil pressure at start up can jump up 50-60 lbs for about a minute. The rubber seal around the oil filter will leak and you can't stop it. I've had it happen with 20W50 but never with 20W40."

    Dana
     
  8. Oct 21, 2014 #68

    Pops

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    On my 1835 cc , 4 cylinder, the start up oil pressure is set at 53-55 lbs by the adjustable spring and piston at the flywheel end of the engine. When oil is hot and at cruise of 2650/2700 rpm the oil pressure is 40-42 lbs. Hot idle (900 rpm) oil pressure is 20 lbs. 30 straight weight oil.

    Dan
     
  9. Oct 21, 2014 #69

    N8053H

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    The oil was changed using Shell Rotella T 30 weight. It has around 2 hrs run time on it.
     
  10. Oct 22, 2014 #70

    N8053H

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    I am still having problems. The oil pressure dropped to 20 lbs right after take off. I put her right back on the runway. Before I flew her or tried to, I ran her on the ground for about a 1/2 hr. Not one problem. The oil pressure went from a cold reading of 85 lbs to 65 when warmed up. I never did get her up to operating temp but she was reading on the gauge.

    I am including a pic of the oil pressure valves. The one on the right is the one I am using or one just like it. This was the valve in the engine when I first purchased the airplane. Could I be using the wrong valve? If I am using the right or correct valve the engine is going back to Hummel. I do not know what else to do. I have had this apart now over 10 times.

    oil valve and mag 004.jpg
     
  11. Oct 22, 2014 #71

    Hot Wings

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    After 10 times and based on the pics you have posted I'm thinking that this is not your problem area.

    There are 5 things that can cause low oil pressure:
    1) Lack of oil
    2) Mechanical failure of the oil system
    3) Too much oil bypassing the bearings/lifters/cracks etc.
    4) Blockage of the oil system
    5) air being sucked into the pump

    If it were in my shop:
    1 How much oil does it hold? More than 1.5 quarts? That is in the sump with the oil cooler and lines full.

    5 Too much oil? Check the oil level in flight attitude, not 3 point. It's possible that too much oil is getting whipped into foam, or at least partially, and the entrapped air is causing the oil pressure loss.

    2+5 Remove the oil pump/filter combination shown and replace it with the smallest stock VW pump that will match the camshaft. There are 2 different camshaft gears that could be installed and each requires a matching oil pump. The pump shown is larger than is needed and could very well be sucking the sump dry. The case shown originally came with a "3 rivet" cam. The later dished cam only works with large capacity oil pumps. You can tell which you have with the oil pump out. It takes a special tool, that can be fabricated, to remove the oil pump.

    3 Cut the filter open one more time and look for metal or trash.

    4+5 Pull the oil sump and inspect for something plugging the pickup tube. Push on the pickup tube to make sure it is still snug and not flopping around. While the pump is out pressure check the tube for leaks. After getting everything back together run the engine on the ground in flight attitude, not 3 point. Running in 3 point on the ground will help drain what little oil may remain in the crankcase back into the sump and could mask a low oil problem. If you notice a pressure drop on the ground with the tail up try adding another 1/2 quart of oil and see if the problem goes away.

    If this doesn't work - I'd be as perplexed as the next guy :ermm:
     
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  12. Oct 22, 2014 #72

    N8053H

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    Well the oil pump you see was installed two years ago. I used it for a long time without any issues. I flew this airplane for 3 years using the marks on the dipstick to fill my oil. I even question this with Scott at Hummel. He said use the markers on the dipstick.

    I think I am seeing some kind of blockage. Not sure where its from. Unless I am using the wrong pressure valve. I am going to try an switch out the valve tomorrow. I am going with the valve on the left in the pic.

    When I am doing my run up I have the tail down. When I taxi I taxi with the tail up. Never an issue. Even tied down I can run full power for 4 mins or until I must lower for CHT. The oil pressure never once moved but held steady.

    I think the engine needs to come apart and be inspected.
     
  13. Oct 22, 2014 #73

    N8053H

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  14. Oct 22, 2014 #74

    N8053H

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    This is the valve I am using today. I will remove this valve and install the one that looks like a slug or piston.

    176.jpg
     
  15. Oct 22, 2014 #75

    N8053H

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    If this was a new to me airplane and engine I would be asking the same questions. But seeing how I operated this airplane for two years and had none of these issue's, I would say I was doing something correct.

    I hate doing a bunch of repairs all at once then not knowing what fixed it. But I want to try these.

    Replacing that pressure valve. Scott really wanted me to not do this. He was concerned that the new valve might be a little bigger in diameter, then its does the same thing. He said he has seen this before.

    Lowing the oil level. I don't under stand why it would not do this running on the ground at wot but on climbout at the same attitude as sitting on the ground I am loosing oil pressure. Happened twice last night on climb out out in the same spot.

    Before I replaced the spring and all, it never did this. It was 10 or so mins into the flight I would start having problems. Now its not long after leaving mother earth. I am still over the runway, I just put her back down. But it happened in the same spot both times.

    Raising the pressure lowers flow. Think of your garden hose. You want more pressure you tighten or squeeze the handle on the nozzle and that gives more pressure but reduces flow. Because of this just maybe I am over full on oil and now its frothing the oil up sooner. Before it took 10 mins now its almost instant after take off.

    You might be on to something Hot Wings.

    I will lower oil level and see what happens. I really hate to fly this airplane though. Not sure how to duplicate this on the ground though. I have not been able to do that as of yet.

    This stuff scares me and wants me to call it quits. I am really close to doing that with this airplane. I spare no expense to make sure my equipment is as close to New or New and kept in that shape. This is frustrating when it happens to good equipment.

    What I don't understand. I flew this airplane for a couple years and not once in that time did my oil pressure do this. I changed the oil all the time or every 10-20 hrs and flew her for almost 100 hrs. Never did she do this.

    But she does have a bigger Crank, and Rods. Maybe now the crank is in the oil and before it was not. Bigger throws on the crank.

    Thoughts?

    Tony
     
  16. Oct 22, 2014 #76

    Hot Wings

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    My suggested experiments/diagnostics are/were based on the fact that I don't have any experience with the plane and engine. If, for example you have been using the oil pump filter combination for many hours with no problem it's a high probability this isn't the source of the problem.

    Since the problem appeared after the rebuild with a longer stroke crank it's also a high probability that the problem is related to those changes. It may be as simple as foamed oil, but my intuition says it isn't.

    Based on the video I'm wondering if the oil pressure loss and change in engine output at the 11:40 mark may be related but the oil pressure drop is not the cause, just a symptom. For lack of lubrication to cause such a significant rpm loss I'd expect to be seeing metal in the oil from distressed bearings.

    "Raising the pressure lowers flow. Think of your garden hose"

    Oil pumps are positive displacement pumps. They will put out the same volume regardless of pressure, it just takes more power to move the oil. Once the pressure gets too high something breaks.

    Without being there with my own eyes and hands on the unit I'm pretty much out of ideas. I'd check with Scott one more time - and give him as much information/history as possible (written, not on the phone) and see what he has to say.
     
  17. Oct 22, 2014 #77

    N8053H

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    The oil pump is not supplying or producing the pressure in this system. Its a restricted system and that causes the oil pressure. The relief valve should relief this pressure as it's name states. The oil pump provides flow. It takes a restriction to produce pressure.

    Again think of your garden hose. Take the nozzle off the end and the water just flows out. Put your finger over the end and you cause a restriction and raise pressure. The main water line still produces how ever many gallons a min flow you just restricted it and that raised pressure and reduced flow. That would also be a positive system. Just like the pump it can only flow so much Per Min.

    The oiling system on a VW uses two Pressure relieve valves. I show both in the one pic. One is to control flow to certain places or uncover passageways to allow oil to flow to oil cooler and such. The other provides the restriction needed to raise the oil pressure.

    On the 1/2 VW they remove the back valve or the one causing pressure. The front valve is now the restriction and cause pressure. The other valve they removed that passage dumps back to tank, it has a drilled orifice of a certain size.
     
  18. Oct 22, 2014 #78

    Pops

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    Tony-- As usual Hot Wing is right on the money on his advice.
    I try to use as little of after market VW parts on my engine as possible because they can be a source of problems.

    Btw-- I relocated the oil dipstick on my VW engine to the rear of the case and calibrated the dipstick with marks with tail down and fuselage level since I keep a stand under the tailwheel and the fuselage level while in the hanger so its easier to walk under the wings. Also the dipstick is not under the nose bowl where it hard to reach.

    Just guessing, with the higher than normal oil pressure and a fluctuating oil pressure, I think there is a good chance of a partially obstruction in the oil passage somewhere raising the pressure and then stopping the flow.

    Don't give up and fight it until you win, and I know you will.
    This is a learning experience for all of us.
    Dan
     
  19. Oct 22, 2014 #79

    Hot Wings

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    I may have misunderstood your garden hose analogy. Maybe to make that analogy better match the VW oil system one should think of 2 hoses connected to the source with a "Y". One hose going to the garden sprinkler that needs water and the second to your thumb on the end of the hose. In this case the thumb closing off the low restriction and forcing the water through the sprinkler is acting the same as the VW oil pressure piston.

    Your pump may or, for what ever reason, may not be delivering oil when the pressure goes down. Neither of us know if it is. If the pump is getting oil with no air in it it WILL pump oil of a certain volume* unless there is a mechanical problem with the pump, such as slipping drive shaft or worn pump housing. Until you have eliminated the variable of the pump by verifying that it is mechanically sound and is receiving pure liquid oil the diagnostics will be little more than an educated guess. To quote Sherlock Holmes - "Once all of the variables have been removed except one................"


    *edit: which varies essentially directly with rpm.
     
    Last edited: Oct 22, 2014
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  20. Oct 22, 2014 #80

    N8053H

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    In order to work on anything one must know the system. I do not understand this oiling system in the VW engine and am trying to learn. The info I posted is what I have been researching. But I still do not fully understand this system.

    I emptied the oil filter or took it off and dumped it. I then turned the prop a few times with this filter removed to get the oil level down. I put the oil level between the marks on the dip stick. This oil is so clean I am having a hard time seeing it. I believe I had way more oil in it then I thought.

    I took her out and ran her. I noticed the oil pressure dropped sooner as it was warming up. I ran her for 45 mins on the ground. twenty five of those mins was running her at 2600 rpm's. As the oil temp rose the pressure went down to around 60 lbs. at a 800 rpm idle I was seeing oil pressure of 25 lbs. The oil pressure never did go to zero it held steady the complete time.

    She will be flown later. I will report back what I find, but I believe I was running to much oil. we will see. I am hopeful.

    Tony
     
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