irishpilot

Maddening Oil Related Problem

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Calling any Bravo or engine smart MSers, my plane partner and I have thrown a bunch of mx time and $ chasing down an elusive problem. Mooney runs great, but has always given low oil px, in the teens and above (below 55 psi). Down low, it shows fine. However, recently the plane exhibits mild surging at WOT (38"/2575 rpm).

As soon as power is pulled back to cruise climb 34"/2400, the surge goes away. We've had the prop gov overhauled, oil cooler inspected, turbo inspected, turbo gaskets replaced, etc. I pulled the JPI data and using Savvy's free website (thanks to the MS pointout). From the graphs, the mild surge starts right when the oil psi drops from 90 to sub 70. Anyone run into this? I'm sending the plane to Ron Fisher at Kestrel on the 27th. I'd like to not spend another $5k chasing this problem. 

Thanks in advance for the help!

25 Jun Test Flight (MAP_FF_RPM_OILPX) Savvy.PNG

25 Jun Test Flight (Surge Zoom) Savvy.PNG

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There is a thread that speaks to this problem.  I'll search around as well.

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Try searching for:

Oil pressure decreasing with altitude in Bravo

or

Low oil pressure in 30 hour engine

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To make this info a shade more usable...

Post the link to the savvy data here... you may need to click the share button too...

The picture is a great way to know where the challenge is happening...

The associated data around the area is the next step... knowing what the data is at various points...

A pic is worth 1k words, a vid is 10X, access to all the data... 100X?

:)

PP thoughts only, not a mechanic...

Best regards,

-a-

Links from @slowflyin

 

 

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Very similar issue I had. As to the first issue, I found that it’s common at high altitudes in the teens that oil pressure drops below 55 and incrementally lower as you climb higher and higher. This has been present on my Bravo ever sine I purchased it and noticed it recently when I purchased digital engine gauges that give me the yellow readings on climbing. I put lots of money overhauling and replacing things and no significant change. This does not seem to affect performance. Haven’t really been given a good explanation as to why this happens (I asked several experts including some from lycoming without good answers) but I stopped chasing that one and just realized that my oil pressure will be in the yellow arc at high teen altitudes. 

 

As far as your surge goes, mine occurred when the max MP setting was too high, and on certain atmospheric conditions, on WOT, it would come close to redline and the wastegate would open to prevent over boosting which would produce surging. You should have your wastegate checked to ensure its working correctly, but mine went away when I adjusted my maximum attainable MP downwards. 

Edited by JohnB

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8 hours ago, JohnB said:

Very similar issue I had. As to the first issue, I found that it’s common at high altitudes in the teens that oil pressure drops below 55 and incrementally lower as you climb higher and higher. This has been present on my Bravo ever sine I purchased it and noticed it recently when I purchased digital engine gauges that give me the yellow readings on climbing. I put lots of money overhauling and replacing things and no significant change. This does not seem to affect performance. Haven’t really been given a good explanation as to why this happens (I asked several experts including some from lycoming without good answers) but I stopped chasing that one and just realized that my oil pressure will be in the yellow arc at high teen altitudes. 

 

As far as your surge goes, mine occurred when the max MP setting was too high, and on certain atmospheric conditions, on WOT, it would come close to redline and the wastegate would open to prevent over boosting which would produce surging. You should have your wastegate checked to ensure its working correctly, but mine went away when I adjusted my maximum attainable MP downwards. 

Thanks @JohnB, I've been having Mx dial in the MP setting as it wasn't making full power, and now it goes slightly above 38" after rotation. I keep it below 38" and it surges. I'll have them dial it down, but I don't want it to be too off from 38". I go out of short fields and want full rated power. 

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On 7/17/2020 at 3:34 PM, irishpilot said:

Thanks @JohnB, I've been having Mx dial in the MP setting as it wasn't making full power, and now it goes slightly above 38" after rotation. I keep it below 38" and it surges. I'll have them dial it down, but I don't want it to be too off from 38". I go out of short fields and want full rated power. 

Good call! I think that explains your surges. Since redline is 38.5, I had mine turned to a max of 37" (or It may have been 37.5"), so on some days it can go as high as 37.7 but no more surges at that setting and plenty of power. When I did have it turned up to 38+, yes it did seem to get a little more power but it was not very efficient as it would quickly get my CHT's up over 400 if I didn't turn it down almost just after liftoff.

 

Sounds like your plane is working just fine, particularly if your surges go away once you turn your Max MP down. Hope this saves you some $$$!

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On 7/17/2020 at 3:34 PM, irishpilot said:

Thanks @JohnB, I've been having Mx dial in the MP setting as it wasn't making full power, and now it goes slightly above 38" after rotation. I keep it below 38" and it surges. I'll have them dial it down, but I don't want it to be too off from 38". I go out of short fields and want full rated power. 

Yikes!  38"MP is too high!!!  Even though that is red line, 100% power is usually around 34½" and varies somewhat with temperature down low.  If you're unhappy with that,  then you're going to be very unhappy when you have to spend $87,000 including R&R on a new reman before 2000 hours TBO because you're running over 100% power.  Have you looked at the Red Lycoming Book re MP vs Altitude?  Sorry to be so harsh, but you are asking for nothing but trouble if you continue with those high MP.  Your mechanic should be ashamed of themselves if they set the MP up that high at sea level.

What field length for takeoff are we talking about?  More importantly what is the landing field length?  The POH gives you the numbers to expect.  You shouldn't be flying into fields of less than 2300 feet at sea level.  If you're trying to get into shorter fields, then you probably are flying the wrong airplane into those fields.  I wouldn't take a student or be in a Bravo landing at a field less than that distance.

 

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6 minutes ago, donkaye said:

Yikes!  38"MP is too high!!!  Even though that is red line, 100% power is usually around 34½" and varies somewhat with temperature down low.  If you're unhappy with that,  then you're going to be very unhappy when you have to spend $87,000 including R&R on a new reman before 2000 hours TBO because you're running over 100% power.  Have you looked at the Red Lycoming Book re MP vs Altitude?  Sorry to be so harsh, but you are asking for nothing but trouble if you continue with those high MP.  Your mechanic should be ashamed of t

Hi Don!

Thanks for weighing in on this. Your experience is well appreciated. What did you have your mechanic set your max MP pressure at? I was thinking the other day that even 37" might be too high, as on warm days, I do get a warm CHT issue on climb. I can always just not push all the way forward which I do sometimes, but then I have to turn on the boost pump on and off manually,. Curious as to what your thoughts are to what max MP setting get the longest life out of your engine while keeping Bravo power on takeoff.

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As someone explained to me after my mechanic turned the density controller nut a little too far, you really need to follow Lycoming service instruction 1187 to properly adjust your takeoff boost.  I'm not sure if this is what's causing your issue but it may be a good place to start:

https://www.lycoming.com/content/service-instruction-no-1187j

Yes, you can get there by trial and error (not recommended), but there is pretty specific guidance on the MP you should be getting based on the density altitude on takeoff....

That nut that adjusts the controller is extremely sensitive and least on my engine, not as snug as you would expect.  It really needs to be properly safety wired to ensure it doesn’t move.

Edited by Davidv

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7 hours ago, JohnB said:

Hi Don!

Thanks for weighing in on this. Your experience is well appreciated. What did you have your mechanic set your max MP pressure at? I was thinking the other day that even 37" might be too high, as on warm days, I do get a warm CHT issue on climb. I can always just not push all the way forward which I do sometimes, but then I have to turn on the boost pump on and off manually,. Curious as to what your thoughts are to what max MP setting get the longest life out of your engine while keeping Bravo power on takeoff.

I'm comfortable with 35" MP on takeoff at sea level--maybe even 35½" when on the takeoff roll, but no higher.

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Is the correct oil pressure spring installed? There are three types I believe. I may have commented in one of those threads above. 
-Matt 

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2 minutes ago, MB65E said:

Is the correct oil pressure spring installed? There are three types I believe. I may have commented in one of those threads above. 
-Matt 

Regarding oil pressure springs; oil pressure was constantly indicating in the yellow when passed about 12,000 feet.  Mark, at Top Gun changed the spring.  The oil pressure now stays in the green.  The downside is that on startup the pressure is in the red and takes about 10 minutes before you can takeoff in the green.  I never had that issue with previous engines.

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Yes, Mark was the one that pointed me in the correct direction too. New Lycoming's have a 115psi redline. I wouldn’t be concerned unless the oil was cold on a takeoff run. 
-Matt 

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3 hours ago, donkaye said:

I'm comfortable with 35" MP on takeoff at sea level--maybe even 35½" when on the takeoff roll, but no higher.

Don! Thank you! I'm going to have mine lowered next maintenance which im sure will fix my CHT on climbout issue.

1 hour ago, donkaye said:

Regarding oil pressure springs; oil pressure was constantly indicating in the yellow when passed about 12,000 feet.  Mark, at Top Gun changed the spring.  The oil pressure now stays in the green.  The downside is that on startup the pressure is in the red and takes about 10 minutes before you can takeoff in the green.  I never had that issue with previous engines.

I went through this!  Got my spring replaced which was already the recommended one I hear with higher tension, and it didn't fix the issue. So now mine like yours, oil pressure starts near redline at startup and requires a longer time for the oil to warm up (I usually wait until oil pressure is 160-165 degrees) so that the pressure is not in the yellow at full throttle forward. At altitude, mine starts to dip into the yellow in pressure above 11,000 feet which I don't worry about anymore. What I did notice is this relationship is also inversely proportional to oil temperature (higher temp, lower pressure), but there is also an altitude component to this which I have no good explanation for. Other than the one person I heard who says if I remember correctly that his M gets around 65psi all the way up to 20k with roller tappets installed, all the rest of the pilots I've talked to notice the incremental drop at higher altitudes (if they have digital gauges). 

I still think this oil pressure yellow at higher altitudes  is an issue that we are all noticing now since we have digital engine gauges, and we get things blinking at us when we drop below 55 in the yellow. I have a picture of my old panel with steam gauges when I was at around 19,000 feet, and looking closely, my analog pressure reading was below 50 in the yellow, but much harder to notice and get an exact number.

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6 hours ago, donkaye said:

I'm comfortable with 35" MP on takeoff at sea level--maybe even 35½" when on the takeoff roll, but no higher.

DMax set mine at 36" FOT.  I have never see it change regardless of the field elevation on take off. I thought there was a barometric/altitude compensating device in the system.

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Don and Irish Pilot

Was your engine recently overhauled? If so by whom?

I experienced similar readings: loss of oil pressure every 1000 feet, oil pressure reached the yellow 57psi at FL 130

We changed the spring and adjusted the nut.  Like you have reported -it increases the oil pressure at sea level 

and while it gets you some additional psi it really does not solve the problem

After spending a great deal of time w Lycoming and the engine OH shop

I proved that earlier engines did Not lose oil pressure as one climbed. Proved by detailed pics and data.

I have a direct reading (analog) Scott gauge and the usual ships oil pressure transducer driven gauge

Thus an argument that it was an indicator issue was not valid 

You can have analog or digital, the oil pressure should Not be in the yellow.

In the end, Lycoming determined that the wet heads on the AF1B do not do well with the new parabolic Tappets/lifters

Engine removed and brought back to the shop, old style tappets/lifters installed. Problem solved

I can climb from sea level to FL240 and my oil pressure does not indicate in the yellow, clearly in the green,

Oil pressure loss on climb is minimal as it was in previous engines

Lastly, setting the density altitude controller should be done by the approved procedure noted by Lycoming. While

I personally saw Mooney set it up without the thermocouple, it can be done but one needs experience and must factor in

ambient field temp etc. 

 

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Bravo engine manifold pressure is adjusted based on MAP and compressor discharge temperature.

Clarence

03511A59-D5E0-4095-8CE6-F05D568253BF.jpeg

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1 hour ago, tls pilot said:

In the end, Lycoming determined that the wet heads on the AF1B do not do well with the new parabolic Tappets/lifters

Engine removed and brought back to the shop, old style tappets/lifters installed. Problem solved

Wow that makes you think twice about a factory reman or overhaul.

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2 hours ago, tls pilot said:

Don and Irish Pilot

Was your engine recently overhauled? If so by whom?

My Reman engine from Lycoming now has 174 hours on it and is still under warranty.  It is a year and a half old.  When did you have your engine redone, how many hours did it have on it, and  did Lycoming reimburse you for the problem?

Since new, my engine has been dripping fuel out of one of the rubber hoses coming out of the cowling on shut down.  The issue has not been diagnosed, although I have spent a bunch of money on it, but none of my other engines did this.  I don't know whether the new or old Tappet/Lifters are in mine but I would assume they are the new ones, if the engine was made before yours.  Could this be related to the "leaking fuel out of the hose" problem on shut down?  I am hesitant to do anything, because this has been the smoothest running engine of all three of them.  Also, on all engines, the pressure differential controller hasn't worked properly.  I always have to monitor the MP on descent or it will increase.  Does yours work properly?

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32 minutes ago, donkaye said:

My Reman engine from Lycoming now has 174 hours on it and is still under warranty.  It is a year and a half old.  When did you have your engine redone, how many hours did it have on it, and  did Lycoming reimburse you for the problem?

Since new, my engine has been dripping fuel out of one of the rubber hoses coming out of the cowling on shut down.  The issue has not been diagnosed, although I have spent a bunch of money on it, but none of my other engines did this.  I don't know whether the new or old Tappet/Lifters are in mine but I would assume they are the new ones, if the engine was made before yours.  Could this be related to the "leaking fuel out of the hose" problem on shut down?  I am hesitant to do anything, because this has been the smoothest running engine of all three of them.  Also, on all engines, the pressure differential controller hasn't worked properly.  I always have to monitor the MP on descent or it will increase.  Does yours work properly?

For what it’s worth I also have to monitor the MP as it will creep up an inch or so in the descent.  I assume your fuel issue isn’t related to the sniffle valve not closing properly on shutdown?

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On 7/19/2020 at 2:47 PM, tls pilot said:

 

In the end, Lycoming determined that the wet heads on the AF1B do not do well with the new parabolic Tappets/lifters

Engine removed and brought back to the shop, old style tappets/lifters installed. Problem solved

I can climb from sea level to FL240 and my oil pressure does not indicate in the yellow, clearly in the green,

Oil pressure loss on climb is minimal as it was in previous engines

 

Old tappets work better? Wow there’s a thought I hadn’t considered. If you still have access to anything from lycoming saying that the old tappets work best with AF1B please send to me, as it will be helpful when I order my new engine when TBO comes up (soon) and I ask them to switch out the lifters? I would love for this yellow at altitude to be gone. 

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12 hours ago, JohnB said:

Old tappets work better? Wow there’s a thought I hadn’t considered. If you still have access to anything from lycoming saying that the old tappets work best with AF1B please send to me, as it will be helpful when I order my new engine when TBO comes up (soon) and I ask them to switch out the lifters? I would love for this yellow at altitude to be gone. 

+1, I'm approaching a rebuild as well.

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On 7/19/2020 at 1:27 AM, donkaye said:

Yikes!  38"MP is too high!!!  Even though that is red line, 100% power is usually around 34½" and varies somewhat with temperature down low.  If you're unhappy with that,  then you're going to be very unhappy when you have to spend $87,000 including R&R on a new reman before 2000 hours TBO because you're running over 100% power.  Have you looked at the Red Lycoming Book re MP vs Altitude?  Sorry to be so harsh, but you are asking for nothing but trouble if you continue with those high MP.  Your mechanic should be ashamed of themselves if they set the MP up that high at sea level.

What field length for takeoff are we talking about?  More importantly what is the landing field length?  The POH gives you the numbers to expect.  You shouldn't be flying into fields of less than 2300 feet at sea level.  If you're trying to get into shorter fields, then you probably are flying the wrong airplane into those fields.  I wouldn't take a student or be in a Bravo landing at a field less than that distance.

 

@donkaye, first thing's first. I'm not telling my A&P to set anything other than what's by the book. If they are doing something that's against the Red Book, then I need to get that fixed. Second, I very well understand that speedinging/overboosting an engine will lead to a rebuild. However, the POH clearly states 38" Max MP and even discusses overboosting above 38". 

 

On 7/19/2020 at 9:28 AM, donkaye said:

I'm comfortable with 35" MP on takeoff at sea level--maybe even 35½" when on the takeoff roll, but no higher.

Where are you getting that data to set 35" or 35.5"? That's arbitrary without a source document or directive. Teaching pilots to set below 100% power on takeoff is dangerous and invalidates told as well as all the POH performance data. What is driving you to set 35"? What is your aircraft rigged for if you select full throttle? 

However, the good news is your post drove me to dig into the Red Book. I am confused as to why Textron numbers are different than the POH. The Textron window is between 35-37" MP. Any insight is appreciated. 

Lastly, there is a big difference between procedure and technique. If pilots are deviated against the POH (procedure), it better be for a good reason. For example, it's well documented that leaning to 1650 TIT eats up cylinders. However, I've not seen the same for going against the POH for takeoff and GA planes should use 100% rated hp at least until they have turn around engine out glide back to the field (technique).

Lycoming MP Chart AF1B.PNG

MP POH.PNG

POH Takeoff.PNG

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Obviously anyone can fly their airplane anyway they want.  Any advice from me comes from experience and my A&P whom I have the utmost confidence in, since he has been working on my airplane since I got it 28 years ago and has been able to answer any question I have presented to him.  He understands engines much better than I do.

A little history:  Mooney wanted to show good numbers when the TLS came out.  As such, they recommended 1750° max on the TIT and 34" MP in cruise.  That is in the POH.  Would you really follow that advice?  I think not.  Shortly after certification my understanding is that both the Lycoming guy and the Mooney guy who came up with those numbers were let go.

So, do what you want.  My first engine made TBO and then some and went 2,295 hours before I changed it out due to discomfort flying it IFR.  The second one was a little short of TBO, but not as a result of an engine issue, but the result of problem at the shop during an Annual.  It, too, would have made TBO.   So, I'''m happy flying it the way I do:  Full power in climb, 29"/2400 rpm in cruise, no less than 15" on descent until in the pattern, maximum CHT differential 50°F.

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