Another max oil pressure question

Another oil pressure thread, because I couldn’t find a definitive answer in the old threads.

I have an Aerosport 0-320-D2A that has been flying for 5 years. Because I occasionally got the flaky pressure readings well documented for VDO senders, I finally swapped them out for the newer Kavlico senders. Nothing else was changed in configuration or operation.

Having said all that, the new oil pressure sender seems to read about 3-5psi higher on climb out than the old, just enough to occasionally send the oil pressure over the 100psi that is my red-line limit for warm-up and take-off. [100psi was derived from the old Lycoming manual Aerosport provided with my engine (see picture below)]. In cruise, and once the oil is 180F or above, the oil pressure maintains mid 70s psi, right in the middle of my 60-90psi green range, more or less like it did with the old senders. Over the course of 4 flights in the last two days, it never got above 105psi in full-power climb, and then settled down in the green once the oil temp increased and cruise power was set. As I also understand it, Lycoming now has newer (and higher) upper-limits for oil pressure than what were published in my manual, perhaps making that 100F maximum that I use a bit outdated any way.

My question, then, is this:
Should I worry about the occasional oil pressure excursion over 100 during climb out? If so, what would you recommend for a oil pressure that would set off my Dynon's alarm?

Thanks for any thoughts.

From the old Lycoming manual Aerosport Power sent with my new engine:

Steve I had high oil pressure reading. Over redline on takeoff. Motor is passed recommended TBO. Replaced the sender with new and everything came back to normal.

Limit

The warm up limit for most of the normally aspirated Lycomings was changed to 115# many years ago.

I wouldn't be worried about it. You don't want to lower your "at temp" pressure, so you accept it. However, I don't think 105 is anything to worry about for intermittent situations. But if it bothers you, go to a multi-viscosity oil or warm up longer.

Larry

jrs14855 said:

The warm up limit for most of the normally aspirated Lycomings was changed to 115# many years ago.

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Vlad said:

Steve I had high oil pressure reading. Over redline on takeoff. Motor is passed recommended TBO. Replaced the sender with new and everything came back to normal.

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lr172 said:

I wouldn't be worried about it. You don't want to lower your "at temp" pressure, so you accept it. However, I don't think 105 is anything to worry about for intermittent situations. But if it bothers you, go to a multi-viscosity oil or warm up longer.

Larry

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Thanks.
I just changed to new Kavlico sensors, Vlad, so that should not be the problem. The only thing that changed was about a +3-5psi in full power climb, so I'm guessing the new sender is "in the ballpark" accurate.

I'm already running 20W-50. Maybe that's why my oil pressure doesn't seem that much different than it did in the winter.

I'm curious what Lycoming means by "warm up" in this context. It's been pretty hot around here the past couple days. The oil has been at least 150F on takeoff when I've gotten these occasional high pressure readings/warnings. Is "warm up" the entire range up to the desired operating temp, e.g. up to 180F?

All that said, I would love to be confident that the occasional 105 psi on takeoff is nothing to be too concerned about.

alpinelakespilot2000 said:

T
I'm curious what Lycoming means by "warm up" in this context. It's been pretty hot around here the past couple days. The oil has been at least 150F on takeoff when I've gotten these occasional high pressure readings/warnings. Is "warm up" the entire range up to the desired operating temp, e.g. up to 180F?

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I thought about that as well, but didn't know so didn't make a comment. My speculation is that this may apply to low RPM warm up acitivity and not full RPM running. However, The primary concern with high oil pressure is wear on the oil pump and potential failure. I suppose that hydro-locking or stalling of the vanes may also be an issue. (You must also consider the PSI rating of the oil filter, which is likely the weak point from a pressure perspective). That said, I would think that an Engineer would specify a max pressure and not an RPM with it. Increased RPMs increase the volume from the pump and therefore an increase in pressure if the relief valve or passageways cannot flow enough due to low viscosity. Logic would seem to imply that pressure is pressure and the running environment is not relevant.

It is also likely that they recognize pressure will be high when the oil is cool and offer the intermittent pressure level to account for that condition. In other words, 100 PSI intermittent is acceptable, but 90 max continuous.

EDIT: I just re-read your post. If you are gettig 105 PSI at 150* on take off and 70 PSI at 180* is cruise, you may have something else going on. In the winter, my oil doesn't usually get higher than 150-160 and I see pressures similar to the summer when it is 180-190. Maybe 5 PSI higher at the most. I don't really consider 150* oil to be in the warm up stage.

Larry
Larry

I think you should be happy that your oil pressure reading is "high"
If you will read the articles at this link http://egaa.home.mindspring.com/valves.html you will understand why.
Where your oil pressure sender plumbs in to get its reading makes a difference and Lycoming has changed this location. Also, valve cooling is related to oil pressure because the lower the pressure the less valve cooling there is according to the articles.

In the ball park,

Your just fine as far as I can guess. The electric senders have never been all that accurate, even new out of the box. They are there to just let you know you are close and that you have pressure in the first place. A good liquid filled gage that is calibrated is the best way to say for sure. The old rule of thumb is to warm up your oil above 120* or more. run the engine at 1400 RPM and look to see that you have around 60 P.S.I.G. with this well warmed oil. I like to fly it to temp. above 180* and then check it. Just for the sake of settings on your IFIS, I set my yellow at 85-95 and the red at 95-110 P.S.I.G. Some times if I don't warm up real good on a per flight I see yellow on take-off until I start pulling back the black nob. After a few minutes of flight every thing stays were it should. The temperature of your oil will make for changes in pressure as the oil is more or less thin if you will. The only real penalty we have seen to running the pressure up higher is it taken more power to run the oil pump it's self from the engine. There is a point at which you can wash out the bearings with to much pressure, and damage the pump and engine with to much pressure. You are not even close to it with 110-120 in our findings. Your in the ball park with this. If you want a little more power for racing turn it down a little but be aware that the real danger is letting your idea pressure drop to low for to long. If you ever see you idea pressure drop below 10-15 P.S.I.G. for more than 10 seconds, Pick the throttle up a little to see if it starts back up, if not shut down and start looking for an answer to why not. It is on this end of the scale I would be more carful of.
Just two pennies for the pot. Yours, R.E.A. III #80888

Pressure

160kt said:

I think you should be happy that your oil pressure reading is "high"
If you will read the articles at this link http://egaa.home.mindspring.com/valves.html you will understand why.
Where your oil pressure sender plumbs in to get its reading makes a difference and Lycoming has changed this location. Also, valve cooling is related to oil pressure because the lower the pressure the less valve cooling there is according to the articles.

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All correct except Cessna changed the pickup location, not Lycoming. So a brand new 172 reading 80 psi is really 90 psi.

160kt said:

I think you should be happy that your oil pressure reading is "high"
If you will read the articles at this link http://egaa.home.mindspring.com/valves.html you will understand why.
Where your oil pressure sender plumbs in to get its reading makes a difference and Lycoming has changed this location. Also, valve cooling is related to oil pressure because the lower the pressure the less valve cooling there is according to the articles.

Click to expand...

Valve cooling is only related to oil flow, not oil pressure and increased pressure does not always translate into increased flow. Lycoming's valve cooling problems stem from the fact that their lifters do not have a bypass circuit to feed the pushrod, like every other hydraulic lifter made since 1940. The only oil that gets to the pushrod is that which bleeds through the very tight clearance between the two components of the hydraulic plunger assembly. To give you an idea how tight this is, this interface can retain the oil and hold a 110 PSI+ pressure from the valve spring for several hours before bleeding down.

In theory, a higher oil pressure will allow more bleed oil through, but I have serious doubt that an additional 10-20 PSI will move much more oil though a .001" clearance.

Larry