High oil pressure in factory Lycoming engine

[jetdriven]

Our factory OH IO-360-A3B6 was delivered last august, and installed. It has 131 hours on it now. The oil pressure is 95-100 PSI in cruise, and the redline on the gauge is marked 100 PSI.

 

I read an article that the new Lycoming IO-360s on the 172R, 172S, 182S, and 206 are now marked with a 115 PSI redline, and further, the oil sender is in the front of the engine, which is 15 PSI lower than the oil pump port, where our sender is mounted.  So it would be making 125-130 PSI at the oil pump, a heck of a lot higher than we are running right now. Speculation is it fixes the valve cooling issues Lycomings have.

 

Is this a problem? I'm inclined to leave it as it is.

 

source: http://www.airplanebroker.com/MARV.HTM

 

http://egaa.home.mindspring.com/new.htm

[clh]

I would tend to agree with your assessment (don't worry too much).  At constant viscosity, the higher the pressure, the higher the flow of oil through the system.  What are your oil temperatures reading? ie lower temperature at constant flow = higher pressure.  With a multi-vis oil, it should not make as much of a difference, but that also may contribute to the higher pressures.   

 

The pressure will likely trend lower as the engine and oil pump wears.  Unless you are concerned with seals, I would let it alone.  ya'll are in winter(even if it is in TX) ,  see if it changes in summer.

 

If it was reading above the red line, I would be much more concerned.

[N601RX]

When I overhauled my engine I set the oil pressure up at 82 PSI.  I think that was with 4 washers under the spring.  Looking back through my JPI data it has never really changed after warming up.  High oil pressure will erode bearings. Lycoming should have done enough testing to know where this will occur and set the red line to prevent it. 

[FloridaMan]

I just asked my A&P friend about this. He says that high oil pressure is good, that you want as high as you can get (115 is fine he says), and that it solves a number of problems, that among these are valve cooling, valve sticking and cam lubrication at startup. 

 

The oil pump is sized so that it's unlikely for the pressure to ever be too high on a warm engine. All modern Lycomings have high pressure and they last much longer with fewer problems. 

 

The load on the bearings is in the neighborhood of 3000 PSI. The oil pressure difference should be insignificant. 

[N201MKTurbo]

I have found that with high oil pressure the engine uses more oil. I have always set my pressure to the bottom of the green in cruse.

[jetdriven]

The IO-360 has piston oil squirters, which can put more oil on the cylinder wall, which may increase oil burn. Right now, it goes through a quart in ten hours or so.  Much (half?) of this is out the breather and on the belly.   It would conceivably put more oil in the rocker box area, where it cools and lubricates the valves, and that is a good thing in Lycomings.

 

The oil temp refuses to move on the ground. The white dot is 75F, and it wont come off that until 3-4 minutes after takeoff, it slowly makes its way to 180F on the gauge after ten minutes.  On the hottest days, even during break-in, when CHT's were high, it never exceeds 180-190F.

 

I called the Lycoming sales rep, he said he never likes to see over 95 PSI on these engines, because it could blow out the crank nose seal. I fail to see how high oil pressure can cause this, there is no pressurized oil on that seal.

 

Bearing washout from high oil pressure is either a myth or reality depending on who you talk to. I wish there was definitave data on this. The new IO-360s on the 172R run 115 PSI redline and this is at the front camshaft gallery, and this is about 125 PSI at the pump, where our oil presssure reading is taken.

 

Iron is 66 PPM in a 50 hour oil change cycle, even 110 hours after overhaul, and that concerns me.  Chromium (rings) is also elevated.  The filter is spotless, except 5-10 pieces of half-mm sized non-magnetic flakes in the filter media.  An acquaintence's IO-390 with 50 hours SNEW also has this.

 

Keep the thoughts coming.

[Awful_Charlie]

High oil pressure also contributes to high oil temperature which can be a concern in some airframes.  I would also be concerned about continually running near any limit, high or low, and so after more than 100 hrs, for the sake of adding/removing a washer I'd go for the correction.  A high pressure is not making a material difference to the amount of oil being circulated around the engine - see http://www.mellingengine.com/Portals/5/pdf/pdf_catalog/pressure-vs-flow.pdf for example, but everything is just being stressed a bit more - mainly the oil pump, but also all the oil lines and so on.