M

markscogg

Well Known Member
Added some washers to the oil pressure relief valve. Changed oil, cleaned screens and now:
Cold idle 80 psi, cold flying 93 psi for the first 15 minutes.
After 30 - 45 minutes flying, idle was 50 psi, flying 75 psi.
Is 93 psi for 15 minutes OK? Leave it like it is and keep flying?
 
Last edited:
What caused it to change in the first place? I would be really uncomfortable pressing on not knowing what caused a sudden 10 psi oil pressure drop and then just adjusting the system pressure for no known reason. Maybe there are details I'm not familiar with. Sorry if this is the case.

One thing that confuses me is concern about the cold operating presssures. What's cold? My engine steadily continues to warm until it reaches a stable temp. Compare the oil pressures at steady, normal operating temperatures at some repeatable power setting.

Is 50 and 75 psi OK? Sounds generally pretty good, but I don't have a Lyc op manual in front of me. But more important, what are the temps and pressures doing over over 10, 100 and even 1000 hr increments of the engine's life. That's why this 10 psi drop in very short time is concerning.
 
Last edited:
markscogg said:
Added some washers to the oil pressure relief valve. Changed oil, cleaned screens and now:
Cold idle 80 psi, cold flying 93 psi for the first 15 minutes.
After 30 - 45 minutes flying, idle was 50 psi, flying 75 psi.
Is 93 psi for 15 minutes OK? Leave it like it is and keep flying?
Click to expand...

Those are within limits. My pressures were about the same in the O-360/RV-8. I had my upper alarm set at 94 PSI, and would trip it momentarily on occasion during cold departures. FWIW....
 
markscogg said:
Added some washers to the oil pressure relief valve. Changed oil, cleaned screens and now:
Cold idle 80 psi, cold flying 93 psi for the first 15 minutes.
After 30 - 45 minutes flying, idle was 50 psi, flying 75 psi.
Is 93 psi for 15 minutes OK? Leave it like it is and keep flying?
Click to expand...

What is your oil temp, what is the OAT?
 
75 psi oil pressure in cruise with 160-195F of oil temp is good. If the temp is hotter the pressure will drop and if colder the pressure will be a bit higher. Cruise oil pressure limits are 55-95psi, target is 75 psi. Top cold redline is 115psi and idle hot is 25 psi or higher.
Sounds like you are right where you should be.
Each washer added or removed normally results in about a 3-5psi change in pressure. Like wise each turn of the adjustable one will yield about the same change as a washer addition or subtraction.
Easy ground setup is to get oil above 130F and set the oil pressure to 60psi at 1400-1500-RPM. Doing that, will normally yield 75psi in cruise at normal operating temps.
Good Luck,
Mahlon
?The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."
 
A bit high but within limits. Next time you're in the engine compartment consider pulling one washer out.
 
me too

I'm diagnosing the same thing right now. O-320. 60 psi idle and 90 psi at take off/cruise power. When the oil gets to 180 to 195 degrees, the pressure drops to 85 psi. I know it is right on the edge of the limits, so I am attempting to drop the pressure 15 pounds or so. Thing is, there were NO washers in there already. Just the spring... The gage is a direct read type that pulls pressure off the back of the Accy case, so I don't think it could be a bad gage.
Been this high since I did the new oil pump gears... Any thoughts?

Dennis
 
mahlon_r said:
75 psi oil pressure in cruise with 160-195F of oil temp is good. If the temp is hotter the pressure will drop and if colder the pressure will be a bit higher. Cruise oil pressure limits are 55-95psi, target is 75 psi. Top cold redline is 115psi and idle hot is 25 psi or higher.
Sounds like you are right where you should be.
Each washer added or removed normally results in about a 3-5psi change in pressure. Like wise each turn of the adjustable one will yield about the same change as a washer addition or subtraction.
Easy ground setup is to get oil above 130F and set the oil pressure to 60psi at 1400-1500-RPM. Doing that, will normally yield 75psi in cruise at normal operating temps.
Good Luck,
Mahlon
?The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."
Click to expand...

Mahlon,

I have an O-320 with the oil pressure sensor connected to the port near the center of the accessory case instead of the one under the upper-right engine mount. I recall hearing many years ago that the center port will indicate a higher pressure than the other one. Is this correct?

Thanks,
 
Oil Pressure Port Depiction

Sam,
You are correct!
I emailed you a JPEG of the various pressures from different ports. I can't get the picture uploaded to ImageShack. Maybe you could post it in this link.

(posted; S. Buchanan)

oilpressure.jpg


Rocky
 
Last edited by a moderator:
Rockyjs said:
Sam,
You are correct!
I emailed you a JPEG of the various pressures from different ports. I can't get the picture uploaded to ImageShack. Maybe you could post it in this link.

(posted; S. Buchanan)

oilpressure.jpg


Rocky
Click to expand...

Thanks, Rocky. I'm using the "110" port--guess that is why I've always seen higher than "normal" pressure. :)

overhaul-17.jpg
 
Last edited:
Dmadd said:
I'm diagnosing the same thing right now. O-320. 60 psi idle and 90 psi at take off/cruise power. When the oil gets to 180 to 195 degrees, the pressure drops to 85 psi. I know it is right on the edge of the limits, so I am attempting to drop the pressure 15 pounds or so. Thing is, there were NO washers in there already. Just the spring... The gage is a direct read type that pulls pressure off the back of the Accy case, so I don't think it could be a bad gage.
Been this high since I did the new oil pump gears... Any thoughts?

Dennis
Click to expand...

There are several oil pressure springs, you should determine which one you have and go to a lower spring. If you already have the lowest tension spring then there is a spacer that can be installed between the oil pressure cap and the case.

Highest tension to lowest are:

LW-18085 1.93 inches free length
LW-11716 2.12 "
61084 2.18 " (Most common spring)
68668 2.04 "
77467 1.90 "

Spacer P/N is 73629 and use two gaskets instead of one.

Good Luck,
Mahlon

?The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."
 
You must log in or register to reply here.