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  #1  
Old 11-27-2021, 03:06 PM
Cth6 Cth6 is offline
 
Join Date: Apr 2017
Location: Central Florida
Posts: 189
Default O-320-E2C Oil Pressure

I wanted to solicit to see if anyone has crossed this bridge already with low oil pressure when temps are cooler.

O-320-E2C - Carbed / Mogas
Normal Oil Temps at cruise 170-180F
Normal Oil Pressure at cruise 70-80 PSI
Normal OAT above 80
P66 Victory 100, 31 Hours and 4 months since change. Good oil history.
340 SMOH
Burns 1QT per 10-12 Hrs
Tempest 48108 filter

This is my first year with this RV. The past two flights have been in colder weather (50-60 F). Yes Winter has made it to Florida.

With the oil cooler air shutter closed (no other changes to the RV), I can get the oil temps up to about 150-155F. EGT and CHTs are normal, maybe slightly lower.

The past two flights the oil pressure has built up to 60psi during run up and take off but then degrades to 45-50psi after 30 or 40 mins of flying at cruise. Pulling the power back to idle to land the oil pressure drops to 30-40 psi.
There are no leaks and oil burn has not changed.

I am used to oil pressure being high when the oil is colder. I am going to test the oil pressure with another gauge (I have the Vans OP sender) to rule out a bad sender. I am also going to check the vernatherm to see if it is stuck open/dirty. I can see the oil temp drop when I open the shutters so I know the cooler is passing oil even at 140F oil temp

If I don't see a change, my next step was to do an early oil change and cut the filter. I can reduce the airflow into the cowl, but I am not sure that will help.

Any thoughts on other areas to look at or test?

Thanks!

Chad
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  #2  
Old 11-27-2021, 03:12 PM
Taltruda Taltruda is offline
 
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Location: Las Vegas, NV
Posts: 986
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Try pulling the oil pressure relief valve ball and spring, and see if something is holding it open.
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  #3  
Old 11-28-2021, 02:18 PM
Cth6 Cth6 is offline
 
Join Date: Apr 2017
Location: Central Florida
Posts: 189
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Quote:
Originally Posted by Taltruda View Post
Try pulling the oil pressure relief valve ball and spring, and see if something is holding it open.
Great call out Tom. The pressure relief completely slipped my mind.
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  #4  
Old 11-28-2021, 02:46 PM
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rv8ch rv8ch is offline
 
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Location: LSGY
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Have you considered using a multi-grade oil like "PHILLIPS 66 VICTORY AVIATION OIL 20W-50?"

https://www.aircraftspruce.com/catal...s_08-17114.php

It seems to have some benefits during these cool weather periods.
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  #5  
Old 11-28-2021, 04:02 PM
Cth6 Cth6 is offline
 
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Quote:
Originally Posted by rv8ch View Post
Have you considered using a multi-grade oil like "PHILLIPS 66 VICTORY AVIATION OIL 20W-50?"

https://www.aircraftspruce.com/catal...s_08-17114.php

It seems to have some benefits during these cool weather periods.
No, but let me explain my logic. At the temperatures I am seeing in the engine (150F) the difference in viscosity between 20W-50 and 100W is negligible. If anything, the 20W-50 is less viscous at 150F.

I am currently running down a situation that I am seeing lower oil pressures in colder weather with a straight weigh oil when the oil is warmed. Reducing the oil viscosity, in theory, will make the situation worse.

If any of my logic is flawed, please call it out. I am not an expert here, just applying what I have learned previously. My end goal is to figure this out and get back to a healthy operating condition.

Chad
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  #6  
Old 11-28-2021, 07:28 PM
Tracer 10 Tracer 10 is offline
 
Join Date: Mar 2011
Location: Oregon
Posts: 158
Default Low Oil Pressure

Quote:
Originally Posted by Cth6 View Post
Great call out Tom. The pressure relief completely slipped my mind.
On my RV6 O-320 160HP I had to replace the Oil Pressure Relief Valve Spring and ball with a new one. It was an older engine and had about 1,500 hours on it since new. This brought the oil pressure up to normal and has not been a problem in the last 200 hours at 80 PSI.
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  #7  
Old 11-29-2021, 08:57 AM
lr172 lr172 is offline
 
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From your description, the ambient temps seem coincidental. Likely the reduced oil pressure is coming from some other source/problems. Pressure relief is a good place to start and verifying the sender accuracy with a mechanical gauge is also a good idea. Several potential causes for sudden oil pressure drop, but best to start with things that are easily fixable before going to those that are not (oil pump, internal leakage, etc.)

vernatherm is not likely to cause pressure drop.

at 150* OT, pretty much all of the oils are going to have a somewhat similar viscosity and OP differences will be minor. 50 weight (i.e. Victory 100) and 20w50 should be VERY similar at 150. Your change is MAJOR and it is too large to be related to oil viscosity/temp IMHO.

Larry
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Last edited by lr172 : 11-29-2021 at 09:05 AM.
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  #8  
Old 11-29-2021, 09:07 AM
Cth6 Cth6 is offline
 
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Location: Central Florida
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Quote:
Originally Posted by lr172 View Post
From your description, the ambient temps seem coincidental. Likely the reduced oil pressure is coming from some other source/problems. Pressure relief is a good place to start and verifying the sender accuracy with a mechanical gauge is also a good idea. Several potential causes for sudden oil pressure drop, but best to start with things that are easily fixable before going to those that are not (oil pump, internal leakage, etc.)

vernatherm is not likely to cause pressure drop.

at 150* OT, pretty much all of the oils are going to have a somewhat similar viscosity and OP differences will be minor. Your change is MAJOR and it too large to be related to oil viscosity IMHO.

Larry
I agree with you Larry. The only reason I am even looking at the vernatherm is that the oil cooler shutters are making a difference even before it gets up to 170 degrees or so. I am surmising that the vernatherm is stuck open letting oil constantly circulate to the cooler, which would drive the lower oil temps that I am seeing. Still secondary to the oil pressure issue though.
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  #9  
Old 11-29-2021, 11:28 AM
mahlon_r mahlon_r is offline
 
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If the gauge checks out, I would take a look at the suction screen. If it is restricted the oil pressure will be lower when the oil is thicker and colder at higher RPMs when the demand to the pump is greater but be normal at idle when the demand to the pump is lower. sounds like what you have...
Good Luck,
Mahlon
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  #10  
Old 11-29-2021, 12:09 PM
BH1166 BH1166 is offline
 
Join Date: Nov 2017
Location: Eatonton Georgia
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Quote:
Originally Posted by Cth6 View Post
I wanted to solicit to see if anyone has crossed this bridge already with low oil pressure when temps are cooler.

O-320-E2C - Carbed / Mogas
Normal Oil Temps at cruise 170-180F
Normal Oil Pressure at cruise 70-80 PSI
Normal OAT above 80
P66 Victory 100, 31 Hours and 4 months since change. Good oil history.
340 SMOH
Burns 1QT per 10-12 Hrs
Tempest 48108 filter
I donít know the difference in oil filters, but for my o320 D1a, I use Tempest 48110-2 Most all o320 use this per tempest.

Easy change to see if a difference appears. I donít think itís temp related. Pressure sender is always my first check when pressure(s) change on my RV. If FL is your normal/majority area of flight, IMHO , you should use a multi viscosity oil always, Victory 20-50 is good stuff.



https://tempestplus.com/wp-content/u...ion-091019.pdf
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Last edited by BH1166 : 11-29-2021 at 12:11 PM.
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