VansAirForceForums  
Home > VansAirForceForums

-POSTING RULES
-Advertise in here!
- Today's Posts | Insert Pics

Keep VAF Going
Donate methods

Point your
camera app here
to donate fast.

  #1  
Old 06-21-2022, 03:36 PM
1flyingyogi 1flyingyogi is offline
 
Join Date: Dec 2015
Location: Long Beach, CA
Posts: 396
Default 20-25psi oil pressure drop during flight

I'll try to provide enough information, but not be too wordy about this very strange problem I've been experiencing.

At start up, I'm getting 79psi for oil pressure. By the time I take off and about 10 minutes into the flight, the pressure drops to about 76-77psi. (I'm thinking this is probably ok as the oil warms up, the viscosity changes and pressure drops). A few more minutes into the flight and it drops to about 74-75psi. As soon as I start doing aerobatics, it drops into the mid to high 60's. Negative Gs drop it much more quickly. Going back to positive G regains some of the lost pressure, but not much. Hard positive Gs also reduce pressure a lot. For example a hard 5G pull to a 45 upline or vertical upline will drop my pressure by about 5psi immediately. If I stop doing aerobatics, and fly level for a few minutes, the pressures come back up by a few psi, but never get back into the 70's. At it's lowest point, it's showing about 54psi (my alarm goes off at 55psi). If I pull the throttle way back (to about 2100rpm), point the nose slightly down, I'll regain about 2psi. Level flying back to the airport and the pressures will very slowly get back up to the high 60s/ low 70s by the time I'm turning final. Back on the ground, I'm back up to about 73psi. On other flights, it never even gets back into the 70's.

But I don't need to do aerobatics for the oil pressure to drop. Even "hard flying" (pulling 3G-4G turns, hard pull to 45 upline, hard push to 45 downline, etc.), or aggressive climb will cause pressure to drop. And yesterday in 100 degree heat and fully loaded with fuel, a passenger, full smoke tank, and about 8lbs of stuff from Aircraft Spruce in the back, I didn't do any aerobatics at all, but the pressure dropped into the high 50's by the time I climbed out to 3000ft.

What is going on?? I have the Raven full inverted oil system, inverted fuel, fuel injection, GRT EIS for engine monitoring.
__________________
Brian RV4
0-320 ~ 170hp, AFP fuel injection, EFII Electronic Ignition, Raven inverted oil, Sterba wood prop, 970lbs empty

Dues Happily Paid
Reply With Quote
  #2  
Old 06-21-2022, 04:01 PM
KeithO KeithO is offline
 
Join Date: Jul 2010
Location: Jackson,MI
Posts: 39
Default

What does the engine manufacturer give as an acceptable oil pressure value ? Your initial oil pressures sound very high frankly. Perhaps the oil pump relief valve is a bit sticky giving you the very high initial numbers ?

It looks like for an O-320 the minimum value is 55psi at cruise speed and I am assuming an oil temp around 180F.
Reply With Quote
  #3  
Old 06-21-2022, 04:54 PM
1flyingyogi 1flyingyogi is offline
 
Join Date: Dec 2015
Location: Long Beach, CA
Posts: 396
Default

Quote:
Originally Posted by KeithO View Post
What does the engine manufacturer give as an acceptable oil pressure value ? Your initial oil pressures sound very high frankly. Perhaps the oil pump relief valve is a bit sticky giving you the very high initial numbers ?

It looks like for an O-320 the minimum value is 55psi at cruise speed and I am assuming an oil temp around 180F.
The green arc is between 55-95psi. So pressures in this range are "normal". I'm more concerned about the big drop and trying to figure out why??

I checked my oil pressure relief valve and no debris or other issues there. For many years, my pressures have stayed right at around 75psi. About a year ago, I noticed that it dropped to about 60psi. I added some washers to the increase the pressure and it stayed at around 65psi. Until recently, I had the Vans analog gauges and as long as it's in the green, I never paid much attention to if it changed in flight. I'll glance at it before take off and landing and maybe a few times in cruise and it's always been in the green.

With my new GRT EIS, I get more precise digital reading and an alarm that's set to go off at 55psi, so that's when I noticed this problem. I again added more washers to get it up to 79psi. But during flight, it drops to anywhere between 55-75psi.

Oil temperature after run-up is about 100 degrees. A few minutes into the flight and it goes up to 190-210, depending on what I'm doing. Cruising is below 200. Aerobatics is about 210-220.
__________________
Brian RV4
0-320 ~ 170hp, AFP fuel injection, EFII Electronic Ignition, Raven inverted oil, Sterba wood prop, 970lbs empty

Dues Happily Paid

Last edited by 1flyingyogi : 06-21-2022 at 04:57 PM.
Reply With Quote
  #4  
Old 06-21-2022, 04:58 PM
RV8Squaz's Avatar
RV8Squaz RV8Squaz is offline
 
Join Date: Feb 2006
Location: Senoia, Georgia
Posts: 935
Default

Hello Brian,

I would confirm the oil pressure by temporarily installing an additional oil pressure sender and mechanical gage with a T-fitting. It could be a bad sender or gage. If that proves ok, then maybe cleaning out the inverted oil system with mineral spirits might be in order. The Christen system calls for this every 300 hours which seems a bit overkill. Iíve been doing it every 500 hours. Iíve never found any issues though. The oil pressure on my RV and Extra has always come back up to normal. Also, I keep the oil quantity at a minimum of 6.5 quarts in my RV-8. Itís easy to uncover the pickup when diving or decelerating with less than 6 quarts on my IO-360A1A powered RV-8. I donít really blow it out because the large air/oil separator captures what would normally blow out.

Good luck,

Jerry
__________________
Jerry Esquenazi
RV-8 N84JE
Reply With Quote
  #5  
Old 06-21-2022, 05:34 PM
Toobuilder's Avatar
Toobuilder Toobuilder is offline
 
Join Date: Jul 2009
Location: Mojave
Posts: 4,928
Default

Check the suction side on the inverted system, in particular the hoses. My Hiperbipe lost most of the oil pressure on my first flight. Turned out the brand new Aeroquip hose collapsed the inner liner, choking most of the supply.
__________________
WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

Michael Robinson
______________
Harmon Rocket II -SDS EFI
1940 Taylorcraft BL-65
1984 L39C - SOLD
RV-8 - SDS CPI - SOLD
Reply With Quote
  #6  
Old 06-21-2022, 07:44 PM
simpkinsona's Avatar
simpkinsona simpkinsona is offline
 
Join Date: Dec 2010
Location: Vacaville, CA
Posts: 220
Default Might be normal

Iím no expert on Lycoming engines, but oil pressure in most engines reflects the oil temperature. In your case the pressure is lower during extended climbs and during aerobatics, exactly what you would expect due to oil temperature. I think as long as your oil pressure is adequate, then thereís no problem.

-Andy
__________________
Andy Simpkinson
RV-9a Subaru engine.
Reply With Quote
  #7  
Old 06-21-2022, 07:54 PM
1flyingyogi 1flyingyogi is offline
 
Join Date: Dec 2015
Location: Long Beach, CA
Posts: 396
Default

Quote:
Originally Posted by Toobuilder View Post
Check the suction side on the inverted system, in particular the hoses. My Hiperbipe lost most of the oil pressure on my first flight. Turned out the brand new Aeroquip hose collapsed the inner liner, choking most of the supply.
Good advice. Thanks. The next thing I was going to do is pull the cowl and check carefully all the hoses for kinks. A kink, or partially collapsed hose, under G would be worse and explain the dropping of oil pressure.
__________________
Brian RV4
0-320 ~ 170hp, AFP fuel injection, EFII Electronic Ignition, Raven inverted oil, Sterba wood prop, 970lbs empty

Dues Happily Paid
Reply With Quote
  #8  
Old 06-21-2022, 08:02 PM
1flyingyogi 1flyingyogi is offline
 
Join Date: Dec 2015
Location: Long Beach, CA
Posts: 396
Default

Quote:
Originally Posted by RV8Squaz View Post
Hello Brian,

I would confirm the oil pressure by temporarily installing an additional oil pressure sender and mechanical gage with a T-fitting. It could be a bad sender or gage. If that proves ok, then maybe cleaning out the inverted oil system with mineral spirits might be in order. The Christen system calls for this every 300 hours which seems a bit overkill. Iíve been doing it every 500 hours. Iíve never found any issues though. The oil pressure on my RV and Extra has always come back up to normal. Also, I keep the oil quantity at a minimum of 6.5 quarts in my RV-8. Itís easy to uncover the pickup when diving or decelerating with less than 6 quarts on my IO-360A1A powered RV-8. I donít really blow it out because the large air/oil separator captures what would normally blow out.

Good luck,

Jerry
Thanks Jerry. I was going to do that, but thought it's not very likely so haven't done it. When I installed my GRT EIS, I pulled the original sender and Vans gauge. The pressure that GRT EIS (with their sender) was showing was the same as what my old Vans gauge and sending unit showed. (at least on the ground). But I'll do that just to know for sure, so I can move on and look at other potential causes.

I'm totally jealous you have an Extra! Which one? I had a chance to fly in the front seat of an Extra 330LT and it was amazing! The feather light controls, amazing roll rate, neutral handling, and seemingly unlimited vertical penetration... Someday. LOL
__________________
Brian RV4
0-320 ~ 170hp, AFP fuel injection, EFII Electronic Ignition, Raven inverted oil, Sterba wood prop, 970lbs empty

Dues Happily Paid
Reply With Quote
  #9  
Old 06-21-2022, 11:58 PM
rv8ch's Avatar
rv8ch rv8ch is offline
 
Join Date: Feb 2005
Location: LSGY
Posts: 4,700
Default

Any chance that your oil suction screen has not been cleaned lately?

https://www.lycoming.com/sites/defau...e%20Action.pdf
__________________
Mickey Coggins
Fresh Ukraine update and photos from RV-6 owner Alex 28 June 2022!
http://www.rv8.ch/help-people-in-ukraine/

Please send him a bit of money so he can keep providing food and essentials to civilians affected by the war.
Reply With Quote
  #10  
Old 06-22-2022, 12:39 PM
1flyingyogi 1flyingyogi is offline
 
Join Date: Dec 2015
Location: Long Beach, CA
Posts: 396
Default

Quote:
Originally Posted by rv8ch View Post
Any chance that your oil suction screen has not been cleaned lately?

https://www.lycoming.com/sites/defau...e%20Action.pdf
It was inspected and cleaned (not much there) at my last CI, September 2021.
__________________
Brian RV4
0-320 ~ 170hp, AFP fuel injection, EFII Electronic Ignition, Raven inverted oil, Sterba wood prop, 970lbs empty

Dues Happily Paid
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 04:46 AM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.