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C90 12F Max oil pressure documentary contradiction

UK Cub Nut

UK Cub Nut

Registered User
Southern UK
Another Q for the C90 gurus

My PA-18 flight manual and the E-252 say that the max oil pressure for my C90 -12F should be 40 PSI, my Pressure gauge even has a red line at this value.

My engine runs beautifully with an indicated oil pressure of 50psi when warmed and running in an OAT of 0deg C

Form X-30010 the FAA approved Overhaul manual for C75,C85,C90,0-200 written by the people who made my engine says
"Oil pressure for cruising (psi) 30-60"

I.e it would appear my indicated oil pressure is within the Design Authority prescribed operating range

Do I need to get my engine looked at? or sail on in the knowlege that this is another one of those minor gray areas that are part of cubbing?

Many thanks

UKCN
 
ukcn,
what sort of gage? steam gauge or ?
my c90-12f has 180 smoh w/millineum cyl. and was done by custom aeromotive and the oil pressure is read on a digital gauge. at start up my pressure reads 41 psi at an oil temp. of 70/80 degrees then after takeoff with the oil temp up to 180 degrees it decrease to about 27-32 psi and at say 200 degree oil temp the psi will be about 26. land and taxi in at 1100 rpm and it will indicate 12 psi with hot oil. always been that way.
hope this helps.
gary
 
The Type Certificate Data Sheet says 30-40 psi for the C90 and 30 to 60 for the O-200. At 0 degrees C I can imagine it would run high. Are you using a multi-grade oil. I would be more concerned on the oil pressure on a hot day. That is always my concern here when it is 100 degrees outside.
 
UK Cub Nut said:
Another Q for the C90 gurus

My PA-18 flight manual and the E-252 say that the max oil pressure for my C90 -12F should be 40 PSI, my Pressure gauge even has a red line at this value.

My engine runs beautifully with an indicated oil pressure of 50psi when warmed and running in an OAT of 0deg C

Form X-30010 the FAA approved Overhaul manual for C75,C85,C90,0-200 written by the people who made my engine says
"Oil pressure for cruising (psi) 30-60"

I.e it would appear my indicated oil pressure is within the Design Authority prescribed operating range

Do I need to get my engine looked at? or sail on in the knowlege that this is another one of those minor gray areas that are part of cubbing?

Many thanks

UKCN
Click to expand...

Did you happen to have any Viagra dust on your hands when you added oil the last time :lol: what Steve said, we need to know what weight oil your running, the pressure relief valve is adjusted with thin washers and if you put to many in you can peg the needle in the gauge, what is the pressure at a 500rpm idle when hot.

Glenn
 
Also, a minor point: The approved data provided by the airframe manufacturer trumps that provided by the engine manufacturer, IF the two disagree.

Otherwise, I think you've got some good points to start with here.

MTV
 
I'm pretty close to Gary's numbers. I'm 125 hrs. out of top overhaul (ECI nick carbide cylinders) and 50 hrs. or so since bottom overhaul (new crank, bearings and case refurb). Gage is a steam gauge.

I see 42 psi on start up and once the oil is around 200 deg. it drops back to 32-34 psi. At idle pressure drops down to the 20s. Oil is Philips X/C 20W-50.

When I was breaking in the new bottom in warm weather and running full throttle in climbs I saw occasional temps in the 215-220 range, begging the question how hot is too hot for oil??
 
What's the approved data for the airplane say is max oil temp?

Second, have you checked your oil temperature probe/gauge for accuracy. I've found more than one of those that were pretty inaccurate.

Immerse the probe in boiling water and check the gauge for accuracy.

MTV
 
jrussell said:
I see 42 psi on start up and once the oil is around 200 deg. it drops back to 32-34 psi. At idle pressure drops down to the 20s. Oil is Philips X/C 20W-50.
Click to expand...

This is identical to what I saw on the C-90 in my Super Cub using the same oil. Also fairly close to what I used to see on the C-90 in my J5.
 
jrussell said:
When I was breaking in the new bottom in warm weather and running full throttle in climbs I saw occasional temps in the 215-220 range, begging the question how hot is too hot for oil??
Click to expand...

I just love these oil temp questions. The answer is whatever the manufacturer says (for the Continental C90 it's 225*F).

The problem we humans have is psycological - the gauge. Most aircraft oil temp gauges have a range that is barely above the max on the temp range. It LOOKS bad when the needle is near the max limit. If your temp gauge went to 1000*F and you were running 220*F you would worry that your oil was too cold (even though it was within 5*F of max allowable) !!

John Scott
 
mvivion said:
Also, a minor point: The approved data provided by the airframe manufacturer trumps that provided by the engine manufacturer, IF the two disagree. MTV
Click to expand...

Exactly right.... but as an owner/operator, I would want to be running as high as possible within the engne limits.... even if that puts you right on the redline of the Manufacturer limits published. If colder operations pushes you "over" the redline, you can make your own operational decision if you know you are below the engine certification limits.
.
 
Useful replys gents, many thanks.

I have an old steam gauge, I am not sure what oil is in the tank as I had just collected the aircraft from vendor. If it were not a multigrade and were the thick stuff for higher ambient temps it would explain the behaviour as described by Steve.

It niggles to find official documents that disagree with each other 20 psi is a big difference when the 0-200 upper limit is just 60 psi.

C-90 Seems a low pressure engine the old 0-290-D2 I used to sit behind would be at 75 psi with the temp at 150 F


UKCN
 
When I overhauled my C-90 a few years ago I bought a new oem oil pressure spring. I noticed it looked heavier than the old one. Continental has apparently jacked the oil pressure up on these engines. The LOWEST mine reads at cruising rpm is 40, oil temp 180. In winter when the hottest the oil temp gets is about 135 I have 48-50 psi.
 
UKCN, one point that is often overlooked in comparing published oil pressures/actual experience between small Continentals and most Lycomings, is that Lycoming measures oil pressure near the discharge side of the oil pump, whilst Continental measures at the return side.

This results in a large apparent difference in the gauge pressure, which may not be reflected by actual oil pressure/flow to internal parts. I sometimes wonder what the return pressure is on the Lycomings, especially as I've seen some really constricted oil galleys at teardowns.

Just another thought to ponder.

Thanks. cubscout
 
Cubscout is correct. Lycoming oil pressures for the reason he noted, are always higher than Continental. A fact which startled me the first time I jumped out of an airplane powered by one into an airplane powered by the other, and had a rather long cruise flight, with nothing else to do but contemplate such niceties..... :lol: The end of that flight quickly resulted in a fast phone conversation with the chief of our aircraft maintenance operation, who explained this to me.

Very much more relaxed on the next day's flight.

MTV
 
Longwinglover said:
jrussell said:
When I was breaking in the new bottom in warm weather and running full throttle in climbs I saw occasional temps in the 215-220 range, begging the question how hot is too hot for oil??
Click to expand...

I just love these oil temp questions. The answer is whatever the manufacturer says (for the Continental C90 it's 225*F).

The problem we humans have is psycological - the gauge. Most aircraft oil temp gauges have a range that is barely above the max on the temp range. It LOOKS bad when the needle is near the max limit. If your temp gauge went to 1000*F and you were running 220*F you would worry that your oil was too cold (even though it was within 5*F of max allowable) !!

John Scott
Click to expand...

John, I think you hit the nail on the head on that one. I've always used 225 for the max and wondered where I initially got that number from. Now I know... :p
 
Dear friends,

myPA18/95 runs a C99-12F

I have just completed 50 hrs of run in with Aeroshell W100 ( major repair after a prop strike ... no damages ... new piston rings)


Changed oil from W100 to 15W50. Clean filter was clean without slag.
Oil 4.8 Qr max level.
At start up press 40 psi as before.
In flight, oil temp 180-200 F and press gradually dropped 30-25 psi. It used to stay between 35-38 psi.
IS IT RIGHT WITH MULTIGRADE OIL THE PRESSURE LOSS UNDER THE SAME CONDITIONS?
Hot idle from 20 psi.
Oil level after 20 min flight OK, no leaks.
Is there any hont on this sibject?
Thank you Mates
 
Just think, 1940’s specs, 1940’s oil, my engine ran 220 oil temps consistently and it ran good with 20 psi oil pressure.
 
mvivion said:
What's the approved data for the airplane say is max oil temp?

Second, have you checked your oil temperature probe/gauge for accuracy. I've found more than one of those that were pretty inaccurate.

Immerse the probe in boiling water and check the gauge for accuracy.

MTV
Click to expand...

The FAA (CAA) Approved Flight Manual trumps all other documents! It is the only "APPROVED" document that lists limitations.
 
astjp2 said:
There is no manual for my airplane, so that is no absolutely absolute. Circa 1941...
Click to expand...

So then your next item in sequence of importance would be ACA309 for your airplane (assuming it still has the same model engine). Of course the 309 was dropped a long time ago in favor of instrument marking. So then all you have is the aircraft listing or TCDS followed by the engine TCDS.


Sent from my iPhone using Tapatalk
 
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