STC to Increase Lycoming Oil Pressure - Relocate Tap

PaulMillner

PaulMillner

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Paul Millner
In the restart Cessnas, Cessna & Lycoming increased maximum oil pressure red line from 100 psig to 115 psig for the restart Cessnas... and made another virtual increase of 10 psig by relocating the sensing point from the back of the engine to the front of the engine, where the pressure is lower.

A friend believes he saw *somewhere* an STC that allows making this change on earlier engines... relocate the pressure tap, and remark the oil pressure red line to 115 from 100. Folks are interested in this to promote better valve train lubrication. See the Bill & Bill discussions in Aviation Consumer and other places in the late 90's... link:

http://secure4host.net/upload/files/...ion2013-08.pdf

Is anyone aware of such an STC? The drawing linked below is supposedly associated with this STC... is Lycoming offering this guidance, or some third party?

Thanks in advance for what you know!

Paul

http://www.secure4host.net/upload/fi...g_oil_line.jpg
 
Are you sure it is an STC and not a service bulletin of some sort?
 
PaulMillner said:
In the restart Cessnas, Cessna & Lycoming increased maximum oil pressure red line from 100 psig to 115 psig for the restart Cessnas... and made another virtual increase of 10 psig by relocating the sensing point from the back of the engine to the front of the engine, where the pressure is lower.

A friend believes he saw *somewhere* an STC that allows making this change on earlier engines... relocate the pressure tap, and remark the oil pressure red line to 115 from 100. Folks are interested in this to promote better valve train lubrication. See the Bill & Bill discussions in Aviation Consumer and other places in the late 90's... link:

http://secure4host.net/upload/files/...ion2013-08.pdf

Is anyone aware of such an STC? The drawing linked below is supposedly associated with this STC... is Lycoming offering this guidance, or some third party?

Thanks in advance for what you know!

Paul

http://www.secure4host.net/upload/fi...g_oil_line.jpg
Click to expand...

Q. Did they also change a specification of the hoses and/ or relocate the cooler?
 
What am I missing here. The oil pressure "sensor" is moved to a place where the pressure is higher so they moved the redline on the gauge. What was done to actually increase the pressure throughout the engine?
 
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luvflyin said:
What am I missing here. The oil pressure "sensor" is moved to a place where the pressure is higher so they moved the redline on the gauge. What was done to actually increase the pressure throughout the engine?
Click to expand...

There's a pretty good write up from a conspiracy theorist that explains the ins and outs. Pressure is increased by adding washers to the backside of the spring / ball regulator assembly located on the engine case (on mine, anyway, there's also a turn to adjust type).
 
So....how much extra can the front main bearing seal take....before it blows?

+100 psi is double normal operating pressure....:eek:
 
I'd think a change to adapt an old engine to a newer configuration would be done using manufacturer's engine specs and parts catalogs as approved data. The bigger problem will be installing that evolved engine into an airframe. That will require an STC or field approval.
 
Checkout_my_Six said:
why yes.....many. I'm an IA.

How many main bearing seals have you replaced?.....I've done a few.
Click to expand...

If you are talking about the crackcase nose seal, there isn't oil pressure trying to push it out...


Not uncommon to find them spinning with the crankshaft once separated from the crankcase.
 
bnt83 said:
If you are talking about the crackcase nose seal, there isn't oil pressure trying to push it out...


Not uncommon to find them spinning with the crankshaft once separated from the crankcase.
Click to expand...
Interesting.....you never seen one leak? :eek:

It's real ugly.
 
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Checkout_my_Six said:
Interesting.....you never seen one leak? :eek:

It's real ugly.
Click to expand...

That space is vented to the rest of the crankcase. Oil coming out of the main bearing just splashes up there and wind (or blowby since the crankase is slightly pressurised) can pull the oil out or do nothing all.

When the seal is spinning with the crankshaft you get a few drops of oil on the windshield every few minutes of a 177B (O360 lycoming with constant speed prop)
 
Stewartb said:
Why don't you tell us?
Click to expand...
just look....
Q0A3158-1024x683.jpg
 
That's not an answer. I've never seen any reference to oil pressure when reading about crankshaft seal leaks. Restricted crankcase breather? Yes. Oil slinger clearance? Yes. Thrust surface wear? Yes. Oil pressure? No. Here's my opportunity to learn something.
 
AKBill said:
Don't need riddles. I would think most is captured between crank and bearings with leakage into oil pan.
Click to expand...
on the front side of the bearing....it will pressurize against the seal....till it leaks down. Excessive pressure above the rating limit will cause it to blow.
 
RAM 160 hp STC for 0320 has you relocate the Oil pressure sensor to the front of the engine, provides a oil pressure line and fittings with the kit
 
luvflyin said:
What am I missing here. The oil pressure "sensor" is moved to a place where the pressure is higher so they moved the redline on the gauge. What was done to actually increase the pressure throughout the engine?
Click to expand...

No. The sensor is moved to the front of the engine where the pressure is 10 psi *lower* and the redline is raised 15 psi... total 25 psi increase....

That allows increasing the pressure throughout the engine...

Paul
 
Checkout_my_Six said:
So....how much extra can the front main bearing seal take....before it blows?

+100 psi is double normal operating pressure....:eek:
Click to expand...

Bottom of the green is 60 psi on Cessna Lycomings. Most engines operate 75-85 after overhaul. No doubling involved. Maybe you're thinking Continental? Their pressures are lower...

Lycoming says do not exceed 150 psi due to front main bearing seal... does that help your big picture?

Paul
 
Checkout_my_Six said:
so....where does the pressure go?
Click to expand...

Out the 1/4 inch hole at the bottom of the oil slinger space, at near zero PSIG, draining into the oil sump. The pressure drop is across the bearing.
 

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