Timberwolf
Well Known Member
Any and all ideas are welcome as we would like to make it down to sun n fun if I can get this one figured out.
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Van's Air Force
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High oil temps
- Thread starter Timberwolf
- Start date
Any and all ideas are welcome as we would like to make it down to sun n fun if I can get this one figured out.
Carl Froehlich
Well Known Member
I offer the oil cooler is mounted wrong. You have air coming in forced to change direction, then exiting the cooler again forced to change directions.
I'd first mount the cooler horizontal, and perpendicular to the firewall. The air then comes in straight and leaves straight. Remake the cooler to SCAT hose adapter to make the transition air flow as straight as possible.
It is hard to tell from your photo, but it looks like the scat hose is not a full 3" in diameter. If not, it needs to be.
Try those first, then as a last step try the 2006X cooler: http://www.aircraftspruce.com/catalog/eppages/xseriesOilCooler.php
Carl
I'd first mount the cooler horizontal, and perpendicular to the firewall. The air then comes in straight and leaves straight. Remake the cooler to SCAT hose adapter to make the transition air flow as straight as possible.
It is hard to tell from your photo, but it looks like the scat hose is not a full 3" in diameter. If not, it needs to be.
Try those first, then as a last step try the 2006X cooler: http://www.aircraftspruce.com/catalog/eppages/xseriesOilCooler.php
Carl
Michael Henning
Well Known Member
Just looking at the picture, it looks like the cooler is mounted close to the firewall and may be restricting the exit airflow.
BillL
Well Known Member
With little information to go on, it sounds like the temp levels off almost regardless of the ambient? If so the vernatherm is working, but could be off. The sensor could be off. The air supply may be leaking at the face of the cooler.
It could also be aggravated by poor pressure differential between upper and lower plenums. And . . advanced timing with oil coming jets.
What size is the air supply?
Is the inlet to the air supply rounded - like 1/2 in radius?
Is the end of the diffuser sealed good to the face of the cooler? There should be no leaks. You can use a leaf blower on the supply and feel for leaks.
What is the ambient at 220f? Does it rise with ambient?
You could have some issue with sensing. A surface temp can be way off what the real temps are. Measuring the exit oil temp with a thermocouple would help eliminate that possibility.
The field will need to be narrowed for any definitive help. Since 220 is not that bad, you might fly to SnF and get some RVers to look at the system to see if there are any obvious baffling (or other) issues.
And why does my post indicate 7:49 PM when I am at either 8:49 (home base) or 9:49 PM (actual local - also on current PC)??
It could also be aggravated by poor pressure differential between upper and lower plenums. And . . advanced timing with oil coming jets.
What size is the air supply?
Is the inlet to the air supply rounded - like 1/2 in radius?
Is the end of the diffuser sealed good to the face of the cooler? There should be no leaks. You can use a leaf blower on the supply and feel for leaks.
What is the ambient at 220f? Does it rise with ambient?
You could have some issue with sensing. A surface temp can be way off what the real temps are. Measuring the exit oil temp with a thermocouple would help eliminate that possibility.
The field will need to be narrowed for any definitive help. Since 220 is not that bad, you might fly to SnF and get some RVers to look at the system to see if there are any obvious baffling (or other) issues.
And why does my post indicate 7:49 PM when I am at either 8:49 (home base) or 9:49 PM (actual local - also on current PC)??
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Reformed SeaSnake
Active Member
More Info?
Sorry if any of this is obvious, but;
What are your CHT's like? Are #2 and #4 running particularly cool?
Are you sure the baffles are well sealed?
You mention oil temp goes to 220 and stays there. does oil temp really stay constant or does it vary somewhat with OAT and CHT?
Sorry if any of this is obvious, but;
What are your CHT's like? Are #2 and #4 running particularly cool?
Are you sure the baffles are well sealed?
You mention oil temp goes to 220 and stays there. does oil temp really stay constant or does it vary somewhat with OAT and CHT?
Timberwolf
Well Known Member
Hey guys thanks for all of the replies. Back at a computer so I can give a little more detail. Temp probe verified with boiling water, new baffling material and all seems well sealed. Ducting is 3" scat right into the cooler. Ducting all to the cooler and the cooler face is well sealed with no leaks. It attaches to the back of the baffling with a tig welded aluminum tube to a flat plate, not exactly contoured. Engine does have oil jets and timing is verified at 20*. Looking at the chart for the X-series coolers, it looks like they recommend no less than a 13 row for oil squirters. I only have a EI scanning egt/cht gauge so not able to log the temps, but I do believe they all evened out one I powered back at cruise. I haven't had a chance to really get up and check with different temps, but all this was around 80 degress OAT. If I remember correctly I want to say my CHT on my #1 was under 290 with everything else leveling out around 340. I'll try to get a flight in today to verify.
Some observations...
This plane doesn't have the front baffle right behind the ring gear. I just cut one out with the plasma and baffling material will be here Monday. Though some air could be escaping to the lower cowl from here, I have it pretty well sealed up with RTV.
Looking at a buddies RV-7 I see he has the ramps on his top cowl. I suspect to speed the air past the front cylinders and make it all the way to the rear cylinders to prevent this very issue.
I've read where others have had some of the same issues and people have put on a firewall cooler as well as the one behind the #4 cyl. I have the previous owner shipping me the 7 row that went behind #4 in hopes that I could run them in series to get the temps down until I can fix it correctly
https://drive.google.com/open?id=0B_6aLvKRR_V2YjhuYTdHcTFUaWM
https://drive.google.com/open?id=0B_6aLvKRR_V2SUxxNnlRSjMyVmM
Some observations...
This plane doesn't have the front baffle right behind the ring gear. I just cut one out with the plasma and baffling material will be here Monday. Though some air could be escaping to the lower cowl from here, I have it pretty well sealed up with RTV.
Looking at a buddies RV-7 I see he has the ramps on his top cowl. I suspect to speed the air past the front cylinders and make it all the way to the rear cylinders to prevent this very issue.
I've read where others have had some of the same issues and people have put on a firewall cooler as well as the one behind the #4 cyl. I have the previous owner shipping me the 7 row that went behind #4 in hopes that I could run them in series to get the temps down until I can fix it correctly
https://drive.google.com/open?id=0B_6aLvKRR_V2YjhuYTdHcTFUaWM
https://drive.google.com/open?id=0B_6aLvKRR_V2SUxxNnlRSjMyVmM
Steve Barnes
Well Known Member
I have nearly an identical set up.
I have a 3" scat to cooler. On hot days my oil was getting a little warm (not as hot as yours). On my fiberglass plenum (very similar to yours) I left a flat area big enough to attach a 2" scat in addition to the 3" just in case my temps were a little high. I added a cockpit adjustable butterfly valve to the 3" so in cold weather I am just running the 2" scat. Since I added the 2" scat my oil temp has come down.
If you don't have a rounded shape over the bottom tube of your engine mount, that may help a little to get air smoothly out of the bottom cowl. On mine I bent a piece of .016 alum around a broom pole and attached to the bottom skin, then around the the bottom tube of the engine mount then rivet to the firewall with monel rivets.
Steve
I have a 3" scat to cooler. On hot days my oil was getting a little warm (not as hot as yours). On my fiberglass plenum (very similar to yours) I left a flat area big enough to attach a 2" scat in addition to the 3" just in case my temps were a little high. I added a cockpit adjustable butterfly valve to the 3" so in cold weather I am just running the 2" scat. Since I added the 2" scat my oil temp has come down.
If you don't have a rounded shape over the bottom tube of your engine mount, that may help a little to get air smoothly out of the bottom cowl. On mine I bent a piece of .016 alum around a broom pole and attached to the bottom skin, then around the the bottom tube of the engine mount then rivet to the firewall with monel rivets.
Steve
scsmith
Well Known Member
Here is a list for you
First, if you have a missing area of baffling around the front of your engine, you have a huge leak path that will tend to equalize pressure in upper and lower cowl areas while doing no cooling. This will make it really hard to get any flow thru the oil cooler. You have to have EVERY possible place for air to go closed off.
Second, the ramps on the top of the cooling openings help get the highest possible pressure in the upper cowl. They are not Super important, but they do help.
Third, your cooler is angled so that the flow out the exit of the cooler is partly obstructed by the firewall. It is not helping to get good flow thru the cooler, especially up in the corner.
Fourth, you should have 4" scat hose. I used 3.5" and my system cools pretty well now, but when I start making a smaller cooling exit on the bottom of the cowl, that raises the pressure in the lower cowl, so I will need to switch to 4" scat to get enough air to the cooler.
First, if you have a missing area of baffling around the front of your engine, you have a huge leak path that will tend to equalize pressure in upper and lower cowl areas while doing no cooling. This will make it really hard to get any flow thru the oil cooler. You have to have EVERY possible place for air to go closed off.
Second, the ramps on the top of the cooling openings help get the highest possible pressure in the upper cowl. They are not Super important, but they do help.
Third, your cooler is angled so that the flow out the exit of the cooler is partly obstructed by the firewall. It is not helping to get good flow thru the cooler, especially up in the corner.
Fourth, you should have 4" scat hose. I used 3.5" and my system cools pretty well now, but when I start making a smaller cooling exit on the bottom of the cowl, that raises the pressure in the lower cowl, so I will need to switch to 4" scat to get enough air to the cooler.
N941WR
Legacy Member
Edit: I just went back and looked at your first picture again, it looks like you have an expansion chamber on your scat tubing.
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One other thing, if your 3" scat tubing is run right up against the oil cooler and doesn't have any room to expand and let the air slow down, you in effect only have seven square inches of cooling surface. (Pi*1.5^2 = 7.07 in-sq)
If you upgrade to a 4" scat tube, you go up to 12.6"sq of cooling surface. (Pi*2^2 = 12.566 in-sq)
If you make a fiberglass transition from your 3" scat tubing to the full size of your oil cooler, you might be ok. Changing the orientation of your oil cooler so the exit air points towards the exit rather than towards the firewall will also help.
I helped a buddy make this transition for his O-360 so he could go from a 3" to 4" tubing and it was almost too much, as his oil temps were not hot enough.
(Click to enlarge)
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One other thing, if your 3" scat tubing is run right up against the oil cooler and doesn't have any room to expand and let the air slow down, you in effect only have seven square inches of cooling surface. (Pi*1.5^2 = 7.07 in-sq)
If you upgrade to a 4" scat tube, you go up to 12.6"sq of cooling surface. (Pi*2^2 = 12.566 in-sq)
If you make a fiberglass transition from your 3" scat tubing to the full size of your oil cooler, you might be ok. Changing the orientation of your oil cooler so the exit air points towards the exit rather than towards the firewall will also help.
I helped a buddy make this transition for his O-360 so he could go from a 3" to 4" tubing and it was almost too much, as his oil temps were not hot enough.
(Click to enlarge)
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Timberwolf
Well Known Member
Lots of great information. Will be ordering 4" scat tube. Got the front baffle fabbed up and in today with zero difference in oil temps. The CHT's may have been helped. I believe once I get in the 7 row behind the #4 cylinder it will help on 2 accounts. During the flight today I scrolled through the EGT/CHT's. EGT's were all at 1310 except #4 which was 1220. CHT's were all 340 except #4 which was 273. By putting the cooler in behind the #4 it should rectify the cool cylinder issues, and hopefully cool the oil...at least enough until I can get back from SNF and put in the 4" scat.
I think I forgot to mention but this is all on a -6 with standard gear.
I think I forgot to mention but this is all on a -6 with standard gear.
Timberwolf
Well Known Member
Dual mags, verified by 2 different IA's on separate occasions before I purchased, but doesn't hurt to make sure.
What I don't get is after the flight yesterday I landed and put an IR temp gun on the cooler and it shows that the cooler was at 175 degrees. Now it is my understanding that the oil then goes straight from that cooler into the filter return where the temp is then read by the gauge. I don't have a firm grasp as to the exact path of oil flow. But as I understand it the temp limits are set by lycoming off of the oil coming in from the cooler at it's coolest point. If the cooler shows it's only 175 that tells me it is at least doing something, but the temp gauge doesn't reflect that.
What I don't get is after the flight yesterday I landed and put an IR temp gun on the cooler and it shows that the cooler was at 175 degrees. Now it is my understanding that the oil then goes straight from that cooler into the filter return where the temp is then read by the gauge. I don't have a firm grasp as to the exact path of oil flow. But as I understand it the temp limits are set by lycoming off of the oil coming in from the cooler at it's coolest point. If the cooler shows it's only 175 that tells me it is at least doing something, but the temp gauge doesn't reflect that.
Can't shoot a bare aluminum oil cooler with an IR gun and get an accurate temperature reading. The exception is a gun with adjustable emissivity. Without adjustment, it's probably preset for 0.95, which is way off for bare metals. If you really want to measure a cooler with an IR gun, paint the surface dull black, or cover the measurement area with masking tape.
Even if accurate, 195F would be pretty close to the ambient temperature of an engine compartment after shutdown. Point is, the measurement made after shutdown may be misleading. Easy to rig a contact measurement if you really want to know inflight temperature.
No way a 3" SCAT with a square-edged intake off the baffle will work on an angle valve with squirters. It's the equivalent of maybe a 2"~2.5" smooth tube.
340F CHT is actually kinda high for an angle valve in cruise with stock exit area. That's roughly where my 390 runs in cruise at 50 OAT and only 30 sq inches of exit. Below I've posted data from a long climb at 125 true, with the cowl door at about 46 sq inches exit area. Overall, I suspect you have limited pressure delta. It's all guesswork without pressure measurement.
Even if accurate, 195F would be pretty close to the ambient temperature of an engine compartment after shutdown. Point is, the measurement made after shutdown may be misleading. Easy to rig a contact measurement if you really want to know inflight temperature.
No way a 3" SCAT with a square-edged intake off the baffle will work on an angle valve with squirters. It's the equivalent of maybe a 2"~2.5" smooth tube.
340F CHT is actually kinda high for an angle valve in cruise with stock exit area. That's roughly where my 390 runs in cruise at 50 OAT and only 30 sq inches of exit. Below I've posted data from a long climb at 125 true, with the cowl door at about 46 sq inches exit area. Overall, I suspect you have limited pressure delta. It's all guesswork without pressure measurement.
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Oil temp
Dan,
I have a new IO-390 in my 8 running 3" SCAT to a firewall mounted 9 row cooler'
fed from the rear baffle behind #3 cylinder.
AT 3000', 75* OAT, 2550rpm X25.5" mp. engine not yet broken in 7 hrs.TT,
I am seeing CHT's < 350*F, oil 217*F. do you think it would be worth the effort to
change to 4" SCAT? What about aluminum dryer vent hose? smoother inside surface?
Dick
Dan,
I have a new IO-390 in my 8 running 3" SCAT to a firewall mounted 9 row cooler'
fed from the rear baffle behind #3 cylinder.
AT 3000', 75* OAT, 2550rpm X25.5" mp. engine not yet broken in 7 hrs.TT,
I am seeing CHT's < 350*F, oil 217*F. do you think it would be worth the effort to
change to 4" SCAT? What about aluminum dryer vent hose? smoother inside surface?
Dick
Carl Froehlich
Well Known Member
You have great numbers. Don't change a thing (other than balancing your injectors).
Carl
At 7 hours it's a bit early to worry about it. It's also a higher than usual cruise power setting, but it's what you need to do for break-in.
Given the conditions and age, the CHT sounds fine. For me, 217F would be an entirely unacceptable oil temperature in the long term. The Lycoming 390 manual is clear; for maximum life, 180F. So yes, I'd be re-working the oil cooler setup.
I don't know about the durability of dryer duct. I use SCEET hose; it has a liner.
Just to add my experience with high oil temps, my motor is an IO320 eci kit engine with squirters rv7a. I have been chasing hi temps since the build now with 140 hrs on the clock . Temps up to 118c and rarely under 102c , chts ok.basically unmanageable
Relieved lower cowl with no change to temps, fitted 13 row remote cooler helped but still to high. When I built the motor I never adjusted the oil pressure relief valve as it was screwed up to maximum so I figured that wasn't a bad thing.
By chance I just fitted a c/s prop and was having surge problems and I deceided to adjust the oil pressure. Oil temps down to 86c constantly . We have been flying with summer temps in the 35c plus range and I have seen 108c on climb then start managing it with air speed and decreasing into the mid 90c .
I guess it was not getting oil cooler saturation.
I'm happy with these figures .
I hope this may help .
Relieved lower cowl with no change to temps, fitted 13 row remote cooler helped but still to high. When I built the motor I never adjusted the oil pressure relief valve as it was screwed up to maximum so I figured that wasn't a bad thing.
By chance I just fitted a c/s prop and was having surge problems and I deceided to adjust the oil pressure. Oil temps down to 86c constantly . We have been flying with summer temps in the 35c plus range and I have seen 108c on climb then start managing it with air speed and decreasing into the mid 90c .
I guess it was not getting oil cooler saturation.
I'm happy with these figures .
I hope this may help .
Greg, what was the original pressure in cruise, and what is the new pressure?
Timberwolf
Well Known Member
hmm. My oil pressure is at 90-95 in cruise I believe.
I took my leaf blower up and blew it into the cowling then stuck my hand behind the cooler. It doesn't feel like much air is getting through it with the 3" scat. The 7 row will be here today and I'll see what difference that makes before I fab up a new fiberglass plenum and the 4" scat.
I took my leaf blower up and blew it into the cowling then stuck my hand behind the cooler. It doesn't feel like much air is getting through it with the 3" scat. The 7 row will be here today and I'll see what difference that makes before I fab up a new fiberglass plenum and the 4" scat.
Oil cooler
Looking at the 2nd photo I see you don't have an inlet screen over the air entrance. This is asking for trouble . Consider what a bird entering that could do to your oil temp if it went in there. Have you checked the cooler for any obstructions ?. This might be the source of your high temp. Put a screen cover over that air entrance ..Hey guys thanks for all of the replies. Back at a computer so I can give a little more detail. Temp probe verified with boiling water, new baffling material and all seems well sealed. Ducting is 3" scat right into the cooler. Ducting all to the cooler and the cooler face is well sealed with no leaks. It attaches to the back of the baffling with a tig welded aluminum tube to a flat plate, not exactly contoured. Engine does have oil jets and timing is verified at 20*. Looking at the chart for the X-series coolers, it looks like they recommend no less than a 13 row for oil squirters. I only have a EI scanning egt/cht gauge so not able to log the temps, but I do believe they all evened out one I powered back at cruise. I haven't had a chance to really get up and check with different temps, but all this was around 80 degress OAT. If I remember correctly I want to say my CHT on my #1 was under 290 with everything else leveling out around 340. I'll try to get a flight in today to verify.
Some observations...
This plane doesn't have the front baffle right behind the ring gear. I just cut one out with the plasma and baffling material will be here Monday. Though some air could be escaping to the lower cowl from here, I have it pretty well sealed up with RTV.
Looking at a buddies RV-7 I see he has the ramps on his top cowl. I suspect to speed the air past the front cylinders and make it all the way to the rear cylinders to prevent this very issue.
I've read where others have had some of the same issues and people have put on a firewall cooler as well as the one behind the #4 cyl. I have the previous owner shipping me the 7 row that went behind #4 in hopes that I could run them in series to get the temps down until I can fix it correctly
https://drive.google.com/open?id=0B_6aLvKRR_V2YjhuYTdHcTFUaWM
https://drive.google.com/open?id=0B_6aLvKRR_V2SUxxNnlRSjMyVmM
Timberwolf
Well Known Member
Not sure I've ever seen a screen on any aircraft for an oil cooler. If I took a bird and saw the temps rise, I would be landing to check out what was going on, but point taken. Checked, nothing is obscuring it.
I got the 7 row in tonight in series and it lowered temps to 200. I can live with that to get it down to SNF until I can get the 4" scat on the 9 row. I think I may be putting in the ramps as well once I get back. Something still isn't right as far as flow in the cowl because despite the change, the #4 is still at 295 on the CHT after leveling off with the others 336-345. I think something needs to be done to ensure the air is flowing all the way to the back and getting through the coolers.
I got the 7 row in tonight in series and it lowered temps to 200. I can live with that to get it down to SNF until I can get the 4" scat on the 9 row. I think I may be putting in the ramps as well once I get back. Something still isn't right as far as flow in the cowl because despite the change, the #4 is still at 295 on the CHT after leveling off with the others 336-345. I think something needs to be done to ensure the air is flowing all the way to the back and getting through the coolers.
A foreign object on the cooler face could be a problem, but screens are really obstructive. Take a look at the charts ("open area") here:
https://www.mcmaster.com/#standard-mesh-filters/=171kr9k
Before you make yourself too crazy, swap probe locations; move the #4 probe to another cylinder and see if the indication moves with it.
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Timberwolf
Well Known Member
back to the basics. I like it. I'll check tomorrow
Oil temp sucsess
Dan , the pressure was 75 psi on cruise now it's around 65 psi ,its quite amazing I think that it's been such a dramatic improvement on my oil cooling , one would think that fitting a 13 row cooler over a 7 row would do the job but the pressure adjustment has done the job.
Dan , the pressure was 75 psi on cruise now it's around 65 psi ,its quite amazing I think that it's been such a dramatic improvement on my oil cooling , one would think that fitting a 13 row cooler over a 7 row would do the job but the pressure adjustment has done the job.
N941WR
Legacy Member
Dan Correct me, if I'm mistaken...
By lowering the oil pressure, I believe you give the oil more time in the cooler, to transfer its heat to the moving mass of air.
Carl Froehlich
Well Known Member
The oil pump is a positive displacement pump. So the pump output volume is for all practical aspects independent of system pressure (for our closed systems) and constant. I offer that since oil is not a prefect fluid the heat generated by the pumping action might add a marginal amount of heat at a slightly higher pressure - but I'd estimate the additional pumping heat between 65 and 75 psig would be hard to measure.
Oil cooler heat rejection is a function of pounds mass of air and air temp rise across the cooler. Bigger cooler - more heat transfer area and better airflow (pounds mass of air). Better cooler then higher air temp rise across the cooler. Better air pressure drop across the cooler (and everything else constant), more pounds mass of air.
Carl
N941WR
Legacy Member
Thanks Carl, everything I learned about this stuff in school many years ago, I have forgotten!
BillL
Well Known Member
The oil does collect air to about 5-8%. Right on the pressure, with that increase the pumping loss would be higher but with 95% efficiency already, marginal, and the total flow would also incrementally be lowered, although the various paths to the sump will change. Nothing jumps out as to why it would have such a pronounced effect on the oil temps. Unless a baffle seal was pushed back into place in the process.
Timberwolf
Well Known Member
probes tested and all are fine. I got a chance to get it up and cruise around a bit today and the CHT's really came down. Still something going on but oil temps are steady around 195-200. It'll get me to SNF and back until I have more time to mess with the 4" scat tube to the cooler. Thanks to everyone for the help. Will post up more after I get a chance to mess with it some.
I have a theory, something I've been kicking around a while. At s&f on a cell phone, more later
I got to hear this. See ya tomorrow.
My initial thought on heat transfer is that the engine is a bucket holding x- heat.
The cooler subtracts heat. The combustion and friction add heat. If more heat is added than subtracted then is has less heat (cooler). If more is added than subtracted then more heat (hotter).
Unless a major amount of oil is by-passing the cooler and the cooler return oil is very cool then I would say no. the cooler is still removing x heat.
I would think that no matter the velocity or volume of oil flowing through the cooler then it will remove x heat. More or cooler air will change the amount of heat removed but the amount of oil will not.
The only other thing that could change the total amount of heat the cooler can remove (other than the mass airflow) would be the temperature delta/difference of the air vs oil temp.
I hope I wrote what I was thinking.
The cooler subtracts heat. The combustion and friction add heat. If more heat is added than subtracted then is has less heat (cooler). If more is added than subtracted then more heat (hotter).
Unless a major amount of oil is by-passing the cooler and the cooler return oil is very cool then I would say no. the cooler is still removing x heat.
I would think that no matter the velocity or volume of oil flowing through the cooler then it will remove x heat. More or cooler air will change the amount of heat removed but the amount of oil will not.
The only other thing that could change the total amount of heat the cooler can remove (other than the mass airflow) would be the temperature delta/difference of the air vs oil temp.
I hope I wrote what I was thinking.
Thanks for the feedback
After reading the feedback and studying the lycoming oil schematic I have a theory.
There is a constant quantity of oil going through the pump AND cooler at a given rpm. The cooled oil is either going to go through the galleys and hot parts of the engine or is going to be dumped back into the sump to recirculate. Setting the oil pressure relief value higher will cause more oil to flow to the hot parts of the engine before returning to the sump resulting in hotter oil in the sump. A lower oil pressure would cause more of the cooled oil to dump back into the sump resulting in a cooler sump temp. I could see a lower oil pressure resulting in a lower oil temp in the sump but higher oil temps in the engine where it actually matters.
Oil schematic found here:
http://www.vansairforce.com/community/showthread.php?t=45548
After reading the feedback and studying the lycoming oil schematic I have a theory.
There is a constant quantity of oil going through the pump AND cooler at a given rpm. The cooled oil is either going to go through the galleys and hot parts of the engine or is going to be dumped back into the sump to recirculate. Setting the oil pressure relief value higher will cause more oil to flow to the hot parts of the engine before returning to the sump resulting in hotter oil in the sump. A lower oil pressure would cause more of the cooled oil to dump back into the sump resulting in a cooler sump temp. I could see a lower oil pressure resulting in a lower oil temp in the sump but higher oil temps in the engine where it actually matters.
Oil schematic found here:
http://www.vansairforce.com/community/showthread.php?t=45548
All the oil goes to the hot parts after the pump. None can bypass the hot parts.
It is possible to bypass the cooler but all the oil will go through the filter and then to hot parts.
Timberwolf
Well Known Member
Is there a kit we can install that will take the vernatherm completely out of the loop and push all of the oil through the cooler? I live in Florida so not too concerned with cold weather flying at this point
This is incorrect, unless you meant that the sump is a "hot part." Right after the output of the oil pump, the oil reaches a control valve. This valve reduces the oil pressure from the pump (assuming it is actually higher - it should be). It does this reduction by dumping excess oil flow directly into the sump. Depending upon how much higher the pump output pressure is, relative to the pressure set in the valve, more oil will overflow to the sump. You can expect a considerable amount of oil is overflowing to the sump.
I would also argrue that most of the "hot parts" are actually not hot. The majority of the oil is flowing through the crank and cam bearings and the oil reduces most all friction there and therefore there is no more heat than the ambient internal case temp (the oil's job is not to reduce heat here, but to create a fluid surface for the journal to spin in, greatly reducing friction). Some of this oil flowing out of the crank bearings will be thrown on to the cylinder walls and pistons and cam lobes. That oil will pick up considerable heat, but that oil is the minority of the oil flowing through the system. Most oil goes straight to the sump at the same temp that it left the sump. This is why it takes so long to heat your oil up a low power settings.
This is why engines with oil squirters have higher oil temps or higher oil-based heat loads. They are sending more oil to the cylinders and therefore absorbing more heat into the oil. Without them, most of the heat is being transferred to the external air.
Larry
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Oil flows directly from the sump to the pump and then to the cooler (assuming vernatherm is closed and max pressure not exceeded.) then through filter and then to pressure relief (overflow to sump) then to galleries.
DeltaP across the vernatherm = cooler pressure drop.
