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High oil temps
https://drive.google.com/file/d/0B_6...w?usp=drivesdk Hey guys I've searched with no avail that explains why I gave high oil temps where others don't. -6 IO-360 angle valve, cooler mounted on firewall (brand new 9 row aero classic) pulling air from behind #3 cylinder. Verified oil temp probe reading correctly. Temps shoot straight up to 220 and stay there. Oil cooler is hot and checked at 195 soon after landing with IR gun. The aircraft is new to me and previous owner moved cooler in hopes that it would fix it. Verrnatherm has not been checked but it is my understanding that if the cooler is that hot it is doing its job. Only thing I can think is lack of airflow at the cooler, but not sure got to rectify that
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. |
I have basically the same setup as you have in my RV8. My temps do not run as high as yours are. You didn't say what type aircraft you have. If you have an "A" model perhaps you need to enlarge your ram air exit.
Good luck! |
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/catalo...sOilCooler.php Carl |
Just looking at the picture, it looks like the cooler is mounted close to the firewall and may be restricting the exit airflow.
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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)?? |
Do you know if your engine had oil squirters on the bottom of your pistons?
What are your CHT's running? |
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? |
Oil Temp
3" duct is inadequate. Start with 4" and if that doesn't bring it down enough change the path of the intake and exit air.
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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_...C1JZDFjSWNDVlU https://drive.google.com/open?id=0B_...jhuYTdHcTFUaWM https://drive.google.com/open?id=0B_...UxxNnlRSjMyVmM |
I had issues as well with the stock cooler and 195 hp. I switched to sn 8001599 cooler and a 4 inch scat tube. It's a lot better now but still have to watch it on climb out. I have piston squirters and a Sam James plenum so it's a lot different
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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 |
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. |
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 would verify timing again.
20* does not seem right. Also do you have EI?? On one side? |
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. |
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. ![]() |
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 |
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Carl |
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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. |
High oil temps
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 . |
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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. |
Oil cooler
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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. |
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back to the basics. I like it. I'll check tomorrow
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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.
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lower pressure = lower oil temp
Can someone explain why this would be as it seems counter intuitive.
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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. |
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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 |
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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.
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It looks like the cooler is discharging towards the firewall? If so it needs turned down towards the bottom it will never work as well like it is
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Oil temps
Just for the record , I have an enclosed plenum, 4inch scat to 13 row cooler, 25' timing . As said previously nothing has changed the temps as dramatically as winding down the oil pressure. I would not have posted my results if it was possibly something else .
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You could try running your oil quantity a bit closer to minimums.
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Could the higher oil pressure been fighting the spring on the vernathurm and therefor holding it off the seat allowing some oil bypass and not full direction to the cooler?
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