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Cool oil temps

Scott Hersha

Well Known Member
I’m trying different things to try to get my oil temps up to what it seems they should be, and it is a challenge. I have a newly finished RV6 with an O-360-A1A, carbed, standard compression. My oil cooler is the 7 row one you get in the FWF kit from Vans. I have it mounted on the firewall, fed through a 3” SCAT tube connected to the #4 aft baffle. The engine is new, just past breakin at 50 hours. On my first several flights with this setup the oil temp was always 175-185 after flying for 20 minutes or so. The OAT at that time (early September) was usually in the 80-90* range. Now that fall/winter is here, and the engine is broken in, I’m having a tough time getting the oil temp back to those early levels, in fact it seems to be impossible. I started with a blocking plate on the forward side of the baffle opening for the SCAT tube that was fashioned to help also cool #4 CHT. It actually helped reduce the #4 CHT just a little, but didn’t make a noticeable difference in oil temperature, see first pic below:

AEFFB43A-C148-4F9E-B7DE-881A365446FC.jpg

Then I made a flat plate instead that blocked off 1/2 of the 3” opening. That helped a little, but on a cold day (OAT in the 30’s), I still couldn’t get the oil temp above 140. I don’t have a picture of that one, but I then made a plate that covered 2/3 of the 3” opening - see below-

7E4B682F-B849-49E5-BB50-09E1071AB2E8.jpg

That one made no noticeable difference over the previous one. If the OAT was in the 50’s, I would see oil temp of about 160, but on a cold day I couldn’t get more than 135-140, depending on what I was doing (acro). So, my latest solution pictured below, is a plate that completely blocks the opening with a 1” hole drilled in the middle of it. I flew yesterday with OAT at 3500’ at 33*F. My oil temp got up to 150-155 after flying for about 30 minutes at 65% burning 8.5gph. When I came back to the airport I did some touch and goes. During this exercise, my oil temp dropped back down to 135-140.

6554BE41-E201-48A2-85B6-4613A3BC9357.jpg

My next step will be to tape over the 1” hole in the plate to see what happens. I’m also going to pull the oil temp probe and test it, but I’m not hopeful I will find anything wrong. I had the same issue on my RV4. I tested the probe (same GRT probe) and it was fine. I put one of those cockpit adjustable Venetian blind blockers on the -4 (front side of the oil cooler feed) and with it completely closed, I couldn’t get it to even 160 in the winter.

My CHT’s all run in the 320-340 range and within 10-12* of each other at cruise speeds. This is strictly an oil temperature issue. Can anybody see anything I might be missing?
 
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I have similar problem with my 6A. In the colder temps I can basically completely close off the scat tube and still not be able to get my oil temps up. Haven't found a solution yet.
 
Me too

I have a Superior XPIO360 with 9/1 pistons built up by JB down in Sebring. I have done just about what you did. I had an 11 row cooler from my old Angle valve engine with 4 in scat. I've blocked the intake down to a 1 1/2 hole and if I'm running ROP I have finally seen near 180 on an OAT of 60-70.
If I run LOP with CHTs in the low 300's, I'm still in the 150-160 range. Now, if I want to warm it up a bit I have to climb slow and keep it just ROP with 380-390 CHTs for a while to "boil out the water" and then back to my normal ops.
I quit worrying about it..
 
I have a Superior XPIO360 with 9/1 pistons built up by JB down in Sebring. I have done just about what you did. I had an 11 row cooler from my old Angle valve engine with 4 in scat. I've blocked the intake down to a 1 1/2 hole and if I'm running ROP I have finally seen near 180 on an OAT of 60-70.
If I run LOP with CHTs in the low 300's, I'm still in the 150-160 range. Now, if I want to warm it up a bit I have to climb slow and keep it just ROP with 380-390 CHTs for a while to "boil out the water" and then back to my normal ops.
I quit worrying about it..

Widget,
I also have a JB engine…….. let’s blame Jimmy…….. I’m not too worried about it either.
 
I used to put a piece of aluminum tape over the face of the cooler.. now I installed the anti splat oil cooler shutter door. That’s probably your best bet, you’ll be able to adjust it in flight with a cable.
 
I used to put a piece of aluminum tape over the face of the cooler.. now I installed the anti splat oil cooler shutter door. That’s probably your best bet, you’ll be able to adjust it in flight with a cable.

I had the same problem as OP, only a little more pronounced reflective of a little more severe climate....20°F Minnesota day and I couldn't get oil temps over about 125°F. Anti-Splat cooler with Bowden cable to the cockpit and problem solved. Flight the other day (30°F ambient) with cooler completely closed got me oil temps of 200° before I noticed and opened it a bit.


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I had the same problem as OP, only a little more pronounced reflective of a little more severe climate....20°F Minnesota day and I couldn't get oil temps over about 125°F. Anti-Splat cooler with Bowden cable to the cockpit and problem solved. Flight the other day (30°F ambient) with cooler completely closed got me oil temps of 200° before I noticed and opened it a bit.


...

Yep. That’s what I did with my RV4. With the cooler completely closed, I couldn’t get the OT above about 150.
I’ll tape mine completely closed after I get it back from paint, but in January/February in Cinci, I’m not confident it will make much difference, so the ASA oil cooler blocker won’t do me any good (I’ve installed two of these - one worked, one didn’t). I’m thinking, the only way to heat up the oil sufficiently, is to restrict oil from even going through the cooler. Larry Vetterman did this years ago on his RV4 using a ball valve from Home Depot, and it worked well. He set his up so that in the fully closed position (controlled from the cockpit with a Bowden cable), it still had a small opening to allow a small amount of oil to flow through the cooler. He said he could control his OT very accurately.
 
Scott,

Have you given any thought into closing off/reducing the cowl exit area cooling air? You may want to consider it.(?)

I had a similar problem as you. For me, even in the summer months I've had very cool oil temps (and CHTs). Because in the summer I was hard pressed to get the oil temp over 155*F (and I have an Oil Shutter, my oil temps were cool even with the oil shutter "fully closed"!).....
I knew the winter months were going to present more oil temp issues for me, however, I had great success controlling my oil temp by restricting the "exit air cooling area".

Simple solution for me was to:
-attach a 1" piece of angle at the cowl exit air area, then I experimented by temporarily attaching different sizes aluminum blocker plates to the angle.
-I flew and noted the oil temps/CHTs with the different size blockers in the exit area. My results were very pleasing, I now can finally and properly control my Oil Temp (185-210*F) range, including better balanced CHT temps.
Reducing the cooling drag exit area effectively improved and has allowed me to control my oil temp, it improved my CHT's numbers and nominally influenced my TAS a few knots

PM me if you're interested and I'll be happy send you some photos.

All the best as you continue with your experiment.

Mike P
RV8
 
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I've got the same problem with my RV4. I just installed the ASA shutter but haven't flown it yet. If that isn't effective I will probably go the ball valve route.
 
Oil temp

I've got the same problem with my RV4. I just installed the ASA shutter but haven't flown it yet. If that isn't effective I will probably go the ball valve route.

Let us know once you fly it as that seems to be a common problem with most of us.
 
Yep. That’s what I did with my RV4. With the cooler completely closed, I couldn’t get the OT above about 150.
I’ll tape mine completely closed after I get it back from paint, but in January/February in Cinci, I’m not confident it will make much difference, so the ASA oil cooler blocker won’t do me any good (I’ve installed two of these - one worked, one didn’t). I’m thinking, the only way to heat up the oil sufficiently, is to restrict oil from even going through the cooler. Larry Vetterman did this years ago on his RV4 using a ball valve from Home Depot, and it worked well. He set his up so that in the fully closed position (controlled from the cockpit with a Bowden cable), it still had a small opening to allow a small amount of oil to flow through the cooler. He said he could control his OT very accurately.

I just installed the Anti-Splat Aero Shutter and it works fantastic at keeping temps up even at 55% power LOP down to 0F in cruise. I installed it on the front as recommended when a baffle repair was required. I wish I did it sooner...did the tape thing for a couple years and that was a PITA.

What I did notice is even the slightest opening in the shutter will permit significant cooling under the certain conditions. Where talking < 1/2 a square inch total. The openings you have larger than that.

I too was wrapped up in the cooling issue, but was reminded that today's multi-weight oils mitigate the issue mostly.
 
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Engine too cool

Hello, Scott and all,
I have been having the same problem with my RV8 with a Thunderbolt IO360, parallel valve, 10:1 pistons and roller camshaft. Below 40 degrees F, I could not get the oil temp above 165 degrees. The CHTs were in the high 290 to low 300 degrees. I have a full blocking oil cooler door on the back of the cooler, controlled by a cable to the cockpit which can block off all airflow. I finally began experimenting with reducing the air inlet area with duct tape. Surprisingly, this brought BOTH the CHT and Oil Temp up together. At 33 degrees F OAT, 2 1/4" of duct tape block on the air inlets the oil temperature came up to 180-185 degrees, and the CHTs came up to 350 degrees, both right where I want them. Now to work out something permanent so I can stop using Goo Gone to clean up the tape residue. :confused:
 
Hello, Scott and all,
I have been having the same problem with my RV8 with a Thunderbolt IO360, parallel valve, 10:1 pistons and roller camshaft. Below 40 degrees F, I could not get the oil temp above 165 degrees. The CHTs were in the high 290 to low 300 degrees. I have a full blocking oil cooler door on the back of the cooler, controlled by a cable to the cockpit which can block off all airflow. I finally began experimenting with reducing the air inlet area with duct tape. Surprisingly, this brought BOTH the CHT and Oil Temp up together. At 33 degrees F OAT, 2 1/4" of duct tape block on the air inlets the oil temperature came up to 180-185 degrees, and the CHTs came up to 350 degrees, both right where I want them. Now to work out something permanent so I can stop using Goo Gone to clean up the tape residue. :confused:

Blocking the FRONT of the cooler is much more effective than blocking the rear of it. You might want to try an experiment either moving the shutter to the front or at least using aluminum tape to see the results..
 
Vernatherm... none?

https://www.kitplanes.com/a-verna-what/

I'm also helping a guy in phase 1 with a new Lycoming o-360 ... with surprisingly low oil temps with OAT around 50F: 155F at full cruise power. All of 3 hours on the engine. Stock small oil cooler.

Don't they put vernatherms in any more (see link above)? I'd expect one to at least handle 50F without resorting to blanking off the cooler. Sensor / Monitor is Dynon HDX.

Did someone cheap out and revert back to installing the old pressure bypass valve instead?
 
https://www.kitplanes.com/a-verna-what/

I'm also helping a guy in phase 1 with a new Lycoming o-360 ... with surprisingly low oil temps with OAT around 50F: 155F at full cruise power. All of 3 hours on the engine. Stock small oil cooler.

Don't they put vernatherms in any more (see link above)? I'd expect one to at least handle 50F without resorting to blanking off the cooler. Sensor / Monitor is Dynon HDX.

Did someone cheap out and revert back to installing the old pressure bypass valve instead?

Need to better examine the Lyc oil system. The vernatherm, when closed, does not fully eliminate oil flowing through the cooler just most of it. The old spring system, when used with a ball valve WILL block flow to the cooler at least until the pressure exceeds it's capacity, typically from very cold oil
 
Hello, Scott and all,
I have been having the same problem with my RV8 with a Thunderbolt IO360, parallel valve, 10:1 pistons and roller camshaft. Below 40 degrees F, I could not get the oil temp above 165 degrees. The CHTs were in the high 290 to low 300 degrees. I have a full blocking oil cooler door on the back of the cooler, controlled by a cable to the cockpit which can block off all airflow. I finally began experimenting with reducing the air inlet area with duct tape. Surprisingly, this brought BOTH the CHT and Oil Temp up together. At 33 degrees F OAT, 2 1/4" of duct tape block on the air inlets the oil temperature came up to 180-185 degrees, and the CHTs came up to 350 degrees, both right where I want them. Now to work out something permanent so I can stop using Goo Gone to clean up the tape residue. :confused:

Try 3M colored duct tape - more aesthetically pleasing and leaves less residue. :)

https://www.homedepot.com/s/3M colored duct tape?NCNI-5
 
Hello, Scott and all,
I have been having the same problem with my RV8 with a Thunderbolt IO360, parallel valve, 10:1 pistons and roller camshaft. Below 40 degrees F, I could not get the oil temp above 165 degrees. The CHTs were in the high 290 to low 300 degrees. I have a full blocking oil cooler door on the back of the cooler, controlled by a cable to the cockpit which can block off all airflow. I finally began experimenting with reducing the air inlet area with duct tape. Surprisingly, this brought BOTH the CHT and Oil Temp up together. At 33 degrees F OAT, 2 1/4" of duct tape block on the air inlets the oil temperature came up to 180-185 degrees, and the CHTs came up to 350 degrees, both right where I want them. Now to work out something permanent so I can stop using Goo Gone to clean up the tape residue. :confused:

As Taltruda said, blocking the front of the oil cooler is much more effective than blocking the back of the cooler. My experience with my two RV-8s:

https://vansairforce.net/community/showpost.php?p=1627411&postcount=17


As far as blocking the air inlets, Steve Melton did some rather extensive experimenting and came up with this for the RV-9s:

https://www.rvplasticparts.com/product-page/rv9-cowl-winter-air-dam
 
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Engine too cool

Taltruda: Thank you for your suggestion of taping over the front of the oil cooler. Unfortunately this still did not raise the oil temps significantly, still in the 165 to 170 degree range at an oat of 33 degrees F. However, by restricting the total airflow with duct tape, both CHT and Oil Temperature came up. This was quite a surprise. Is it possible that the main case and sump (M1A) offer enough cooling for the oil in a new engine? All I can report are the results, I'm still looking for a good explanation.
Jon: 3-M colored tape is a great idea. I'm heading to the hardware store for some.
Carl: I like the idea of the printed block-off plugs The only downside I see is that the plugs are not adjustable. I usually check the temperatures aloft forecast to determine how much inlet area to tape over. Maybe I'll invent an inlet butterfly valve, adjustable from the cockpit. (This may be too many things to fiddle with, along with prop, mixture, RPM, Oil Temperature control door, and too much information on the EFIS and allowing time to fly the airplane...)
Thank you all for the great replies!:eek:
 
Thank you for your suggestion of taping over the front of the oil cooler. Unfortunately this still did not raise the oil temps significantly, still in the 165 to 170 degree range at an oat of 33 degrees F.

I've applied the AL foil tape on the front side of the oil cooler so I can fold it up or down, depending on the season and how much of the cooler I want to cover. If you have the oil cooler mounted on the baffle behind Cyl #4, you may have to unbolt the cooler so you can get the AL foil tape all the way down to the bottom of the cooler, since the cylinder is in the way otherwise.

This keeps the oil temps above 170°F with an OAT of 20°F or so. 160°F to 170°F is fine. For the O-360 series engines, Lycoming specifies a minimum oil temp of 140°F for continuous operation.

i-PXKvCRk-XL.jpg
 
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I should mention, I previously blocked 1/2 of the cooler inlet chasing high CHT. That helped my CHT and raised oil temp a little with 70 deg ambient. Like some others I am confused why the Vernatherm isn't more effective. On my Pitts S-1 the Vernatherm always maintained 180 deg in ALL conditions year round. Both RV4 and Pitts have an O-360. Pitts had same cooler but in front left inlet/baffle.
 
I ferried a 172 with an O-360 in the dead of winter.. I had to completely block the oil cooler just to get the temps to come off the peg.
 
Sensor grounding

I just got a tip from Dynon...
they've seen low oil temp readings because the oil filter adapter is not well grounded to the engine. This could apply to anyone that has a similar 1 wire temperature sensor.

Thinking about this, once we put some goo onto the threads, the sensor might not even be well grounded to the filter adapter.

Obviously if you have a two wire sensor (like JPI) this won't be your issue.
 
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