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Would like input on High or Low Oil temps to solve problem

hecilopter

Well Known Member
Just trying to get a handle on what is different, as we are having oil temp problems on a new RV-7A. After reading tons of posts, I think it is coming down to engine configuration to explain high oil temp. We have tried the SW 8406R oil cooler ($500+) and it may have lowered temps 10-15 degrees over the Aero Classic from Van's. Before we start cutting the cowling for exit air or adding louvres, I would like some input to try and find a clue as to what configurations seem to run hot.

Here is our scenario: 2 identically cowled and baffled RV-7A's. Both have oil coolers mounted on the baffle behind cylinder #4. The top cowl inlet ramps sealed on both. Both have the vertical draft intake with the cowl scoop. We have verified no blockage in the oil cooler hoses, and the oil temp probe reads within 1 degree of a thermometer when both dipped in boiling water. When flying together side by side the other day Plane 1 was showing oil temps at 155, Plane 2 was showing temps at 230. We ran for 10 minutes side by side, OAT about 75 degrees.

Plane 1 - Superior XP-360, carb, Slick mags, 8.5:1 pistons, Hartzell BA prop. Has run cool (< 180 degrees) since first start, sometimes too cool, now has 310 hrs. All fairings and wheelpants, but did NOT have them during break-in. Aero Classics oil cooler from Van's FWF kit.

Plane 2 - ECI IO-360, Precision Silverhawk FI, Dual P-mag, 9:1 pistons, Hartzell BA prop, cam oil squirters. Ran at 235 degrees with Aero Classic cooler, runs about 220 degrees with SW 8406R cooler. Has about 7 hrs now. CHT's in the 340-360 range on all. No wheelpants. Running at 24"/2400 RPM for break-in.

What I want to know is, does the electronic ignition and/or 9:1 pistons and cam oilers or piston oilers have anything to do with it. Plane 1 has none of these.

Does anyone out there have an -A model, or either model for that matter that has a baffle mounted cooler, 9:1 pistons or higher, electronic ignition, and cam or piston oilers that has never run hot?

Another way to say it, does anyone out there have a baffle mounted cooler, 8:5:1 or less pistons, mags and NO cam or piston oilers that has had cooling problems?

Just trying to get to the bottom of this and would appreciate input from anyone with either of the above configurations to see if it is an engine configuration problem causing the high temps.

Thanks in advance!
 
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I'll add another data point and configuration.

Aero Sport Power, IO-360-B2B, Fixed Pitch (Catto 66 x 76), One Lightspeed, One Slick Mag, Precision Silver Hawk fuel injection, oil cooler on #4 baffle. CHT's range from 355-375F.

Break in was normal with full power for the initial period. Oil temps were a little on the high side but put those initial thoughts aside as the engine was breaking in.

With the warmer coming, I noticed my oil temps creeping up with the standard Van's oil cooler. Recently saw 220F at 7500' the other day on my 70 hr engine. The next day I ordered and installed the SW8046R oil cooler. Plane has flown 3 times since then but in significantly cooler temps. A recent formation flight revealed 196F oil temp after about 35 min of maneuvering.

So I am still awaiting a decision on the new setup... I dont have enough flights in the warmer temps to verify the benefit of the oil cooler. Will keep everyone posted.
 
Another data point

Hi Rusty,

I made a similar post about a week ago requesting the part number of a ?better? oil cooler. My SW8406R cooler came yesterday and I will post the results once installed.

I did manage to get oil temps down about 10 degrees (after taking the ambient difference into account) by installing an air diverter (for lack of a better term) over the oil cooler. I have a cobbled up plenum that comes to an acute angle over the oil cooler. I believe the air was just swirling around rather than flowing through the cooler. I also believe that there are more gains to be had (at least in my case) by diverting the air into the cooler.

Here are the numbers from my last flight with the diverter: TMX O-360, 9.2 pistons, 1 mag, 1 LS ignition, cam oil squirters, carb. Oil temp was 190 with Aero Classic, ambient temp was mid 70?s. Engine has 21 hrs, CHT 300?325 range on all, wheel pants installed. Running at 21?/2500 (FP climb prop). Altitude was 3500? , full rich. Length of flight was one hour. Hope this helps.
 
May also want to check the vernatherm on Plane 2. A quick test will rule that out as a possible reason for running hot oil.
 
You may see another 5-15 degree reduction as the engine breaks in and after you switch to a semi-synthetic oil.

One question is whether the oil coolers have identically sized holes feeding 'em and if there is any difference at all in between the oil cooler installations?

On my airplane, I ran higher oil temperatures than I liked for the first year or so. I added a "cool collar", which is a heat sink that straps to the oil filter. Also, I shrouded the cool collar and ducted cool air to it. This made *some* difference. By the way, this is very similar to the installation that came from the factory on Piper Tomahawks. At two different points, I increased the size of the hole in the baffles feeding air to the oil cooler. Also, I switched from the first edition Positech cooler (a poor design - Positech replaced mine for free) to an identically sized replacement from Positech.

Anyway, what made a difference that was immediately noticable was switching out the "bad" Positech and enlarging the hole in the baffles which fed air to the cooler. The other adjustments made a difference, but it wasn't large enough to cause a Eureka moment...
 
Oil jets that cool the underside of the pistons will definately result in higher oil temps. Make sure you have #8 hoses running to the cooler. These provide near twice the flow to the cooler as the #6 hoses used in some installations. High compression pistons will raise the temperature some too. All togehter you could end up with substatially higher oil temps than a comparable aircraft with none of the above.

My 7A with a IO-360M1 Superior engine and dual P-Mags has the standard Van's cooler mounted on the baffle behind #4 cylinder and runs oil temps between 150 to 175F (45F OAT and 85 OAT respectively). I cover up 4/5th of the cooler in the winter month to keep the oil warm enough. My RV6 with a Lyc O-360A1A runs about the same temps.

Martin Sutter
building and flying RV's since 1988
 
I've seen a high oil temp problem solved on a Rocket by attaching a
plenum on the back side of the oil cooler with a 4 or 5 inch scat tube attached
to the rear of the plenum. The scat tube runs to the exhaust exit area of the
cowl. I suppose the lower pressure area at the outlet helps to "pull" the air
through the oil cooler. That and it directs the air directly to the outlet instead
of mixing with the air heated passing through the cylinders in the lower pressure
area of the lower cowl. Just a thought.
 
Thanks everyone for the replies

Went flying again yesterday and the temps came down to the 200 - 210 range (60 degrees ambient). We have replaced the vernatherm just to be sure. The setup is the standard Van's baffling on cylinder #4 with the #8 hoses in the FWF kit.

The plan now is to fly another couple of hours, change the oil at 10 hrs to Aeroshell 15/50, and see where we are.

From the replies, it seems that engine configuration may make some difference, but nothing really stands out.

Thanks!
 
The fact that your CHT is also high (considering relatively cool OAT) I would look very closely at the basics like the P mags and mixture. If possible you may try to borrow a regular mag and run it to see if there is a major difference or not as there is no way to confirm actual timing when you're flying. You should also check it with a timing light but this becomes difficult at anything much above idle speeds. The other main driver on temps (at higher power settings mostly) is mixture but if you don't have full monitoring on EGT it can be tough to tell what's going on there.
 
Scott

Do you know if your engine has higher than 8.5:1 compression or the piston oilers/cam squirters? Is it ECI, Superior, or Lycoming cyls?

Thanks!
 
Yo Rusty

If you need to borrow a mag and some plugs let me know, I have one I could loan you for a check out. I've seen you around enough to "know" you! I fly the flag RV7A out of 52F and I think you bought some fine wires from me a while back.
Walt
 
Carbon Deposits

Engine runs hot during break-in because there are no carbon deposits on the combustion chamber and piston crown. No kidding. It acts like a thermal barrier much like ceramic coating. Is that the whole reason? Don't know but part of it. Temps should go down. Oh yes 9:1 adds a few degrees, but still you are OK at 220F break-in with the CHT's in the high 300's.
 
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Bring thread BACK to LIFE

This was started 3 years ago and now I am having the same problem.

AND ROOSTER AND WOODY ARE FLYING BUDS:D
Details as follows:

ECI IO-360 8.5 to 1 NO SQUIRTERS
Lightspeed + Slick mag
James cowl and plenum 300 CHT #3 & #4
Vetterman 4 pipe
EGT (now working:eek:) 1150-1200 @2300sq
Checked Verni----OK
Checked OIL Temp probe and guage.
Oil cooler on #4
Temps 220* at 23sq.

Cant run anything higher or the temps go to 240 to 250.

Replaced oil cooler with SW 8406 --gained 5*
and put on new lines (No Changes)
Covered Louvers------gained 5*
Cut off 2 1/2 inches cowl tunnel-----5*


Could it be Lightspeed ??
Try and fly on mag only for 30 min and watch temps.
Oil cooler needs ducted to outlet area with scat tube??

HELP
 
Make sure your temp gages are calibrated. I had high temp with a Dynon EMS but it turned out the factory had to re program it. 30 degree difference. Calibrate your probs. Place the probe in a can of oil and heat it with a soldering iron. Use a calibrated themometer to compare.
 
This from sac sky ranch (it was easier to steal than 'splain):

Here's one method for checking vernatherm seat contact: Coat seat face with layout glue (Dykem is available at industrial supply stores). Fly once around pattern. Pull out vernatherm and look for a rub mark all the way around the vernatherm seat face. If there isn't 100% seating, replace vernatherm and reface seat. Lycoming makes a tool, part number ST-388, for refacing the seat.

Don't remove more than .010 of an inch of material when refacing the vernatherm contact seat. The removal of material from the seat face increases the distance from the vernatherm to the seat and decreases the amount of valve opening. This decreases the amount of oil that bypasses the oil cooler at any given oil temperature.

On many Lycoming aircraft engines the vernatherm screws into the oil filter adapter (part number 77852.) If you have this style then it's less expensive and easier to replace the adapter then refacing the seat.

This could be it (or not).
 
AerHead---

Check it and it moved out HOTTER about 3/8".

Is that all this thing is suppose to move.

I thought more like 3/4 " .
 
I recently owned a Velocity and like many folks with them I had oil temp issues and engine cooling issues (big time)..First thing most of them jump on is the vernatherm (as did I). Don't EVER remember anyone saying that solved anything. My thoughts on your problem are either the P-Mags as an outside issue or simply airflow. I had done LOTS of airflow tests and was amazed on how even minor variations of baffling, openings and air deflection could significantly affect cooling. Ramping and/or deflectors may help. Bottom line on the Velocity was that it really needed a 2nd cooler. I had mounted a small 5 row on the baffles and it dropped temps from 245 to 180. (engine had 10 to 1s) One other minor thing to check. Look at the hose connections from the cooler to the engine and see if they are the same on both engines. Although it's just a loop, the temp sender is very close to one connection and that should be the return (cooler oil coming from cooler rather than hot oil from engine).
When I bought my 6, I took one look at the Vans, firewall mounted cooler with a small 2" duct tube and just knew I'd have oil temp issues. It doesn't, and the hottest I've seen is 190 in a long climb on a nearly hundred degree day---go figure.
 
Opposite problem

I fly a -7A with a factory Lycoming 0-360. My oil temperature has never hit 180 degrees. I pulled the sensor and stuck it in heated oil with a thermometer and it appeared to read with in 10 degrees of the oil temp gauge. I put an aluminum plate on the front of my oil cooler to obstruct one third of the oil cooler and it still shows maybe 160 at best. Do I need a new sensor or a new gauge?

Bill Near
 
Bill,

Order both. They are cheap.

Ordered new guage and
I still have 3 senders and all them
check fine so the guage is off. WE THINK.

If my temp is 180* I am coming to FL
 
Don't EVER remember anyone saying that solved anything.

I do. Ask Rosie.

From Rosie: A couple of years ago, I took off on a cold winter day to fly to Chino to see Checkoway & Co. On leveling off at 9.5K, I noticed the oil temp approaching 220 deg; not right for a below-freezing day. I kept an eye it and it continued climbing. I started my downhill into Chino (about 7 minutes away), and that seemed to stabilize the temps down near 225 deg. Dan and Gary Sobek helped me troubleshoot the problem, and we tested the vernatherm first: it had failed. Mike Holland had a new plane under construction so he lent me his vernatherm off his engine to get me home; temps were 180deg heading home :)
 
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I fly a -7A with a factory Lycoming 0-360. My oil temperature has never hit 180 degrees. I pulled the sensor and stuck it in heated oil with a thermometer and it appeared to read with in 10 degrees of the oil temp gauge. I put an aluminum plate on the front of my oil cooler to obstruct one third of the oil cooler and it still shows maybe 160 at best. Do I need a new sensor or a new gauge?

Bill Near

Same here. I've checked the indicating system (EIS 4000) with hot water and it is right on.

Today with an OAT of 92F, oil temp got up to 177F. If the 4" air duct from #4 baffle to the remote mounted SW cooler is closed off, oil temp will rise to 210.

During winter months it is a challenge to get it up to 160 with air shut off.

Go figure. I don't know why oil cooling is not a problem here while it is with other installs.
 
Might as well

Who knows what my temps really are. It appears I'm not the only one with this problem.

Bill
 
Re: Opposite problem

Bill

If you only blocked 1/3 of the flow that will not make much difference. I have an RV-4 with a o-320 and my oil temp would seldom get above 160. First I put a plate on the rear of the cooler which covered the complete rear with the exception of about a 3/8 inch gap on each end of the plate. This only raised the oil temps about 10 degrees. Next I added a round restrictor plate in the 3 inch scat tube that brings air to the cooler. I drilled a single 3/8 hole in the center of the plate. With both of these plates installed on a hot summer day I have now seen my oil temp get as high as 203 degrees. On cool days it never gets above 192 degrees.
 
I have 6 hours on my ECI o-320 with dual P-mags. Oil temps are hanging around 210-220 and CHT's around 420. That's at 24-2500 RPM (FP). I'd like to see the temps come down a bit and am hoping that it'll start to run cooler soon. I don't see a problem with temps below 230 or so. Seems that 180 would be low and not likely to burn off water vapor. Maybe I am wrong.

I am very curious how others have solved their cooling issues.
 
Bill

If you only blocked 1/3 of the flow that will not make much difference. I have an RV-4 with a o-320 and my oil temp would seldom get above 160. First I put a plate on the rear of the cooler which covered the complete rear with the exception of about a 3/8 inch gap on each end of the plate. This only raised the oil temps about 10 degrees. Next I added a round restrictor plate in the 3 inch scat tube that brings air to the cooler. I drilled a single 3/8 hole in the center of the plate. With both of these plates installed on a hot summer day I have now seen my oil temp get as high as 203 degrees. On cool days it never gets above 192 degrees.

Wow,I can't believe it would take that much to raise my oil temp. It would make me wonder once again whether my gauge and/or sensor were working.

Bill Near
 
This was started 3 years ago and now I am having the same problem.

AND ROOSTER AND WOODY ARE FLYING BUDS:D
Details as follows:

ECI IO-360 8.5 to 1 NO SQUIRTERS
Lightspeed + Slick mag
...
HELP
Bruce,

Check the Lightspeed. With the E/P-mags I recommend that people plug the vacuum advance and run them on the "A" curve which limits the max advance and by plugging the vacuum line the E/P-mags limit the advance. This forces them to operate fairly close a standard mag. Once they get 10+ hours on a new engine, then they can play with the timing and vacuum advance.

Best of luck!
 
Wow,I can't believe it would take that much to raise my oil temp. It would make me wonder once again whether my gauge and/or sensor were working.

Bill Near

Your temp measuring system almost for sure is ok.

These guys simply haven't figured out it is the EI that is causing high oil temp. That long, early burn pattern is causing more heat and engine oil is sucking it up.

Long live SLICK mags. :)
 
I have 6 hours on my ECI o-320 with dual P-mags. Oil temps are hanging around 210-220 and CHT's around 420. That's at 24-2500 RPM (FP). I'd like to see the temps come down a bit and am hoping that it'll start to run cooler soon. I don't see a problem with temps below 230 or so. Seems that 180 would be low and not likely to burn off water vapor. Maybe I am wrong.

I am very curious how others have solved their cooling issues.

Those CHT's are noticably higher than most folks have, and the oil temp is warm too. Do your baffles seal well? Are the seals turned inward? Did you seal the little tunnel that the inlet ramps form? That can leak a fair amount of oil.

Have you had an experienced RV guy look at your installation? An experienced "eye" might notice something.
 
I'm still a little confused

Your temp measuring system almost for sure is ok.

These guys simply haven't figured out it is the EI that is causing high oil temp. That long, early burn pattern is causing more heat and engine oil is sucking it up.

Long live SLICK mags. :)

My oil temp gauge is in the green but doesn't reach beyond about 160 even in a Florida summer. Should I quit worrying even though it doesn't reach the magic 180 degrees? It sounds like others are in a similar situation.

Bill Near
 
Guys, make sure your baffle seals are really tight, and good RTV seal all the way around. Then, don't hesitate to try a jet one size larger (richer) in your injection unit or carb. Changing the jet one size can change CHT's by over 20 degrees F and oil temps by 20 degrees, too.
I have data to substantiate this. I was running a size 48 jet in my RV-10. In a climb to 10K' in the hot Atlanta weather I was seeing max CHT's of 390 and max oil temps of 189. This is on a 100 hour engine now, so I feel it is broken in. I also had over 250 degrees F from full rich to lean in cruise, so I changed the jet one size leaner. I am now getting CHT's of 420 on the hottest cylinder, and oil temps about 199F before everything starts to drop off in the cooler air around 6-7K'. I actually then start leaning to keep EGT's around 1300 and the CHT's stay below 400, with the oil temp maxing out around 199.

And especially for those of you with carbs, one of the operating procedures I have seen that causes high temps on climbout is this "wives" tale of needing to climb at 25 squared. That's ridiculous. Carbs actually have an enrichment valve in them for operating under full power. It adds extra fuel to the cylinders to cool them. Leave the throttle in full and pull the prop back to 2500 RPM's. Guess what, you would be flying it that way with a fixed pitch prop. :). And yes, you can do the same thing with injected engines. I have always operated mine in this manner.
RV's climb so fast that within minutes you are below 25" of MP. I assure you that you are not harming your engine. In fact, you are treating it better.

Vic
 
I have 6 hours on my ECI o-320 with dual P-mags. Oil temps are hanging around 210-220 and CHT's around 420. That's at 24-2500 RPM (FP). I'd like to see the temps come down a bit and am hoping that it'll start to run cooler soon. I don't see a problem with temps below 230 or so. Seems that 180 would be low and not likely to burn off water vapor. Maybe I am wrong.

I am very curious how others have solved their cooling issues.

Tony, I would suggest ensuring that you are running well rich before doing anything else. O-320s are known for running lean out of the box in RVs. At 6000' or so, <65%, lean off and look at the EGT rise as you lean. You should see at least 150* rise from full rich. If lower, or if there is no rise, you are running too lean, your main jet will likely have to be reamed. The typical size that several people have ended up at is 0.106" diameter - often +0.007" from standard.

Yes, 180* is what you should see on the oil temp gauge - the gauge is not at the hottest point in the circuit, max temp will be sufficiently high to boil off any water.

Pete
 
Tony, I would suggest ensuring that you are running well rich before doing anything else. O-320s are known for running lean out of the box in RVs. At 6000' or so, <65%, lean off and look at the EGT rise as you lean. You should see at least 150* rise from full rich. If lower, or if there is no rise, you are running too lean, your main jet will likely have to be reamed. The typical size that several people have ended up at is 0.106" diameter - often +0.007" from standard.

Yes, 180* is what you should see on the oil temp gauge - the gauge is not at the hottest point in the circuit, max temp will be sufficiently high to boil off any water.

Pete

Thanks Pete. I do see a significant rise of EGT when I lean. I have only leaned on the most recent flight. It didn't really seem to affect the oil temps which were around 205 or so at the time. EGT went from around 1200 to over 1300. I wasn't too aggressive but the next flight I will make this my objective. I am going to take a closer look at my baffles as well. They look pretty tight but it's possible there's a leak. The intake ramps seem to be a possible area. Most people have told me it "would run hot" for the first 10 hours. I am not sure about that. In any case it's time to start looking at cooling it down.
 
Guys, make sure your baffle seals are really tight, and good RTV seal all the way around. Then, don't hesitate to try a jet one size larger (richer) in your injection unit or carb. Changing the jet one size can change CHT's by over 20 degrees F and oil temps by 20 degrees, too.
I have data to substantiate this. I was running a size 48 jet in my RV-10. In a climb to 10K' in the hot Atlanta weather I was seeing max CHT's of 390 and max oil temps of 189. This is on a 100 hour engine now, so I feel it is broken in. I also had over 250 degrees F from full rich to lean in cruise, so I changed the jet one size leaner. I am now getting CHT's of 420 on the hottest cylinder, and oil temps about 199F before everything starts to drop off in the cooler air around 6-7K'. I actually then start leaning to keep EGT's around 1300 and the CHT's stay below 400, with the oil temp maxing out around 199.

And especially for those of you with carbs, one of the operating procedures I have seen that causes high temps on climbout is this "wives" tale of needing to climb at 25 squared. That's ridiculous. Carbs actually have an enrichment valve in them for operating under full power. It adds extra fuel to the cylinders to cool them. Leave the throttle in full and pull the prop back to 2500 RPM's. Guess what, you would be flying it that way with a fixed pitch prop. :). And yes, you can do the same thing with injected engines. I have always operated mine in this manner.
RV's climb so fast that within minutes you are below 25" of MP. I assure you that you are not harming your engine. In fact, you are treating it better.

Vic

Any idea how to know which part number jet would be the next size larger? Spruce sells them but lists by part number only.
 
I have 6 hours on my ECI o-320 with dual P-mags. Oil temps are hanging around 210-220 and CHT's around 420. That's at 24-2500 RPM (FP). I'd like to see the temps come down a bit and am hoping that it'll start to run cooler soon. I don't see a problem with temps below 230 or so. Seems that 180 would be low and not likely to burn off water vapor. Maybe I am wrong.

I am very curious how others have solved their cooling issues.

The oil temp sender is near the cooler return line. Actual oil temps in and exiting the engine will be hotter.
Interesting that you have P-Mags like the OP and running hot too.
 
Thanks Vic, I will call them and find a larger one.

What do you thing the optimum oil pressure would be in order to run temps at 180?
 
The oil temp sender is near the cooler return line. Actual oil temps in and exiting the engine will be hotter.
Interesting that you have P-Mags like the OP and running hot too.

That certainly makes sense. I too have the number 180 that sticks in my head as being the target.
 
I worked on my baffles a bit, seal the inlet ramps and adjusted the oil pressure. Temps were better, but still high. At 2500 RPM about 209.
 
Oil Temperature Control

Hi Guys,

I've got a Mattituck IO-360 (with a 90 degree filter adapter), and got interested in the oil temp thing after seeing mine routinely peak out at 165 (lower at endurance power settings) on typical 40 degree days. This caused me to pull my Vernatherm, test operation on the stove, confirm my oil temp probe calibration, etc. My manual says I should have 170 degrees at ambient temps 0-70 degrees, so I wanted a 5 degree boost.

I can understand why some are having problems: there is only a .03" movement of the Vernatherm when cooled from 175 to 165 degrees. I think my Vernatherm was fully blocking the bypass port at 165 degrees. So I installed a .015 arbor shim on the Vernatherm (I ground out a .875 ID shim to 1.0625). Flight test confirmed the temp peaks out at 171 degrees now.

My take-aways from this are:
1. High oil temps are likely associated with a Vernatherm that does not seat properly (allowing hot oil to bypass the oil cooler). I suspect that 3rd party parts like filter adapters cause more problems than OEM.
2. Low oil temps are causes by premature Vernatherm seating (a good problem to have, because a little arbor shim can fix you right up).

IMHO, I think this operation should be looked at and corrected first, and then the oil cooler air can be manually blocked to help get the temps up for winter flying.

Hope this helps fill in the blanks for someone else!
 
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