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Oil Temps too High

I monitor the oil temps in three spots. The sump, the cooler output and the filter adaptor. I see oil temps in the sump run ~ 230 to ~ 245f. Temps at the cooler output run ~ 185f and temps at the filter adaptor run ~ 180 to ~ 220f depending of flight and OAT.

Randy, any chance your sump sensor (installed in a tapped hole the oil screen cap?) is seeing some radiant heat from the exhaust? Your sump numbers look high.

There's a theory that the sensor length could have an effect on the oil temp reading, reading closer to the sump oil temp and less at the cooler return temp which are close to each other in the adaptor.

I suspect it's true. The two flows are assumed to mix before the sensor, but under some conditions I suspect they remain separated or only partially mixed until entering the filter.
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For a 1/8" thermocouple, the insertion is 1.2-2" and the reading will be pretty accurate. That is probably not what you are using, but a reference for you.

Oil temps of relevance to an engine designer.

1. Sump Temps - this will affect how long the oil will last. Oxidation being the primary variable. Typically 250F to an absolute max of 270F for long life 350hrs +. Synthetics can be higher.

2. Oil to bearing temperatures - this relates to viscosity per the reference tables and minimum oil film thicknesses. Lycoming and Conti engines run pretty high bearing cross section pressures, but good L/D ratios. At cruise, the loads are much lower (NA engines) and oil cooler.

3. What single number will allow a user to keep out of trouble - varies. This is where each design has the guidelines for an operator.

254F in a sump sounds high but if the oxidation levels measured in an oil analysis are within range, then this alone is not cause for concern. It can go higher, but keep in mind that oxidation rates will double for every 10C.

To the OP, I would recommend inspection my a builder with some experience in cooling to inspect. Like the ends of the air inlet "diffuser" typically allows a lot of air to escape. Rope foam can be used to seal that and make a huge difference.

Also, timing can be a large factor, esp with piston cooling jets like this angle valve. We are seeing this installation though the OP eyes and good/bad things will be filtered. If he knew what he was seeing, he would have fixed it.

If it is to be solved in the forum, then more information is needed. Pictures (many) of oil cooler, baffles, intersection baffles and of the oil cooler hose supply return. Also, models of mags or ignition.
 
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Randy, any chance your sump sensor (installed in a tapped hole the oil screen cap?) is seeing some radiant heat from the exhaust? Your sump numbers look high.

I suspect it's true. The two flows are assumed to mix before the sensor, but under some conditions I suspect they remain separated or only partially mixed until entering the filter.
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No, my exhaust isn't very close to the sump or the sensor. But at the point where I have the sensor it's where the hot oil would flow the most. Also, for those that use a cold induction system, remember you no longer have cold air flowing through a sump under the hot oil.

Concerning the sensor depth, I think I'm going to test that theory. I'll look for an adaptor to raise the sensor up maybe 1/2 ~ 1" and see how that effects the reading.
 
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For those that want to see the relative oil temps (as my engine shows) here's the graph of a flight a few days ago. Pink=Sump, White=Adapter Sensor, Green=Cooler return.
Cold engine - Flight to fuel stop.
Oil-temps-2.png


This was a hot engine on a fuel stop.
Oil-temps.png



Now, here's a pix of the sensor in the filter adapter. Seeing as it's far out of the flow I no longer subscribe to the length theory.
Sensor.jpg
 
Randy, any chance your sump sensor (installed in a tapped hole the oil screen cap?) is seeing some radiant heat from the exhaust? Your sump numbers look high.



I suspect it's true. The two flows are assumed to mix before the sensor, but under some conditions I suspect they remain separated or only partially mixed until entering the filter.
.

Thank you Dan for providing this schematic. I am wondering if it is possible for the oil pressure to push the valve of the Verntherm open slightly. I am assuming the function of the spring in the Verntherm is that it can be pushed back with enough force?

My situation is that I believe my oil temp, for the same condition, is slowly creeping up compared to a year ago. The difference in the oil temp is around 10F so it is not great but it is higher and have been looking for the cause.

I have checked the airflow thru the cooler and have actually increased that by going to a 5" scat tubing in place of the 4". Double checked timing, checked the temp sensor as well as Vernterm and they all checked out. I did not push the valve by hand to see if it it opens up easily or not. I am not sure what else could cause this creeping up the temp.
 
For those that want to see the relative oil temps (as my engine shows) here's the graph of a flight a few days ago. Pink=Sump, White=Adapter Sensor, Green=Cooler return.
Cold engine - Flight to fuel stop.
Oil-temps-2.png


Now, here's a pix of the sensor in the filter adapter. Seeing as it's far out of the flow I no longer subscribe to the length theory.
Sensor.jpg

Randy, that's a thought-provoking pair of illustrations.

Consider...if the vernatherm bypass is closed (vernatherm extended firmly enough to seal), the white and green plots should be very close.
 
Thank you Dan for providing this schematic. I am wondering if it is possible for the oil pressure to push the valve of the Verntherm open slightly. I am assuming the function of the spring in the Verntherm is that it can be pushed back with enough force?

The vernatherm is designed to be against the seat at 185F. Further extension of the wax pellet cylinder compresses the spring. The Rosta drawing says cracking pressure is 60-90 psi at 195F. It also says the spring force is 15-20 lbs at .050" compression from the at rest position against the tip nut.

The nominal bypass hole is (I think) 0.56"D, so we have 0.246 sq in. The 60 psi cracking pressure x 0.256 is 14.8 lbs, a likely spring pressure at initial seat contact.

So, my guess is deltaP would have to be pretty high to push the spring loaded tip open when oil is hot/low viscosity. The worst cooler for pressure drop is the 8324 double pass at about 15 psi.

Here we assume (1) the seat and valve cone are in good shape, and (2) the dimension from the vernatherm seal surface to the seat is correct.
 
Just to add some more data points to this thread, I have flown multiple RV-14's that have been built to stock, including the factory airplane, which I flew for about a year and a half. I just completed 12.8 hours on a brand new RV-14. ALL of them seem to exhibit the same temps: Climbing on a REALLY hot day with a new engine will yield oil temps around 220-222 at TOC, and then settles out in the 190's in cruise, with high OAT's.

At normal Oregon OAT's, I see the oil temps topping out in the high 190's and then back into the high 180's-low 190's depending upon power settings.

Playing around with the cooling air, especially making sure there are NO leaks at the front where the top and bottom cowls meet, seems to directly affect the temps.

Frankly, I don't see a problem with these temps. It ensures the oil really does burn off all of the water, and there's nothing wrong with running the temps in the mid 180's-mid 190's in cruise.

Personally, I think the IO-390 oil temp runs hotter. It is certainly noticeable in that the oil warms up much more rapidly after startup than any of the other RV's I have flown.

I don't think it's anything to fret about. Just my opinion.

Vic
 
Thank you Vic for chiming in on your experience with RV14/14A which matches very closely to the temps I see.

One other data point that I can provide, which has been a bit disappointing, I recently upgraded from a 4” to a 5” scat tubing to the oil cooler and was hoping to have a very noticeable effect. Sadly the result has been minimal in reducing the oil temp. My CHTs have gone up a bit, around 20 Degrees and now in cruise are about 330-340 but my oil temp, either in a steady climb or cruise has not been reduced significantly, perhaps 5F. My oil temp will reach a 215-220F when climb to 12000 from seal level and lower if I reduce the rate of climb to 500 FPM and in cruise will be in the 185-195 depending on OAT. My typical power setting is WOT and 2500 RPM.

I just checked my oil temp sensor accuracy, Vernterm operation, PMAG timing and my cowl baffles are pretty tight. I don’t know if it is worth checking the oil cooler or not.

I would be very interested in ways to lower the temp if all possible.
 
Here is an example flight in my RV14. I like to upload my G3X files to Savvy and break down the data there. I was doing performance measurements at 500' increments 6500-8000' density altitude at various power and RPM settings. Ground temp was about 95 degrees; high pressure clear day.

My #2 CHT was high; since then did cowl rework and baffle work and now it is sig lower; still the highest though.

The high temp was 2500 RPM, the low temps at 2300 RPM. The up and down correlate directly to my power setting. I like to cruise at 2400 WOT most of the time now, and with that my oil temp is 188-190 every time. You can see in my data 2500 WOT has oil temp at 200, and 2300 WOT has oil temp around 185. There is a lag between reducing power and oil temp coming down. Oil temp goes up pretty quick when power goes up. This was a lot of engine change so I think it shows the high end of my temps, especially given the Louisiana summer day it was taken.

My temps are a lot lower in cruise at 14-16000' but I don't have a graph of that handy. 2400 WOT at 16000 temp is around 180.
 

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Thank you Vic for chiming in on your experience with RV14/14A which matches very closely to the temps I see.

One other data point that I can provide, which has been a bit disappointing, I recently upgraded from a 4” to a 5” scat tubing to the oil cooler and was hoping to have a very noticeable effect. Sadly the result has been minimal in reducing the oil temp. My CHTs have gone up a bit, around 20 Degrees and now in cruise are about 330-340 but my oil temp, either in a steady climb or cruise has not been reduced significantly, perhaps 5F. My oil temp will reach a 215-220F when climb to 12000 from seal level and lower if I reduce the rate of climb to 500 FPM and in cruise will be in the 185-195 depending on OAT. My typical power setting is WOT and 2500 RPM.

I just checked my oil temp sensor accuracy, Vernterm operation, PMAG timing and my cowl baffles are pretty tight. I don’t know if it is worth checking the oil cooler or not.

I would be very interested in ways to lower the temp if all possible.


I think you are not going to get any better. The temps match what I have seen across multiple 14's with IO-390's.

Vic
 
One thing to keep in mind when comparing oil temps between different RV's is that even if they are the same model and engine configuration, differences in oil temp will be fairly common.

A primary reason for this is the differing levels of ring seat that occurs on different engines.
A major factor on steady state oil temp is how well the rings seal in the cyl. The seal is not 100% in even the best engine, but some engines are less optimal than others.

The hot blow-by gases are going directly into the oil sump and can have a noticeable influence on oil temps. It is not uncommon for there to be a noticeable change in oil temp (sometimes higher, sometimes lower) from what was previously the norm, after replacing an engine with a different one (or one that has been overhauled) but changing nothing else on the engine installation.
 
I am not sure if this has already been mentioned.

My oil temps were reading a little high so the first thing I did was compare the temperature measured through my Dynon to the temperature of the oil in the sump immediately after landing, using a long steel thermometer.

I realise that the locations of taking the sample would mean some difference but here was enough of a difference that I then replaced the oil temperature sender, which happily resolved the matter.

So FWIW before disappearing too far down the rabbit hole I would suggest checking the source of your data.

Good luck
 
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One thing to keep in mind when comparing oil temps between different RV's is that even if they are the same model and engine configuration, differences in oil temp will be fairly common.

A primary reason for this is the differing levels of ring seat that occurs on different engines.
A major factor on steady state oil temp is how well the rings seal in the cyl. The seal is not 100% in even the best engine, but some engines are less optimal than others.

The hot blow-by gases are going directly into the oil sump and can have a noticeable influence on oil temps. It is not uncommon for there to be a noticeable change in oil temp (sometimes higher, sometimes lower) from what was previously the norm, after replacing an engine with a different one (or one that has been overhauled) but changing nothing else on the engine installation.

Scott,
This is possibly the best explanation for my situation and possibly one of the differences between RV of the same type/setup.

One of the reason that I have been on the quest to reduce my oil temp is the perceived notion that my oil temp has been steadily go up since the beginning of flying or compared to a year ago. I do remember just shortly after phase I, was climbing straight to 12000 and oil temp hitting 212F which I thought it was high. Now, 100 TAC time hours later and close to the same condition, I can hit around 218-220F.
on the annual which is coming up very soon, I will be checking my compression test and be interested to see if that has changed any. Of course we are talking only not a great degree of difference in oil temp.

If of any interest to you, the 5" scat tubing did not make much difference for my temp.
 
I was considering changing the oil cooler scat setup - now I'm going to keep it the same. Thanks for saving me a lot of hassle.
 
If of any interest to you, the 5" scat tubing did not make much difference for my temp.

While developing the FWF for the EXP119 engine we wanted to try and balance relationship of the oil temp to the CHT's a little better.

We did a lot of very detailed flight testing as we worked through the design and changing to the 5" SCAT did provide a measurable reduction in oil temp (it was the only thing changed at the time we did the comparison testing.

It wasn't a huge reduction (I don't remember the delta right now) but it was enough that we didn't just discount it as being a slight data variation on one test flight.
Granted, we didn't do any testing with it using the original cowl configuration, just the new cowl with the cowl flap in the open position.

This should be very similar to the original cowl as far as gross airflow and pressure differentials go so we fully expect it would make a detectable difference, but like I said there wasn't and detailed testing done on the old cowl configuration so maybe that is a factor.
 
While developing the FWF for the EXP119 engine we wanted to try and balance relationship of the oil temp to the CHT's a little better.

Scott,
While my numbers are not scientific and under exact condition, my best guess is about 5F decrease in oil temp both in cruise and climb to 12000 AGL which has been my semi standard test case.

But my CHT has gone up and I am actually happy about it. With my pervious setup, I would often see in the upper 290-305 range CHT in cruise.

JDA_BTR
The change to 5" scat tubing was really not that much work. I end up keeping the rear baffle and just cut the hole to the size. I have oil cooler shutter and wanted to keep that, so there was a bit of work to create a new 5" shutter. The cost was about $150 of the parts , if you were interested.
 
Scott,
While my numbers are not scientific and under exact condition, my best guess is about 5F decrease in oil temp both in cruise and climb to 12000 AGL which has been my semi standard test case.

But my CHT has gone up and I am actually happy about it. With my pervious setup, I would often see in the upper 290-305 range CHT in cruise.

JDA_BTR
The change to 5" scat tubing was really not that much work. I end up keeping the rear baffle and just cut the hole to the size. I have oil cooler shutter and wanted to keep that, so there was a bit of work to create a new 5" shutter. The cost was about $150 of the parts , if you were interested.

Lowering the oil temp and raising the CHT was the expected change with the larger cooler SCAT.

Has your oil cooler shutter been installed since first flight? Reason I ask is they can be more restrictive to air flow to the cooler than a lot of people would think. If it is something other than a traditional throttle plate (round plate rotating within a cylindrical passage, which has nearly zero resistance), you could do a test flight with it temporarily removed. You might be surprised with the results.

We do not use an inflight adjustable oil cooler air control on the company demonstrators. We have block-off plates we install over the SCAT attachment hole in the rear baffle during cold weather that reduces the hole diam. to about 2".
 
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Lowering the oil temp and raising the CHT was the expected change with the larger cooler SCAT.

Has your oil cooler shutter been installed since first flight? Reason I ask is they can be more restrictive to air flow to the cooler than a lot of people would think. If it is something other than a traditional throttle plate (round plate rotating within a cylindrical passage, which has nearly zero resistance), you could do a test flight with it temporarily removed. You might be surprised with the results.

Correct Scott, I have had the oil cooler shutter from the beginning and as you said, removing it had had near zero affect on the oil temp, tried it before went to the 5" scat.
The setup is exactly as you have described it and I have incorporated into the 5" scat with the same type configuration.
 
Scott,
While my numbers are not scientific and under exact condition, my best guess is about 5F decrease in oil temp both in cruise and climb to 12000 AGL which has been my semi standard test case.

But my CHT has gone up and I am actually happy about it. With my pervious setup, I would often see in the upper 290-305 range CHT in cruise.

JDA_BTR
The change to 5" scat tubing was really not that much work. I end up keeping the rear baffle and just cut the hole to the size. I have oil cooler shutter and wanted to keep that, so there was a bit of work to create a new 5" shutter. The cost was about $150 of the parts , if you were interested.

Mehrdad, I struggle to keep my CHTs above 300 in cruise. What are you seeing now with the 5" scat tubing?

-Rick
 
Mehrdad, I struggle to keep my CHTs above 300 in cruise. What are you seeing now with the 5" scat tubing?

-Rick

Rick,
My CHTs are in the 320-330 range in cruise and 360-370s in steady climb. I had the same numbers as yours and that is why I didn't mind going to the 5" scat tubing.
 
5" SCAT Mod

All,

I have 20 hours on my new IO 390. I have been concerned about the oil temps. First flight I saw a steady 225 at 75% power cruise, 4500'. I spent a lot of time sealing baffles and on last flight I had 211 at 75% power cruise, 4500'. What concerns me is I cant seem to get temps much lower at other power settings. 24 squared gave me 207. And 23 squared gave me 210! (I attribute that to the slower speed and reduced airflow). CHT's have been around 320 or a little lower in cruise. OAT at altitude has been around 60 for most flights. EGTs around 1220 running full rich. Leaning at all results in increased oil temps.

The ONLY time I see oil temps below 200 is on final and after landing (197 degrees). Last flight, immediately after the prop stopped, I had a helper shoot the oil filter with a thermal gun and it read 196. Oil temp sensor showed 197. I am comfortable that my oil temp probe is accurate based on that check.

I ASSUME that my vernatherm is working correctly since it is a new engine. Thoughts?

I ordered the 5" SCAT modification kit from Vans and it arrived yesterday. It did not include part # FF-01406C (Oil Cooler Inlet Sides). I didn't want to drill out rivets and destroy the 4" transition so I ordered another 1406C. It should be here Thursday and I hope to install it this weekend.

I'm hoping the 5" SCAT helps, but based on previous comments I am going to have to wait and see.

Cowling and everything is stock. No cowl flaps, etc. Neither wheel pants nor gear leg covers are installed so there is some airflow leaving the cowling around the gear leg cutouts (taildragger).

My friend with an RV-14 thinks my temps are way out of where they should be and he swears he was seeing 185-195 in cruise during his break in sorties. He has the 4" SCAT AND cowl flaps.

I'm not ready to mod the cowl yet but I guess that is next if the 5" SCAT disappoints.

Any comments would appreciated.
 
5" SCAT Mod

Tom,

Thanks. I will look for the area behind #3 cylinder you mentioned. I don't recall sealing anything there.
 
I would add that you should see lower temps when you install gear leg fairings and wheel pants. Their installation will add between 10 and 15 knots of airspeed (= cooling) for the same power settings.
 
Locations on the baffles that others have suggested you check/seal are good, but the best investigation process is the use of a flash light in a darkened hangar.
Shine the light from below, along the entire perimeter where the baffling interfaces with the engine. There should be no light able to pass from one side to the other. If there is, seal it up.
Also confirm there is a good seal between the baffle seals and the top cowl by looking for uninterrupted rub marks on the cowling (some portions of this can also be checked with the light method if you have a helper).
 
All good suggestions especially Keith's about gear leg.

I have sealed my baffles meticulously and had the same issue with the baffle materials flipping inward around the Governor, a blub of RTV now works as a retainer to keep it in place. My oil temp is not as high as Rob and have installed the 5” scat mod with rather small decrease in oil temp. I also created a diffuser for the exit portion of the oil cooler with very little, if any, affect. I has been removed it since it was ineffective.
I am very interested to see the result of 5” SCAT tubing in Rob test.
My next annual is coming up next month and be interesting to see if there is an appreciable compression change to account and support ideal of hot gases escaping the cylinder and adding to the oil temp.
 
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EXP-119 oil temps

Reading numerous posts it seems the larger 5 inch scat has had little effect at lowering the oil temps.

Wondering if the new "exhaust ramp cooling flap system" on the new EXP-119 package combined with the redesigned lower cowling have a greater effect at cooling the oil or does a cowl flap primarily effect mainly just the CHT's?


Curious,
Jim
 
Reading numerous posts it seems the larger 5 inch scat has had little effect at lowering the oil temps.

Wondering if the new "exhaust ramp cooling flap system" on the new EXP-119 package combined with the redesigned lower cowling have a greater effect at cooling the oil or does a cowl flap primarily effect mainly just the CHT's?

Curious,
Jim

It would control pressure in the lower cowl. DeltaP (upper vs lower) dictates mass flow for both cylinder fins and oil cooler.
 
5" SCAT Mod

Tom and others,

I thought I found the smoking gun on the high oil temp. I failed to RTV any of the baffles at the base of the cylinders. I spent an hour or so caulking those and then used a light to look for holes. I flew today expecting lower oil temps, BUT NO! OAT was about 10 degrees warmer (62) than previous flight (52) and oil temps were 7 degrees hotter than last flight!! Here are my numbers at 21.5 hours on the engine.

75% Power, MAP 24.2, RPM 2500, Full Rich, 4500'
OIL 217
CHTs 333, 340, 311, 309
EGTs 1215, 1200, 1245, 1235

71% Power, MAP 24, RPM 2400, Full Rich 4500'
OIL 212
CHTs 330, 345, 309,307
EGTs 1215, 1195, 1240, 1230

I have no confidence the 5" SCAT mod I'm going to do this weekend will help.

Van's site says to check the operation of the Venatherm if CHTs are normal (or low) and oil temps are high but they don't tell you how to check it. So, how does one CHECK the Vernatherm?

I'm about ready to order a new temp sensor, Vernatherm and oil cooler and just replace all components.

Also, I bought a bore scope thing to look at the baffles under the cowl and they are all folded the correct direction and making contact with the cowl. No obvious issues with baffle/cowl contact.

Thoughts again?
 
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Bob,
It is a good idea to check both the sensor and Vernatherm but I am not too optimistic to find issues with those.
Both are rather easy to check, I did both of them and they checked out right on the spot. I pulled the temp sensor and put it in the hot liquid while still connected and had a thermometer in the same jar of hot liquid. I also bought another sensor and compared it and both were right on the money.

I pulled the Vernatherm and put it in pot and slowly brought it to boil. You measure the length it increases at different temps. At 212F, it should increase by around .244” and also I made sure that it is seating in place and fully closes the passage when closed. Again, mine was right on the money.

With these engines, I think you will need to aim for incremental improvements rather a big jump. The 5” scat tubing will help but won’t bring it to 180 or 190 if you are expecting that.

If you have not double checked your timing, I would highly suggest to do that. I have PMAG and if I reduce the advance to 4 degree instead of 10 in the air, I see a change in oil temp within just a couple of minutes.
 
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Emag Timing

Mehrdad,

Can you expand on your emag timing comment? Does reducing the advance lead to higher temps or lower temps? I am running dual emags, jumper installed, set at TDC (or very close to it). Reading the emag manual, I can set the mags up to 6 degrees after TDC to "reduce the advance further." What would you recommend trying to reduce oil temps?
 
Mehrdad,

Can you expand on your emag timing comment? Does reducing the advance lead to higher temps or lower temps? I am running dual emags, jumper installed, set at TDC (or very close to it). Reading the emag manual, I can set the mags up to 6 degrees after TDC to "reduce the advance further." What would you recommend trying to reduce oil temps?

Bob,
If you have set your timing at TDC, that is incorrect and you are advancing about 15 degrees instead of the 10 with the jumper in. This certainly yield a higher oil temp and I believe it may account for your situation.

Please note that PMAG, unless it is reprogrammed, fires at 25BDC by default which is for most 320/360 engines whereas IO390 timing is at 20BDC. So, you will need to either reprogram your PMAG or retard the timing set by around 5-6 degree which is the easiest.

To answer your question, reducing the advance, lowers the oil temp. I have EICommander and can change the timing in the air.

If any further question on this, we can talk for further clarification.
 
Mehrdad,

Thanks. I will adjust timing and fly again later today. Fingers crossed.

I will post my results.
 
Mehrdad,

I was finally able to get in the air again. I clocked the emags at 5 degrees after TDC (retarded 5 degrees) as discussed previously. Jumpers in. Unfortunately it had little if any impact on oil temps. Here is my data from todays flight:

Alt 4500'
OAT 55 degrees (8 degrees cooler than last flight)
MAP 24.0
RPM 2400
Mixture Full Rich
OIL TEMP 210 (2 degrees colder than last flight)
CHTs 334, 344, 308, 309
EGTs 1230 1195 1240 1240

Next step is to install the 5" SCAT, but am not getting my hopes up for lower oil temps.

Temp Probe was tested by shooting oil filter with temp gun after landing. Filter showed 196 and oil temp on gauge was 197.

I have not removed vernatherm for testing. Considering new oil cooler also.

I will report back after the 5" SCAT install and test.
 
Rob,
Thank you for reporting back. The 5 degree retard was certainly needed to set the timing correct for this engine but I was hoping to have a bigger impact on your oil temp, sorry it did not.

Considering your CHTs are also higher from what I would expect them to be and compared to most RV14s , especially for the relatively low OAT, it may also be good to look at your baffling. The 5” scat tubing ought to help but please keep in mind that I will also affect your CHT.

Some other random thoughts that you might want to do,
- Do a compression check to see if there is possibly some excess gas/heat is passing your rings
- Check your oil temp in the sump right after landing and compare to oil temp reported by the sensor
- Double check your baffles
- Do you have your wheel pants/fairing installed, if you are slower than this could affect your temp
 
Probably it would have been considered in developing the -EXP119, but would a larger oil cooler be helpful/practical? Or just expose my ignorance on the subject? Airflow Performance makes 15 and 17 row coolers, in addition to the 2006X. Also, the company's website advises "Go up one size for piston squirters, cold air induction, aerobatic and/or float plane applications."
 
I'm sure this isn't the issue causing the higher oil temps but after reading about higher temps with the wheel fairings off (less airflow) I thought I should mention this just in case. When I thought I had completed the fiberglassing/sanding of the the cowl inlet holes, I stepped back to take a look and to my surprise, the left inlet was much wider than the right. After many hours of re-forming the holes etc, I ended up with 2 even holes but both were, what I considered, much larger than the original. I haven't flown mine yet, so I can't offer a comparison.
 
5" SCAT Installed - Little Change

I installed the 5" SCAT tube to the oil cooler using the Vans supplied parts. I saw no change in oil temps at cruise, however, slower speeds in the pattern had lower oil temps (around 195-205).

Data for todays flight (25 hours on IO-390)
OAT 53
ALT 4500 MSL
MAP 24
RPM 2400
Mixture - Full Rich
Oil Temp 212 (No change from 4" SCAT)
CHTs 325, 315, 298, 299
EGTs 1210, 1185, 1225, 1225

My frustration with high oil temp remains. Here are my takeaways at this point.

1) Oil Cooler airflow is maxed out at cruise. The 5" SCAT had zero impact to oil temps or CHT's . The 4" SCAT was providing the max airflow that could make it thru the cooler at cruise. Maybe a little lower oil temps in the pattern while doing touch and go's with the 5" SCAT, which may be worth it.

2) I have RTVed every seam, crack, hole, etc around baffles. Multiple tubes of RTV and multiple sessions. Nothing changed in oil temp although CHT's have been lowered.

3) Oil temp sensor has been verified with testing.

Something seems to be regulating the oil temp around 210 degrees at cruise power settings. In my mind either the vernatherm is not working at the proper temp or the oil cooler has restricted oil flow.

So, I need your votes on whether to replace the vernatherm or the oil cooler next?
 
My oil temps were very similar around 212 in cruise. Only within the past 5 hours have the temps started to normalize. I now have 68 hours, standard 390, dual Pmags.
 
My oil temps were very similar around 212 in cruise. Only within the past 5 hours have the temps started to normalize. I now have 68 hours, standard 390, dual Pmags.

RobB52, I was thinking about break-in when I saw the above comment. With only 25 hours on the engine, isn't there a good possibility that it's still breaking in and the temps will fall after more time? I seem to remember reading somewhere that it's not unusual for this engine to still be breaking in up to the ~50 hr point.
 
Thanks for the comments. I am going to press on with the break in and re-address after 50 hours and changing out the mineral oil.
 
Rob I wouldn't change anything just yet, definitely wait a while until the engine is broken in completely. My last flight at 9000 feet and 64% power had a steady 190 degree oil temp. I have the standard 4" tube and dual PMags and 128 hours on the engine.
 
Rob,
I to am right there with Chris, I have about 135 hours on a very standard build. I have one P-Mag and my temp's are always 185-191.

Thanks,
Heywood
 
Oil Temp Lower with Wheel Pants

Y'alls advice and patience has produced good results. I finally completed my wheel pants and first flight with them was today. I gained 16 KIAS at 24 squared, 5000', and oil temp was 15 degrees lower.

45 total hours on airframe.

Speed increased from 142 KIAS to 158 KIAS and oil temps decreased from 214 to 199. OAT's were similar.

Still on mineral oil. Changed at 40 hours. I wasn't convinced oil consumption had stabilized but it appears to be holding around 6.25 quarts now.

Thanks for all the inputs.
 
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