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BIGGER oil cooler, anyone tried it?

seagull

Well Known Member
For those of us that live and fly in the HOT south west. Keeping oil temps reasonable on full power climb outs requires step climbing, or power reduction. It seems if we could get 20% more efficiency from the oil cooler it would solve the problem.
Does anyone know of another oil cooler that would fit without excessive cowl modifications?
 
For those of us that live and fly in the HOT south west. Keeping oil temps reasonable on full power climb outs requires step climbing, or power reduction. It seems if we could get 20% more efficiency from the oil cooler it would solve the problem.
Does anyone know of another oil cooler that would fit without excessive cowl modifications?

What are your temps avg on climb out and max?
 
What are your temps avg on climb out and max?

I back off RPM at 240f, on a 100 degree day that will usually get me 2000', if I stay at full power it will keep climbing in temp. I have checked the calibration on the sending unit / Dynon with heated oil removed from the engine and the Dynon is accurate.

I have flown it this way for 3 years / 650 hrs, it is manageable, I am looking for an improvement.
 
I back off RPM at 240f, on a 100 degree day that will usually get me 2000', if I stay at full power it will keep climbing in temp. I have checked the calibration on the sending unit / Dynon with heated oil removed from the engine and the Dynon is accurate.

I have flown it this way for 3 years / 650 hrs, it is manageable, I am looking for an improvement.

What does Van's claim for improvement with their newly designed and improved $1900 exhaust system? An expensive solution, I know.

Have not heard anyone making comments about hot oil temps with the 912 IS in the RV-12IS package, yet.
 
Have not heard anyone making comments about hot oil temps with the 912 IS in the RV-12IS package, yet.

The 912is has a completely different cowl. Both radiators are up front, there are NACA scoops on both sides. A lot more area to let air in for cooling.
How much difference is made in oil temp having the muffler spacing 1.2" (legacy with mod), or 3.5" (current 912is), is questionable.
 
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I have a legacy RV-12. I’m considering enlarging the air inlet in front of the oil cooler. Has anyone tried that? I’m reluctant to do it because if it causes more problems reversing the mod will really look ugly.
 
I have a legacy RV-12. I’m considering enlarging the air inlet in front of the oil cooler. Has anyone tried that? I’m reluctant to do it because if it causes more problems reversing the mod will really look ugly.

I have considered the same thing but am not sure the current oil cooler can do much more. Yesterday I added a temporary baffle in the plenum to direct more air to the oil cooler and less to the water radiator. It did its job redirecting the air based on higher coolant temps but didn’t really reduce oil temp.

I have a couple more non invasive ideas to try this week.

I heard Rotax did change the oil cooler part number, I wonder if the new one is more efficient.
 
For those of us that live and fly in the HOT south west. Keeping oil temps reasonable on full power climb outs requires step climbing, or power reduction. It seems if we could get 20% more efficiency from the oil cooler it would solve the problem.
Does anyone know of another oil cooler that would fit without excessive cowl modifications?

I think most of us bit the bullet and moved the oil cooler forward by 1-1.5" by modifying the cowl. There was quite an extensive tutorial on here by one of the super-builders (Joe or Tony?) but the pics might have disappeared it was a long time ago. I did it and was dreading it but recall it wasn't really that bad. Of course if yours is already painted I get the reluctance.

Usually in PHX in summer oil temp will hit 220-230 pretty quickly - cruise climb helps. As does leveling off.

That said I was considering upgrading to the Flightlines and Thermostasis oil system and getting the new cooler at the same time when I hit the 10 year oil line replacement mark.

https://store.vansaircraft.com/886-015.html
 
I think most of us bit the bullet and moved the oil cooler forward by 1-1.5" by modifying the cowl. There was quite an extensive tutorial on here by one of the super-builders (Joe or Tony?) but the pics might have disappeared it was a long time ago. I did it and was dreading it but recall it wasn't really that bad. Of course if yours is already painted I get the reluctance.

Usually in PHX in summer oil temp will hit 220-230 pretty quickly - cruise climb helps. As does leveling off.

That said I was considering upgrading to the Flightlines and Thermostasis oil system and getting the new cooler at the same time when I hit the 10 year oil line replacement mark.

https://store.vansaircraft.com/886-015.html

I DO HAVE the cooler moved forward, also HAVE the Aircraft Specialty Flightlines hoses and thermostatis installed. I have also added a IR reflective shield between the muffler and cooler.
 
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I recently modified the lower cowling fiberglass and moved my oil cooler 1” forward. Prior to that, I tried to improve air flow (extraction) from the lower cowl by adding a temporary “Cowl Flap” like a Cessna 180 series. I didn’t find it to be much help, but perhaps with your elevated ambient temps, it might be of some value. Easy to try. I just used double-sided 3M Body Side Molding tape to hold the angled aluminum in place. Thought being... a Cowl Flap will produce more negative pressure and increase air flow.
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I DO have the cooler moved forward, also the Flightlines hoses and thermostatis. I have added a IR reflective shield between the muffler and cooler.


Hmmmm. I dunno then. Might be worth a shot. If you do it let us know the outcome!

I just did a flight up to 7000' PHX 930 am OAT take off temp was like 95 - oil temps ranged up to 230 high on initial climb out (I leveled off and accelerated) - but even in cruise at 7000' I was still showing 215 at 5500 RPM. OAT was 67.
 
I recently modified the lower cowling fiberglass and moved my oil cooler 1” forward. Prior to that, I tried to improve air flow (extraction) from the lower cowl by adding a temporary “Cowl Flap” like a Cessna 180 series. I didn’t find it to be much help, but perhaps with your elevated ambient temps, it might be of some value. Easy to try. I just used double-sided 3M Body Side Molding tape to hold the angled aluminum in place. Thought being... a Cowl Flap will produce more negative pressure and increase air flow.
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I will add that to my list of things to try.
I did make spacers and longer screws for the bottom 4 cowl screws where the air exits. I lowered it 5/8” creating a bigger exit but didn’t see a change in temps.
 
I just did a flight up to 7000' PHX 930 am OAT take off temp was like 95 - oil temps ranged up to 230 high on initial climb out (I leveled off and accelerated) - but even in cruise at 7000' I was still showing 215 at 5500 RPM. OAT was 67.

It's counter intuitive…. At altitude, air is colder by air is less dense (molecules further apart). High power air-cooled piston engines can easily overheat at altitude...
 
I also HAVE the Aircraft Specialty Flightlines hoses and thermostatis installed. .

That is some new information that I don’t recall you providing when we have communicated directly. It would be very interesting to see if there was any impact on your cooling efficiency if you deleted or bypassed the Thermo stasis valve. I can easily see that it could induce some flow restriction through the oil cooler system.
 
That is some new information that I don’t recall you providing when we have communicated directly. It would be very interesting to see if there was any impact on your cooling efficiency if you deleted or bypassed the Thermo stasis valve. I can easily see that it could induce some flow restriction through the oil cooler system.

I suspect same reasoning for liquid-cooling system not have thermostat as a flow restricting device, and perhaps, point of failure...
 
That is some new information that I don’t recall you providing when we have communicated directly. It would be very interesting to see if there was any impact on your cooling efficiency if you deleted or bypassed the Thermo stasis valve. I can easily see that it could induce some flow restriction through the oil cooler system.

When I added it, (the thermostasis) the ambient was in the 80’s, I saw a 3-4 degree rise but that is very subjective. The oil temp rises fast on takeoff but then virtually stops rising while the thermostat opens and dilutes the hot oil with cooler oil from the canister.
To add the thermostat it involves two additional hoses so the oil capacity increases a little, that may or may not be beneficial.

In the end I like the quicker warmup. From a $$ point of view when calculated over the 2000 hrs of TBO time it gives me an extra 100 hrs of flight time.
 
When I added it, (the thermostasis) the ambient was in the 80’s, I saw a 3-4 degree rise but that is very subjective. The oil temp rises fast on takeoff but then virtually stops rising while the thermostat opens and dilutes the hot oil with cooler oil from the canister.
To add the thermostat it involves two additional hoses so the oil capacity increases a little, that may or may not be beneficial.

In the end I like the quicker warmup. From a $$ point of view when calculated over the 2000 hrs of TBO time it gives me an extra 100 hrs of flight time.

I am fully aware of the benefits, and reasons that people choose to install them. I have done some testing with them in the past so I am also aware of the installation details

You are looking for ideas to help with your oil temp, so this was offered as a potential influence. No guarantee that it would make any difference but it would be very simple to bypass with a couple of union fittings tying the hoses together from each side of the thermal valve.
 
When I trimmed the aft edge of the lower cowling to increase air flow I was surprised to see my CHT’s drop about 5F, but not much reduction, if any in oil temperature. I wasn’t expecting that. I also bolted a couple of air deflectors to the bottom cowling trying to create a low pressure at the cowling outlet. I think I may have set the deflection angle too high creating some turbulence at the outlet actually hindering air flow. Without any wind tunnel data or CFD model, that is just a guess. I am going to flatten the deflectors at oil change and see if it affects the oil temperature. BTW, I also put a thin insulating wrap on my muffler. I know AROTAX advises against that as they say it may lead to corrosion and cracks, but I have to do something. I don’t know if the insulation helps because I have to resolve the deflector angle first.
 
What did Van's do in the redesign on the RV-12IS such tha high oil temps while climbing is no longer an issue?

Will let Scott comment.... but think the distance between the muffler and oil cooler was increased a few inches with the new exhaust pipes.
 
Will let Scott comment.... but think the distance between the muffler and oil cooler was increased a few inches with the new exhaust pipes.

The distance between the cooler and the muffler is increased but I think the more significant change is the fact that the oil cooler is right out in the open on the front of the cowl (below the coolant radiator).
 

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I believe the props pitch setting will also help lower oil temps, I made a blade wrench that enables me to be a lot more accurate, I have it set to 71.4 and have picked up about 150 rpm at climb to around 5200-5250 so the engine is not lugging so much. I'm in S.C. and in the summer it's normally mid to high 90's and I'm just flying local less than 2000' 5200-5300rpm and my oil temp is around 215.
 
Has any of you tried a scavenger tube?

A larger tube - maybe 1.5x diameter of the standard exhaust pipe - wrapped around the smaller hot exhaust pipe would seem to help get the hot gasses out of the cowling? You see the same thing every day - underneath the right side of a Ford F-250 - but you would fabbed up a somewhat smaller second pipe...having a cone inlet around the second tube inlet might also help.

You might look at early Apaches and Beech twins too...it's called an extractor exhaust.
 
The distance between the cooler and the muffler is increased but I think the more significant change is the fact that the oil cooler is right out in the open on the front of the cowl (below the coolant radiator).

The increase in airflow volume going through the cowl looks to be an increase of 300% over the legacy cowl. There is the additional opening for the coolant radiator also 3 additional NACA scoops and louvers, and a bigger exit to accommodate all that.
 
The increase in airflow volume going through the cowl looks to be an increase of 300% over the legacy cowl. There is the additional opening for the coolant radiator also 3 additional NACA scoops and louvers, and a bigger exit to accommodate all that.

Lucky sobs! lol.

can I retrofit that cowling to my ULS?! lol.
 
The increase in airflow volume going through the cowl looks to be an increase of 300% over the legacy cowl. There is the additional opening for the coolant radiator also 3 additional NACA scoops and louvers, and a bigger exit to accommodate all that.

It doubtful that it is that much of a difference.
If it were, the RV-12iS would be quite a bit slower just from the cooling drag difference.

For the purpose of adding a bit more clarity to my other post, the 12iS cowl wasn't redesigned in order to correct a cooling deficiency that exists on the ULS RV-12. It was to deal with the higher cooling requirements that exist in the 912iS, compared to the 912ULS.

There are numerous differences between the two engines that increased the cooling needs for the 912iS engine. One that very few people know about is the cooling of the charging system. Many people know that the 912iS has dual generators that provide for a lot more ships power capability than the ULS has, but few people know that they are cooled by the engine oil. This alone puts a much larger cooling load on the oil cooling system.
There are other differences as well. All which have some increased level of load on the oil cooling.

In very hot conditions, it is normal for oil temps on the iS engined airplanes to get to the upper end of what is acceptable during climb (refer to the Rotax operating manual... short term operation in the yellow range is not a criticle situation).
 
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I do not agree the 912is produces that much more heat than the ULS, especially enough requiring 3X more airflow. Maybe the voltage regulator produces a bit more but it has a dedicated NACA scoop to keep it cool.

The difference in amp draw from the legacy to the current 912is model is probably not 42 amps but I will use that number since it is easy. To produce 504 watts (12 volts @ 42 amps) of power requires .373 hp. That is not creating enough additional heat to consider.

Heat for our purposes is wasted energy, since the 912is is producing the same 100hp as the ULS on the same or less fuel intake it isn’t wasting much energy (producing extra heat).

Heat is a form of energy, you don’t produce it for free, either you use fuel or take from HP to produce it.

The 3X cowl opening area will produce some drag but a cooler running engine is more efficient and that may make up for the small speed loss. There are a few small improvements in the airframe that may also offset the slight speed loss.

I HAVE increased the airflow into the cowl, I DID see a small increase in cooling, I did NOT notice an airspeed loss.

I opened the oil door 1 ½ “, sealed 3 sides so only the front was open. The area of the opening is small about 4.5 square inches. This forced a lot of air over the top of the oil tank and out the cowl bottom taking some heat with it. Clearly not the most efficient method or position for an inlet but it was just a test. I am not going to keep it that way because it looks terrible, I don’t want to cut into the cowl either and mess up a good looking plane. I am going to go in the direction of a more efficient oil cooler.
 
I do not agree the 912is produces that much more heat than the ULS, especially enough requiring 3X more airflow.

I HAVE increased the airflow into the cowl, I DID see a small increase in cooling, I did NOT notice an airspeed loss.

I opened the oil door 1 ½ “, sealed 3 sides so only the front was open. The area of the opening is small about 4.5 square inches. This forced a lot of air over the top of the oil tank and out the cowl bottom taking some heat with it. Clearly not the most efficient method or position for an inlet but it was just a test. I am not going to keep it that way because it looks terrible, I don’t want to cut into the cowl either and mess up a good looking plane. I am going to go in the direction of a more efficient oil cooler.

You are of course free to not agree, but that doesn't make you correct.

It is well known within the industry that the iS engine has higher cooling requirements than the ULS does. One interesting indicator of this is that the oil temp on a 912iS warms up waaay faster than it does on a ULS. 912iS installations do not utilize an optional oil cooler by-pass to speed up oil warm up because even in very cold temps it warms up very quickly without one.

There are many test points for temp. values spelled out in the install manual that must be met. We went through many hrs of testing and iterative modifications to get to the point where the RV-12iS met all of them.

The mod you did with your oil door shouldn't have help at all with cooling because it is adding extra air to the cowl plenum aft of the heat ex changers. This will have the net effect of reducing the delta P (pressure difference) across the radiator and oil cool, effectively reducing their cooling efficiency. So even if you were adding some cooling to the oil with some colder air blasting on the oil tank, your are at the same time reducing the effectiveness of the oil cooler.

One additional tidbit of info.... the louvers on the front top of the RV-12iS cowl aren't for additional cooling in flight. In fact, because of their location (in a rather high pressure area), we don't think there is any outflow during high speed flight. Their purpose is to act as passive vents to let hot air escape when the airplane has been parked and shut down. The ign. coils are directly below the louvers, and there is a max. temp for them that must not be exceeded. The louvers made the RV-12iS meet that requirement.
 
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I started this thread to ask about oil cooler options, it morphed into discussion about ways to cool the engine and now comparing ULS to IS.

At no time was my intent to dispute Van’s research, I only shared my results.

Based on the lack of response nobody has traveled down the path to experimenting with a different oil cooler, I may be the first, stay tuned.
 
Success!

I have added a second oil cooler and the the first test flights were today. Starting at 1570’ I climbed to 7500’ continuous at 600fpm, oil temp never exceeded 220f. OAT 85f.
The same flight was done with the second cooler blocked and I got to 5000’ with 245f oil temp.
 
I have added a second oil cooler and the the first test flights were today. Starting at 1570’ I climbed to 7500’ continuous at 600fpm, oil temp never exceeded 220f. OAT 85f.
The same flight was done with the second cooler blocked and I got to 5000’ with 245f oil temp.

Is this a modification worth posting pictures of your install and putting it under the Modifications thread at the top of the RV-12 section, for our warm weather RV-12 owners?
 
I am creating a blog of modifications I have made to the -12. The additional oil cooler will be first up. I can get into more detail, add pics and descriptions on a blog better than I can do here. I'll try to get it going in the next week and link it in my signature.

As I put more hours on this modification I am convinced it is a worthwhile improvement for those that fly in hot weather.
 
First I read this thread.

I was expecting Dan H to weigh in by this point.

Has anybody "tested" their oil cooler installation by using a manometer or Magnahelic ahead and behind of the cooler core.

Proper radiator choice involves more than just # of rows and size.

The manufacturer has important specifications that are overlooked by the typical user. "Happy wife, happy life" so to speak.
 
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I am creating a blog of modifications I have made to the -12. The additional oil cooler will be first up. I can get into more detail, add pics and descriptions on a blog better than I can do here. I'll try to get it going in the next week and link it in my signature.

As I put more hours on this modification I am convinced it is a worthwhile improvement for those that fly in hot weather.

There is more information on the additional oil cooler mod here;
http://waltsrv12.com/engine/adding-second-oil-cooler
take a look around at some of the other things I have done.
 
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