[00Dan]

I'm looking to further optimize my oil cooler setup, in a ROP cruise I'm seeing temperatures between 210-220 *F at OATs of around 40*; CHTs in this cruise regime are 380-390*; my engine is a parallel valve 320 with piston squirters. My cooler is a 7 row Aero Classic (PN 8000075) supplied by -8 hoses, mounted on the firewall and fed by a 3" SCAT run from the rear baffle above the left side of the case. The cable actuated door under the cooler exhaust vents to the cabin for a form of marginal cabin heat. As the attached photos show, this is a decidedly non-standard mounting solution. The cooler is getting oil and air, easily proven by moving the door to vent the cooler to the cabin rather than the lower plenum, and seeing the oil temperature increase rapidly. Placing my hand by the vent tells me the cooler is warm, although there isn't much air going through it. Of note, cylinder #4 is typically my coldest cylinder.

Any input as to potential solutions here that could make this setup workable are welcome. I'm so far leaning towards 3D printing a bell mouth for the inlet and maybe a better transition piece for the cooler face. Moving to a 4" SCAT would be tricky with how the baffling is trimmed, and would need to be off #4 most likely, as there isn't sufficient room where the existing 3" duct flange is.

 

[Aden Rich]

I will be quite honest with this setup. It's not optimal at all. You are forcing the oil cooler air back into the pressurized chamber behind the engine. It (the air in the oil cooler) has to overcome the pressure to go back outside the discharge side of the oil cooler chamber and turn 90 degrees to get out and go down and out the exhaust duct. I would get rid of this entire setup and go with a smaller 13 row Setrab oil cooler mounted on the baffling behind #4 cylinder. I can send you some installation pics on my RV-6 that should work on your -4. And before the folks come out of the wallpaper- yes, I said "Setrab" oil cooler, not Harrison or the other style aviation oil coolers. Have installed 6-7 of them with better results than the heavier, bulkier, baffling cracking Harrisons (and clones). The installation is tighter and cleaner, takes up less space behind the cowling and weighs less. Too boot, it works better too! Proven time and time again with flight testing. Even in back East 100 degree plus temps all summer long. Properly installed, that cooler will outperform the others. If interesting, text me at 425-238-0075 and I will shoot you some installations.

 

[YellerDaisy]

Yep, some improvements can be made to your setup.

I previously had an O-320 in my RV-4 and always fought high oil temperature. I had the old style cooler on the baffles and later moved it off the baffles and added an expanding duct. It didn't make much difference. When I installed the O-360, I purchased a new 10-row cooler and 3D printed a duct. The location of the cooler and shape of the duct is certainly not ideal but we work with what we've got. The duct has internal vanes to assist the air with making turns that it doesn't want to make. The result is oil temperature than very rarely moves off of 180-185 degrees. The success may have more to do with the different engine that the new oil cooler and/or my printed duct, I don't know. I just know I'm satisfied.

The PA6-GF30 filament (30% glass fiber reinforced Nylon 6 Copolymer) is holding up very well and has about 140 hours of time on it.

These are early 'during design & installation' photos. Oh... I should note that I was learning 3D modeling and had great difficulty getting the software to do what I had in my head. Someone that knows what they are doing could probably model a much better solution.

The following blog posts document the oil cooler and duct installation.
https://jdfinley.com/lycoming-oil-cooler-duct/
https://jdfinley.com/rv-4-cowling/
https://jdfinley.com/new-rv4-engine-runs/

 

[PaulvS]

I'm looking to further optimize my oil cooler setup, in a ROP cruise I'm seeing temperatures between 210-220 *F at OATs of around 40*; CHTs in this cruise regime are 380-390*; my engine is a parallel valve 320 with piston squirters. My cooler is a 7 row Aero Classic (PN 8000075) supplied by -8 hoses, mounted on the firewall and fed by a 3" SCAT run from the rear baffle above the left side of the case. The cable actuated door under the cooler exhaust vents to the cabin for a form of marginal cabin heat. As the attached photos show, this is a decidedly non-standard mounting solution. The cooler is getting oil and air, easily proven by moving the door to vent the cooler to the cabin rather than the lower plenum, and seeing the oil temperature increase rapidly. Placing my hand by the vent tells me the cooler is warm, although there isn't much air going through it. Of note, cylinder #4 is typically my coldest cylinder.

Any input as to potential solutions here that could make this setup workable are welcome. I'm so far leaning towards 3D printing a bell mouth for the inlet and maybe a better transition piece for the cooler face. Moving to a 4" SCAT would be tricky with how the baffling is trimmed, and would need to be off #4 most likely, as there isn't sufficient room where the existing 3" duct flange is.

Picture #4 shows some of the baffle seal material and that indicates another item to consider as part of the optimization. I'd be surprised if there aren't leaks that are stealing cooling air from the oil cooler and the cylinder fins e.g. the back corner may not be sealing properly against the cowl and it looks like there are gaps where the rubber sheet has puckered up between the fasteners. How does the rest of the cowl baffling look?

 

[Freemasm]

With the limited info available, I agree with Mr. Rich. Chances are your setup provides plenty of mass flow; I would guess that it's not letting the air our (creating enough delta P). I'd try a temporary on the cooler outlet side down to cowl exit before I tried anything else. Keep us informed.

 

[D-Dubya]

Lots of good suggestions so far. From what little I remember from the engineering classes I took way back in the last century, those two "hard" right angle turns (the one going into the cooler and the exit from the cooler) are causing problems. YellerDaisy is spot on with his 3D inlet fix, if you're dead set on having the cooler mounted there. A more gradual turn of the air is going to smooth out the flow and have less pressure drop, and the turning vanes he designed make that solution even better. If you don't have access to a 3D printer, I'd look at relocating the cooler where you can smooth out both the inlet and outlet from the cooler. If you do a search here in the forum, I think you'll find some rather innovative and effective solutions others have come up with. People have fabricated some fiberglass transition pieces that will likely solve most, if not all of your problem.

 

[Carl Froehlich]

A few thoughts.
- I always mount the oil cooler on the firewall (too much weight hanging off the back of the engine for me).
- You can make a simple plenum to connect the 3” line from the rear baffle. I made a one using some standard rigid wall insulation cut to make the shape I wanted. Wrapped that with clear packing tape than laid carbon fiber over it. Photo attached.
- As been suggested, keep the airflow to the cooler straight (no hard bends). Same goes for the oil cooler exit air.
- Assuming your RV is like most, the lower plenum will be at a higher pressure than the cabin, so your observation of oil temps going up would indicate the setup is restricting airflow to (or from) the cooler when directing exit are to the cabin. As the first step I’d remove whatever you are using to redirect this exhaust air and take new data.
- The piston oil squirters add a large heat load not normal to a standard 320. This tells me your seven row cooler is undersized for the job. I suggest a larger cooler, perhaps the nice 10 row 2004X from AirFlow Systems.

Carl

 

[Toobuilder]

I see a few red flags - all of which are likely partial contributors.

- no bellmouth on the inlet to SCAT
- SCAT instead of SCEET
- SCAT too long
- Sharp, airflow unfriendly 90 degree entrance and exit from cooler
- Overall baffle leaks

If you are dead set on keeping that horrible remote mount, easiest solutions is to add a bellmouth, change to SKEET, and shorten the hose as much as possible. See if that helps and gets you into range. If not, I think it’s time for a new plenum top with a divergent design, with the inlet tube pointed at the baffle inlet (to shorten the hose even more), work on smoothing the exit flow out of the cooler somehow, and of course work on the overall baffle sealing.

 

[00Dan]

Good replies so far. I definitely would not have gone with this configuration if I was building it myself but at this point I'm seeing how far I can get with what I have, in the interest of not taking the airplane down for a lengthy retrofit. I'm sure the builder found this setup perfectly adequate for the 150 HP engine he originally installed.

A couple of notes on my end:

• The baffling is sealed up with RTV and passes a flashlight test with the top cowling in place.
• I've ordered the parts to install a viscosity valve just to sanity check my vernatherm.
• The door to direct the cooler exhaust between the cabin and the lower cowl plenum is normally closed so the cooler exhausts into the cowl, I mention the results of opening it merely as a data point.
• I'm a bit concerned the 7 row cooler is insufficient for any engine with squirters, but moving to a larger cooler would force my hand on repositioning the cooler.

I've been brainstorming how to smooth out the existing air pathway, and in addition to the bellmouth and diverging plenum mentioned, I wonder if adding an elbow with vanes partway between the hose would help ease that turn the hose is currently making.

 

[Bill Boyd]

I think adding an intake bell mouth would be the simplest of steps for you to to start with. I'm getting ready to add one to my -10 setup because of a recent, isolated experience with temps to 250 in climb/cruise the other day that did not duplicate itself on the return leg and was probably more due to suboptimal positioning of the air butterfly vane - but overall my temps run higher than necessary and I'd like to see them stabilize in the 190's rather than the 210's.

Here's what I'm probably going to order and try, once I verify congruence between my SCAT inlet ID and the OD of the bell mouth piece: https://www.amazon.com/AUTOHAUX-Bel...319-a173-216e74453f46&pd_rd_i=B0924LDX8V&th=1

Of course, you would be shopping for a 3" piece, not a 4".

 

[jrs14855]

A seven row Harrison style will cool a stock parallel valve 360 on a Pitts turning 3300 r/m on every aerobatic flight. My non RV with 0 320 10-1 compression with same cooler runs too cold much of the time. 110 ambient, 190 oil on long climb. 9500' cruise the oil temp is 180.
The op issues:
The duct size is too small. 4" is minimum
Much better to mount the cooler on the #3 baffle. I use a welded sheet metal mount that mounts the cooler at a 15 degree angle. Use thru bolts and bushings in six places with "fender washer" four places each bolt. The spacer should be heavy wall aluminum tubing sized so there is zero distortion of the flanges. The angle mount is .050 4130 sheet for the sides and mild steel for the top. .063 aluminum doubler on the rear baffle. Tubular angle brace on the upper left corner and .040 steel doubler on the side baffle picks up one of the mounting holes for baffle on cylinder.
I do have a plenum which adds a lot of strength to the cooler mount.

 

[ChiefPilot]

Consider an exit diffuser. It made a world of difference in my setup.

VAF Thread

 

[fixnflyguy]

Here is my set-up I put on my 160HP O-320 in my RV-4. Temps run below 200 even in the hot NC summers. I was initially looking to do the remote cooler and duct like yours, but baffle attached was simpler. I fabricated all my baffle, so it's a bit more robust than the VANs kit parts.

 

[bjdecker]

I have an IO-360-A1B6, Lycoming, Stock 8.7:1 Pistons - Roller Tappets, Piston Squirts, Electronic Ignitions. Lot' of heat goes into the oil in the Angle Valve engines due to the squirters.

My setup:

3" duct, SCEET, large bend radius, fed from behind #4 jug.
SW 10599R oil cooler (the real deal, not an NDM, or other clone)
Plenum to transition from 3" to square oil cooler face.
Custom baffle/plenum.

OT runs 185°F - 190°F in cruise (75% power, 13GPH, 178KTAS).
Higher OAT == Higher OT, Lower forward airspeed = Higher OT, and so on...



Things I've learned:

Oil cooler fin pitch/fin density is more important than "rows" , e.g. a gappy 7 row (20002) isn't as efficient as a tight 7 row (SW 8406R)
If you have an oil cooler with finned end tanks, make sure the little gaps are sealed up - don't allow any air to escape.
Smooth ducts are better than rough bumpy ones
Gentle transitions, no right-angle turns, no sharp edges, squares adjacent to any airflow. Don't make or allow the air stream to "trip"
Exit diffuser *may* help -- still waiting on data.

Cheers!

B

 

[lr172]

I believe you have inadequate cooling airflow around the cylinders. piston squirters remove more heat via oil than those without them and therefore tends to produce lower CHTs and higher OTs than the engines without them. Your CHTs in cruise are QUITE high for a 320 without squirters, let alone an engine with them. The lack of cooling air flow keeps the cyl temps up, pushing even more heat into the oil. Engines with squirters require oil coolers a good 20% larger than those used on non squirter engines. If you used the standard cooler recommended for a 320, no surprise you are seeing 210-220 OT.

Suggest you start searching for threads on improving the efficiency of your cooling airflow (i.e. make evert molecule of air pass over the cyl fins). Many posts on this subject. I suspect that once you get the cooling airflow to properly cool the cylinders, the OTs will drop a bit. Still may need a larger cooler or some of the tips above to increase the effectiveness of existing cooler. But you need to address the high CHT problem before tackling the high OT problem. The high CHT is not due to a deficiency in the oil cooler, but instead a deficiency in cooling airflow.

Larry

 

[bjdecker]

Consistent with @lr172's comments -- the exit from your oil cooler "could" be raising the pressure of the cowl "bottom", thus reducing the DeltaP, thus increasing your CHT's.

If possible, move the oil cooler lower/closer to the cowl bottom exit area, or shroud & and route the exit to the free stream and *not* into the lower cowl area.

 

[Kyle Boatright]

Here's what I'm probably going to order and try, once I verify congruence between my SCAT inlet ID and the OD of the bell mouth piece: https://www.amazon.com/AUTOHAUX-Bel...319-a173-216e74453f46&pd_rd_i=B0924LDX8V&th=1

I think the ID of that one is gonna be smaller than what you want. Thankfully, Amazon has a ton of similar products.

 

[00Dan]

I printed a basic bellmouth from PETG and RTV’d it in place for testing purposes. I don’t expect it to last under post shutdown temps but it shouldn’t melt entirely and will serve as a proof of concept.

I also pulled the plug forward of the oil filter adapter to install a viscosity valve and found, to my surprise, one already installed. So much for blaming the vernatherm…

I’m working on a CAD model for a filter intake plenum, that’s my next step after testing just the bell mouth.

 

[Roadjunkie1]

Here's mine. Cooler mounted to the engine mount with steel brackets. Plenum made from aluminum and welded. Didn't have CAD then. Well: Cut And D'weld..... Exit gate cable-controlled from the cockpit; it's usually closed. I have to block off most of the intake, especially in the Winter as the oil is always on the cool side of the gauge. The third picture is of the sophisticated intake blocking mechanisms. The upper is for cold weather, the lower for warmer weather. PS: since these pictures were taken, the nuts have been replaced with steel locknuts. CHT on that cylinder: consistently in the 280-300 range, cruise; 350-370 extended climb.

 

[gordiem]

I will be quite honest with this setup. It's not optimal at all. You are forcing the oil cooler air back into the pressurized chamber behind the engine. It (the air in the oil cooler) has to overcome the pressure to go back outside the discharge side of the oil cooler chamber and turn 90 degrees to get out and go down and out the exhaust duct. I would get rid of this entire setup and go with a smaller 13 row Setrab oil cooler mounted on the baffling behind #4 cylinder. I can send you some installation pics on my RV-6 that should work on your -4. And before the folks come out of the wallpaper- yes, I said "Setrab" oil cooler, not Harrison or the other style aviation oil coolers. Have installed 6-7 of them with better results than the heavier, bulkier, baffling cracking Harrisons (and clones). The installation is tighter and cleaner, takes up less space behind the cowling and weighs less. Too boot, it works better too! Proven time and time again with flight testing. Even in back East 100 degree plus temps all summer long. Properly installed, that cooler will outperform the others. If interesting, text me at 425-238-0075 and I will shoot you some installations.

 

[gordiem]

Aden. Which Setrab model are you using for the RV6?

 

[Bill Boyd]

I think the ID of that one is gonna be smaller than what you want. Thankfully, Amazon has a ton of similar products.

The ID of the standard Vans duct is 3.875" (measured with a ruler, not a caliper). Given the spacing of internals in the vicinity of the Lyc 540 rear baffle, I think it's going to take a lot of Dremel work to get any kind of C.O.T.S. velocity stack bell mouth to fit there, and in places it will need to be largely skeletonized. Still, I'd be interesting to see what effect it has.

Edit: on further reflection and after a somewhat futile search for a short aluminum thin wall pipe of appropriate diameter to act as an internal coupling sleeve between bell mouth piece and SCAT mounting flange, I thought I'd just buy a piece of 4" OD tube and slit it to compress enough to fit inside the 4" OD components. Then I realized I was going to be doing something of a hack job on the bell mouth itself to clear the fins on cylinder 6, and thought "Why not just cut a lengthwise slit in the bell mouth and curl it in on itself enough to fit inside the mounting flange, and skip the coupler idea altogether?" $22 later, I will have some results to report later this spring...

In an effort to address a cool-running clylinder 4, as well as direct a little more air to the oil cooler, I added a couple of smallish aluminum tape air dams over top of #4 on the pushrod tubes. Hopefully can get a test flight in tomorrow and see what effect it has. Right now, #4 cruises about 10-20F cooler than 2 and 6, which are equal.

 

[hgerhardt]

......... I think it's going to take a lot of Dremel work to get any kind of C.O.T.S. velocity stack bell mouth to fit there, and in places it will need to be largely skeletonized. .......... futile search for a short aluminum thin wall pipe of appropriate diameter to act as an internal coupling sleeve between bell mouth piece and SCAT mounting flange,..........

In the spirit of "education and recreation", why not learn how to design a bellmouth and have it made from nylon-12 via SLS or MJF process? If that's too hard, I'll save you the trouble and send files. The parts below have been on my -6 for about 4 years now and are holding up fine. Send me a PM if interested.

 

[Aden Rich]

Aden. Which Setrab model are you using for the RV6?

13 row

 

[Bill Boyd]

@hgerhardt, "in the spirit of education and recreation," I really should get a 3D printer It's on my list, but not at the top. I'll ask for one for Christmas this year. I'm probably one of those boomer guys who would be forever "borrowing" files but never learning to create his own in SolidWorks or whatever, but printing them would be fun.

The stock Vans install kit for the firewall mounted oil cooler seems to limit ones options for intake diffusers and turning vanes without substantial rework, but the smooth elbow and vanes you made look potentially useful at the rear baffle. Thanks for posting that.

 

[YellerDaisy]

"in the spirit of education and recreation," I really should get a 3D printer It's on my list, but not at the top. I'll ask for one for Christmas this year. I'm probably one of those boomer guys who would be forever "borrowing" files but never learning to create his own in SolidWorks or whatever, but printing them would be fun.

3D printing is amazing. However; before purchasing, be aware that materials that will hold up to some amount of heat are a bit different than what you typically see mentioned and what a typical printer can print out of the box (PLA is 'typical'). Keeping in the spirit of 'nothing is easy,' of course.... A mass of information is available for your reading & viewing pleasure.

 

[hgerhardt]

@hgerhardt, "in the spirit of education and recreation," I really should get a 3D printer ...............

Sorry, I should have been more clear: there is no consumer-grade 3d printer available which can make parts suitable for "underhood" (firewall-forward) applications. I said to use the SLS or MJF process, and those machines are typically north of $100k... and quite messy.

What you do is upload the files that I can give you to a vendor which makes parts for hire. There are tons of them out there nowadays. One week later, you have robust, high-quality parts.

My favorite vendors today are https://craftcloud3d.com/ and https://www.jawstec.com/. Select SLS or MJF as the process, and PA12 as the material. As an example, I just now got a quote for my bellmouth: $31 including shipping from Craftcloud, made by a vendor in Texas. The elbow and oil cooler plenum were $120 additionally.

@YellerDaisy Definitely be aware of how plastic materials hold up to heat. That's why I selected PA12 (nylon) for material, and MJF or SLS process which makes fully-dense parts. When I first installed my oil cooler duct, I checked bolt preload after every flight until I was satisfied the material wasn't moving. I thru-bolted the bellmouth to the duct behind it with 10-32 bolts and nut plates. If the plastic were getting soft, that preload would become less than when I installed it, and today it's as tight as four years ago.

 

[Bill Boyd]

I found an aluminum bell mouth on Amazon that should be the correct OD to mate with the duct flange - will still need Dremel surgery due to clutter in the vicinity. I will report back later after annual C.I. is done.

 

[Laird]

13 row
View attachment 61792

Aden, Please be careful. I had the same setup on my RV-6 in 2000, although mounting was probably different. My oil cooler cracked (at one of the bosses where the hose attach) and didn't realize it until oil was leaking in the cockpit. Luckily I got it on the ground before any damage happen.
What I saved on the cost of the oil cooler almost cost me an engine overhaul and potential off airport landing.

Just speaking from experience.....

Regards,
Laird