Oil cooler placement

[Battson]

Do NACA ducts provide ram air or just passive offtake?
If you made a diffuser and everything lined up right, you would almost certainly get away with a short 3" duct without any bends. Refer to Mark's first post on this thread. A good diffuser would be important, and a large cooler. If the cold air is going nice and slow over a large cooler, it will be more effective (in theory) than ramming air across a smaller cooler.

I've got about 11" of 4" diameter SCAT duct these days, with a 90 degree bend in it. With EI the temps are only just acceptable on a hot summer day. I need to lean the engine more aggressively (LOP) to keep temps at 95*C, else they creep up above boiling point. I am sure the sharp bend and long duct are the issue. The coarse mesh screen at the duct intake doesn't help either.

[zkelley2]

Do NACA ducts provide ram air or just passive offtake?
If you made a diffuser and everything lined up right, you would almost certainly get away with a short 3" duct without any bends. Refer to Mark's first post on this thread. A good diffuser would be important, and a large cooler. If the cold air is going nice and slow over a large cooler, it will be more effective (in theory) than ramming air across a smaller cooler.

I've got about 11" of 4" diameter SCAT duct these days, with a 90 degree bend in it. With EI the temps are only just acceptable on a hot summer day. I need to lean the engine more aggressively (LOP) to keep temps at 95*C, else they creep up above boiling point. I am sure the sharp bend and long duct are the issue. The coarse mesh screen at the duct intake doesn't help either.

They don't capture as much air as say putting a scoop external to the cowl would. But they still get a large percent of the velocity of the airflow. The big advantage they provide is they don't increase drag very much.

[Nev]

Good point Jon, they're not designed for ram air intake air. Installing them in engine cowl area should provide a higher positive pressure area though, particularly when mounted towards the mid/front part of the engine cowl. On the boot cowl should be sufficient for fresh air vents on the instrument panel.

A search of the Vans forums indicates that to be successful I’d need to vent the oil cooler discharge well into the low pressure outflow area. Overall it appears to have mixed results when vented into the lower engine compartment.

[svyolo]

Yeah I would guess venting a NACA ducted cooler to the inside of the cowl, the higher pressure inside the lower cowl might limit airflow from the NACA duct.

I wonder if the same would be true with tapping air from the baffling. Maybe have a separate oil cooler exit, with "something" causing a negative pressure. Louvers?

[Nev]

My limited understanding at this point is that when the oil cooler is ducted from the rear baffle area, it is effectively ram air, which I think may be Jon’s point. Louvers could well be a valid concept. The Vans guys that used a NACA intake had to add a discharge duct down to the engine compartment outlet area to get the pressure differential. These are all things I had absolutely no idea about in my GA days!

[Nev]

PS John I bet we’ve crossed paths in a bar around Asia at some point

[svyolo]

I was looking at some engine installation pictures and I came across a few oil coolers that were mounted with both the inlet and the outlet facing down. I thought that might be a problem but then I realized I really didn't know the internal layout of my oil cooler. You really can't tell by looking at it. I mounted mine so the outlet it as the high point, so air can not get trapped.

What is the internal layout of an oil cooler? A single tube, snaking back and forth throughout? A parallel flow arrangement, where there is a manifold on either side with interconnecting tubes?

Mine is a Positech. I think it is similar to the AeroClassic style. I couldn't find any info on my particular brand, or any other brand. Their was some info on their type of construction.

[Bcone1381]

Boy, thats a great question!

[JimParker256]

In the Rotax world, where there is a radiator to cool the cylinder heads, getting the radiator to completely fill with coolant can be an issue. Several aircraft cowl designs have the radiator in a horizontal (or near-horizontal) position. There are all sorts of stories about the gyrations they go through to get those radiators to completely fill... Some go so far as to drill a small hole near the top of the radiator housing to allow air to vent, then insert a screw with LockTite to close the hole.

With that as background, I would think that ensuring the oil cooler actually completely fills with oil after an oil change would be pretty important to effective cooling, and that svyolo's idea of mounting with the outlet on top would be a good idea. You may be able to see through the fins to determine the orientation of the internal tubes, and if so, it seems logical that you'd want those to run horizontally so as to not trap air where they turn 180 degrees.

The one thing that's working in our favor with filling the oil cooler is that oil is, in fact, much thicker than water, and may "flush" the air out of the cooler more easily. But why make it fight for it?

[svyolo]

I have done a lot with cooling systems, including a few "difficult" ones. With the oil cooler it depends on the configuration. Does it functions as a tank (two manifolds joined by cross tubes) or is it a continuous tube snaking back and forth. The latter will self purge the air. The former will not without a vent at the top, or a specific procedure to purge the air when you fill it.

I was looking at different engine installations and for some reason a couple of them caught my eye for having the cooler installations "upside down". Some builders have perpetual oil temp issues, even after installing ever larger coolers.

Just wondering.

[James]

Hi Guys,

I'm up to the FWF, and I'm just trying to set out my components. As usual, I have no idea the best way to do anything with these engines, and so I might be barking up the wrong tree!

1) Oil cooler - I have a the old oil cooler from the previous STC installation of my engine (a beechcraft duchess), and an ultrasonic bath. If I make up my own flushing rig and spend a few hours really getting everything out, then pressure test it for leaks / cracks, would this allay concerns about reusing an old cooler rather than buying new?

2) I have a 4-place BH, an O-360 Lycoming, and a FP metal two blade prop. I'm keen to put as much weight forward as possible, and notice that previously Bob (in his patrol) put his cooler in front of the No2 cylinder - see Brooks' post above in this thread.

3) What is below this horizontal installation? Is there any ducting underneath the cooler? I assume the cooler at this location will just work via air pressure differential between the top and bottom of the engine compartment. Is this sufficient, compared with ram air? Steve W (above) has the cooler facing into the airstream, but doesn't have any more info

Does anyone have any more info on how / if I can put the oil cooler at this location? I'm hoping to avoid SCAT tube down to the firewall, and the chance of cracking the aft baffle wall :-)


Thanks guys,

James

[Mark Goldberg]

Hello James. Here there are companies that clean and inspect oil coolers. They have special equipment for flushing them out and getting any internal debris out so the oil cooler does not lose efficiency. Of course a leaking oil cooler could ruin your day. A pressure test is in order at the least.

Placing it forward would certainly make sense in your case trying to move weight forward. Not sure how Bob placed it there and supported it as I have never put a cooler in that place. Mark

[Bcone1381]

I'm working on that right now. I mounted my nose bowl a few days ago.

Eric Newton's manuals gives details on how he did it. For those who may not be familiar with this resource, it has several volumes. The last one is 574 pages and titled "Finish Manual". Section 10 of the Finish Maunal is "Exhaust System, Engine Baffles, Firewall Hook Ups." Section to, P.36 of 52 (which is p. 479 of 574) is subtitled "Mounting the Cooler". Eric has us build the Baffling from the Vans Baffle kit. In front of cylinder #2 he begins with .032, then fouls that piece up for a combined thickness is .064 to support the cooler.
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[James]

Geeze Brooks - I feel silly, I have Eric's manuals, but only refer to them when I get stuck. I didn't think to check what he did with his cooler - I'll check it out!
You put a huge amount of work into sharing info and helping other people on this forum - it's good to hear you're also progressing on your own plane mate

Thanks N942VT for the confirmation that this will work out there in the real world :-)

James

[Bcone1381]

I think I what I wrote may not have communicated my intent. I wanted to answer your question, but also help someone new, or considering the Bearhawk Build to know that a couple detailed manual exists to help him/her.

[N942VT]

Did mine as Brooks copied above from Newton's manual. O360 c/s. 9 row cooler. 800 hrs and it cooled great in our climates, saw temps over 200 only a couple time in the summer heat while loitering. I did need a small blister on the nose bowl for the left side oil hose fitting.
I've done rear mounted and remoted mounted coolers and I liked this the best if you have the room.

[Bcone1381]

Ahhh...Blisters. Another idea!

[whee]

I agree with the other guys. I like the front mounted cooler. The BH I flew with a 360 had the cooler mounted there and it worked great even on hot summer days with super high DAs.

Think about how expensive your bearings, crankshaft, camshaft, etc are. It would be unfortunate to kill your bearings because you didn’t get the cooler clean. IMO, cleaning a cooler is a job for a shop with the proper tools. I made an adapter for my cooler then found a local shop with a “hot flusher” and they cleaned my cooler for $40.

[zkelley2]

We don't get super warm temps but I remote mounted mine off the rv10 battle kit as vans instructs. I have to block some of it off this time of year and oil temps run right at 200 in the summer.

[Bcone1381]

Regarding the progress on my build....It seems like I don't do much the easy way. When I have to start developing my own way, it takes me a lot of energy.

Like mounting the oil cooler. If I did not have Erics manual or Bob's photo, or Van's directions for placing it aft of the engine, It would take me HOURS to decide to try something that might not work out in the end.

So, at least I know I want it where Eric placed it. But will it fit? Well, I mount the nose bowl, and I am unsure still, so that calls for fabricating up the Cylinder #2 baffling at the intake because that will determine the orientation of the cooler at the inlet. But before I went down this path, I was trying to figure out how to move oil line that carries the return oil out of the #2 cylinder Rocker Arm Cover. So for the next few weeks I am doing baffling. Maybe I wont have to learn how to bend aluminum tubing with frozen soapy water inside of it to prevent the tube from collapsing during the bending because my tubing bender is unable to start the bend right next to the fitting. (You can see the oil line in the second photo.)

Or should I adjust my spinner to move the nose bowl away from the firewall? And could I do that without reinstalling the Prop? OR is there another oil cooler that is as capable that is smaller in size? See what I mean. Fabricators dont think like me and they get stuff done. Folks like Colin Campbell.

At least I am not mounting the cooler then installing the nose bowl only to find out I chose the wrong spot to install the cooler.

Why I like the cooler in front of #2.....All space behind the engine is high cost real estate. Anything I can do to keep things out of here and in an otherwise empty place helps me in the future. I never know what I might want or will need to move to maintain something. This is even more critical to me in a tandem seat aircraft that has less width to its firewall.

But I have no experience....but I saw and talked with Bob about his and he sure likes it.....just like every one that has chimed in on this thread. AND the complaints of those who dont, like cracked baffles and such. We'll see. I don't know much though. At this point This topic is just my preference as opposed to truth and knowledge.

[svyolo]

If I was doing a 4 cylinder I am pretty sure I would put it on the rear baffle. Mostly because it is simpler and has shorter lines.

After a bunch of iterations of making my own owl cooler(IO-540) mount/plenum, I found the FWF instructions for the RV-10 including their firewall mounted plenum. It was almost an exact fit for the cooler that I already bought. I bought the plenum kit from Van's. It would not be hard to scratch build, but it was so cheap I would rather just buy it, so I did. I can' remember the price but it was way under a 100 bucks. Maybe closer to half of that. Vans cooler is about average in price, but with the bargain plenum kit, the whole thing is a pretty good deal. I wish I had know that in the beginning.

[Bcone1381]

Where I am at, what I learned, and where I'm going regarding oil coolers.

I confirmed that a 9 row Aeroclassic draw cup oil is too big to fit in front or Cylinder #2 with the nose bowl I chose. Two Nose Bowls are available from Mark. One is nice and fits the Hartzell Spinner but its shape impacts the space in front of takes up space cylinder #2. The other nose bow gives more space up front.

I learned that the Vans Aircraft baffle and oil cooler installation kit is set up for the 7 row oil cooler rather than my 9 row oil cooler.

I learned that a Beech Sundowner, Sierra, Cessna Cardinal, Mooney, Comanche, Archer, 260 hp Cherokee 6, used the same 7 row cooler, but the Supercubs, Mauls, Aztecs, used the 9 row

So I ordered a 7 row cooler and have a 9 row cooler that will collect some dust.

Hey wait a minute.....will the 7 row fit up front? I feel like Spooky, a dog I once knew that chased his tail. I follow svyolo's advice and place it on the baffling.

[Battson]

I can hardly get my oil cold in summer with the 11-row cooler. I mean, it runs on the red line all day. I have no idea how the others get away with a 7 row cooler... I am not an expert but I assume more passes means cooler oil. I would not recommend less than 11 rows for a -540 Bearhawk in a warm climate with temps regularly above 25C

[Nev]

Where I am at, what I learned, and where I'm going regarding oil coolers.

This is brilliant Brooks.

I just unwrapped my oil cooler this evening, an hour ago. Also the prop governor, alternator etc. My plan this coming week is to establish where each ancillary part will be mounted and to ensure adequate clearance, particularly on the firewall. I’m planning to raise the engine up against the firewall tomorrow and starting drawing lines.

I have the Vans IO540 firewall forward kit, which included the 13 row Aavid Niagara 20006A Oil cooler and plenum mount for the firewall. I’ve got no idea how this compares to others, it just seemed a simple way to order at the time and cost effective.