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Oil Cooler Install: One More Way To Skin That Cat

Toobuilder

Toobuilder

Well Known Member
During the repair of the -8 a couple of years ago, I decided to improve the oil cooling. After flying it a bunch, I can claim success.

My goal was to isolate the cooler from the radiant heat of the cylinder head without remote mounting the cooler. I also hoped to improve airflow through the cylinder fins at the same time. The concept is a small plenum that draws air from the top of the cowl and also acts as a radiant heat barrier.

Works great. The cylinder is now my coolest and the oil never breaks a sweat. In fact, you can see it is blocked off for winter flying.

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First was the plug, then the mold for the plenum. The green stuff is the water soluble mold release.

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The geometry fits the -8 engine mount. Slightly angled, was trying to get as much volume in the plenum as possible without hitting the engine mount.

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Pretty simple fiberglass piece, riveted to a new rear baffle plate.

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Any questions, shoot!
 
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Toobuilder said:
t7l3rs.jpg
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Nice looking molds, and nice looking part!

It looks like there's a bit of whitening around the anchor nuts riveted to the fiberglass part where the anchor nut rivets have locally crushed the laminate. Where I have concentrated loads on a composite part like that, I will usually laminate in a reinforcing patch or strip of Garolite G10 with the shiny surfaces scuff sanded for tooth. For the part at hand, I'd probably use 1/8" thickness. You might consider trying that instead of the aluminum strip if you make any more.

Thanks, Bob K.
 
Oil cooler plumbing

Well, I have my oil cooler remotely mounted on my firewall with an angled RV-10 type plenum http://i.imgur.com/LhbIS.jpg http://i.imgur.com/LhbIS.jpg Like Chris, I was going to use a NACA duct on the side of the cowling to get ram air and duct it over to the top intake of my oil cooler plenum and then build a plenum for the exhaust side of the oil cooler and duct that air out of the bottom of the cowling. By doing it that way, I was hoping to isolate all of the airflow related to the oil cooler so that cowling pressures would have no effect on the flow of air going through the oil cooler. Now, I think the first thing I'm going to try is to come off the back of #4 cylinder baffle with a 3" or 4" scat hose over to the top of the oil cooler plenum and just leave the exhaust side of the oil cooler open as shown in the pictures. If the pressure gradient isn't sufficient enough, I may have to duct the oil cooler exhaust air closer to the lower cowling exit or do as I originally planned and actually install a dedicated 4" exhaust out of the bottom of the cowling for the oil cooler air to exit.

Mark
 
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Bob Kuykendall said:
...It looks like there's a bit of whitening around the anchor nuts riveted to the fiberglass part where the anchor nut rivets have locally crushed the laminate...
Click to expand...

Good eye... but that is a result of a resin starved layup in the deep corner of the mold, not localized crushing. As with many of my prototype parts, I often throw them on the airplane just to see if they work. The intent is always to go back and build the part "nice" if they do, but more often than not, the test period lasts indefinitely. My first attempt at this plenum was a riveted aluminum piece that destroyed itself in short order - I'm waiting for the same to happen here, but the composite part is showing no signs of distress after several seasons of flying.

At any rate I still have the mold, so I can crank out a new one in no time. Next one will be carbon fiber (just for the "cool factor").
 
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Mark33 said:
...By doing it that way, I was hoping to isolate all of the airflow related to the oil cooler so that cowling pressures would have no effect on the flow of air going through the oil cooler...
Click to expand...

Well, I've not done any differential testing, but my experience with this 200hp installation indicates there is plenty of airflow with the stock Vans cowl. The baffles on this airplane leak like a sieve yet I now can't break 300 CHT or 165 OT in cruise without restricting the outlet. Some of that is the cooler weather and some is the fact that I run LOP most of the time, but I have seen some substantial incremental improvements as a result of localized airflow management like this oil cooler plenum and the cylinder head baffle mods detailed elsewhere on this site.
 
I suspect that with an oil cooler that big, you will have no problem keeping the oil temps in line. It would be very easy to build a small plenum off the back of the baffle to accept the SCAT tube. That way you could keep the opening above the fins and still pull enough air for both the cooler and the cylinder.
 
Toobuilder said:
I suspect that with an oil cooler that big, you will have no problem keeping the oil temps in line. It would be very easy to build a small plenum off the back of the baffle to accept the SCAT tube. That way you could keep the opening above the fins and still pull enough air for both the cooler and the cylinder.
Click to expand...

That's what I'm hoping for. Do you think a 3" will work or should I go with a 4" SCAT?

Mark
 
My gut tells me that 3 inch should work since it is such a short run, but this is one case where you can't really hurt anything by going too big. If you have the room, start with 4 inch and be done with it.
 
Very effective

Here is the installation on my -10 wich works extremely well.
It starts with a 5" into 4" cone and connects via scat to the plenum.
There is an additional 2" flange I installed in case the 4" would not have been enough but it is not needed. The butterfly valve on the other hand is needed as temps are difficult to get up near 180 in the California winter.
Cylinder temps are even accross within 20 degrees or so.
The extra cowl louvers on the bottom may play a more important part in the overall cooling picture than I had first imagined.

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That's pretty sano Ernst! You're fortunate with the -10 to have so much room above the cylinder to pull air. With the -8 I had to make a fairly unusual hole to ensure I did not impinge on the fins of the adjacent cylinder. Doing it over, I'd still try to stay as high on the baffle as i could to stay as far away from the fins as possible.
 
Ernst,
That's a slick setup that you have there and that's exactly how I'm doing mine, with the butterfly valve and everything. Where did you get that 5" to 4" cone? Also, I see that curved baffle inside your oil cooler plenum...it looks like the incoming air will only blow on the top half of your cooler...can you elaberate more on that? I too have a curved baffel inside my plenum to help smooth out the airflow, but that incoming air will make contact with my entire cooler face.

Mark
 
A couple more pics to clarify the splitter.
It serves the purpuse of routing air to the top and bottome of the cooler,
at least I think it does. The butterfly valve stops against the splitter.
When I installed the splitter I was more concerned about having to pump more air into the plenum and wanted to be sure it was forced through the cooler baffles.
I made the fiberglass cone out of an ABS drain elbow, of course it needed some foam and Bondo before it was reafy for a lay up.
I made the cone so that I could start with a 4 " SCAT and cutting further back would allow for an increasinly larger hose to slip over the cone.

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Mark

I found some more pics from my -8.
I had originally installed the oil cooler horizontally on the fire wall and routed a 3 " SCAT to it. I fiddled with all sorts dedicated exit lovers and baffles but that set up was never going to cool the IO 360 in my 8.
Mounting it behind #4 solved that problem instanly but left me with several cracked mounting angles until I beefed up the entire baffle area in that corner. That is what kept me from doing it in the first place.

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Ernst

Ernst,

Thanks for some great pictures! I was going mount my cooler on the back of the baffling like you did on your 8 but I too was concerned about the strength factor and possible cracking. I may just try to go with a 4" SCAT from my baffle down to the cooler plenum.

Mark
 
Thats very similar to the Mooney M20J oil cooler mounting. The oil temp never exceeds 185 on the hottest days..
 
Toobuilder said:
At any rate I still have the mold, so I can crank out a new one in no time. Next one will be carbon fiber (just for the "cool factor").
Click to expand...

Side note....the low modulus of glass fiber is the property making life easy for the aluminum cooler and the engine baffles. Switching to carbon would bump stiffness upward by a factor of 3 to 5.
 
Indeed it would, but at those temps the resin is pretty soft, so the whole thing should still move around enough to keep the baffles happy. This flexibility was one of the things I was counting on after the failure of the aluminum version.
 
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