Back to business...what the frick is Dan up to NOW?!
It's my new concept for a "free flow" oil cooler. Yeah, that's the ticket.
On my engine (200hp IO-360-A1B6), my oil temp has been running slightly high since day one. Usually around 205 in cruise at 75% best power at 55F OAT. At lower OATs, say 45F, the oil temp would drop to 195. The biggest problem has been in the pattern, when the airspeed drops down to 90mph or so...when doing pattern after pattern, the oil temp would get up into the 220s easily.
My engine is the "big" IO-360, which I've been told generates considerably more heat than the vastly different O-360. But for all 360 models, maximum oil inlet temp is 245F. Some have said my "high" oil temps are acceptable, and that I shouldn't worry about it, but I really do want to shoot for under 200F for the long haul. I want to take care of this engine, and I believe that 10 or 20 degrees can make a big difference in wear and tear over 2000 hours. 180F to 190F would be ideal. Interestingly, my CHTs have been nice and cool, around 330-350F. The highest CHT I've seen is about 375F in the worst of conditions. So baffling *probably* wasn't the problem.
After break-in, the oil temp didn't really drop too much. Maybe 10 degrees or so on average. After break-in was done, I switched to AeroShell 15W50 multigrade oil, which is what I've always used in my other planes and love it.
Several folks advised me to use a straight 50-weight oil such as 100W, and a few people said that their temps actually dropped 10 degrees or more when they switched to 100.
At my last oil change a week ago, I switched to 100W. I flew several hours and didn't notice any improvement...in fact, I saw the opposite effect if anything, maybe 5 degrees hotter oil temp on average.
I had heard that just about everybody with the 200hp angle valve IO-360 has had oil temp problems with Van's "stock" oil cooler. Dan Masys, I believe, switched to a 9-row and saw a major improvement. Well, I don't want to reconstruct my baffles if I don't have to...so...I wanted to experiment with what is theoretically a more efficient oil cooler at the same form factor. I had read some reviews (thanks Randy...you'll notice that I've gleaned an awful lot from Randy) that the Stewart Warner oil coolers are the most efficient ones out there at any size. I spoke with Wayne at Pacific Oil Coolers, who confirmed that the Stewart Warner is basically the best cooler available for this application.
So today I broke down and drove up to Pacific Oil Coolers in South El Monte, and bought a Stewart Warner 8406R oil cooler. I slapped the $419 down (includes the $25 core) and bit the bullet. It's a 6-plate oil cooler, instead of a 7-row like the Aero Classics. The Stewart Warner cooler has larger fin area due to more space between plates. It's heavier, but it's much more durable. The end tanks are a much beefier design. The form factor is *almost* identical to the Aero Classics 7-row...close enough that I could just swap 'em and go. It's much more expensive, but let's see if it's worth it for my particular setup...
Here you can see the original Aero Classics on top and the Stewart Warner on the bottom. Very similar shape and size.
This is mostly for my own records...just keeping the model and serial numbers handy.
The end tanks are very different. The Stewart Warner has a robust tank, whereas the Aero Classics has a thinner/lighter fin-oriented design. It would appear that the Aero Classics has more surface area and would cool better because of this...(not)
Another view of the difference in the ends.
Here you can see the six plates on the Stewart Warner oil cooler. There's one fewer oil path, but the area of the fins is larger. This is what Pacific Oil Coolers had told me makes a big difference. Also, when you're working on the Stewart Warner, you can just clamp it in a vise on the plates and you won't damage it.
I wouldn't even think of doing that with the Aero Classics. Here you can see the Aero Classics fins. They're thinner and lighter, and more fragile, that's for sure.
What Wayne at Pacific Oil Coolers mentioned is that even though you should use a backing wrench when installing the fittings on the Stewart Warner, because of its durability it's basically not necessary. If you don't use a backing wrench on the Aero Classics you risk tearing it apart.
Just look at the manufacturing quality...
The SW cooler is visibly a nicer product.
This afternoon I did the swap, but I hit a snag. Van's calls out using aluminum -8D fittings on the oil cooler as per their FWF plans. I know most people advise using steel firewall forward, especially for fuel lines and stuff...and I did. But this was the exception. I just blindly followed the plans. DO NOT USE ALUMINUM FITTINGS ON YOUR OIL COOLER. I learned this the hard way. I threaded the fittings into the new oil cooler, the threads galled. I even used a teflon pipe sealant paste -- the stuff that the AeroClassics cooler had come with originally (Loctite 565, a white teflon lube/paste). Despite that, the threads were destroyed. As I removed the aluminum fitting from the oil cooler, the threads broke off and chewed up the oil cooler's threads. Dag bernit!
I drove back to Pacific Oil Coolers, and they were friggin' AWESOME. Paul got me right into a repair scenario...he had one of his techs take the cooler and re-tap it. They told me that you should never use aluminum fittings on an aluminum oil cooler...different grades of aluminum, different rates of expansion/contraction, etc...not good. Wayne said that even though the threads may look & feel fine, aluminum will gall easily. USE STEEL FITTINGS. After cleaning the threads and tapping it, the tech pressure tested it to 180 psi in a water tank. After some teflon tape (they advise to USE TEFLON TAPE, not the paste...these are the oil cooler experts here, folks, I'm just repeating what they said) was applied to the fitting, the leak test passed. They threw the oil cooler on their two-way circulatory pressure fluid cleaner for a few minutes, blew it out, and it was basically like getting an "overhaul" on the spot. "Go upstairs and pay the lady 20 bucks." Cool! That was a bargain for an on-the-spot fix that included two steel fittings! Anyway, an educational experience for sure. Use steel! Pacific Oil Coolers saved my butt, took care of my walk in business, and didn't rip me off. Good folks. http://www.oilcoolers.com
Ok...so when I got back to the airport I installed the new oil cooler, hooked up the hoses, RTV'd the gaps, etc. I went flying (with Dave Richardson...finally got him a ride!). I didn't have high expectations, since the oil cooler was the same basic form factor. Pacific Oil Coolers had said that I would probably see an improvement, and it may be a drastic one, it may not. But they were sure I'd see an improvement.
It was dramatic.
We climbed from field elevation (650'MSL) to 8000' at 95-100 mph indicated the whole way (I normally climb at about 125-130mph indicated). The temp didn't go above 212F (OAT at 8000' was about 57F). Ok, could be a fluke, just a cold start...let's see how it levelled out in cruise. Normally before, when it would hit 220 in a climb, it would take forever to get back down to 210 or so. Today, after levelling off, the oil temp quickly (within a minute or two) settled down to 192. Woohoo!! That was at full throttle, 2500 RPM, leaned to within 75 of peak (on both sides).
After powering down to about 22" and 2400 RPM, it settled down around 182F. Bitchin!
Then we flew about 3 or 4 patterns at French Valley. This would be a decent test. For the first two patterns, it didn't go above 190. On the third, it did go up to 210, then up to 214 on a 4000' climbout. Once levelling off at cruise about 55-65% power, it came back down to 180. Nice, that's more like it!
So if you're going to hang a 200hp IO-360 on your RV, I strongly advise leaving whatever oil cooler Van's would otherwise send you out of your FWF kit and going with the Stewart Warner. The next size up would be even better, but I believe this 6-plate 8406R will do the job. We'll see how it handles the worst days in summer...
Anyway, lots learned today, and I'm much happier that my engine is happy! As I mentioned above, the old oil cooler is for sale. I think it would be a perfectly good oil cooler on an O-360 or O-320.
Got this shot of Dave Richardson enjoying his first RV-7 ride.
He got this shot of me putting on the full RV smirk.
