Hey Mark, I guess the only other logical reason would be an air-lock caused by orientation … but if you’ve got two exactly = the same, that is highly unlikely.

Incidentally, I have two, 6.25”x11”2.75” o= il coolers in series – I’m over-cooled with 2 but found 1 wasnR= 17;t enough.

JWW

From: Rotary motors= in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Mark Stei= tle
Sent: Monday, December 14, 2009 12:00 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Oil Cooling

Well guys, here is a new one... at least for me. =

I've never been able to get my 20B oil temps quit= e low enough for comfort. I chaulked most of it up to t= he high Texas temps and an engine that produces gobs of horsepower (just kiddi= ng on the "gobs of horsepower" part). I'm running a 10&qu= ot; x 11" x 2 3/4" Fluidyne dual-pass oil/air cooler and a large (and heavy) Fluidyne oil/water exchanger. Water temps were fine but the oil temps would reach 240*-245* on climb, and just barely down= to 200* in cruise. I tried different plumbing arrangements, added a cowl= flap (which helped some), etc. Still, the temps didn't want to come down. Well, yesterday I ran the engine with the cowl off (d= oing some fuel pressure monitoring/adjusting), and I had just finished gett= ing things up to operating temperature, verified that fuel pressure was good, and then shut it down. I just happened to touch the e= nd tank on the Fluidyne oil/air exchanger and to my surprise, IT WAS STON= E COLD! I touched the other end (inlet/outlet) and it was HOT!&nbs= p; I thought this was odd. The only thing that I could figure is that= the dual-pass oil cooler was defective. Since the cooler has no thermosta= t, I can only conclude that the internal tank separator, which is how they make a single-pass cooler into a dual-pass cooler, was = allowing the oil to bypass the core and go directly from the inlet to= the outlet. Well, no wonder I can't get the oil temps to come down!!!

I replaced the cooler with another unit I had on = hand, ran the engine, and low and behold, both end tanks come up to temp together. I did a couple of ground runs and themps look encouraging. But unfortunately, it was too late to do = a test flight yesterday. I'm sure the new cooler will make a = big improvement. I'm hoping it will be enough to permit me to remove = the oil/water exchanger.

Moral of the story... DON'T TAKE ANYTHING FOR GRANTED!= TRUST BUT VERIFY!!!

Mark S.

Lancair ES/20B