Well guys, here is a new one... at least for me.
I've never been able to get my 20B oil temps quite low enough for comfort. I chaulked most of it up to the high Texas temps and an engine that produces gobs of horsepower (just kidding on the "gobs of horsepower" part). I'm running a 10" 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 (doing some fuel pressure monitoring/adjusting), and I had just finished getting things up to operating temperature, verified that fuel pressure was good, and then shut it down. I just happened to touch the end
tank on the Fluidyne oil/air exchanger and to my surprise, IT WAS STONE COLD! I touched the other end (inlet/outlet) and it was HOT! 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 thermostat, 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