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” oil
coolers in series – I’m over-cooled with 2 but found 1 wasn’t
enough.
JWW
From: Rotary motors in
aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Mark Steitle
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 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!!!