Everything is much cooler now, with CHT's below 400 except in climb
where #3 still gets up to around 450. It was only 16 degrees C this
morning, so that must have helped, too. My oil now might be too cool,
though, as it only got up to about 160 degrees F. I may have to remove
some of those lips on the cowl if I want to run it warmer. I'll leave it
a bit for now, and see how it goes.
Anyway, I am real happy with my Rebel now, and it sure feels great to
finally get this thing in the air.
Walter Klatt wrote:
*-----------------------------------------------------------------------------------*Thanks, Wayne, this information is very helpful.
My engine has 911 hours since the last overhaul, so it is definitely
broken in. However, it has one new (overhauled) cylinder in the #1
position (previous one had a crack there), but ironically this one ran
the coolest. I wanted to run it for at least an hour to break in the new
cylinder, but decided to come down early because of the overheating.
My prop pitch is definitely on the course side, too, as I think I was
only getting about 2450 or 2500 on climb. I didn't run it flat out on
cruise as I was trying to cool the hot cylinder down when I wasn't
climbing, so not sure what it would wind up to. Will check that next
time.
Tomorrow and Sunday, I want to get the cowl done, so hope to fly it
again on Monday.
Thanks again for your great advice.
"Wayne G. O'Shea" wrote:*-----------------------------------------------------------------------------------*Walter, is the engine Zero'd or a used engine? If overhauled, CHT temps
usually run about 50 to 60 degrees hot until everything seats. Oil temp will
run about 20 or 30 degrees hot. I fly a minimum of 2 hours on an overhauled
engine in level flight at almost full power, with minor throttle changes
every 10 minutes or so. At about 1 hour 45 minutes I usually see the temps
suddenly drop to indicate that everything has seated in nice. Coming in any
sooner can glaze the cylinders and you will eat oil for ever.
If this is the case with you (zero'd engine) then maybe you just need to get
it back in the air and fly around until everything seats! Keep the nose down
to keep the air flow at max through the cowling on climb out! If not the
case and you have a previously broken in engine then yes open up the cowl
exit some more. Try the quick open up first. Then try the lip if necessary.
Angled lip will usually help drop the temps a few degrees, but also causes
drag.
Your temps on climb out are similar to what Howard experienced with his
during the first few flights. ie: about 500 F on Cylinders and 235/245 on
oil. These are not outside the Lycoming operating temperature range, but are
definitely on the high end. I ran 235 to 245 F oil temperature for 4 years
on my oil cooler less O-235-C with no detrimental effects, but this IS a
little high. Just don't open things up too much and drop the oil temp down
below 195/200 or you won't get the moisture out of the engine oil and the
motor will corrode.
One other thing! Is your propellor pitch allowing the engine to wind up to
full engine rated R.P.M in level flight with full throttle (or slightly
redline)? If you are not getting full R.P.M. then you are lugging your
engine and this will really cause the temps to rise. It's like pulling a
trailer up a step grade in high gear!!!
Hope there was some help in there!
Wayne G. O'Shea
www.irishfield.on.ca
-----Original Message-----
From: Walter Klatt <Walter.Klatt@home.com>
To: (Murphy Rebel Builders List) <murphy-rebel@dcsol.com>
Date: Friday, June 30, 2000 10:01 PM
Subject: Re: Another Rebel flys
thatMy hottest CHT was cyl #3 and it would go right up to 500 at full power
in climb. Backing off to cruise power brought it down to about 450
degrees. Yes, very hot, so I only stayed up for about 1/2 hour for the
first flight. I will say that I was quite anxious there for awhile as I
watched that gauge climb straight up after the first take off.
The oil temp got up to about 235 degrees. My oil cooler is mounted at
the back of cyl #3, which explains why it was hotter than #4.
I have a weird old conical mount O320 with the carb at the back of the
oil pan, so my cut-out extends to the underside of the carb heat box. In
fact, the carb heat box probably helps block some of the airflow.
I had my opening cut out to about 100 square inches, and am planning to
increase it to about 126 with 1 inch lips for my next try. I can grind
the lips back later if the cooling is more than adequate.
Anyway, that's my current plan. Any other thoughts? Thanks.
"Wayne G. O'Shea" wrote:All"circle"inchonflaps*---------------------------------------------------------------------------*-------------------------------------------------------------------------- *--------------------------------------------------------------------------
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