I need some help with figuring out my
cooling problems.
Just so it doesn’t get lost in the
following BS, I need to state that I think the problem is related to the
coolant pressure. It seems to me to be way too high. I am beginning
to think that the coolant is somehow partially blocked.
Now the rest of the story….
After I did the flight described in the attached
email, I installed an opening in the bottom of the cowl that would work
something like a cowl flap that is permanently open. The new opening is 9
inches by 5 inches or 54 sq in.. There is a flare in front of the opening
that is at an angle of 45 degrees and extends down into the airstream about 4
inches. (it is 6 inches long.) This opening is in addition to two 6
X 6 openings, one of which has a 3 inch diameter exhaust pipe in it.
This helped a little, but nothing like I expected
it would. The pressure inside the radiator inlet dropped from 10 inches
of water to 8 inches of water. (by the way, Steve was right about it being
inches of water and not inches of Hg.)
The pressure after the radiator and inside
the cowl dropped to 8 inches as well. The temperature of the water
dropped to 208 and the oil a couple of degrees. Neither of these had the
result that I expected.
My water pressure cap is rated at 21
lbs. I have not calibrated the sender that came with my EM-2 and it shows
3 lbs when the engine is cold. I assume that this is zero. When in
flight the pressure climbs to 24 lbs and stays there. I assume that at
this point, the cap is at 21 lbs and is bleeding off air. There is about
a pint to a quart of air above the coolant in the bleed tank.
This morning I ran the engine on the
ground for about 10-15 minutes at an rpm of 3000 to 3200. The OAT was 75
degrees.
I read the temps and pressures every
minute or two during the run. I hope this doesn’t get jumbled
during transmission.
Oil temp – 80
103
130
139
144 155
162 165
Air temp after cooler - 97
109
122
129
133 134
Water temp
-
86 126
161
173
178
190
198 199
Air temp after rad
-
109
133
157
169
179 183
Water pressure
- 2
11
17 20
21
24
I noticed that the water pressure could be
brought from 2 lbs to 9 lbs by changing the rpm while the engine was still relatively
cool
What should I expect for water pressure at
lower temps and how could I go about making a determination that the water
passages are clear?
I am beginning to think that a rag has
been left either in the engine or the radiator. I have never torn the
engine down and I sent the radiator out to have a leak repair a couple of years
ago. It is a double pass radiator. I can look into the end that has
both sides connected thru the radiator cap neck, but not into the inlet and
outlet end.
Suggestions???
Thanks,
Bill B
From: Bill Bradburry
[mailto:bbradburry@bellsouth.net]
Sent: Sunday, March 20, 2011 5:29
PM
To: 'Rotary
motors in aircraft'
Subject: On the subject of
installations...
My water temp has been running between 199
and 217, depending on the OAT. The oil is pretty steady at around
175. Today I finally got to fly with pressure probes inside the
cowling. I was all set to try and enlarge the inlet to the radiator to
solve the problem. It turns out that “in” is not the problem,
it is “out” that is the problem!
I have 10 inches of Hg pressure in the
radiator inlet and 10 inches of Hg on the outlet side as well as the same
pressure everywhere I measured inside the cowl. I need to open up the
cowl some so more air can get out. I had considered a cowl flap but that
would not work in this instance because the problem is at cruise. I need
a permanent opening. I am considering louvers and I am looking for a
source. I know some of you are using them. Where did you get them
and how are they installed so that they look ok?
I am also considering some kind of flare
around the exit area to create a low pressure area to help suck air out.
Do any of you have those and do they seem to work?
While I look into this, I also need to do
something about my muffler…Thank you, Bobby!
I wonder about that spiral muffler some of
you are trying??
Bill B 9 hours and counting…
By the way, I was considering putting a 1
or 2 inch wide piece of cardboard across the bottom of the oil cooler to
partially block it in the hopes that more air would then flow through the
radiator. Sort of like truckers do with the radiator in cold
weather. What opinions do you have about that idea? I realize it would
make more sense if the oil was really cool, but I think the oil might not get
much hotter if an inch or so was blocked. What do you think???