Perry Mick wrote:
Recently Jon Lauter asked why I was using a 24 psi pressure
cap. I think we need to discuss this. It was Tracy who originally
advocated using higher pressure caps for high altitude use. I
think Ed Anderson is also running a higher pressure cap, while
I'm throwing names out.
The 2nd gen RX-7 uses 13 psi caps, the 3rd gen 16 psi. I was
running a 16 psi cap initially but changed to 24 psi during my
flight test period. My coolant pressure is typically between
10 and 15 psi, so I think 13 and 16 psi is a little marginal.
I think I'm also running a little higher temperature/pressure
than normal because I have a relatively small volume of
coolant. This will change slightly in the future when I install
a real radiator with end tanks.
I would like to hear what others are using and think about
this issue.
--
Perry J. Mick
Duckt N7XR
http://www.ductedfan.com
Jim M wrote:
I have been using a 16 lb. cap since I started flying, my
pressure
has never gone over 12 lbs. Mind you I also have never had the bird over
9500 ft. either.
Jim mosur
RV6 13B
Brampton, Ontario
Jim has two of these very nice, large area, relatively thin radiators in
oblique ducts. Correct me if I am wrong Jim, you are also
using a thermostat so you would not know if you were overcooling
most of the time.
My reasoning goes like this; if you keep it cool enough
the system pressure will never get very high.
Paul Lamar
-Jim M wrote:
You are right Paul I do have a standard Mazda thermostate, I normally run
around 184-187 degrees, in a long hard climb in warm weather I have seen
temp at 194-196. I guess we all know that the oil and water temps have a
great effect on each other, since I repositioned and rescooped my oil cooler
a 100 hrs. ago and got very nice cooling on the oil (175-180) I found it
necessary to install the thermostate because the oil cooling dragged the
water temp down to 150 or less in let down even in warm weather. My oil temp
drops to 160-165 in let down now and water temp stays around 182-184 even at
very low power setting in let down. I have had no problems with overheat on
the ground even on very hot days, I have not timed how long I have sat on
the ground running but I would estimate 40 min. plus or minus and not just
idling.
Jim Mosur-
I think your airplane would be prime candidate for VW thermostat controlled
cowl flaps Jim. Maybe you could keep the temps up in a let down by sealing
off the cowl. They don't have to be on the side of the cowling as shown
here in this sketch but they could be. Should make an impression at
Oskosh with the judges. As far as I know they would be the first
thermostat controlled cowl flaps in the world. I could be wrong on that.
I know I would give you an award for engineering innovation if you got
them to work if it was up to me.
BTW I am reading this magazine on WW I aircraft and manually controlled
cowl flaps were used way back then.
Paul Lamar
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