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I suspect that you temp sensor location may be the problem
rather than calibration. If its outside the main flow channel, then its
hard to tell just how close or far off of the main flow temps it may be
registering.
On the other hand if your coolant engine outlet temp is
measuring only 161F (and assuming that is somewhere near the actual temp) then
you radiator is clearly doing its job by cooling down the coolant before it
enters the engine. When I am cruising at 5400 rpm my coolant temps range
from 155F-175F depending on OAT. This is temp out of the engine.
Since your temp is in the same ball park, it appears your radiator is doing
a good job especially given the 90F OAT.
Ed
----- Original Message -----
Sent: Saturday, September 29, 2007 10:13
PM
Subject: [FlyRotary] Re: Oil Delta -
T
Ed,
OK, I'll recallibrate the sensors ONE MORE TIME! They were reading
within a degree of each other before I relocated one of them. I did take
the time to verify the EC-2 sensor was reading correctly at 212* during the
switch. But I didn't check it lower than that. I'll use ambient
temp for a low reference.
I suspect the problem may be where one of the sensors is
located. The first sensor is located on the WP housing at the outlet
from the engine. Since that is one of the factory locations, I don't see
any problem there. The second sensor is on the WP housing inlet, but not
on the main line, it is on the one returing from the swirl tank, but is very
close to where the main WP inlet is located. It is fed by a line
that runs through the swirl tank from the outlet side of the radiator,
but at the top instead of the bottom (to draw any air out of the
radiator). Directly across from this fitting is the "hot" inlet to the
radiator. I'm sure that some of the coolant goes straight across the
core to the swirl tank fitting. (Yes, this is confusing me too) I
questioned the wisdom of putting the sensor where I did, but did it anyway due
to the ease of installation (No draining the cooling system, no drilling, no
tapping). Anyway, this was supposed to be a "temporary" test
setup.
So, it looks like I probably need to find a better place to locate the
second sensor. I'll check the accuracy of this sensor at around
150* and see what it shows. If there is a significant error, I'll dive
into the EC-2 calibration system one more time (heaven help
me).
Mark
On 9/29/07, Ed
Anderson <eanderson@carolina.rr.com>
wrote:
Mark, if you really had excess air flowing
through your radiators the coolant would drop more than 4 Deg F. In
fact, the more air flow the more coolant Delta T you would drop through the
radiator. So if you had something like 180F in and 120F out then I
might suspect too much air flow through the cores, but not with a drop of
only 4 deg F. In fact if that delta T is correct (which I
suspect it is not), then you would need tremendous coolant flow rates for it
to carry away the engine heat it needs to at 5200 rpm.
I did some back of envelope
calculations.
IF your coolant flow was 30 GPM at 8.25 lb/gal
coolant with a 0.65 (50/50 mix) Cp, then a 4 degreeF drop in coolant temp
would only be getting rid of 644 BTU/Min.
At 5200 rpm and a 19:1 A/F ratio you would need
to get rid of approx 3100 BTU/Min through your radiator. I suspect
that the 4 degree drop you are measuring may be in error. I
assume you are measuring temp at radiator inlet (engine outlet) and
radiator outlet (or engine inlet) It would take something like a
20 deg coolant temp drop at 30 GPM flow or a flow rate of 150 GPM at 4
deg drop to get rid of that much heat.
On the other hand if you were flowing 60 gpm of pure
water and had a 6.5F drop that would get rid of the required BTUs. I
have no clue as to the flow rate of a 20B water pump, but suspect my guess
of 60 gpm might be on the high side.
Since you are apparently cooling just fine with the
radiators, then :
1. My calculations are incorrect
2. Your coolant temp drop is more than 4
Fdeg
3. your flow rate is >50 gpm
4. You oil system is dumping the excess heat
that your radiators are not getting rid of.
FWIW
Ed
----- Original Message -----
Sent: Saturday, September 29, 2007
7:51 PM
Subject: [FlyRotary] Re: Oil Delta -
T
Tracy,
I flew again today. I'm still staying very close to the airport
and was forced to limit my altitude to 2500' due to
clouds. OAT was about 90* and oil got to 215, but came right down
after leveling off and settled in at 190*. The strange thing is the
water temps in economy cruise (5200 engine rpm, 1800 prop rpm) were in the
157* range. I'm measuring water temp in and out. Water out was
about 161*, so I'm getting very little temp drop through the
radiator. We're figuring that this is probably due to too much
air to the water radiator or too rapid coolant flow through the
radiator (I'm running the 20B pump). My main pulley has been
downsized, but I may also need to enlarge the wp pulley a little
to slow the flow. I'm considering doing a quick mod to check this
theory. If that's true, then my oil temps should drop because I
suspect airflow through the two radiators are fighting for the exit space
and the water radiator is winning.
Mark
On 9/29/07, Tracy
Crook <tracy@rotaryaviation.com > wrote:
Haven't had any 100+ days since installing the Renesis but cooling
is similar to the 2nd gen I had a few years ago when we had 10
consecutive days of 100+ temps. Didn't have to wait it out but
simply limited power after initial climbout. Still had more ROC
than most certified planes at the reduced power setting. I start
with around 2500 FPM on a standard day and never had to settle for less
than ~1000 fpm due to heat issues.
Hope my 20B RV-8 does as well or better but I will install spray
bar for initial tests.
Tracy (delayed 20B test schedule due to motorcycle
distraction)
On 9/27/07, Mark
Steitle <msteitle@gmail.com
> wrote:
Tracy,
So, what do you call a "hot" day? In Austin, it is normal
during the summer for temps to be in the upper 90's and even above 100
on occasion. I don't want to be grounded waiting for the Texas
heat to subside. I guess I could install a spray bar for summer
flying. Right now I can keep temps in the green up into the low
90's. Living in Texas, I would like a little more margin
than that. Not everyone can swing a summer
home in Colorado. ;-)
Mark S.
(Just happy to be flying again.)
On 9/26/07, Tracy Crook <tracy@rotaryaviation.com > wrote:
Engine will cool at any throttle setting that enables the plane
to fly. The coolant & oil temp curve looks about like the
power required curve of the airframe, minumum at around 95 mph and
rises on either side of that speed. Only exception is WOT at
Vx on hot day. Engine will exceed redline temps if
this is maintained more than a minute or so. Fortunately
there is never any real need to do that.
Tracy
On 9/26/07, Mark Steitle <msteitle@gmail.com > wrote:
Tracy,
Is there a particular speed that you must reach before your
system cools?
Mark
On 9/26/07, Tracy Crook <tracy@rotaryaviation.com > wrote:
For another data point, the delta T on oil cooler depends
on power setting on my installation (no big surprise). It
is around 40 degrees F at higher power settings.
Tracy
On 9/18/07, Mark Steitle <msteitle@gmail.com > wrote:
For those that are flying (rotaries), I'm curious as to
what delta-T you're seeing across the oil cooler. And at
what speed you attain adequate cooling.
Mark
S.
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