Ok folks, made the first flight today with my reduced/reshaped radiator
inlet for the left evaporator core. The right evaporator core was left
unmodified to provide a safety net sufficient to do the pattern and
land if
take off temps exceeded expectations. Fortunately, that was not
necessary.
OAT on first take off was a humid 85 degrees. No temperature increased
noted during ground run up, so launched and made max rate of climb, not
seeing any abnormal temp increase I left the pattern and continue Max
rate
climb to 4500 MSL. Max temp of coolant during climb was 210F (normal
for
max rate climb at these OAT temps is 205F), Max oil temp was 200F
nominal
for max power climb. Max temps were reached about 2/3 of the way through
the
climb.
In level flight, my coolant temperatures normally run 5 degrees colder
than
my oil temp. Today my coolant and oil temps were the same. So average
coolant temp was increased by 5 Degrees F. Total radiator inlet duct
area
was decreased from 48 square inches to 33 square inches. 24 Square
inches
for the right inlet duct and 9 square inch inlet for the modified right
duct. Probably some drag benefit, but did not try to investigate that
aspect.
I flew to an airfield 50 miles away to have my transponder recertified
and
when I launched out of it, the OAT (ground level) was 92F
After level off I ran at different power settings to see the effect.
5800 rpm burning 11.9 GPH at 4500 MSL with OAT at 78F My oil and
coolant
were both 190F.
5400 rpm burning 9.6 GPH at 4500 MSL with OAT 80F My Oil and coolant
were
both 185F
5200 (My normal cruise rpm) burning 7.25 GPH at 4500 MSL with OAT 80F
My
oil and coolant were both 180F
In summary, the 33 % reduction in total radiator inlet area appeared to
have increased coolant temps by an average of 5 Deg above the normal
(the
old duct). It could be that both the remaining radiator and perhaps the
oil
cooler are rejecting any additonal load with no problem.
It appears that smoothing out the path for the air from inlet to
radiator
surface has benefited the cooling situation. It could be that
additional
heat may be rejected by the right (second in series) radiator as the
coolant
it received from the left radiator was probably now a bit hotter. I also
observed that the plate of the PSRU covers an area 3 " in from top to
bottom
of the rear of each radiator and the plate is only 2" from the rear of
the
fins at its closest, so that is obviously not helping flow, the Ross
Bell
housing did not, so a bell housing might improve flow conditions .
I strongly suspect I would probably find that a similar reduction of
the
right radiator inlet duct to 9 square inches would see my coolant (and
probably oil) temps increase considerable more than another 5 F. OAT at
ground level was 94F when I landed, so not the hottest of days, but not
the
type I normally prefer to fly in.
>From what I have seen so far, I think it worth pursuing a reduction
with the
right radiator duct. I will probably not reduce it as much for the
reason
mentioned above. With some other things to take care of, probably won't
get
to it until later part of Sept at the earliest. But, I have no problem
flying with current asymmetrical ducts, so will leave it as is for the
time
being and collect some more data.
It it appears that some cooling benefit is derived from providing a
smoother
transition from duct to radiator (even if far from a perfect
implementation
of the K&M approach) than my old duct provided.
Oh, yes, as an aside, its been 25 hours since I replaced the spark plugs
and
right on schedule - on the way back, I got the first SAG (Sparkplug
Attention Getter) indication. So it appears 25 hours on 100LL about
the
average time for replacing plugs in my case. I finally got a spark plug
cleaner, so need to clean a set (as the electrods do not appear worn)
and
see if getting the lead off the ceramic cone helps any.
Best Regards
Ed Anderson
Ed please don't do anything until you get that cooling temp measuring
system working.
We will learn a lot more about your system when that is working.
Great data. Thanks.
Paul Lamar
Ok, Paul, I agree. It should be interesting to see what is happening with
the downsized inlet duct radiator and the larger duct since both see the
same coolant flow (radiator would see it a bit cooler of course) . IF the
downsized duct is still rejecting approx the same (more?) heat than the
larger duct then that would pretty much confirm the improvement. On the
other hand, if it has simply passed the heat load on to the other radiator
(and perhaps oil), then the results still seem good, but would not be quite
as impressive.
A question related to the data collection. If I can't get the total system
(including the GPS switch) functioning, I know you said to ship it back.
However, I know the thermocouple system worked as we got to that point early
on. Would the temp data without the GPS data be of any value?
Ed Anderson
Sure as long as you manually record air speed and ambient temp.
BTW your recent cooling data was taken under rather benign conditions.
I want to emphasize for the new guys that liquid cooling systems are extremely
sensitive to ambient temp. Much much more so than air cooled systems.
This is because of the temp differential. Liquid cooling systems are limited
by the 220 degree F or so temp of the coolant so a ten degree increase in out
side temp makes much more of a difference than if you are dealing with
a 400 degree F air cooled cylinder head.
Paul Lamar
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