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While digging through some old photos of my project, I
found these photos of the various stages in my attempt to solve my oil temp
problems . Sort of embarrassing to show what I started out with - showed
how very little I understood about airflow and cooling at the time. This
has been an educational project for certain!!!
To the left side of the photo (First Oil Coolant
Ducts.jpg) near the firewall is a rectangular oil cooler (one of Earl's).
Its core volume was approx 30% larger than the stock RX-7 oil cooler - but that
was about the only thing I did that was half-way smart. Well, I had done a
little reading (but much less understanding) about plenums, so I knew you needed
one. Rear of oil cooler was 10" from firewall which didn't help the exit -
but probably didn't really matter as I didn't have much air going into the
cooler that needed to exit. {:>)
The orange/rust colored box over my oil cooler is a
fiberglass plenum with a small 2 1/2 " dia air hose going to one
corner. This photo (I am certain) tells why my first flight
lasted only 4 1/2 minutes (as fast as I could bend it around the pattern) due to
an ah-hem minor oil temp overheat problem {:>). But the oil in that
corner probably cooled just fine.
I later "improved" the plenum by extending its depth from
the core face from the 3 " before to approx 10" and enlarging the air inlet so
that I had a 5" dia hose running from the Naca duct (Oc1.jpg) you see in
the second photo to the oil cooler. All of this make marginal improvements
in that I could fly on days that did not push 90F with one eyeball on the oil
temps.
It was not until I moved a stock RX-7 oil cooler up under
the front and opening a duct under the spinner that my oil and coolant problems
were solved (FinsCowl.jpg). It only took about 5 attempts to get the oil
temp problem solved {:>)
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