Oil Cooler/s for RX-8 engine

    What size oil cooler should I be looking at if we don't have the
    standard one
    and maybe some suggestions on which ones / brands might be the options

    Anyone got some suggestions?

    Thanks

    Regards David

    For a two hundred HP RX8 engine you will need something about 300
    cubic inches.
    Preferable about two inches thick or thinner. The best shape would
    be square or
    about 12 inches high  by about 12 inches wide by about two inches thick.
    Make sure it will withstand 150 psi minimum. Internal finning in the
    tubes
    improves the heat transfer from the oil to the metal. Also lower weight
    oils cool the engine better for the same reason. Use 10W fully
    synthetic or
    lower in the engine while mixing two cycle oil with the fuel as it
    burns better.

    Don't go on the manufactures engine HP recommendations as the rotary
    rejects
    three times the oil heat. Most piston engines reject only 10% to
    cooling the oil while
    the rotary rejects 30% or more. In other words as far as oil coolers
    are concerned
    a 200 HP rotary requires a 600 HP piston engine oil cooler.

    Setrab is a good international company.
    http://www.setrab.com/index.php?id=68
    --
    Paul Lamar ...No rotor no motor.


Paul,

Nice discussion about oil.  You mention the Setrab coolers.  Since that
is what I use I thought I would share my experience.  You outlined the
11x18" cooler but I started out with the 11x15" and found that was
larger than I needed.  I am now using the 11x10" cooler (PN 50-634).
Even then I have about 20 sq in of the face covered with duct tape just
to get oil temps up to about 150.  Worst case is a 100 deg day, heat
soaked engine (I was giving rides to multiple people) and 85 kt climb
out at 34" MAP [turbo] and I finally got the oil to climb above 200 (my personal
red line).  Flattening the climb to 100 kts without reducing power quickly
brought the temps back down.  WOT in level flight oil temps never exceed
150.

Now, I should mention that my oil cooler is very well-fed with air (the
entire right cowl inlet).    If I were to use a larger face radiator and
smaller cowl opening I could probably achieve the same results with less
cooling drag.  Also, 34" MAP in a steep climb out for me, with my
over pitched prop and 2.17 gear box is significantly less than 200 h.p.

One other thing I should mention about the Setrab.  I have had a
recurring problem with a small leak in the same location on 3 coolers.
I kept thinking that I has some sort of mounting issue causing the leak
until I dissected one of the coolers and found that there was faulty
brazing in the trouble spot.  A dab of JB weld fixed the leak and has
held for the last 50+ hrs (it is a fairly small leak anyway).  I called
the company and they just wanted to keep blaming over torque on
installation (but I used a torque wrench).  It was clear that they have
had a big problem with customers "over torquing" the AN fittings when
installed.  Best they could do was offer me a replacement cooler at a
discount - which I still have since the one with JB weld is working fine.

Will sell that one for $290+ shipping if anyone is interested, JB weld
not included :-)