Al,
I've had a 1970 VW Bus since Jan 1971. Enlarged original engine to 1835cc, which generated more heat. I instrumented the engine with Manifold Pressure gage, oil pressure, and oil temp.
. . . I REPLACED the stock oil cooler "tower" with an adapter to take the oil out of the engine to an external oil cooler - and added a small (maybe 6" X 10") 5/8" thick aluminum finned oil cooler inside the engine bay (think it was a small air conditioner device?) - hung it from "ceiling" of engine compartment with coat hanger wire. It lay horizontally, not perpendicular to any air coming down and over toward fan housing opening near center of compartment.
. . . Point is, no hope of any significant airflow - it was all "convection" (rising heated air) and "surface area". It cooled just fine (better than stock).
This arrangement gave exellent cooling. That is point #1
Point #2: I've heard others recommend, "If one stock Mazda oil cooler doesn't cool enough, put in a 2nd." I don't have any anecdotes of anyone doing that.
. . . I do know that we are all "wired" to "think airflow", "ducts", etc.
My hypothesis: Just put another Mazda oil cooler in-line with the existing one - without any regard to ducting or orientation - just get the extra cooler volume and cross section out somewhere (away from the exhaust radiant heat), somewhere where it will fit, and let it "radiate" and "convect" and I'll bet your temps will come down 10 to 15 degrees - with no changes or mods to your ducting. That is what my non-ducted, hanging in the bay, VW experience suggests.
David

    ----- Original Message -----
    *From:* Al Gietzen <mailto:ALVentures@cox.net>
    *To:* Rotary motors in aircraft <mailto:flyrotary@lancaironline.net>
    *Sent:* Friday, September 15, 2006 12:08 PM
    *Subject:* [FlyRotary] Flight test

    Finally got the proper alignment of the planets (basically test
    pilot schedule) for further flight of Velocity 755V – 20B. Plane
    was in the air for ½ hour this time, basically at level cruise
    orbiting the airport. OAT was about 90F and flight was at DA of
    about 7000’.

    Since the first flight when oil temps were high, I added a
    temporary ram scoop under the ‘wing root’ oil cooler inlet. Oil
    temp reached near 230 during climb but later stabilized at 200 -
    205F. Coolant stabilized at 180-185F.

    <snip>

    Al