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 :-)

      --
      David Leonard

      Turbo Rotary RV-6 N4VY
      http://N4VY.RotaryRoster.net
      http://RotaryRoster.net




      ----------------------------------------------------

      We never did get pictures of your new installation Dave.
      I would still like to see them. Here are some old ones
      dating back to Dec. 2007. Nicely done, well sealed K&W oil
      cooler duct on the right side.


   Paul, those are the latest pictures (except for the first one).  Dec.
   2007 was not that long ago, nothing has changed since then.  In fact, I
   have only removed the cowl a couple times since December - too busy
   flying.  280 hrs now on the Hobbs.


      Do you have movable cowl flaps on it yet? :)


   Yes, you can see it in the pictures you sent.  Though it does not seem
   to have much authority to change the temps much one way or another (can
   only affect 5 deg or so).   I fly around with it full closed all the
   time.


      What are the oil and water temps flat out at top speed?


   70 deg C [160 F] for both on a warmish day.  Colder than that if I
   am not flat
   out - which is usual given the price of gas.  Typical cruse of 150-160
   ktas, 130-150 KIAS, 60C for both temps.


      What is the top speed? When you are climbing out at 85 kts
      what is the gross weight and rate of climb (FPM)? From that one
      can calculate the climb HP being used.


   According to the fuel burn calcs  on Ed Anderson's fuel computer, I am
   putting out about 235 h.p. at best power and 200 h.p. lean of peak
   (where I usually fly).  I think that is using .55 BSFC.(but will have to
   check with Ed).

   I cant say that I have good numbers for climb out and never do it at 80
   (I was letting the pax fly that day until the oil got above 95C).  Vy is
   closer to 100 kts.  It seem that solo and low fuel I will see around 2k
   ft/min.  Full Gross of 1800lbs is closer to 1300.  Not outstanding
   numbers for an RV-6, but very good for an over pitched f.p. prop.
    RPM on
   climb out is only about 4600 RPM in that condition.  I could get a lot
   more climb if I had a couple less inches of pitch.

   Flat out down low RPM is still only 5300 and 38" MAP.  I cant really
   unload the prop until I get above 10K, so that is where I see my fastest
   true air speeds (around 190 KTAS [219 MPH] give or take) at just
   over 6k RPM.

   Craig Catto says he can re-pitch my prop without too much trouble which
   I may eventually do. In the mean time I have ordered up a second turbo
   identical to my current [mod 2nd-gen] one except I will keep the
   waste gate flapper
   intact.  I still plan to limit max boost to 40" MAP, but I will be able
   to carry much more power up high.  After I see where I stand there, I
   will know how much, if any, I want to trim back on the prop.

   I know you would love to see me optimize everything to post impressive
   numbers, but my goal is to just have a reliable aircraft that sacrifices
   nothing to performance compared to my Lycoming buddies.  Basically I
   have that now.  In the Sharpie 500 race, looking at only other similar
   configuration aircraft that were also going for top speed, I was right
   in the middle.  I lost to a 200 hp RV-7 and was edged out by a 180 hp.
   RV-6.  I also beat a 200+ hp RV-7 and a 180+hp RV-7A - all of whom had
   c/s props.  So I am right were I need to be (and paid $15-30K less for
   the experience).  My fuel burn was right in the middle of that group as
   well.  I have met my goals and often have second thoughts about changing
   anything at all.  But there is the part of me that knows how easy it
   would be to get an extra 10-20 knots top speed (with the new turbo) and
   some extra rate of climb (by trimming the prop).  That guy will probably
   eventually win out and I'll start breaking stuff again.  :-)


      When you cut it open did you notice fins inside the tubes?


   Sorry, didn't notice



      BTW I suggest testing the cooler to 150 PSI with hot oil before
      using them as
      the rotary is much much harder on coolers than a piston engine
      that typically operates on only 40 psi. We see oil pressures
      on the dyno when the rotary engine oil is still cold at well over
      100 psi.

      A hydraulic hand pump from a cheap Chinese jack will work along
      with a pressure gage. Boil the low viscosity oil so it gets above
      250 F or so
      before you pour it into the cooler. Oil cooler failures are serous
      as we have had at least two in flight oil fires and one fatality due
      to failed oil coolers in the last ten years. Mistral has also had
      an oil cooler expand due to over pressure.

      The stock 2nd gen oil coolers work fine but they are getting scarce.
      I think they were custom built by Modine for Mazda.

      I am surprised about the Setrab leak. Perhaps we need to find
      another supplier.


   I would still use the Setrab again.  Primarily because I have not found
   anything better, especially that has so many stock sizes to choose from
   and is not too expensive.  Since the leak has always been in the same
   spot, I thing is is an assembly line issue but luckily it is easy to
   fix.  We'll see how long the current core lasts.  It has 60 hrs so far.


   --
   David Leonard

   Turbo Rotary RV-6 N4VY
   http://N4VY.RotaryRoster.net
   http://RotaryRoster.net


   Thanks for the performance report Dave. You probably have the fastest
   rotary powered aircraft around at the moment.
   For some video of it in action see:

   http://www.youtube.com/watch?v=CYmpAIJWykU
   http://www.youtube.com/watch?v=2iSzGqirbsI
   http://www.youtube.com/watch?v=OxYw4grU0Nk


   Here are some more pictures for the new guys.

   Paul Lamar ...No rotor no motor.

------------

Now THOSE are old pictures.

Thanks for the vote of confidence in my speed, but I think it is
undeserved.  Al Giltzen would definately out run me, as would Steve
Brooks (when he is flying) and John Slade.  Tracy's RV-4 sure posted a
much faster race time than I did, though under different condition.  His
RV-8 will no doubt be much faster.  Also Tom Parks is no doubt faster.
Maybe Rich Nadig in ex-Rustys RV-3 as well.

Lets see, where was that bigger turbo?  :-)