> This is Dave's current system. He is not entirely happy
        > with the water cooling.
        > Air flows through the inter cooler on the left side and the oil
        > cooler on the right side and then through the 2 inch thick rad
        > mounted below the engine and out the exit below the cowl.
        > The air is also heated by passing over the turbo charger
        > and exhaust manifold before it flows through the rad.
        >
        > Does anybody have any suggestions what Dave could to to improve
        > the water cooling?
        >
        > Oil cooling and inter cooling are fine.

       Leave the oil cooler and intercooler ducted & positioned as-is.
   Leave
       the radiator positioned as-is, but add a chin scoop and duct to the
       current backside of the radiator. Let the airflow through the
   radiator
       be reversed from the current pathway. Add vents on the top of
   the cowl
       slightly ahead of the firewall. If the windscreen is near the
   firewall,
       that area of the cowl should be a lower pressure area (compared
   to the
       rest of the cowl; it's still high relative to the static port).

       Russell Kent

   Russel,
   I like that Idea best so far, as it would be the easiest to implement
   and would leave the cleanest looking cowl..

   There is little doubt that the other suggestions could be made to work
   as well.  Some would be impossible because of limited space.

   However, I would like to now throw out some other points for
   consideration:

   1) The point of improving my cooling system is all about going faster.
   After all, it works perfectly fine (em... recent incident excluded) to
   get average performance for an RV.

   2) up above 200 mph. (the speed I now travel at)  reduction in drag
   becomes more important than increases in power

   3) Cooling drag is 10% of overall drag - give or take.

   4) Therefore, maintaining low cooling drag, or decreasing it, should
   take priority in any planned improvements - for reasons of both speed
   and economy.  After all, we want to disprove the rotary's reputation as
   a gas gussler.

   So given the 'minimize cooling drag' premise, I submit that:
   1)  All air used for cooling must be heated to the maximum extent -
   otherwise it is waisted cooling drag.

   And I know from measuring temperatures in my cowl that:
   1) The intercooler and oil cooler add very little temperature rise to
   the incoming air, about 10-20 deg.  There is plenty more cooling to be
   had from it (as is proved by the relative success of my current system).

   So, until convinced otherwise, I am more or less committed to the
   minimization of cooling drag and the re-use of my intercooler and oil
   cooler air for at least some of the water cooling.

   That being said, improvement is needed.  Clearly, more air is part of
   that solution.  The other part of the solution appears to be more
   radiator volume - used to obtain more cooling from each bit of air.
   Weight penalty yes, but still more efficient IMHO.

   Paul is a big proponent of a cowl flap, and I agree.  As soon as things
   are cooling so well that I need to warm things up in cruise, it will be
   a simple matter to add a cowl flap to close down the air outlet.

   A spray system is still an excellent addition for augmenting climb
   cooling without adding drag.  Used mostly for bragging rights etc. but I
   have not ruled that out yet.

   And that's all I know.  (well, pretty sure of anyway  :-)

   BTW, I have also come to accept the wisdom that the rotary does not
   tolerate temperatures above 180 very well.  My previous red-line was
   230  and I would not start reducing power until it hit 210.  In the
   future, my "reduce power" limit will be 190 and redline (dramatically
   reduce power) will be 210.  The goal is to not get there very often.

   Unfortunately, that is the big problem with the turbo. I can always
   make
   more power.  And BHP is like money:  not matter how much I have, I
   always would like a little more.

   --
   Dave Leonard
   Turbo Rotary RV-6 N4VY
   http://members.aol.com/_ht_a/rotaryroster/index.html
   http://members.aol.com/_ht_a/vp4skydoc/index.html


   One rule of thumb that seems to apply here is every decrease
   in air temp going through the rad increases the cooling by 1%.
   This is because of the temp difference between air and rad.
   Assuming 100 degree air going in and a 200 degree rad temp.


   Another rule of thumb is the first half of the rad (thickness) does
   3/4 of the cooling.

   Lets review a few cooling principles. We need x amount of airflow
   given in cubic feet per minute raised to temperature x to carry
   away the necessary heat.

   If we had a hole in the front of the airplane with enough  area
   to take in the requires CFM of air at the speed of the airplane in
   question and that hole was connected to the back of the airplane
   with a duct and there was no heat exchanger in the duct the "cooling"
   drag would be the skin friction of the air in the duct alone. This
   is a lower limit on the "cooling" drag. As we install a heat
   exchanger in the duct the friction or drag on the air and the airplane
   increases.


   The drag added depends on how easy it is for the air to flow
   through the heat exchanger. A highly porous heat exchanger
   is very little drag. The thicker the heat exchanger the harder it is
   for the air to flow through it. In other words it becomes less
   porous.

   Now a few years back it was discovered that the drag in the heat
   exchanger was proportional to the square of the speed of the air
   flowing through the heat exchanger. If we increase the frontal area
   of the heat exchanger somehow keeping the air volume flow the same
   and slow
   the air going through it we can decrease the drag on the heat exchanger
   and the airplane. That was done  by a diverging area duct called a
   diffuser.
   What we also  need to do however is speed the air back up before we let
   it exit the duct.

   If we slow the air we must also increase the frontal area of the heat
   exchanger to keep the CFM the same. If we want to keep the volume
   flow the
   same we must make it thinner. It just so happens that that makes the
   heat
   exchanger more efficient in the bargain.  Now here is a quote from
   Kays &
   London on the subject.

   "highly compact surface geometries [read optimum heat transfer for a
   given
   HE core volume] is that the resulting core shapes are  characterized
   by large
   flow frontal area and short flow lengths for the  gas-flow path."

   Now if we do nothing other than make the heat exchanger thicker with
   out greatly adding to the transfer of heat from the heat
   exchanger  to the
   air stream all we have really done is greatly increase the drag
   along with
   a slight increase in the cooling.

   All this is assuming of course one has a converging duct on the out let
   side of the heat exchanger. That is where the cowl flaps come in.
   They ARE the
   converging duct.

   Dave is attempting to increase the cooling keeping the drag the same
   without making the hole in the front of the airplane larger in area and
   without using cowl flaps and at the same time increasing the temp of
   the air flowing through the water rad.

   Good luck Dave :)

   For the new guys read http://www.rotaryeng.net/how-to-cool12.html

   Paul Lamar ...No rotor no motor.


I am in complete agreement about surface area of a radiator being more
efficient than thickness.  Especially the part about cooling drag being
related to the square of the velocity.  It is important to have the
radiator as wide and thin as possible. No question.

However, there is only so much surface area available in a given
installation.  But there is still no substitute for adequate volume
either.  When you reach the limits of the space provided but still need
more radiator volume, there is no where to go but thicker.   It's not
optimum but it can be effective (aka. P-51)

In my discussion above I never mentioned a thicker radiator.  I said
more volume.  Truth is that will probably mean more surface area as well
as thickness.

I feel that I need more volume because my exit air is not hot enough.
You have to admit that using my cheek inlets only to go through an
intercooler and then get dumped overboard just 10 deg warmer than when
it came in is a waste of energy.

I also never said that I did not intend to increase my inlet area.  That
is definitely in the plan.  I just refuse to waste the air that is
already through the intercooler (and oil cooler) when that air has
already proven that it is still good for removing enough BTU's of heat
to cool at least 160h.p.

By continuing to use that that air my new air scoop only needs to be
large enough for, say, 70 hp. (worth of cooling) as opposed to the full
230h.p. sized scoop that would be required if I just dump the air that
is already in the cowl.