>
> > 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/rotaryroster/index.html>
>
http://membersaol.com/_ht_a/vp4skydoc/index.html
<http://members.aol.com/_ht_a/vp4skydoc/index.html>
>
>
Dave,
Bearing in mind the rule of thumb that a Paul uses about the
effect
higher temperatures decreasing the available cooling I think you
would be
better off not preheating the air for your coolant. You are right
though
about about making the air going into your intercooler and oil
cooler do
more work. Why not use less air into these, idealy to the point
where the
outcoming air is at some maximum desirable level. Use the remaining
unused
air and possibly a little more to cool the coolant using properly
designed
ducts. This way your radiator is seeing cooler air thus
allowing the
use of
less air overall.
John
John, that is exactly what Paul suggested. And to some extent you are
correct. The problem is then that oil and especially intercooler
cooling becomes insufficient. Both oil and air have low coefficients of
heat transfer and therefore tend to be more finicky than water.
But the real reason I cant do that is that there is no room behind
either for a duct, and no good way to duct the incoming air around them
to the rad.
I appreciate all the help. The radiator is going to get some more fresh
clean air, the exit will get bigger, and there will be more radiator
volume. The partially used air will do its part to help out, and there
will be no more cooling problems.
Have no fear I will not stop until I can cool at least 210h.p. on a hot
day - yet I will not have to stay up at night worrying about all my
waisted cooling drag. :-)
BTW, here are the numbers I am working out:
By adding 1/2 inch thickness to my rad, the core volume will go from 540
cu.in
<http://cu.in>. to 720 cu.in
<http://cu.in>.
(I may add a full inch, bringing the volume to 900 cu.in
<http://cu.in>.
- I'm open to suggestions on this issue)
AND I will increase the frontal inlet (and exit) area by 50% (worth
about 80h.p. worth of cooling) - all of that going directly to the
radiator.
AND it will fit and only take a couple months to do the fiberglass work.
Anyone think that's not enough?
--
Dave Leonard
Don't want to rehash the old thick vs thin rad again but I agree
with your proposed approach but there may be a better way (not
necessarily easier though).
The hit you are taking with the heat from the exhaust plumbing is
probably greatly underestimated here. My guess is that if you could
find a way to isolate that and duct it out into the existing outlet
area you would be close to your goal without making any other changes.
Tracy Crook
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